FIG. 6.
(A) Myocardial elasticity during embryogenesis. Histograms of elastic moduli (∼150 locations per sample) determined from quail embryos show two peaks, one indicating passive elasticity of contractile myocardium (E-Stiff) and a softer, second peak (E-Soft) that surrounds the myocardium and increases in frequency with development. Results for normal and infarcted rat myocardium are indicated for comparison5,9; (B) CMs and fibroblast spreading. CMs and pericardial fibroblasts were plated from 10-day-old embryonic myocardium without purification, and spread areas were measured after 4 or 24 h5; (C) In vitro striation of CMs. Purified CMs from 10-day-old embryonic myocardium were plated onto substrates of varying elasticity to observe striated cytoskeletal organization with skeletal α-actinin. Many cells on both soft gels and intermediate E* gels reassembled myofibrils, whereas cells on hard matrices exhibited less myofibril reassembly. Inset images show magnified views of the larger images (reproduced with permission from Engler et al.5).