Authors: Pratyush Dayal, Olga Kuksenok, and Anna C. Balazs.
Title: Directing the Behavior of Active, Self-Oscillating Gels with Light
Summary: In the biological realm, light can act as a powerful stimulus, promoting both positive and negative phototaxis. Using computational modeling, we attempt to design systems that display analogous biomimetic behavior by exhibiting directed, autonomous motion in response to light. We specifically focus on polymer gels that undergo the oscillating Belousovâ€“Zhabotinsky (BZ) reaction and thus manifest periodic chemomechanical pulsations, which can be modulated with light. Reviewing our recent computational studies, we describe how long, rectangular samples of BZ gels, or â€œwormsâ€, can perform self-sustained movement and via a distinct form of negative phototaxis migrate along complex paths under nonuniform illumination. When the ends of multiple rectangular BZ gels are anchored to a surface, the dynamic behavior of the cilia-like layer can be tuned by light to resemble the motion of a keyboard. With BZ gel pieces that move freely on a surface, we show that these gels exhibit autochemotaxis and, thereby, can self-organize in response to self-generated chemical signals. These examples illustrate that BZ gels constitute optimal materials for creating millimeter-sized soft robots whose self-sustained movement can be regulated through the use of light.
Authors: Dutta-Moscato J, Solovyev A, Mi Q, Nishikawa T, Soto-Gutierrez A, Fox IJ, Vodovotz Y.
Title: A multiscale agent-based in silico model of liver fibrosis progression.
Summary: Chronic hepatic inflammation involves a complex interplay of inflammatory and mechanical influences, ultimately manifesting in a characteristic histopathology of liver fibrosis. We created an agent-based model (ABM) of liver tissue in order to computationally examine the consequence of liver inflammation. Our liver fibrosis ABM (LFABM) is comprised of literature-derived rules describing molecular and histopathological aspects of inflammation and fibrosis in a section of chemically injured liver. Hepatocytes are modeled as agents within hexagonal lobules. Injury triggers an inflammatory reaction, which leads to activation of local Kupffer cells and recruitment of monocytes from circulation. Portal fibroblasts and hepatic stellate cells are activated locally by the products of inflammation. The various agents in the simulation are regulated by above-threshold concentrations of pro- and anti-inflammatory cytokines and damage-associated molecular pattern molecules. The simulation progresses from chronic inflammation to collagen deposition, exhibiting periportal fibrosis followed by bridging fibrosis, and culminating in disruption of the regular lobular structure. The ABM exhibited key histopathological features observed in liver sections from rats treated with carbon tetrachloride (CCl4). An in silico â€œtension testâ€ for the hepatic lobules predicted an overall increase in tissue stiffness, in line with clinical elastography literature and published studies in CCl4-treated rats. Therapy simulations suggested differential anti-fibrotic effects of neutralizing tumor necrosis factor alpha vs. enhancing M2 Kupffer cells. We conclude that a computational model of liver inflammation on a structural skeleton of physical forces can recapitulate key histopathological and macroscopic properties of CCl4-injured liver. This multiscale approach linking molecular and chemomechanical stimuli enables a model that could be used to gain translationally relevant insights into liver fibrosis.
Authors: Lui VW, Peyser ND, Ng PK, Hritz J, Zeng Y, Lu Y, Li H, Wang L, Gilbert BR, General IJ, Bahar I, Ju Z, Wang Z, Pendleton KP, Xiao X, Du Y, Vries JK, Hammerman PS, Garraway LA, Mills GB, Johnson DE, Grandis JR.
Title: Frequent mutation of receptor protein tyrosine phosphatases provides a mechanism for STAT3 hyperactivation in head and neck cancer.
Title: Potential Barriers to Human Hepatocyte Transplantation in MUP-uPAtg (+/+)Rag2-/-?C-/- Mice
Summary: Primary human fetal and adult hepatocytes have been considered feasible donor cell sources for cell transplantation. We compared the engraftment efficiencies between adult human, fetal human, and adult porcine hepatocytes after transplantation into MUP-uPAtg (+/+)Rag2-/-?C-/- mice. Transplantation of adult human hepatocytes yielded a thousand-fold higher serum albumin level compared to transplantation of fetal human hepatocytes, while transplantation of adult porcine hepatocytes resulted in a hundred-fold higher serum albumin level than adult human hepatocytes. These results suggest that adult liver cells are superior to fetal liver cells for transplantation, and caution should be applied if porcine hepatocytes are used for preclinical studies as a proof of concept for human hepatocytes.
Summary: We examined the influence of regulatory dendritic cells (DCreg), generated from cytokine-mobilized donor blood monocytes in vitamin D3 and IL-10, on renal allograft survival in a clinically relevant rhesus macaque model. DCreg expressed low MHC class II and costimulatory molecules, but comparatively high levels of programmed death ligand-1 (B7-H1), and were resistant to pro-inflammatory cytokine-induced maturation. They were infused intravenously (3.5-10 x 10(6) /kg), together with the B7-CD28 costimulation blocking agent CTLA4Ig, 7 days before renal transplantation. CTLA4Ig was given for up to 8 weeks and rapamycin, started on Day -2, was maintained with tapering of blood levels until full withdrawal at 6 months. Median graft survival time was 39.5 days in control monkeys (no DC infusion; n = 6) and 113.5 days (p < 0.05) in DCreg-treated animals (n = 6). No adverse events were associated with DCreg infusion, and there was no evidence of induction of host sensitization based on circulating donor-specific alloantibody levels. Immunologic monitoring also revealed regulation of donor-reactive memory CD95(+) T cells and reduced memory/regulatory T cell ratios in DCreg-treated monkeys compared with controls. Termination allograft histology showed moderate combined T cell- and Ab-mediated rejection in both groups. These findings justify further preclinical evaluation of DCreg therapy and their therapeutic potential in organ transplantation.
Authors: Tan C, Saurabh S, Bruchez MP, Schwartz R, Leduc P.
Title: Molecular crowding shapes gene expression in synthetic cellular nanosystems
Summary: The integration of synthetic and cell-free biology has made tremendous strides towards creating artificial cellular nanosystems using concepts from solution-based chemistry, where only the concentrations of reacting species modulate gene expression rates. However, it is known that macromolecular crowding, a key feature in natural cells, can dramatically influence biochemical kinetics via volume exclusion effects, which reduce diffusion rates and enhance binding rates of macromolecules. Here, we demonstrate that macromolecular crowding can increase the robustness of gene expression by integrating synthetic cellular components of biological circuits and artificial cellular nanosystems. Furthermore, we reveal how ubiquitous cellular modules, including genetic components, a negative feedback loop and the size of the crowding molecules can fine-tune gene circuit response to molecular crowding. By bridging a key gap between artificial and living cells, our work has implications for efficient and robust control of both synthetic and natural cellular circuits.
Authors: Phillippi JA, Green BR, Eskay MA, Kotlarczyk MP, Hill MR, Robertson AM, Watkins SC, Vorp DA, Gleason TG.
Title: Mechanism of Aortic Medial Matrix Remodeling is Distinct in Bicuspid Aortic Valve Patients
Summary: OBJECTIVES: Patients with bicuspid aortic valves (BAV) are predisposed to developing ascending thoracic aortic aneurysms (TAA) at an earlier age than patients who develop degenerative TAAs and have a tricuspid aortic valve (TAV). The hypothesis tested is that BAV associated aortopathy is mediated by a mechanism of matrix remodeling that is distinct from that seen in TAAs of patients with tricuspid aortic valves.
Authors: Gramignoli R, Dorko K, Tahan V, Skvorak KJ, Ellis E, Jorns C, Ericzon BG, Fox IJ, Strom SC.
Title: Hypothermic storage of human hepatocytes for transplantation.
Summary: Transplantation of human hepatocytes is gaining recognition as a bridge or an alternative to orthotopic liver transplantation for patients with acute liver failure and genetic defects. Since most patients require multiple cell infusions over an extended period of time, we investigated hepatic functions in cells maintained in University of Wisconsin solution at 4°C up to 72h. Eleven different assessments of hepatic viability and function were investigated both pre and post hypothermic storage, including plating efficiency, caspase 3/7 activity, ammonia metabolism and drug metabolizing capacity of isolated hepatocytes. Long-term function, basal and induced cytochrome P450 activities were measured after exposure to prototypical inducing agents. Cells from 47 different human liver specimens were analyzed. Viability significantly decreased in cells cold-stored in UW solution, while apoptosis level and plating efficiency were not significantly different from fresh cells. Luminescent and fluorescent methods assessed phase I and II activities both pre and post 24-72h of cold preservation. A robust induction (up to 200-fold) of phase I enzymes was observed in cultured cells. Phase II and ammonia metabolism remained stable during hypothermic storage although the inductive effect of culture on each metabolic activity was eventually lost. Using techniques that characterize 11 measurements of hepatic viability and function from plating efficiency, to ammonia metabolism, to phase I and II drug metabolism, it was determined that while viability decreased, the remaining viable cells in cold-stored suspensions retained critical hepatic functions for up to 48 h at levels not significantly different from those observed in freshly isolated cells.
Authors: Wells A, Grahovac J, Wheeler S, Ma B, Lauffenburger D.
Title: Targeting tumor cell motility as a strategy against invasion and metastasis.
Summary: Advances in diagnosis and treatment have rendered most solid tumors largely curable if they are diagnosed and treated before dissemination. However, once they spread beyond the initial primary location, these cancers are usually highly morbid, if not fatal. Thus, current efforts focus on both limiting initial dissemination and preventing secondary spread. There are two modes of tumor dissemination – invasion and metastasis – each leading to unique therapeutic challenges and likely to be driven by distinct mechanisms. However, these two forms of dissemination utilize some common strategies to accomplish movement from the primary tumor, establishment in an ectopic site, and survival therein. The adaptive behaviors of motile cancer cells provide an opening for therapeutic approaches if we understand the molecular, cellular, and tissue biology that underlie them. Herein, we review the signaling cascades and organ reactions that lead to dissemination, as these are non-genetic in nature, focusing on cell migration as the key to tumor progression. In this context, the cellular phenotype will also be discussed because the modes of migration are dictated by quantitative and physical aspects of the cell motility machinery.
Title: Bench to bedside review: Extracorporeal carbon dioxide removal, past present and future.
Summary: Acute respiratory distress syndrome (ARDS) has a substantial mortality rate and annually affects more than 140,000 people in the USA alone. Standard management includes lung protective ventilation but this impairs carbon dioxide clearance and may lead to right heart dysfunction or increased intracranial pressure. Extracorporeal carbon dioxide removal has the potential to optimize lung protective ventilation by uncoupling oxygenation and carbon dioxide clearance. The aim of this article is to review the carbon dioxide removal strategies that are likely to be widely available in the near future. Relevant published literature was identified using PubMed and Medline searches. Queries were performed by using the search terms ECCOR, AVCO2R, VVCO2R, respiratory dialysis, and by combining carbon dioxide removal and ARDS. The only search limitation imposed was English language. Additional articles were identified from reference lists in the studies that were reviewed. Several novel strategies to achieve carbon dioxide removal were identified, some of which are already commercially available whereas others are in advanced stages of development.
Authors: Gerlach JC, Over P, Turner ME, Thompson RL, Foka HG, Chen WC, Peault B, Gridelli B, Schmelzer E
Title: Perivascular Mesenchymal Progenitors in Human Fetal and Adult Liver
Summary: The presence of mesenchymal stem cells (MSCs) has been described in various organs. Pericytes possess a multilineage differentiation potential and have been suggested to be one of the developmental sources for MSCs. In human liver, pericytes have not been defined. Here, we describe the identification, purification, and characterization of pericytes in human adult and fetal liver. Flow cytometry sorting revealed that human adult and fetal liver contains 0.56%±0.81% and 0.45%±0.39% of CD146(+)CD45(-)CD56(-)CD34(-) pericytes, respectively. Of these, 41% (adult) and 30% (fetal) were alkaline phosphatase-positive (ALP(+)). In situ, pericytes were localized around periportal blood vessels and were positive for NG2 and vimentin. Purified pericytes could be cultured extensively and had low population doubling times. Immunofluorescence of cultures demonstrated that cells were positive for pericyte and mesenchymal cell markers CD146, NG2, CD90, CD140b, and vimentin, and negative for endothelial, hematopoietic, stellate, muscle, or liver epithelial cell markers von Willebrand factor, CD31, CD34, CD45, CD144, CD326, CK19, albumin, α-fetoprotein, CYP3A7, glial fibrillary acid protein, MYF5, and Pax7 by gene expression; myogenin and alpha-smooth muscle actin expression were variable. Fluorescence-activated cell sorting analysis of cultures confirmed surface expression of CD146, CD73, CD90, CD10, CD13, CD44, CD105, and ALP and absence of human leukocyte antigen-DR. In vitro differentiation assays demonstrated that cells possessed robust osteogenic and myogenic, but low adipogenic and low chondrogenic differentiation potentials. In functional in vitro assays, cells had typical mesenchymal strong migratory and invasive activity. In conclusion, human adult and fetal livers harbor pericytes that are similar to those found in other organs and are distinct from hepatic stellate cells.
Authors: Jennifer L Collinger, Brian Wodlinger, John E Downey, Wei Wang, Elizabeth C Tyler-Kabara, Douglas J Weber, Angus JC McMorland, Meel Velliste, Michael L Boninger, Andrew B Schwartz
Title: High-performance neuroprosthetic control by an individual with tetraplegia
Paralysis or amputation of an arm results in the loss of the ability to orient the hand and grasp, manipulate, and carry objects, functions that are essential for activities of daily living. Brain—machine interfaces could provide a solution to restoring many of these lost functions. We therefore tested whether an individual with tetraplegia could rapidly achieve neurological control of a high-performance prosthetic limb using this type of an interface.
Title: A Versatile Synthetic Platform for a Wide Range of Functionalized Biomaterials
Summary: The introduction of functionalities to synthetic biomaterials represents a major direction and a significant challenge in biomedical engineering. A synthetic platform using novel acid-induced epoxide ring-opening polymerization promoted by a newly designed catalyst to produce a variety of biodegradable and functionalized biomaterials is reported. The polymerization proceeds smoothly in the presence of functional groups including alkenyl, aromatic, ether, ester, and free hydroxyl groups. The functionalities of the resultant biomaterials can be further enriched using many post-functionalization methods. This platform yields biomaterials with a wide range of hydrophilicity, crystallinity, charge, mechanical properties, and cell interactions. This platform for functionalized biomaterials is simple, versatile, and can be easily adapted to specific cell types and tissues of interest.
Summary: Some forms of acute vital organ injury leading to death or severe disability have appropriately attracted significant attention among clinicians, researchers, and the public. There is almost universal public understanding of the concept of a heart attack. Many members of the public also are now familiar with the concept of a brain attack. Unlike medical expressions such as myocardial infarction or stroke, lay terms including the word attack convey a sense of urgency and importance. Such terms have helped to achieve considerable progress in treatment or outcome by focusing public attention, encouraging early clinician intervention, and establishing a research agenda.
Authors: Komori J, Boone L, Deward A, Hoppo T, Lagasse E.
Title: The mouse lymph node as an ectopic transplantation site for multiple tissues.
Summary: Cell-based therapy has been viewed as a promising alternative to organ transplantation, but cell transplantation aimed at organ repair is not always possible. Here we show that the mouse lymph node can support the engraftment and growth of healthy cells from multiple tissues. Direct injection of hepatocytes into a single mouse lymph node generated enough ectopic liver mass to rescue the survival of mice with lethal metabolic disease. Furthermore, thymuses transplanted into single lymph nodes of athymic nude mice generated functional immune systems that were capable of rejecting allogeneic and xenogeneic grafts. Additionally, pancreatic islets injected into the lymph nodes of diabetic mice restored normal glucose control. Collectively, these results suggest the practical approach of targeting lymph nodes to restore, maintain or improve tissue and organ functions.
Authors: Duncan AW, Hanlon Newell AE, Bi W, Finegold MJ, Olson SB, Beaudet AL, Grompe M.
Title: Aneuploidy as a mechanism for stress-induced liver adaptation.
Summary: Over half of the mature hepatocytes in mice and humans are aneuploid and yet retain full ability to undergo mitosis. This observation has raised the question of whether this unusual somatic genetic variation evolved as an adaptive mechanism in response to hepatic injury. According to this model, hepatotoxic insults select for hepatocytes with specific numerical chromosome abnormalities, rendering them differentially resistant to injury. To test this hypothesis, we utilized a strain of mice heterozygous for a mutation in the homogentisic acid dioxygenase (Hgd) gene located on chromosome 16. Loss of the remaining Hgd allele protects from fumarylacetoacetate hydrolase (Fah) deficiency, a genetic liver disease model. When adult mice heterozygous for Hgd and lacking Fah were exposed to chronic liver damage, injury-resistant nodules consisting of Hgd-null hepatocytes rapidly emerged. To determine whether aneuploidy played a role in this phenomenon, array comparative genomic hybridization (aCGH) and metaphase karyotyping were performed. Strikingly, loss of chromosome 16 was dramatically enriched in all mice that became completely resistant to tyrosinemia-induced hepatic injury. The frequency of chromosome 16-specific aneuploidy was approximately 50%. This result indicates that selection of a specific aneuploid karyotype can result in the adaptation of hepatocytes to chronic liver injury. The extent to which aneuploidy promotes hepatic adaptation in humans remains under investigation.
Authors: Rami A. Namas, Maxim Mikheev, Jinling Yin, Patrick Over, Matthew Young, Gregory M. Constantine, Ruben Zamora, Jörg Gerlach, and Yoram Vodovotz.
Title: A Biohybrid Device for the Systemic Control of Acute Inflammation
Summary: Properly regulated inflammation facilitates recognition and reaction to injury or infection, but inadequate or overly robust inflammation can lead to disease. Sepsis is an inflammatory disease that accounts for nearly 10% of total U.S. deaths, costing more than $17 billion. Acute inflammation in sepsis may evolve too rapidly to be modulated appropriately, and we suggest that therapies should focus not on abolishing inflammation, but rather on attenuating the positive feedback cycle of inflammation?damage?inflammation. In Gram-negative sepsis, bacterial endotoxin causes inflammation and is driven and regulated by the cytokine tumor necrosis factor-a (TNF-a), which is, in turn, negatively regulated via its endogenous inhibitor, soluble TNF-a receptor (sTNFR). We generated stably gene-modified variants of human HepG2 hepatocytes, using lentiviral constructs coding for mouse sTNFR driven by the constitutive cytomegalovirus promoter, and seeded them in a scaled-down, experimental liver bioreactor. When connected to anesthetized, cannulated rats subjected to endotoxin infusion and maintained solely by the animals’ circulation, this biohybrid device elevated circulating sTNFR, reduced the levels of TNF-a and other key inflammatory mediators, alleviated hypotension, and reduced circulating markers of organ damage. This novel class of biohybrid devices may be modified for patient- and disease-specific application, and, thus, may represent a disruptive strategy that offers the potential for rational inflammation reprogramming.
Authors: Badylak SF, Weiss DJ, Caplan A, Macchiarini P.
Title: Engineered whole organs and complex tissues.
Summary: End-stage organ failure is a key challenge for the medical community because of the ageing population and the severe shortage of suitable donor organs available. Equally, injuries to or congenital absence of complex tissues such as the trachea, oesophagus, or skeletal muscle have few therapeutic options. A new approach to treatment involves the use of three-dimensional biological scaffolds made of allogeneic or xenogeneic extracellular matrix derived from non-autologous sources. These scaffolds can act as an inductive template for functional tissue and organ reconstruction after recellularisation with autologous stem cells or differentiated cells. Such an approach has been used successfully for the repair and reconstruction of several complex tissues such as trachea, oesophagus, and skeletal muscle in animal models and human beings, and, guided by appropriate scientific and ethical oversight, could serve as a platform for the engineering of whole organs and other tissues.
Authors: Manni ML, Czajka CA, Oury TD, Gilbert TW.
Title: Extracellular Matrix Powder Protects Against Bleomycin-Induced Pulmonary Fibrosis.
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.
Title: Injectable fibroblast growth factor-2 coacervate for persistent angiogenesis.
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.
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.