Professor: Jonathan Butcher
Project Description: Over 750,000 Americans suffer from myocardial infarctions (heart attacks) annually due to blockage of the coronary arteries, with about 16% of cases leading to mortality. Currently, no viable clinical cardiac regenerative therapy exists to completely restore heart function following a myocardial infarction. Due to the limited capacity for adult mammalian hearts to regenerate, myocardial infarctions lead to deleterious remodeling that results in the deposition of nonfunctional fibrotic tissue that can progress to congestive heart failure as the heart is unable to meet the work load demands. In contrast, embryonic/fetal staged mammalian hearts have an enhanced regenerative capacity with little to no deposition of fibrotic scars following injury. The underlying mechanisms associated with this regenerative capacity transition are not well understood but several studies have eluded to the role of the extracellular matrix (ECM) and mechanics.
The extracellular matrix not only provides structural support to cells but also is laden with a variety of biochemical cues that can direct cellular fates. Several studies have demonstrated that fetal staged cardiac ECM can induce a greater increase in cardiomyocyte proliferation in contrast to adult cardiac ECM. Therefore, from a clinical therapy perspective, implanting fetal staged cardiac ECM within adult mammalian infarcts may facilitate the restoration of heart function. However, many gold-standard decellularization protocols to isolate cardiac ECM utilize harsh detergent reagents, such as sodium dodecyl sulfate (SDS), which eliminates many of the potential cell fate directing factors within the matrix. Likewise, decellularizing embryonic tissues using these detergent based techniques is difficult due to the greater fragility of embryonic tissue and the fact they contain more cellular content per unit of mass than adult tissue. To overcome the limitations associated with detergent based decellularization, our lab has developed a novel non-detergent based decellularization protocol that can be utilized to decellularize any embryonic organ/tissue of interest while preserving many of the essential extracellular matrix factors that may be beneficial for a pro-regenerative response.
Another promising approach to restore heart function is the development of tissue engineered myocardium, which could potentially be implanted within the infarcted zone to restore cardiac function. Decades of research have been poured into the development of tissue engineered cardiac tissues but with limited success. One major issue with cardiac constructs is the overall fetal-like immaturity of the cardiomyocytes, which do not integrate well with the surrounding host tissue and often induce unwanted ventricular arrythmias. To study cardiomyocyte maturity, our lab has developed a novel high-throughput in vitro platform system to create functional three-dimensional engineered cardiac tissues around elastic posts that serve as mechanical constraints and a mode for the cardiac cells to work against. Utilizing this platform, we are developing a bioreactor system that can mechanical stimulate (stretch) and electrically stimulate (pace) the engineered tissues to recapitulate the in vivo stimulation the cardiac cells experience.
This project will consist of two fronts: 1) testing the regenerative capacity of decellularized cardiac ECM, and 2) developing/optimizing the bioreactor system for stimulating cardiac constructs. For the cardiac ECM front, you will learn how to optimize the decellularization of a variety of embryonic chick ECMs, isolate and culture primary embryonic chick cardiac cells in two dimensional as well as three-dimensional engineered culture systems and perform in vitro culture experiments with cardiac cells to test the bioactivity of the matrices. Likewise for the bioreactor front, you will help design and optimize the system for high-throughput stretching and pacing of cardiac tissues, create three-dimensional engineered tissues, as well as test/validate the bioreactor system.