Stiffness of thermoresponsive gelatin-based dynamic hydrogels affects fibroblast activation

Abstract

Myocardial infarction is the underlying cause for many heart failure cases and is characterized by progressive stiffening of the myocardium leading to differentiation of cardiac fibroblasts to myofibroblasts. Static in vitro culture substrates are unable to mimic the dynamic behavior of the myocardium experienced following a myocardial infarction. Here, gelatin-based dynamic hydrogels that can undergo softening via thiol–disulfide exchange reactions have been used to study cardiac fibroblast differentiation. The hydrogels were formed by crosslinking thermoresponsive poly(N-isopropylacrylamide-s-2-hydroxypropyl methacrylate-s-mercaptoethyl acrylate) synthesized using reversible addition–fragmentation chain transfer polymerization with gelatin. The stiffness of the hydrogels is controllable and gels with storage moduli from 5.2 to 18.8 kPa were prepared. Cardiac fibroblasts were cultured on hydrogels of varying stiffness, and cell area and smooth muscle actin reporter expression increased with hydrogel stiffness. The hydrogels could be softened by 2.7–3.5 kPa using thiol–disulfide exchange reactions. Cell area reduced upon softening the initially stiffest gels.