Objective: To explore the mechanism about the cardiac differentiation of human mesenchymal stem cells(MSCs) induced by rat cardiomyocytes.Methods:To induce the cardiac differentiation of human MSCs by using rat cardiomyocytes in different ways(three dishes for each way):(1) Cocultured with rat cardiomyocytes at the ratio of 1:1;(2)Cultured with the conditional medium

which got from the culture of rat cardiomyocytes and mixed with fresh medium by 1:1;(3) Cultured with the supernatant

which got from the minced rat cardiomyocytes and mixed with fresh medium by 1:10.The human MSCs were harvested at the day of 2

5 and 7

respectively.Then the cells were stained with desmin and cardiac troponin I monoclonal-antibodies

and fluorescent in situ hybridization to human DNA was used to mark the cells from human.Results: No desmin or cTnI was detected in the human MSCs cultured with conditional medium or supernatant.While for the human MSCs cocultured with rat cardiomyctes

desmin was detectable at the day of 2 and cTnI at the day of 5.Until the day of 7

about 35% of cocultured-human MSCs expressed those cardiac specific antigens.Conclusion:Human MSCs could be induced to differentiate into cardiomyocyte-like cells by coculture with rat cardiomyocytes

but not by the conditional medium or the supernatant of rat cardiomyocytes.