Publication of the Month
Publication of the Month | january 2012 |
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| Authors: | Smith EJ, Stroemer RP, Gorenkova N, Nakajima M, Crum WR, Tang E, Stevanato L, Sinden JD, Modo M. |
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| Title: | Implantation Site and Lesion Topology Determine Efficacy of a Human Neural Stem Cell Line in a Rat Model of Chronic Stroke. |
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| Summary: | Stroke remains one of the most promising targets for cell therapy. Thorough preclinical efficacy testing of human neural stem cell (hNSC) lines in a rat model of stroke (transient middle cerebral artery occlusion) is, however, required for translation into a clinical setting. Magnetic resonance imaging (MRI) here confirmed stroke damage and allowed the targeted injection of 450,000 hNSCs (CTX0E03) into peri-infarct tissue, rather than the lesion cyst. Intraparenchymal cell implants improved sensorimotor dysfunctions (bilateral asymmetry test) and motor deficits (footfault test, rotameter). Importantly, analyses based on lesion topology (striatal versus striatal+cortical damage) revealed a more significant improvement in animals with a stroke confined to the striatum. However, no improvement in learning and memory (water maze) was evident. An intracerebroventricular injection of cells did not result in any improvement. MRI-based lesion, striatal and cortical volumes were unchanged in treated animals compared to those with stroke that received an intraparenchymal injection of suspension vehicle. Grafted cells only survived after intraparenchymal injection with a striatal+cortical topology resulting in better graft survival (16,026 cells) than in animals with smaller striatal lesions (2,374 cells). Almost 20% of cells differentiated into GFAP+ astrocytes, but <2% turned into FOX3+ neurons. These results indicate that CTX0E03 implants robustly recover behavioral dysfunction over a 3 month time frame and that this effect is specific to their site of implantation. Lesion topology is potentially an important factor in the recovery, with a stroke confined to the striatum showing a better outcome compared to a larger area of damage. |
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Publication of the Month | December 2011 |
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| Authors: | Daly KA, Liu S, Agrawal V, Brown BN, Johnson SA, Medberry CJ, Badylak SF. |
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| Title: | Damage associated molecular patterns within xenogeneic biologic scaffolds and their effects on host remodeling. |
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| Summary: | The immune response is an important determinant of the downstream remodeling of xenogeneic biologic scaffolds in vivo. Pro-inflammatory responses have been correlated with encapsulation and a foreign body reaction, while anti-inflammatory reactions are associated with constructive remodeling. However, the bioactive and bioinductive molecules within the extracellular matrix (ECM) that induce this polarization are unclear, although it is likely that cellular remnants such as damage associated molecular patterns (DAMPs) retained within the scaffold may play a role. The present study investigated the immunomodulatory effects of common ECM scaffolds. Results showed that tissue source, decellularization method and chemical crosslinking modifications affect the presence of the well characterized DAMP - HMGB1. In addition, these factors were correlated with differences in cell proliferation, death, secretion of the chemokines CCL2 and CCL4, and up regulation of the pro-inflammatory signaling receptor toll-like receptor 4 (TLR4). Inhibition of HMGB1 with glycyrrhizin increased the pro-inflammatory response, increasing cell death and up regulating chemokine and TLR4 mRNA expression. The present study suggests the importance of HMGB1 and other DAMPS as bioinductive molecules within the ECM scaffold. Identification and evaluation of other ECM bioactive molecules will be an area of future interest for new biomaterial development. |
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Publication of the Month | November 2011 |
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| Authors: | Fang PA, Conway JF, Margolis HC, Simmer JP, Beniash E. |
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| Title: | Hierarchical self-assembly of amelogenin and the regulation of biomineralization at the nanoscale.Extracellular Matrix Powder Protects Against Bleomycin-Induced Pulmonary Fibrosis. |
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| Summary: | Enamel is a highly organized hierarchical nanocomposite, which consists of parallel arrays of elongated apatitic crystallites forming an intricate three-dimensional microstructure. Amelogenin, the major extracellular matrix protein of dental enamel, regulates the formation of these crystalline arrays via cooperative interactions with forming mineral phase. Using cryoelectron microscopy, we demonstrate that amelogenin undergoes stepwise hierarchical self-assembly. Furthermore, our results indicate that interactions between amelogenin hydrophilic C-terminal telopeptides are essential for oligomer formation and for subsequent steps of hierarchical self-assembly. We further show that amelogenin assemblies stabilize mineral prenucleation clusters and guide their arrangement into linear chains that organize as parallel arrays. The prenucleation clusters subsequently fuse together to form needle-shaped mineral particles, leading to the formation of bundles of crystallites, the hallmark structural organization of the forming enamel at the nanoscale. These findings provide unique insight into the regulation of biological mineralization by specialized macromolecules and an inspiration for bottom-up strategies for the materials design. |
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Publication of the Month | October 2011 |
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| Authors: | Manni ML, Czajka CA, Oury TD, Gilbert TW. |
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| Title: | Extracellular Matrix Powder Protects Against Bleomycin-Induced Pulmonary Fibrosis. |
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| Summary: | Pulmonary fibrosis refers to a group of lung diseases characterized by inflammation, fibroblast proliferation, and excessive collagen deposition. Although the mechanisms underlying pulmonary fibrosis are poorly understood, current evidence suggests that epithelial injury contributes to the development of fibrosis. Regenerative medicine approaches using extracellular matrix (ECM) scaffolds have been shown to promote site-specific tissue remodeling. This led to the hypothesis that particulate ECM would promote normal tissue repair and attenuate bleomycin-induced pulmonary fibrosis. C57BL/6 mice were treated intratracheally with bleomycin or saline with or without a particulate form of ECM scaffold from porcine urinary bladder matrix (UBM-ECM) or enzymatically digested UBM-ECM. Mice were sacrificed 5 and 14 days after exposure. Compared to control mice, bleomycin-exposed mice had similar increases in inflammation in the bronchoalveolar lavage fluid regardless of UBM-ECM treatment. However, 14 days after exposure, lung histology and collagen levels revealed that mice treated with bleomycin and the particulate or digested UBM-ECM had negligible fibrosis, whereas mice given only bleomycin had marked fibrosis. Administration of the particulate UBM-ECM 24 h after bleomycin exposure also significantly protected against pulmonary injury. In vitro epithelial cell migration and wound healing assays revealed that particulate UBM-ECM promoted epithelial cell chemotaxis and migration. This suggests that promotion of epithelial wound repair may be one mechanism in which UBM-ECM limits pulmonary fibrosis. |
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Publication of the Month | September 2011 |
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| Authors: | Chu H, Gao J, Chen CW, Huard J, Wang Y. |
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| Title: | Injectable fibroblast growth factor-2 coacervate for persistent angiogenesis. |
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| Summary: | Enhancing the maturity of the newly formed blood vessels is critical for the success of therapeutic angiogenesis. The maturation of vasculature relies on active participation of mural cells to stabilize endothelium and a basal level of relevant growth factors. We set out to design and successfully achieved robust angiogenesis using an injectable polyvalent coacervate of a polycation, heparin, and fibroblast growth factor-2 (FGF2). FGF2 was loaded into the coacervate at nearly 100% efficiency. In vitro assays demonstrated that the matrix protected FGF2 from proteolytic degradations. FGF2 released from the coacervate was more effective in the differentiation of endothelial cells and chemotaxis of pericytes than free FGF2. One injection of 500 ng of FGF2 in the coacervate elicited comprehensive angiogenesis in vivo. The number of endothelial and mural cells increased significantly, and the local tissue contained more and larger blood vessels with increased circulation. Mural cells actively participated during the whole angiogenic process: Within 7 d of the injection, pericytes were recruited to close proximity of the endothelial cells. Mature vasculature stabilized by vascular smooth muscle cells persisted till at least 4 wk. On the other hand, bolus injection of an identical amount of free FGF2 induced weak angiogenic responses. These results demonstrate the potential of polyvalent coacervate as a new controlled delivery platform. |
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Publication of the Month | August 2011 |
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| Authors: | Stauffer WR, Lau PM, Bi GQ, Cui XT. |
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| Title: | Rapid modulation of local neural activity by controlled drug release from polymer-coated recording microelectrodes. |
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| Summary: | We demonstrate targeted perturbation of neuronal activity with controlled release of neurochemicals from conducting polymer-coated microelectrodes. Polymer coating and chemical incorporation are achieved through individually addressable electrodeposition, a process that does not compromise the recording capabilities of the electrodes. Release is realized by the application of brief voltage pulses that electrochemically reduce the polymer and dissociate incorporated neurochemicals; whereby they can diffuse away and achieve locally effective concentrations. Inhibition of evoked synaptic currents in neurons within 200 µm of a 6-cyano-7-nitroquinoxaline-2,3-dione releasing electrode lasts for several seconds. Spiking activity of neurons in local circuits recorded extracellularly near the releasing electrode is silenced for a similar duration following release. This methodology is compatible with many neuromodulatory chemicals and various recording electrodes, including in vitro and implantable neural electrode arrays, thus providing an inexpensive and accessible technique capable of achieving sophisticated patterned chemical modulation of neuronal circuits. |
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Publication of the Month | July 2011 |
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| Authors: | Mi Q, Constantine G, Ziraldo C, Solovyev A, Torres A, Namas R, Bentley T, Billiar TR, Zamora R, Puyana JC, Vodovotz Y. |
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| Title: | A dynamic view of trauma/hemorrhage-induced inflammation in mice: principal drivers and networks. |
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| Summary: | BACKGROUND: Complex biological processes such as acute inflammation induced by trauma/hemorrhagic shock/ (T/HS) are dynamic and multi-dimensional. We utilized multiplexing cytokine analysis coupled with data-driven modeling to gain a systems perspective into T/HS. METHODOLOGY/PRINCIPAL FINDINGS: Mice were subjected to surgical cannulation trauma (ST) ± hemorrhagic shock (HS; 25 mmHg), and followed for 1, 2, 3, or 4 h in each case. Serum was assayed for 20 cytokines and NO(2) (-)/NO(3) (-). These data were analyzed using four data-driven methods (Hierarchical Clustering Analysis [HCA], multivariate analysis [MA], Principal Component Analysis [PCA], and Dynamic Network Analysis [DyNA]). Using HCA, animals subjected to ST vs. ST + HS could be partially segregated based on inflammatory mediator profiles, despite a large overlap. Based on MA, interleukin [IL]-12p40/p70 (IL-12.total), monokine induced by interferon-γ (CXCL-9) [MIG], and IP-10 were the best discriminators between ST and ST/HS. PCA suggested that the inflammatory mediators found in the three main principal components in animals subjected to ST were IL-6, IL-10, and IL-13, while the three principal components in ST + HS included a large number of cytokines including IL-6, IL-10, keratinocyte-derived cytokine (CXCL-1) [KC], and tumor necrosis factor-α [TNF-α]. DyNA suggested that the circulating mediators produced in response to ST were characterized by a high degree of interconnection/complexity at all time points; the response to ST + HS consisted of different central nodes, and exhibited zero network density over the first 2 h with lesser connectivity vs. ST at all time points. DyNA also helped link the conclusions from MA and PCA, in that central nodes consisting of IP-10 and IL-12 were seen in ST, while MIG and IL-6 were central nodes in ST + HS. CONCLUSIONS/SIGNIFICANCE: These studies help elucidate the dynamics of T/HS-induced inflammation, complementing other forms of dynamic mechanistic modeling. These methods should be applicable to the analysis of other complex biological processes. |
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Publication of the Month | June 2011 |
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| Authors: | Badylak SF, Hoppo T, Nieponice A, Gilbert TW, Davison JM, Jobe BA. |
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| Title: | Esophageal preservation in five male patients after endoscopic inner-layer circumferential resection in the setting of superficial cancer: a regenerative medicine approach with a biologic scaffold. |
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| Summary: | As a result of injury caused by chronic gastroesophageal reflux, Barrett's esophagus with high-grade dysplasia and esophageal adenocarcinoma are rapidly increasing problems in the United States. The current standard of care involves esophagectomy, a procedure associated with a high morbidity, a negative impact on long term quality of life, and a mortality rate of 1-6 percent. An entirely endoscopic technique for circumferential, long segment en bloc removal of the mucosa and submucosa with subsequent placement of a biologic scaffold material that promotes a constructive remodeling response and minimizes stricture is described herein. The results of this approach are reported for five patients with 4-24-month follow-up. Restoration of normal mature, K4+/K14+, squamous epithelium, and return to a normal diet without significant dysphagia is reported for all patients. Two of five patients show a small focus of recurrent Barrett's esophagus at the gastroesophageal junction, but the entire length and circumference of the reconstituted esophageal mucosa remains free of disease. This experience provides evidence that a regenerative medicine approach may, for the first time, enable aggressive endoscopic resection of early stage neoplasia without the need for esophagectomy and its associated complications. |
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Publication of the Month | May 2011 |
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| Authors: | Hoppo T, Komori J, Manohar R, Stolz DB, Lagasse E. |
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| Title: | Rescue of lethal hepatic failure by hepatized lymph nodes in mice. |
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| Summary: | BACKGROUND & AIMS: Hepatocyte transplantation is a potential therapeutic approach for liver disease. However, most patients with chronic hepatic damage have cirrhosis and fibrosis, which limit the potential for cell-based therapy of the liver. The development of an ectopic liver as an additional site of hepatic function represents a new approach for patients with end-stage liver disease. We investigated the development and function of liver tissue in lymph nodes in mice with liver failure. METHODS: Hepatocytes were isolated from 8- to 12-week-old mice and transplanted by intraperitoneal injection into 8- to 12-week-old fumarylacetoacetate hydrolase mice (Fah(-/-)), a model of the human liver disease tyrosinemia type I. Survival was monitored and the locations and functions of the engrafted liver cells were determined. RESULTS: Lymph nodes of Fah(-/-) mice were colonized by transplanted hepatocytes; Fah(+) hepatocytes were detected adjacent to the CD45(+) lymphoid cells of the lymphatic system. Ten weeks after transplantation, these mice had substantial improvements in serum levels of transaminases, bilirubin, and amino acids. Homeostatic expansion of donor hepatocytes in lymph nodes rescued the mice from lethal hepatic failure. CONCLUSIONS: Functional ectopic liver tissue in lymph nodes rescues mice from lethal hepatic disease; lymph nodes therefore might be used as sites for hepatocyte transplantation. |
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Publication of the Month | April 2011 |
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| Authors: | Lee KW, Stolz DB, Wang Y. |
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| Title: | Substantial expression of mature elastin in arterial constructs. |
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| Summary: | Mature elastin synthesis is a key challenge in arterial tissue engineering. Most engineered vessels lack elastic fibers in the medial layer and those present are poorly organized. The objective of this study is to increase mature elastin synthesis in small-diameter arterial constructs. Adult primary baboon smooth muscle cells (SMCs) were seeded in the lumen of porous tubular scaffolds fabricated from a biodegradable elastomer, poly(glycerol sebacate) (PGS) and cultured in a pulsatile flow bioreactor for 3 wk. We tested the effect of pore sizes on construct properties by histological, biochemical, and mechanical evaluations. Histological analysis revealed circumferentially organized extracellular matrix proteins including elastin and the presence of multilayered SMCs expressing calponin and α-smooth muscle actin. Biochemical analysis demonstrated that the constructs contained mature elastin equivalent to 19% of the native arteries. Mechanical tests indicated that the constructs could withstand up to 200 mmHg burst pressure and exhibited compliance comparable to native arteries. These results show that nontransfected cells in PGS scaffolds in unsupplemented medium produced a substantial amount of mature elastin within 3 wk and the elastic fibers had similar orientation as those in native arteries. The 25-32 μm pore size supported cell organization and elastin synthesis more than larger pore sizes. To our knowledge, there was no prior report of the synthesis of mature and organized elastin in arterial constructs without exogenous factors or viral transduction. |
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Publication of the Month | March 2011 |
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| Authors: | Hong Y, Huber A, Takanari K, Amoroso NJ, Hashizume R, Badylak SF, Wagner WR. |
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| Title: | Mechanical properties and in vivo behavior of a biodegradable synthetic polymer microfiber-extracellular matrix hydrogel biohybrid scaffold. |
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| Summary: | A biohybrid composite consisting of extracellular matrix (ECM) gel from porcine dermal tissue and biodegradable elastomeric fibers was generated and evaluated for soft tissue applications. ECM gel possesses attractive biocompatibility and bioactivity with weak mechanical properties and rapid degradation, while electrospun biodegradable poly(ester urethane)urea (PEUU) has good mechanical properties but limited cellular infiltration and tissue integration. A concurrent gel electrospray/polymer electrospinning method was employed to create ECM gel/PEUU fiber composites with attractive mechanical properties, including high flexibility and strength. Electron microscopy revealed a structure of interconnected fibrous layers embedded in ECM gel. Tensile mechanical properties could be tuned by altering the PEUU/ECM weight ratio. Scaffold tensile strengths for PEUU/ECM ratios of 67/33, 72/28 and 80/20 ranged from 80 to 187 kPa in the longitudinal axis (parallel to the collecting mandrel axis) and 41-91 kPa in the circumferential axis with 645-938% breaking strains. The 72/28 biohybrid composite and a control scaffold generated from electrospun PEUU alone were implanted into Lewis rats, replacing a full-thickness abdominal wall defect. At 4 wk, no infection or herniation was found at the implant site. Histological staining showed extensive cellular infiltration into the biohybrid scaffold with the newly developed tissue well integrated with the native periphery, while minimal cellular ingress into the electrospun PEUU scaffold was observed. Mechanical testing of explanted constructs showed evidence of substantial remodeling, with composite scaffolds adopting properties more comparable to the native abdominal wall. The described elastic biohybrid material imparts features of ECM gel bioactivity with PEUU strength and handling to provide a promising composite biomaterial for soft tissue repair and replacement. |
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Publication of the Month | February 2011 |
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| Authors: | Du Y, Roh DS, Funderburgh ML, Mann MM, Marra KG, Rubin JP, Li X, Funderburgh JL. |
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| Title: | Adipose-derived stem cells differentiate to keratocytes in vitro. |
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| Summary: | Adipose-derived stem cells (ADSC) are an abundant population of adult stem cells with the potential to differentiate into several specialized tissue types, including neural and neural crest-derived cells. This study sought to determine if ADSC express keratocyte-specific phenotypic markers when cultured under conditions inducing differentiation of corneal stromal stem cells to keratocytes. METHODS: Human subcutaneous adipose tissue was obtained by lipoaspiration. ADSC were isolated by collagenase digestion and differential centrifugation. Side population cells in ADSC were demonstrated using fluorescence-activated cell sorting after staining with Hoechst 33342. Differentiation to keratocyte phenotype was induced in fibrin gels or as pellet cultures with serum-free or reduced-serum media containing ascorbate. Keratocyte-specific gene expression was characterized using western blotting, quantitative RT-PCR, and immunostaining. RESULTS: ADSC contained a side population and exhibited differentiation to adipocytes and chondrocytes indicating adult stem-cell potential. Culture of ADSC in fibrin gels or as pellets in reduced-serum medium with ascorbate and insulin induced expression of keratocan, keratan sulfate, and aldehyde dehydrogenase 3 family, member A1 (ALDH3A1), products highly expressed by differentiated keratocytes. Expression of differentiation markers was quantitatively similar to corneal stromal stem cells and occurred in both serum-free and serum containing media. CONCLUSIONS: ADSC cultured under keratocyte-differentiation conditions express corneal-specific matrix components. Expression of these unique keratocyte products suggests that ADSC can adopt a keratocyte phenotype and therefore have potential for use in corneal cell therapy and tissue engineering. |
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Publication of the Month | January 2011 |
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| Authors: | Lopez F, Di Bartolo C, Piazza T, Passannanti A, Gerlach JC, Gridelli B, Triolo F. |
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| Title: | A quality risk management model approach for cell therapy manufacturing. |
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| Summary: | International regulatory authorities view risk management as an essential production need for the development of innovative, somatic cell-based therapies in regenerative medicine. The available risk management guidelines, however, provide little guidance on specific risk analysis approaches and procedures applicable in clinical cell therapy manufacturing. This raises a number of problems. Cell manufacturing is a poorly automated process, prone to operator-introduced variations, and affected by heterogeneity of the processed organs/tissues and lot-dependent variability of reagent (e.g., collagenase) efficiency. In this study, the principal challenges faced in a cell-based product manufacturing context (i.e., high dependence on human intervention and absence of reference standards for acceptable risk levels) are identified and addressed, and a risk management model approach applicable to manufacturing of cells for clinical use is described for the first time. The use of the heuristic and pseudo-quantitative failure mode and effect analysis/failure mode and critical effect analysis risk analysis technique associated with direct estimation of severity, occurrence, and detection is, in this specific context, as effective as, but more efficient than, the analytic hierarchy process. Moreover, a severity/occurrence matrix and Pareto analysis can be successfully adopted to identify priority failure modes on which to act to mitigate risks. The application of this approach to clinical cell therapy manufacturing in regenerative medicine is also discussed. |
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Publication of the Month | December 2010 |
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| Authors: | Ambrosio F, Wolf SL, Delitto A, Fitzgerald GK, Badylak SF, Boninger ML, Russell AJ. |
| Title: | The emerging relationship between regenerative medicine and physical therapeutics. |
| Summary: | Dramatic changes in the health care landscape over the next few decades undoubtedly will affect rehabilitation specialists' practice. In the multidisciplinary field of regenerative medicine, cell, tissue, or organ substitutes are used to enhance the healing potential of the body. Given that the restoration of normal functioning of injured or diseased tissues is expected to be the ultimate goal of these therapies, the future of regenerative medicine is, undeniably, tightly intertwined with that of rehabilitation. Rehabilitation specialists not only must be aware of cutting-edge medical advances as they relate to regenerative medicine but also must work closely with basic scientists to guide the development of clinically relevant protocols. The purposes of this article are to provide a current perspective on biological approaches to the management of musculoskeletal disorders and to highlight the needed integration of physical therapeutics with regenerative medicine. |
| Source: | Phys Ther. 2010 Dec;90(12):1807-14. |
Publication of the Month | November 2010 |
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| Authors: | Bear DM, Szczodry M, Kramer S, Coyle CH, Smolinski P, Chu CR. |
| Title: | Optical coherence tomography detection of subclinical traumatic cartilage injury. |
| Summary: | OBJECTIVES: Posttraumatic arthritis is a major cause of disability. Current clinical imaging modalities are unable to reliably evaluate articular cartilage damage before surface breakdown, when potentially reversible changes are occurring. Optical coherence tomography (OCT) is a nondestructive imaging technology that can detect degenerative changes in articular cartilage with an intact surface. This study tests the hypothesis that OCT detects acute articular cartilage injury after impact at energy levels resulting in chondrocyte death and microstructural changes, but insufficient to produce macroscopic surface damage. METHODS: Bovine osteochondral cores underwent OCT imaging and were divided into a control with no impact or were subjected to low (0.175 J) or moderate (0.35 J) energy impact. Cores were reimaged with OCT after impact and the OCT signal intensity quantified. A ratio of the superficial to deep layer intensities was calculated and compared before and after impact. Chondrocyte viability was determined 1 day after impact followed by histology and polarized microscopy. RESULTS: Macroscopic changes to the articular surface were not observed after low and moderate impact. The OCT signal intensity ratio demonstrated a 27% increase (P = 0.006) after low impact and a 38% increase (P = 0.001) after moderate impact. Cell death increased by 150% (P < 0.001) and 200% (P < 0.001) after low and moderate energy impacts, respectively. When compared with unimpacted controls, both Mankin histology and David-Vaudey polarized microscopy scores increased (P = 0.036 and P = 0.002, respectively) after moderate energy impact. CONCLUSIONS: This study shows that OCT detects acute cartilage changes after impact injury at levels insufficient to cause visible damage to the articular surface but sufficient to cause chondrocyte death and microscopic matrix damage. This finding supports the use of OCT to detect microstructural subsurface cartilage damage that is poorly visualized with conventional imaging. |
| Source: | Journal of Orthopaedic Trauma. 2010 Sep;24(9):577-82. |
Publication of the Month | October 2010 |
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| Authors: | He W, Nieponice A, Soletti L, Hong Y, Gharaibeh B, Crisan M, Usas A, Peault B, Huard J, Wagner WR, Vorp DA. |
| Title: | Pericyte-based human tissue engineered vascular grafts |
| Summary: | The success of small-diameter tissue engineered vascular grafts (TEVGs) greatly relies on an appropriate cell source and an efficient cellular delivery and carrier system. Pericytes have recently been shown to express mesenchymal stem cell features. Their relative availability and multipotentiality make them a promising candidate for TEVG applications. The objective of this study was to incorporate pericytes into a biodegradable scaffold rapidly, densely and efficiently, and to assess the efficacy of the pericyte-seeded scaffold in vivo. Bi-layered elastomeric poly(ester-urethane)urea scaffolds (length = 10 mm; inner diameter = 1.3 mm) were bulk seeded with 3 x 10(6) pericytes using a customized rotational vacuum seeding device in less than 2 min (seeding efficiency > 90%). The seeded scaffolds were cultured in spinner flasks for 2 days and then implanted into Lewis rats as aortic interposition grafts for 8 weeks. Results showed pericytes populated the porous layer of the scaffolds evenly and maintained their original phenotype after the dynamic culture. After implantation, pericyte-seeded TEVGs showed a significant higher patency rate than the unseeded control: 100% versus 38% (p < 0.05). Patent pericyte-seeded TEVGs revealed extensive tissue remodeling with collagen and elastin present. The remodeled tissue consisted of multiple layers of alpha-smooth muscle actin- and calponin-positive cells, and a von Willebrand factor-positive monolayer in the lumen. These results demonstrate the feasibility of a pericyte-based TEVG and suggest that the pericytes play a role in maintaining patency of the TEVG as an arterial conduit. |
| Source: | Biomaterials. 2010 Nov;31(32):8235-44. Epub 2010 Aug 3. |
Publication of the Month | September 2010 |
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| Authors: | Cherra SJ 3rd, Kulich SM, Uechi G, Balasubramani M, Mountzouris J, Day BW, Chu CT |
| Title: | Regulation of the autophagy protein LC3 by phosphorylation |
| Summary: | Macroautophagy is a major catabolic pathway that impacts cell survival, differentiation, tumorigenesis, and neurodegeneration. Although bulk degradation sustains carbon sources during starvation, autophagy contributes to shrinkage of differentiated neuronal processes. Identification of autophagy-related genes has spurred rapid advances in understanding the recruitment of microtubule-associated protein 1 light chain 3 (LC3) in autophagy induction, although braking mechanisms remain less understood. Using mass spectrometry, we identified a direct protein kinase A (PKA) phosphorylation site on LC3 that regulates its participation in autophagy. Both metabolic (rapamycin) and pathological (MPP(+)) inducers of autophagy caused dephosphorylation of endogenous LC3. The pseudophosphorylated LC3 mutant showed reduced recruitment to autophagosomes, whereas the nonphosphorylatable mutant exhibited enhanced puncta formation. Finally, autophagy-dependent neurite shortening induced by expression of a Parkinson disease-associated G2019S mutation in leucine-rich repeat kinase 2 was inhibited by dibutyryl-cyclic adenosine monophosphate, cytoplasmic expression of the PKA catalytic subunit, or the LC3 phosphorylation mimic. These data demonstrate a role for phosphorylation in regulating LC3 activity. |
| Source: | Journal of Cell Biology. 2010 Aug 23;190(4):533-9. Epub 2010 Aug 16. |
Publication of the Month | August 2010 |
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| Authors: | Chandler JM, Lagasse E |
| Title: | Cancerous stem cells: deviant stem cells with cancer-causing misbehavior |
| Summary: | Stem cells maintain homeostasis in adult tissues via self-renewal and generation of terminally differentiated cells. Alterations in this intricate balance can result in disease. It has become increasingly evident that cancer can be initiated at the level of stem cells. Therefore, understanding what causes stem cells to become cancerous may lead to new therapeutic approaches. Multiple signaling pathways ultimately affect stem cell survival and proliferation, thus maintaining homeostasis in the gut. Changes in these pathways could perturb normal stem cell behavior, leading to cancerous stem cells. In addition, cancerous stem cells show resistance to current therapies and may lead to a dangerous selection process resulting in recurrence and metastasis. Genomic instability, the driving force of mutation and resistance, may give cancerous stem cells an adaptive advantage, especially when subjected to cancer therapies. Targeting the unique characteristics of cancerous stem cells to promote either terminal differentiation or destruction would effectively eradicate cancer and improve patient care and survival. |
| Source: | Stem Cell Res Ther. 2010 May 20;1(2):13. |
Publication of the Month | July 2010 |
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| Authors: | Richardson WM, Sodhi CP, Russo A, Siggers RH, Afrazi A, Gribar SC, Neal MD, Dai S, Prindle T Jr, Branca M, Ma C, Ozolek J, Hackam DJ. |
| Title: | Nucleotide-Binding Oligomerization Domain-2 Inhibits Toll-Like Receptor-4 Signaling in the Intestinal Epithelium. |
| Summary: | BACKGROUND & AIMS: Factors that regulate enterocyte apoptosis in necrotizing enterocolitis (NEC) remain incompletely understood, although Toll-like receptor-4 (TLR4) signaling in enterocytes plays a major role. Nucleotide-binding-oligomerization domain-2 (NOD2) is an immune receptor that regulates other branches of the immune system, although its effects on TLR4 in enterocytes and its role in NEC remain unknown. We now hypothesize that activation of NOD2 in the newborn intestine inhibits TLR4, and that failure of NOD2 signaling leads to NEC through increased TLR4-mediated enterocyte apoptosis. METHODS: The effects of NOD2 on enterocyte TLR4 signaling and intestinal injury and repair were assessed in enterocytes lacking TLR4 or NOD2, in mice with intestinal-specific wild-type or dominant-negative TLR4 or NOD2, and in mice with NEC. A protein array was performed on NOD2-activated enterocytes to identify novel effector molecules involved. RESULTS: TLR4 activation caused apoptosis in newborn but not adult small intestine or colon, and its intestinal expression was influenced by NOD2. NOD2 activation inhibited TLR4 in enterocytes, but not macrophages, and reversed the effects of TLR4 on intestinal mucosal injury and repair. Protection from TLR4-induced enterocyte apoptosis by NOD2 required a novel pathway linking NOD2 with second mitochondria-derived activator of caspase/direct inhibitor of apoptosis-binding protein with low PI, both in vitro and in vivo. Strikingly, activation of NOD2 reduced second mitochondria-derived activator of caspase/direct inhibitor of apoptosis-binding protein with low PI expression, attenuated the extent of enterocyte apoptosis, and reduced the severity of NEC. CONCLUSIONS: These findings reveal a novel inhibitory interaction between TLR4 and NOD2 signaling in enterocytes leading to the regulation of enterocyte apoptosis and suggest a therapeutic role for NOD2 in the protection of intestinal diseases such as NEC. Copyright © 2010 AGA Institute. Published by Elsevier Inc. All rights reserved. |
| Source: | Gastroenterology. 2010 May 24 [Epub ahead of print] |
Publication of the Month | June 2010 |
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| Authors: | Antaki JF, Ricci MR, Verkaik JE, Snyder ST, Maul TM, Kim J, Paden DB, Kameneva MV, Paden BE, Wearden PD, Borovetz HS |
| Title: | PediaFlow Maglev Ventricular Assist Device: A Prescriptive Design Approach |
| Summary: | This report describes a multi-disciplinary program to develop a pediatric blood pump, motivated by the critical need to treat infants and young children with congenital and acquired heart diseases. The unique challenges of this patient population require a device with exceptional biocompatibility, miniaturized for implantation up to 6 months. This program implemented a collaborative, prescriptive design process, whereby mathematical models of the governing physics were coupled with numerical optimization to achieve a favorable compromise among several competing design objectives. Computational simulations of fluid dynamics, electromagnetics, and rotordynamics were performed in two stages: first using reduced-order formulations to permit rapid optimization of the key design parameters; followed by rigorous CFD and FEA simulations for calibration, validation, and detailed optimization. Over 20 design configurations were initially considered, leading to three pump topologies, judged on the basis of a multi-component analysis including criteria for anatomic fit, performance, biocompatibility, reliability, and manufacturability. This led to fabrication of a mixed-flow magnetically levitated pump, the PF3, having a displaced volume of 16.6 cc, approximating the size of a AA battery and producing a flow capacity of 0.3-1.5 L/min. Initial in vivo evaluation demonstrated excellent hemocompatibility after 72 days of implantation in an ovine. In summary, combination of prescriptive and heuristic design principles have proven effective in developing a miniature magnetically levitated blood pump with excellent performance and biocompatibility, suitable for integration into chronic circulatory support system for infants and young children; aiming for a clinical trial within 3 years. |
| Source: | Cardiovascular Engineering. 2010 Mar 1;1(1):104-121 |
Publication of the Month | May 2010 |
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| Authors: | Gangadharan B. Sajithlala, Kristi Rothermunda, Fang Zhangb, David J. Dabbsc, Jean J. Latimer, Stephen G. Grant, Edward V. Prochownika |
| Title: | Permanently Blocked Stem Cells Derived from Breast Cancer Cell Lines |
| Summary: | Cancer stem cells (CSCs) are thought to be resistant to standard chemotherapeutic drugs and the inimical conditions of the tumor microenvironment. Obtaining CSCs in sufficient quantities and maintaining their undifferentiated state have been major hurdles to their further characterization and to the identification of new pharmaceuticals that preferentially target these cells. We describe here the tagging of CSC-like populations from four human breast cancer cell lines with green fluorescent protein (GFP) under the control of the Oct3/4 stem cell-specific promoter. As expected, GFP was expressed by the CSC-enriched populations. An unanticipated result, however, was that these cells remained blocked in a CSC-like state and tended to be resistant to chemotherapeutic drugs as well as acidotic and hypoxic conditions. These CSC-like cells possessed several other in vitro attributes of CSCs and were able to reproducibly generate tumors in immunocompromised mice from as few as 100 cells. Moreover, the tumors derived from these cells were comprised almost exclusively of pure CSCs. The ability of the Oct3/4 promoter to block CSC differentiation underscores its potential general utility for obtaining highly purified CSC populations, although the mechanism by which it does so remains undefined and subject to further study. Nonetheless, such stable cell lines should be extremely valuable tools for studying basic questions pertaining to CSC biology and for the initial identification of novel CSC-specific chemotherapeutic agents, which can then be verified in primary CSCs. |
| Source: | Stem Cells, Volume 9999 Issue 999A, Published Online: 7 Apr 2010 |
Publication of the Month | April 2010 |
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| Authors: | German V. Kolmakov, Ravindra Revanur, Ravisubhash Tangirala, Todd Emrick, Thomas P. Russell, Alfred J. Crosby, Anna C. Balazs |
| Title: | Using Nanoparticle-Filled Microcapsules for Site-Specific Healing of Damaged Substrates: Creating a “Repair-and-Go” System |
| Summary: | Using a hybrid computational approach, we simulate the behavior of nanoparticle-filled microcapsules that are propelled by an imposed shear to move over a substrate, which encompasses a microscopic crack. When the microcapsules become localized in the crack, the nanoparticles can penetrate the capsule’s shell to bind to and fill the damaged region. Initially focusing on a simple shear flow, we isolate conditions where the microcapsules become arrested in the cracks and those where the capsules enter the cracks for a finite time but are driven to leave this region by the imposed flow. We also characterize the particle deposition process for these two scenarios, showing that the deposition is greater for the arrested capsules. We then determine the effect of utilizing a pulsatile shear flow and show that this flow field can lead to an effective “repair-and-go” system where the microcarriers not only deliver a high volume fraction of particles into the crack but also leave the fissure and, thus, can potentially repair additional damage within the system. |
| Source: | ACS Nano, 2010, 4 (2), pp 1115–1123. |
Publication of the Month | March 2010 |
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| Authors: | Nathaniel T. Remlinger, Caitlin A. Czajka, Mark E. Juhas, David A. Vorp, Donna B. Stolz, Stephen F. Badylak, Sebastien Gilbert, Thomas W. Gilbert |
| Title: | Hydrated xenogeneic decellularized tracheal matrix as a scaffold for tracheal reconstruction |
| Summary: | Tracheal injury is a rare but complex problem. Primary tracheal reconstructions are commonly performed, but complications such as tension and inadequate vascular supply limit the length of surgical resection. The objective of the present study was to determine whether a hydrated, decellularized porcine tracheal extracellular matrix showed the potential to serve as a functional tracheal replacement graft. Porcine tracheas were decellularized and evaluated to characterize their biochemical composition and biomechanical behavior. Hydrated decellularized tracheal matrix (HDTM) grafts (>5 cm) were implanted heterotopically beneath the strap muscle and wrapped in the omentum in a canine model for 2 and 8 weeks followed by histologic and mechanical analysis. HDTM patches (2 x 3 cm) were also used in a patch tracheoplasty model. The repair site was evaluated bronchoscopically and radiographically, and the grafts were analyzed by histologic methods to evaluate epithelialization and persistence of the cartilage rings. The present study showed that HDTM maintains mechanical characteristics necessary for function under physiologic loading conditions even after 8 weeks of heterotopic implantation. After orthotopic implantation, the grafts were shown to support development of a columnar, pseudostratified, ciliated epithelium, but the cartilage structures showed histologic evidence of degradation and limited new cartilage formation. The results of the study showed tracheal ECM scaffolds support the formation of site-specific epithelium and provide sufficient mechanical integrity withstand physiologic pressures in the short-term. However, for long-term success, it appears that pre-implantation to allow vascularization or preseeding of the graft with chondrocytes will be necessary. Copyright 2010 Elsevier Ltd. All rights reserved. |
| Source: | Biomaterials. 2010 May;31(13):3520-6. Epub 2010 Feb 7. |
Publication of the Month | February 2010 |
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| Authors: | Polk AA, Maul TM, McKeel DT, Snyder TA, Lehocky CA, Pitt B, Stolz DB, Federspiel WJ, Wagner WR |
| Title: | A biohybrid artificial lung prototype with active mixing of endothelialized microporous hollow fibers |
| Summary: | Acute respiratory distress syndrome (ARDS) affects nearly 150,000 patients per year in the US, and is associated with high mortality ( approximately 40%) and suboptimal options for patient care. Mechanical ventilation and extracorporeal membrane oxygenation are limited to short-term use due to ventilator-induced lung injury and poor biocompatibility, respectively. In this report, we describe the development of a biohybrid lung prototype, employing a rotating endothelialized microporous hollow fiber (MHF) bundle to improve blood biocompatibility while MHF mixing could contribute to gas transfer efficiency. MHFs were surface modified with radio frequency glow discharge (RFGD) and protein adsorption to promote endothelial cell (EC) attachment and growth. The MHF bundles were placed in the biohybrid lung prototype and rotated up to 1500 revolutions per minute (RPM) using speed ramping protocols to condition ECs to remain adherent on the fibers. Oxygen transfer, thrombotic deposition, and EC p-selectin expression were evaluated as indicators of biohybrid lung functionality and biocompatibility. A fixed aliquot of blood in contact with MHF bundles rotated at either 250 or 750 RPM reached saturating pO(2) levels more quickly with increased RPM, supporting the concept that fiber rotation would positively contribute to oxygen transfer. The presence of ECs had no effect on the rate of oxygen transfer at lower fiber RPM, but did provide some resistance with increased RPM when the overall rate of mass transfer was higher due to active mixing. RFGD followed by fibronectin adsorption on MHFs facilitated near confluent EC coverage with minimal p-selectin expression under both normoxic and hyperoxic conditions. Indeed, even subconfluent EC coverage on MHFs significantly reduced thrombotic deposition adding further support that endothelialization enhances, blood biocompatibility. Overall these findings demonstrate a proof-of-concept that a rotating endothelialized MHF bundle enhances gas transfer and biocompatibility, potentially producing safer, more efficient artificial lungs. |
| Source: | Biotechnology and Bioengineering. 2010 Jan 20. |
Publication of the Month | January 2010 |
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| Authors: | Rajaie Namas, Ali Ghuma, Andres Torres, Patricio Polanco, Hernando Gomez, Derek Barclay, Lisa Gordon, Sven Zenker, Hyung Kook Kim, Linda Hermus, Ruben Zamora, Matthew R. Rosengart, Gilles Clermont, Andrew Peitzman, Timothy R. Billiar, Juan Ochoa, Michael R. Pinsky, Juan Carlos Puyana, Yoram Vodovotz |
| Title: | An Adequately Robust Early TNF-a Response Is a Hallmark of Survival Following Trauma/Hemorrhage |
| Summary: | Trauma/hemorrhagic shock (T/HS) results in cytokine-mediated acute inflammation that is generally considered detrimental. Paradoxically, plasma levels of the early inflammatory cytokine TNF-a (but not IL-6, IL-10, or NO2-/NO3-) were significantly elevated within 6 h post-admission in 19 human trauma survivors vs. 4 non-survivors. Moreover, plasma TNF-a was inversely correlated with Marshall Score, an index of organ dysfunction, both in the 23 patients taken together and in the survivor cohort. Accordingly, we hypothesized that if an early, robust pro-inflammatory response were to be a marker of an appropriate response to injury, then individuals exhibiting such a response would be predisposed to survive. We tested this hypothesis in swine subjected to various experimental paradigms of T/HS. Twenty-three anesthetized pigs were subjected to T/HS (12 HS-only and 11 HS + Thoracotomy; mean arterial pressure of 30 mmHg for 45–90 min) along with surgery-only controls. Plasma obtained at pre-surgery, baseline post-surgery, beginning of HS, and every 15 min thereafter until 75 min (in the HS only group) or 90 min (in the HS + Thoracotomy group) was assayed for TNF-a, IL-6, IL-10, and NO2-/NO3-. Mean post-surgery6HS TNF-a levels were significantly higher in the survivors vs. nonsurvivors, while non-survivors exhibited no measurable change in TNF-a levels over the same interval. Contrary to the current dogma, survival in the setting of severe, acute T/HS appears to be associated with an immediate increase in serum TNF-a. It is currently unclear if this response was the cause of this protection, a marker of survival, or both. |
| Source: | PLoS ONE 2009. 4:e8406. |
Publication of the Month | December 2009 |
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| Authors: | Wang F, Li Z, Khan M, Tamama K, Kuppusamy P, Wagner WR, Sen CK, Guan J. |
| Title: | Injectable, Rapid Gelling and Highly Flexible Hydrogel Composites as Growth Factor and Cell Carriers. |
| Summary: | A family of injectable, rapid gelling and highly flexible hydrogel composites capable of releasing insulin-like growth factor (IGF-1) and delivering mesenchymal stromal cell (MSC) were developed. Hydrogel composites were fabricated from Type I collagen, chondroitin sulfate (CS) and a thermosensitive and degradable hydrogel copolymer based on N-isopropylacrylamide, acrylic acid, N-acryloxysuccinimide and a macromer poly(trimethylene carbonate)-hydroxyethyl methacrylate. The hydrogel copolymer was gellable at body temperature before degradation and soluble at body temperature after degradation. Hydrogel composites exhibited LCSTs around room temperature. They could easily be injected through a 26-gauge needle at 4(o)C, and were capable of gelling within 6 seconds at 37(o)C to form highly flexible gels with moduli matching those of the rat and human myocardium. The hydrogel composites showed good oxygen permeability, the oxygen pressure within the hydrogel composites was similar to that in the air. The effects of collagen and CS contents on LCST, gelation time, injectability, mechanical properties and degradation properties were investigated. IGF-1 was loaded into the hydrogel composites for enhanced cell survival/growth. The released IGF-1 remained bioactive during a 2-week release period. Small fraction of CS in the hydrogel composites significantly decreased IGF-1 release rate. The release kinetics appeared to be controlled mainly by hydrogel composite water content, degradation and interaction with IGF-1. Human MSC adhesion on the hydrogel composites was comparable to that on the tissue culture plate. MSCs were encapsulated in the hydrogel composites and were found to grow inside during a 7-day culture period. IGF-1 loading significantly accelerated MSC growth. RT-PCR analysis demonstrated that MSCs maintained their multipotent differentiation potential in hydrogel composites with and without IGF-1. These injectable and rapid gelling hydrogel composites demonstrated attractive properties for serving as growth factor and cell carriers for cardiovascular tissue engineering applications. |
| Source: | Acta Biomaterialia. [Epub ahead of print] |
Publication of the Month | November 2009 |
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| Authors: | Aoun E, Muddana V, Papachristou GI, Whitcomb DC. |
| Title: | SPINK1 N34S Is Strongly Associated With Recurrent Acute Pancreatitis but Is Not a Risk Factor for the First or Sentinel Acute Pancreatitis Event. |
| Summary: | Serine protease inhibitor Kazal type 1 (SPINK1) gene mutations have been associated with chronic pancreatitis of different etiologies; however, little is known about their role in the pathogenesis of acute pancreatitis (AP). Our aim was to study the prevalence of the SPINK1 N34S polymorphism in patients with sentinel and recurrent AP (RAP).METHODS:Patients with AP were enrolled, and genetic tests were carried out to detect the SPINK1 N34S polymorphism. Subjects without pancreatitis from the North American Pancreatitis Study were used as controls.RESULTS:A total of 188 patients (116 with sentinel AP and 72 with recurrent attacks) and 670 controls were evaluated. The SPINK1 N34S polymorphism was detected in 1 of 232 alleles in patients with sentinel AP, 11 of 144 alleles in patients with RAP, and in 19 of 1,340 control alleles. There was no difference in the prevalence of the polymorphism between sentinel attack patients and controls. Patients with the polymorphism were more prone to develop recurrent attacks (odds ratio (OR)=19.1, 95% confidence interval (CI): 2.4-149.6). CONCLUSIONS: The SPINK1 N34S polymorphism was not associated with the sentinel AP attack, but it substantially increases the risk of recurrent attacks. Additional studies are needed to further elucidate the mechanism of SPINK1-associated protection in AP. |
| Source: | American Journal of Gastroenterology. 2009 Nov 3. |
Publication of the Month | October 2009 |
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| Authors: | BP Witteman, TJ Foxwell, S Monsheimer, A Gelrud, GM Eid, A Nieponice, RW O'Rourke, T Hoppo, ND Bouvy, SF Badylak, BA Jobe. |
| Title: | Transoral Endoscopic Inner Layer Esophagectomy: Management of High-Grade Dysplasia and Superficial Cancer with Organ Preservation. |
| Summary: | Limitations of endoscopic therapies for Barrett's esophagus and superficial cancer include a compromised histological assessment, the need for surveillance, subsequent procedures, and stricture formation. Circumferential en bloc resection of the mucosa-submucosa complex followed by deployment of a biologic scaffold onto the remaining muscularis propria may address these concerns. The objective of this study was to determine technical feasibility of transoral resection of the esophageal lining. MATERIALS AND METHODS: Transoral endoscopic inner layer esophagectomy was performed in ten swine. Endpoints included procedure duration, hemorrhage, number of perforations, and adequacy of resection length and depth. RESULTS: Procedures were successfully completed in all animals without perioperative mortality. Procedure times averaged 179 min (range 125-320). No perforations were found, and a mean of 1.7 (0-4) interventions for hemorrhage was required. Complete longitudinal resection was achieved in nine of ten animals. Resection depth included all mucosal layers in 100% of tissue sections, the submucosal layers, SM1 in 100%, and SM2 in 96%. A portion of SM3 was adherent to the muscularis propria in 70%. CONCLUSION: Transoral endoscopic resection of the inner esophageal layers was feasible and reproducible. This technique may facilitate a single-step definitive treatment and staging tool for early neoplastic lesions, obviating the need for esophagectomy. |
| Source: | Journal of Gastrointestinal Surgery. 2009 Oct 14. |
Publication of the Month | September 2009 |
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| Authors: | Anna C. Balazs and Irving R. Epstein |
| Title: | Emergent or Just Complex? |
| Summary: | Efforts toward creating artificial cells are shedding light on how life may have emerged. The concept of emergence in the physical and biological sciences is an elusive one. The term refers to phenomena in which the complexity of structures or behaviors in systems with many interacting components exceeds that predicted from knowledge of the individual components and the forces between them. |
| Source: | SCIENCE; 25 SEPTEMBER 200; VOL 325; pp 1632-1634 |
Publication of the Month | August 2009 |
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| Authors: | Wognum S, Lagoa CE, Nagatomi J, Sacks MS, Vodovotz Y. |
| Title: | An Exploratory Pathways Analysis of Temporal Changes Induced by Spinal Cord Injury in the Rat Bladder Wall: Insights on Remodeling and Inflammation. |
| Summary: | Background: Spinal cord injuries (SCI) can lead to severe bladder pathologies associated with inflammation, fibrosis, and increased susceptibility to urinary tract infections. We sought to characterize the complex pathways of remodeling, Methodology/Principal Findings: Experimental data were obtained from the study of Nagatomi et al. (Biochem Biophys Res Commun 334: 1159). In this study, bladders from rats subjected to surgical SCI were obtained at 3, 7 or 25 days post-surgery, and Affymetrix GeneChipH Rat Genome U34A arrays were used for cRNA hybridizations. In the present study, Ingenuity Pathways Analysis (IngenuityH Systems, www.ingenuity.com) of differentially expressed genes was performed. Analysis of focus genes in networks, functional analysis, and canonical pathway analysis reinforced our previous findings related to the |
| Source: | PLoS ONE 4(6): e5852. doi:10.1371/journal.pone.0005852. |
Publication of the Month | July 2009 |
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| Authors: | |
| Title: | Cell derived hierarchical assembly of a novel phosphophoryn-based biomaterial. |
| Summary: | Phosphophoryn (PP) is an acidic phosphoprotein belonging to the small integrin-bindingligand N-linked glycoprotein (SIBLING) protein family. PP is highly phosphorylated with approximately 200 phosphates per molecule and has a high affinity for calcium. The aim of this manuscript is to demonstrate that PP has the ability to self-assemble when it is overexpressed in a mammalian cell in the presence of calcium. Our data show that when PP is overexpressed using an adenovirus, the self-assembly occurs in the endoplasmic reticulum (ER) which contains high calcium concentration. We hypothesize that the physicochemical properties of the highly phosphorylated state and acidic nature of PP are playing an important role in its assembly in the ER. It appears that when a critical concentration of PP is reached, the assembly is then favored and facilitated. This self-assembly could be due to several factors. (1) The ER provides an ideal environment for this phenomenon to occur, since the ER environment usually promotes aggregation [Stevens and Argon: Semin Cell Dev Biol 1999;10:443-454]. (2) In addition to PP's physicochemical properties, the unfolded protein response could also be playing a role in this self-assembly [Schroder and Kaufman: Mutat Res 2005;569:29-63]. Unfolded protein response could be activated by a broad spectrum of insults that result in protein misfolding and ultimately blocking of the protein synthesis progression to the Golgi apparatus resulting in an accumulation of the protein in the ER. In summary, our data show that PP has the ability to self-assemble in a hierarchical manner |
| Source: | Cells Tissues Organs. 2009;189(1-4):252-5. |
Publication of the Month | June 2009 |
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| Authors: | Santiago LY, Clavijo-Alvarez J, Brayfield C, Rubin JP, Marra KG |
| Title: | Delivery of adipose-derived precursor cells for peripheral nerve repair |
| Summary: | To test the hypothesis that the transplantation of adipose precursor cells (APCs) improves nerve regeneration and functional recovery, human APCs were transplanted into the lumen of a nerve guide in a 6-mm unilateral sciatic nerve defect in athymic rats. The three control groups for the study were biodegradable, polycaprolactone-based nerve conduit without APCs, autograft, and empty defect. Behavioral tests were performed every 3 weeks, and the sciatic functional index (SFI) was calculated based on measurements from the hindlimb prints. After 12 weeks, the nerve as well as right and left gastrocnemius muscles were removed and preserved for histological evaluation. Full regeneration of the sciatic nerve occurred on the rats that received the autograft, the guide, and the guide with APCs; no regeneration was observed on any of the rats in which the defect was left untreated (empty defect). APCs survived transplantation for up to 12 weeks in the injured peripheral nerve. No significant colocalization was observed between the immunostaining for glial fibrillary protein and anti-human lamin A/C, implying that the APCs did not differentiate into Schwann cells at the site of injury. In comparison with the rats with untreated defects, a decrease in muscle atrophy was observed on those rats that received the autograft and the guide with cells as indicated by the gastrocnemius muscle weight ratio and the muscle fiber ratio. Significant differences in SFI were observed 3 weeks postinjury between the rats in which the guide was left empty and those that received the guide with APCs; however, these differences were not observed at 12 weeks. The transplantation of APCs promoted the formation of a more robust nerve as evidenced by the results from the cross-sectional area of regenerated nerve, and the transplantation of APCs produced a decrease in muscle atrophy. |
| Source: | Cell Transplant. 2009;18(2):145-58 |
Publication of the Month | May 2009 |
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| Authors: | Parekh A, Mantle B, Banks J, Swarts JD, Badylak SF, Dohar JE, Hebda PA. |
| Title: | Repair of the tympanic membrane with urinary bladder matrix. |
| Summary: | OBJECTIVES: To test urinary bladder matrix (UBM) as a potential treatment for tympanic membrane (TM) healing and regeneration. STUDY DESIGN: This prospective pilot study was designed to provide both qualitative and semiquantitative assessment of temporal and spatial healing events in the chinchilla model of chronic TM perforations with and without UBM patching. METHODS: Bilateral myringotomies were performed and repeated as necessary to create subtotal perforations over an 8-week period. Myringoplasty was then performed, with left TMs serving as controls and right TMs receiving UBM patches. TMs were excised at 4 weeks, 8 weeks, and 12 weeks. Fixed tissue samples were characterized for gross morphology, then processed for microscopic evaluation. RESULTS: Chronic perforations were maintained with one or more repeated myringotomies. Although both control and patched TMs were thicker than native tissue, patched TMs were transparent and uniform in thickness without any inclusions. UBM patches were readily degraded and replaced by newly deposited and organized host tissue that recapitulated the native TM layers. CONCLUSIONS: UBM scaffolds were an effective biological scaffold for TM closure and tissue remodeling, leading to thicker than normal anatomy but otherwise normal morphology. Future studies are required to determine functional and temporal outcomes as well as alternative patch orientations. The results show particular promise as a superior alternative means of reconstructing not only chronic TM perforations but also dimeric TMs associated with retraction pockets and atelectasis. |
| Source: | Laryngoscope. 2009 Apr 8;119(6):1206-1213. |
Publication of the Month | April 2009 |
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| Authors: | Rothstein SN, Federspiel WJ, Little SR. |
| Title: | A unified mathematical model for the prediction of controlled release from surface and bulk eroding polymer matrices. |
| Summary: | A unified model has been developed to predict release not only from bulk eroding and surface eroding systems but also from matrices that transition from surface eroding to bulk eroding behavior during the course of degradation. This broad applicability is afforded by fundamental diffusion/reaction equations that can describe a wide variety of scenarios including hydration of and mass loss from a hydrolysable polymer matrix. Together, these equations naturally account for spatial distributions of polymer degradation rate. In this model paradigm, the theoretical minimal size required for a matrix to exhibit degradation under surface eroding conditions was calculated for various polymer types and then verified by empirical data from the literature. An additional set of equations accounts for dissolution- and/or degradation-based release, which are dependent upon hydration of the matrix and erosion of the polymer. To test the model's accuracy, predictions for agent egress were compared to experimental data from polyanhydride and polyorthoester implants that were postulated to undergo either dissolution-limited or degradation-controlled release. Because these predictions are calculated solely from readily attainable design parameters, it seems likely that this model could be used to guide the design controlled release formulations that produce a broad array of custom release profiles. |
| Source: | Biomaterials. 2009 Mar;30(8):1657-64. Epub 2008 Dec 19. |
Publication of the Month | March 2009 |
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| Authors: | Scott MJ, Liu S, Shapiro RA, Vodovotz Y, Billiar TR. |
| Title: | Endotoxin uptake in mouse liver is blocked by endotoxin pretreatment through a suppressor of cytokine signaling-1-dependent mechanism. |
| Summary: | The liver is the main organ that clears lipopolysaccharide (LPS) and hepatocytes are a major cell-type involved in LPS uptake. LPS tolerance, or desensitization, is important in negative regulation of responses to LPS, but little is known about its mechanisms in hepatocytes. Primary isolated C57BL/6 hepatocytes, and liver in vivo, internalized fluorescent LPS, and this was dependent on Toll-like receptor 4 (TLR4) at the cell surface but not on TLR4-TIR signaling through MyD88. LPS clearance from plasma was also TLR4-dependent. Pretreatment of C57BL/6 hepatocytes with LPS prevented uptake of LPS 24 hours later and this LPS-mediated suppression was dependent on TLR4 signaling through MyD88. Many regulators of TLR4 signaling have been identified and implicated in LPS desensitization, including suppressor of cytokine signaling 1 (SOCS1). SOCS1 mRNA and protein expression increased after LPS stimulation in hepatocytes and in whole liver. LPS uptake in hepatocytes and liver was significantly reduced following infection with adenoviral vectors overexpressing SOCS1. Similarly, inhibition of SOCS1 using small interfering (si)RNA-mediated knockdown prevented LPS desensitization in hepatocytes. SOCS1 is known to interact with Toll/IL-1 receptor associated protein (TIRAP) and cause TIRAP ubiquitination and degradation, which regulates TLR signaling. We have also shown previously that TIRAP regulates LPS uptake in hepatocytes. SOCS1 coimmunoprecipitated with TIRAP in wild type hepatocyte cell lysates up to 8 hours after LPS stimulation, but not at later times. In the same samples, ubiquitinated TIRAP was detected after 4 hours and up to 8 hours after LPS stimulation, but not at later times. Conclusion: These data indicate hepatocytes are desensitized by LPS in a TLR4 signaling-dependent manner. LPS-induced SOCS1 upregulation increases degradation of TIRAP and prevents subsequent LPS uptake. The exploitation of these mechanisms of LPS desensitization in the liver may be important in future sepsis therapies. |
| Source: | Hepatology. 2009 Feb. 9 [Epub ahead of print]. |
Publication of the Month | February 2009 |
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| Authors: | El-Kurdi MS, Hong Y, Stankus JJ, Soletti L, Wagner WR, Vorp DA. |
| Title: | Transient elastic support for vein grafts using a constricting microfibrillar polymer wrap. |
| Summary: | Arterial vein grafts (AVGs) often fail due to intimal hyperplasia, thrombosis, or accelerated atherosclerosis. Various approaches have been proposed to address AVG failure, including delivery of temporary mechanical support, many of which could be facilitated by perivascular placement of a biodegradable polymer wrap. The purpose of this work was to demonstrate that a polymer wrap can be applied to vein segments without compromising viability/function, and to demonstrate one potential application, i.e., gradually imposing the mid-wall circumferential wall stress (CWS) in wrapped veins exposed to arterial levels of pressure. Poly(ester urethane)urea, collagen, and elastin were combined in solution, and then electrospun onto freshly-excised porcine internal jugular vein segments. Tissue viability was assessed via Live/Dead staining for necrosis, and vasomotor challenge with epinephrine and sodium nitroprusside for functionality. Wrapped vein segments were also perfused for 24h within an ex vivo vascular perfusion system under arterial conditions (pressure = 120/80 mmHg; flow = 100 mL/min), and CWS was calculated every hour. Our results showed that the electrospinning process had no deleterious effects on tissue viability, and that the mid-wall CWS vs. time profile could be dictated through the composition and degradation of the electrospun wrap. This may have important clinical applications by enabling the engineering of an improved AVG. |
| Source: | Biomaterials. 2008 Aug;29(22):3213-20. Epub 2008 May 2. |
Publication of the Month | January 2009 |
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| Authors: | Wescoe KE, Schugar RC, Chu CR, Deasy BM. |
| Title: | The Role of the Biochemical and Biophysical Environment in Chondrogenic Stem Cell Differentiation Assays and Cartilage Tissue Engineering. |
| Summary: | The field of regenerative medicine offers hope for the development of a cell-based therapy for the repair of articular cartilage (AC). Yet, the greatest challenge in the use of stem cells for tissue repair, is understanding how the cells respond to stimuli and using that knowledge to direct cell fate. Novel methods that utilize stem cells in cartilage regeneration will require specific spatio-temporal controls of the biochemical and biophysical signaling environments. Current chondrogenic differentiation research focuses on the roles of biochemical stimuli like growth factors, hormones, and small molecules, and the role of the physical environment and mechanical stimuli, such as compression and shear stress, which likely act through mechanical receptors. Numerous signals are associated with chondrogenic-like activity of cells in different systems, however many variables for a controlled method still need to be optimized; e.g., spatial and temporal application of the stimuli, and time of transplantation of an engineered construct. Understanding the necessary microenvironmental signals for cell differentiation will advance cell therapy for cartilage repair. |
| Source: | Cell Biochem Biophys. 2008;52(2):85-102. |