Fig. 5. Cardiomyocyte beating is sensitive to matrix elasticity. Purified cardiomyocytes were plated at low density on matrices of varied stiffness, and beating was observed in phase contrast. (A) Beat frequency is elasticity-dependent, with cells on hard matrices slowing their beat frequency over days. (B) The percentage of cells beating was also quantified after 4, 24 and 48 hours post isolation. Beating cells persisted only on matrices with EE*. Error bars are ± s.d. for >5 cells, 10 seconds each in triplicate.