Promotion of cardiac differentiation of brown adipose derived stem cells by chitosan hydrogel for repair after myocardial infarction

The ability to restore heart function by replacement of diseased myocardium is one of the great challenges in biomaterials and regenerative medicine. Brown adipose derived stem cells (BADSCs) present a new source of cardiomyocytes to regenerate the myocardium after infarction. In this study, we explored an injectable tissue engineering strategy to repair damaged myocardium, in which chitosan hydrogels were investigated as a carrier for BADSCs. In vitro, the effect and mechanism of chitosan components on the cardiac differentiation of BADSCs were investigated. In vivo, BADSCs carrying double-fusion reporter gene (firefly luciferase and monomeric red fluorescent protein (fluc-mRFP)) were transplanted into infarcted rat hearts with or without chitosan hydrogel. Multi-techniques were used to assess the effects of treatments. We observed that chitosan components significantly enhanced cardiac differentiation of BADSCs, which was assessed by percentages of cTnT⁺ cells and expression of cardiac-specific markers, including GATA-4, Nkx2.5, Myl7, Myh6, cTnI, and Cacna1a. Treatment with collagen synthesis inhibitors, cis-4-hydroxy-d-proline (CIS), significantly inhibited the chitosan-enhanced cardiac differentiation, indicating that the enhanced collagen synthesis by chitosan accounts for its promotive role in cardiac differentiation of BADSCs. Longitudinal in vivo bioluminescence imaging and histological staining revealed that chitosan enhanced the survival of engrafted BADSCs and significantly increased the differentiation rate of BADSCs into cardiomyocytes in vivo. Furthermore, BADSCs delivered by chitosan hydrogel prevented adverse matrix remodeling, increased angiogenesis, and preserved heart function. These results suggested that the injectable cardiac tissue engineering based on chitosan hydrogel and BADSCs is a useful strategy for myocardium regeneration.