Assessment of the effects of four crosslinking agents on gelatin hydrogel for myocardial tissue engineering applications.

Cardiomyocyte (CM) transplantation is a promising option for regenerating infarcted myocardium. However, poor cell survival and residence rates reduce the efficacy of cell transplantation. Gelatin (GA) hydrogel as a frequently-used cell carrier is a possible approach to increase the survival rate of CMs. In this study, microbial transglutaminase (mTG) and chemical crosslinkers glutaraldehyde (GTA), genipin (GP), and 1-ethyl-3-(3-dimethyl aminopropyl)-carbodiimide (EDC) were employed to prepare GA hydrogels. The mechanical properties and degradation characteristics of these hydrogels were then evaluated. Neonatal rat CMs (NRCMs) were isolated and inoculated on the surface of these hydrogels or encapsulated in mTG- hydrogels. Cellular growth morphology and beating behavior were observed. Cellular viability and immunofluorescence were analyzed. Intracellular Ca2+ transient and membrane potential propagation were detected using fluorescence dyes (Fluo-3 and di-4-ANEPPS, respectively). Results showed that the chemical crosslinkers exhibited high cytotoxicity and resulted in high rates of cell death. By contrast, mTG- hydrogels showed excellent cell compatibility. The CMs cultured in mTG-hydrogels for a week expressed CM maturation markers. The NRCMs begun independently beating on the third day of culture, and their beating synchronized after a week of culture. Furthermore, intracellular Ca2+ transient events with periodicity were observed. In conclusion, the novel mTG-crosslinked GA hydrogel synthesized herein has good biocompatibility, and it supports CM adhesion, growth, and maturation.