Cardiomyoblast (H9c2) Differentiation on Tunable Extracellular Matrix Microenvironment

Abstract

Extracellular matrices (ECM) obtained from in vitro-cultured cells have been given much attention, but its application in cardiac tissue engineering is still limited. This study investigates cardiomyogenic potential of fibroblast-derived matrix (FDM) as a novel ECM platform over gelatin or fibronectin, in generating cardiac cell lineages derived from H9c2 cardiomyoblasts. As characterized through SEM and AFM, FDM exhibits unique surface texture and biomechanical property. Immunofluorescence also found fibronectin, collagen, and laminin in the FDM. Cells on FDM showed a more circular shape and slightly less proliferation in a growth medium. After being cultured in a differentiation medium for 7 days, H9c2 cells on FDM differentiated into cardiomyocytes, as identified by stronger positive markers, such as alpha-actinin and cTnT, along with more elevated gene expression of Myl2 and Tnnt compared to the cells on gelatin and fibronectin. The gap junction protein connexin 43 was also significantly upregulated for the cells differentiated on FDM. A successive work enabled matrix stiffness tunable; FDM crosslinked by 2wt% genipin increased the stiffness up to 8.5 kPa, 100 times harder than that of natural FDM. The gene expression of integrin subunit alpha 5 was significantly more upregulated on FDM than on crosslinked FDM (X-FDM), whereas no difference was observed for beta 1 expression. Interestingly, X-FDM showed a much greater effect on the cardiomyoblast differentiation into cardiomyocytes over natural one. This study strongly indicates that FDM can be a favorable ECM microenvironment for cardiomyogenesis of H9c2 and that tunable mechanical compliance induced by crosslinking further provides a valuable insight into the role of matrix stiffness on cardiomyogenesis.