Nano-sized collagen I molecules enhanced the differentiation of rat mesenchymal stem cells into cardiomyocytes.

The aim of this study was to investigate the ability of nano-sized collagen I molecules (nanoparticles or nanofibrils) and a 5-azacytidine (5-aza) treatment to enhance the differentiation of rat mesenchymal stem cells (MSCs) toward a cardiomyogenic phenotype in vitro. Second passaged MSCs were cocultured with nano-sized collagen I molecules for 24 h and then treated with 10 μM 5-aza for 24 h. The results demonstrated that the size of the cells increased significantly and acquired a flattened, triangular-shaped morphology after treatment with nano-sized collagen I molecules and 5-aza. The cells are connecting with adjoining cells by forming myotube-like structures. Additional treatment of the MSCs with nano-sized collagen I fibrils significantly increased two transcription factors GATA-4 (12.6-fold increase) and Nkx2.5 (4.8-fold increase) expressions compared with MSC groups treated only with 5-aza at 3-day culturing. Furthermore, MSCs pretreated with nano-sized collagen fibrils significantly increased the expressions of cardiac genes of troponin I, β-myosin heavy chain, and cardiac α-actin compared with MSC groups treated only with 5-aza (all, p < 0.01 or better). These results indicate that culturing MSCs with nano-sized collagen I molecules, which may act as scaffolds or soluble protein ingredients, leads to alterations in gene expression and affects the differentiation fate induced with 5-aza.