Effect of biophysical cues on reprogramming to cardiomyocytes.

Reprogramming of fibroblasts to cardiomyocytes offers exciting potential in cell therapy and regenerative medicine, but has low efficiency. We hypothesize that physical cues may positively affect the reprogramming process, and studied the effects of periodic mechanical stretch, substrate stiffness and microgrooved substrate on reprogramming yield. Subjecting reprogramming fibroblasts to periodic mechanical stretch and different substrate stiffness did not improve reprogramming yield. On the other hand, culturing the cells on microgrooved substrate enhanced the expression of cardiomyocyte genes by day 2 and improved the yield of partially reprogrammed cells at day 10. By combining microgrooved substrate with an existing optimized culture protocol, yield of reprogrammed cardiomyocytes with striated cardiac troponin T staining and spontaneous contractile activity was increased. We identified the regulation of Mkl1 activity as a new mechanism by which microgroove can affect reprogramming. Biochemical approach could only partially recapitulate the effect of microgroove. Microgroove demonstrated an additional effect of enhancing organization of sarcomeric structure, which could not be recapitulated by biochemical approach. This study provides insights into new mechanisms by which topographical cues can affect cellular reprogramming.