Abstract: [Abstract] Objective To investigate the feasibility of inducing rat bone marrow mesenchymal stem cells(MSCs) differentiating into cardiomyocytes by Oxytocin(OT). Methods SD rat MSCs were isolated and cultured from rat bone marrow, then induced by OT for 72 h. The cultured cells were observed by phase-contrast microscope. The laser scanning confocal microscope (LSCM) was used for the expression of desmin, α-sarcomeric actin and C-TnT. GATA-4 and α-MHC expression was detected by relative quantitative RT-PCR after 7, 21, 28 days of induction respectively. Results The cultured cells grow stablely and proliferate faster, mainly appeared as fusiform and fibroblastic shape. After induced by OT for one week, most cells became spindle-like and pillar-form with oval nuclei lying in the center of cells and similar to cardiomyocytes. The direction of the cell arraying was similar gradually. After four weeks, a majority of cells enlarged,lengthened，showed stick-like shape and paralleled closely.The direction of the cell arraying was similar gradually. MSCs induced by OT could be identified by the positive staining for desmin, α-sarcomeric actin and C-TnT. laser scanning confocal microscopy indicated that desmin(α-sarcomeric actin ) was signed red, cTnT was green.When they were both been showed,it changed to yellow.RT-PCR assessment showed that the differentiated cells began to express GATA-4 from day 7 to day 28 of differentiation and began to express α-MHC from day 21 to day 28 of differentiation. Conclusion　MSCs can differentiate into cardiomyocytes in vitro after induced by OT.

Key words: marrow mesenchymal stem cells, Oxytocin, cardiomyocytes, differentiation, cell culture, rat