Sinoatrial node cells phenotype expression is induced by direct bone marrow stem cells contact with sinoatrial node cells

OBJECTIVE: To observe the differentiation of bone mesenchymal stem cells (BMSCs) co-cultured with purified sinoatrial node cells (SNC) of neonate rats. METHODS: SNC from neonatal SD rat were cultured and purified with differential attachment method and labeled with BrdU. Rat BMSCs were isolated by a Percoll's gradient solution and cultured in DMEM. After 2 passages, these BMSCs were transfected with pEGFP-N1 by Lipofectamine and labeled with GFP. EGFP-BMSC were co-cultured with SNC in a rate of 1:5 for 1 week. EGFP-BMSC cultured in SNC culture medium served as controls. SNC marker hyperpolarization activated cyclic nucleotide gated cation channel 4 (HCN4) and connexin 45 (Cx45) expressions were determined by immunofluorescence staining. RESULT: Positive immunofluorescence staining against HCN4 and Cx45 were detected in EGFP-BMSC co-cultured with SNC but not in EGFP-BMSC cultured in SNC culture medium. CONCLUSION: Direct cell-to-cell contact between BMSCs and SNC cells may induce BMSCs differentiation into sinus node-like cells.