Description: Physical mechanical processes are central to the morphogenesis of embryos and their organs. The goal of this proposal is to apply a multi-scale analysis of the mechanics of convergent extension, identifying biomechanical mechanisms that establish passive tissue properties such as stiffness as well as active processes that generate forces of extension, regulate cell behaviors and tissue deformation, and how passive mechanics and active force generating processes are coordinated within the frog embryo. Studies outlined in this proposal will answer: (1) How are cell-scale structures and tissue mechanics are integrated during elongation? Early development is marked by dramatic changes in the mechanical properties of embryos. To understand how and why these properties change we test simple models of tissue mechanics based on synthetic closed-cell foams using bioengineering and biophysical methods to disrupt features from large scale architecture to the subcellular actomyosin-dependent cortex. (2) What single-cell mechanical processes contribute to convergent extension? We extend our analysis of cell behaviors to an unbiased approach that combines wide-field confocal microscopy with descriptive biomechanical analyses from the level of the cell, to the local neighborhood, to the strain fields of the entire embryo. Combining analyses of neural plate and paraxial somitic mesoderm we describe the dependence of these movements on planar polarity signaling. Using systems approaches we seek to test the dependencies of specific cell behaviors on both upstream signaling systems and their targeted downstream effectors. (3) How are tissue polarity cues transduced into polarized cell behaviors? We hypothesize that polarized cell behaviors and the oriented forces they generate are the result of cues produced by anisotropic strain. To test the roles of polarized intracellular factors and mechanical strain in organizing cell behaviors we use magnetogenetics and micro-scale tissue stretchers. Results from this project will complement ongoing efforts to identify the molecular regulators of morphogenesis by providing a conceptual framework developing new hypotheses of morphogenesis and bioengineering tools to test them. The significance of our work provides researchers a more complete understanding of the contribution of cell- and tissue-mechanics to development, to understand the role of tissue mechanics in oncogenesis, and to provide fundamental physical principles for future functional tissue engineers.
Description: This technology is a new ex-vivo application for sonothrombolysis (SNT), which combines the use of ultrasound (US) probes and microbubbles timely infused through the arterial port of liver allografts being preserved by a machine perfusion (MP) system. The US probe pulses induces microbubble oscillation and bursting in a process called cavitation. This ex-vivo technology is intended to remove red blood cells (RBCs) plugs and cellular debris from the hepatic arterial peri-biliary plexus (PBP) prior to liver allograft implantation from organs obtained from donors after cardiac death (“DCD”) These patients experience extended periods of hypoperfusion under anoxic conditions prior to organ recovery. The use of DCD livers poses a significant risk for the subsequent development of ischemic cholangiopathy (IC) by the recipient in the post-operative period. IC is an irreversible complication stemming from prolonged ischemia to the PBP leading into recurrent biliary sepsis and subsequent liver allograft failure. This lethal condition requires mandatory retransplantation while yielding prolonged hospital stays and excessive post-operative costs. Previous attempts to prevent IC after DCD liver transplantation using different technologies have failed. IC is caused by progressive clotting of the small blood vessels supplying the PBP, which prevents blood and oxygen from reaching the biliary tree effectively once the liver is transplanted. The ex-vivo SNT technology was designed to remove the clots ex-vivo while enhancing the oxygenation of the bile duct system before the liver is transplanted. It can be used with all current MP systems currently being evaluated for liver preservation.
Title: 3D Bioprinted Human Trachea for Pediatric Patients
Description: The overall goal of this project is the development and preclinical testing of a tissue engineered trachea for use in pediatric patients. The natural growth of pediatric patients requires that an engineered tissue or organ vital to life must “grow” with the patient. The present project will design, develop, and test in preclinical models, a bioengineered trachea consisting of naturally occurring extracellular matrix (ECM), as a scaffold, that is custom manufactured by 3D printing (Feinberg Laboratory, Carnegie Mellon University). The combined expertise of the Badylak Laboratory, which will acquire and prepare the matrix materials, with the Feinberg Laboratory that has expertise in 3D printing, will produce engineered tracheas that will be tested in a rapidly growing porcine model at the McGowan Institute for Regenerative Medicine. The project is milestone driven and consists of two years of development followed by three years of testing.
PI: William Federspiel, William Wagner, Peter Wearden
Title: Ambulatory Assist Lung for Children
Description: Acute and chronic lung diseases remain the most life threatening causes of death and hospitalization in the pediatric population. Cystic fibrosis (CF), pulmonary hypertension and pulmonary fibrosis have been observed to be the most frequent causes of lung failure in pediatric patients. Mechanical ventilation (MV) and extracorporeal membrane oxygenation (ECMO) have been used to bridge sick kids to transplant. These procedures can lead to poor post-transplant outcomes by their very restrictive nature on mobility. This project will develop a compact respiratory assist device for pediatric patients, the Pittsburgh Pediatric Ambulatory Lung (P-PAL) to replace ECMO as a bridge to transplant or recovery in kids with acute and chronic lung failure. The P-PAL is a wearable and fully integrated blood pump and gas exchange module that will be designed for implantation of inflow cannula and outflow cannula/grafts in the right atrium and pulmonary artery, respectively. The P-PAL will be designed for longer-term respiratory support (1-3 months before cartridge change-out) at 70-90% of normal metabolic oxygenation requirements, while pumping blood from 1 to 2.5 Liters/min. The specific aims of project are 1) To modify the design and operational parameters of the P-PAL to meet requirements for blood pumping, gas exchange, priming volume, and form factor, 2) To build P-PAL prototypes along the design development pathway for bench characterization studies of pumping performance, gas exchange, and hemolysis, 3) To improve the hemocompatibility of the P-PAL by exploiting novel polymeric zwitterionic coatings that we have already begun to develop for our adult wearable assist lung, and 4) To perform acute and chronic studies in healthy lambs to demonstrate the in-vivo performance and hemocompatibility of the PAAL device and to study its interaction with the cardiopulmonary system.