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. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A: 2808–2816, 2013.