Differentiation induction of cardiac c-kit positive cells from rat heart into sinus node-like cells by 5-azacytidine

Cardiac stem cells (CSCs) can differentiate into cardiac phenotypes representing early cardiomyocyte-like cells. However, CSCs-derived specification into sinus nodal cells is rarely known. Using the demethylating agent, 5-Aazacytidine (5-Aza), we tried to follow the process of cardiac specialization into sinus node-like cells. The c-kit+ cells were isolated from 1-month-old rat hearts and sorted by a flow cytometry cell sorting system. Then, analyses of immunofluorescence and reverse transcription polymerase chain reaction were performed on the cells. The sorted c-kit+ cell are self-renewing and clonogenic. Some of the c-kit+ cell could spontaneously express GATA-4, cardiac troponin I (cTnI), smooth muscle actin (SMA) and CD31. At week 8, the cells treated with 10 μM 5-Aza expressed GATA-4 and cTnI at rates of 31.4 ± 2.6% and 32.6 ± 8.5%. Correspondingly, the rates were 21.4 ± 8.1% and 18.7 ± 4.3% in the cells without 5-Aza. The difference of GATA-4 or cTnI expression rate between two groups was of significance respectively, P < 0.05. The cultured cells could express mRNA of GATA4, hyperpolarization-activated cyclic nucleotide-gated 2 (HCN2) and HCN4. The mRNA expression was also up-regulated in cells treated with 10 μM 5-Aza and growth factors. By week 2 after cell sorting, inward currents could be recorded in a fraction of the cultured cells. In conclusion, 10 μM 5-Aza could promote the differentiation of c-kit+ cells into sinus node-like cells. 5-Aza-mediated differentiation seems to be helpful in future cell therapy for the patients suffering from loss of sinus node cells.