Mesenchymal stem cells enhance the differentiation of c-kit+ cardiac stem cells.

C-kit+ cardiac stem cells (CSCs) were isolated from neonatal rat and tested for the expression of Nkx2.5 and GATA-4 genes which are important in cardiac development. C-kit+ CSCs were plated into the well below the insert of transwell inserts and bone marrow mesenchymal stem cells (BMMSCs) were plated into the inserts. The expression of cardiac Troponin T (cTnT), p27, CDK2, transforming growth factor-beta receptor II (TGF-beta R II), and Smad2 protein in CSCs were tested by western blot. Expression of p27, TGF-beta R II and Smad2 was found to be upregulated in the co-culture group. In contrast, the expression of CDK2 was downregulated. Our results suggest that BMMSCs could promote the differentiation of c-kit+ CSCs, probably through paracrine activity via the TGF-beta signaling pathway.