Controlling the cellular organization of tissue-engineered cardiac constructs.

There are currently no effective treatments to restore the cardiac muscle lost because of ischemia for the millions of people who suffer heart attacks annually. Cell therapy procedures have emerged as novel therapeutic strategies for treatment of heart failure after myocardial infarction but have been hampered by the lack of adequate cell sources of cardiomyocytes and by the inability to integrate cell grafts into cardiac muscle. A cardiac patch composed of organized and functional cardiomyocytes could drastically enhance the efficacy of this important clinical approach. Here, we report our ongoing efforts to develop a bioartificial cardiac muscle capable of synchronized multidirectional contraction within a three-dimensional hydrogel scaffold. Neonatal rat cardiomyocytes, smooth muscle cells, and reconstituted polymeric collagen enriched with growth factors and hormones are used. A bioreactor system is used to impart precise strains onto the developing tissue constructs in vitro. The results demonstrate that cell-mediated collagen compaction is significantly enhanced by strain preconditioning, resulting in a more favorable cellular organization. Furthermore, the results demonstrate that strain stimulation guides cellular orientation in the direction of applied strain (i.e., in the circumferential direction). Hence, we demonstrate the importance of mechanical preconditioning as a means of promoting the in vitro development of engineered cardiac muscle for use with myocardial regeneration therapies.