|Ph.D Student||Shapira-Schweitzer Keren|
|Subject||An Injectable Biomaterial for Cardiac Tissue Engineering|
|Department||Department of Biomedical Engineering||Supervisor||Professor Dror Seliktar|
|Full Thesis text|
There are currently no clinically treatments that can be applied to reverse the long-term remodeling associated with myocardial infarction. Cardiac cell therapy is a new treatment approach which aims to promote the formation of a new cardiac tissue by delivering healthy cells into the damaged area of the heart. The objective of this work is to validate PEGylated Fibrinogen (PF), a biosynthetic biomaterial developed in our laboratory - as a cell carrier for cardiac cell therapy. In vitro experiments using neonatal rat cardiomyocytes (NRVCM) were performed to investigate the relationship between material modulus and spontaneous contraction of cells within the construct. An image analysis algorithm was applied to in order to characterize spontaneous contraction and to correlate temporal displacement patterns to the material composition and cell density . By using an optimized composition of the hydrogel, we evaluated the ability of the cardiomyocytes derived from human embryonic stem cells (hESC-CM) in comparison to NRVCM to survive and generate a functional cardiac syncytium in the hydrogel. Each cell type was cultured in a PF hydrogel while maturation and cardiac function were documented in terms of spontaneous contractile behavior and biomolecular organization. The NRVCM demonstrated the fastest maturation and the most significant spontaneous contraction. The hESC-CM maturation occurred between 10-14 days in culture, and exhibited less contraction amplitude and synchronization in comparison to the NRVCM. Cellular responsiveness to isoproterenol, carbamylcholine and heptanol provided further evidence of the cardiac maturation in the PF and identified the potential to use this system for in vitro drug screening. In vivo experiments were conducted to test the hypothesis that combined delivery of the PF and cardiomyocytes into the rat myocardial infarction model will result in superior functional outcome, compared to each intervention alone. Infarcted rat hearts were randomized to injection of saline, NRVCMs, biopolymer, or combined delivery of the biopolymer and NRVCMs. Injection of NRVCMs or biopolymer alone significantly altered the remodeling process. Co-injection of the biopolymer and NRVCMs resulted in a significant increase in the cell-graft area and eventually to the best functional outcome, with FS improving by 26.3±6.6%. Feasibility studies demonstrated the ability of the biopolymer to act as an effective carrier of hESC-CMs and to significantly alter the remodeling process. Taken together, these experiments demonstrate the ability of the PF to function as an effective cardiomyocyte carrier and provide further benefit to the effect of the cells by preventing post-infarction cardiac remodeling.