<正>Objective: To investigate the feasibility of bone marrow stromal cells （BMSCs） differentiating into cardiomyocyte-like cells in heterogeneous cardiomyocytes microenvironment in vitro. Methods: Mouse GFP-BMSCs were isolated by centrifugation through a Ficoll step gradient and purified by plating culture and depletion of the non-adherent cells. Neonatal rat cardiomyocytes （CMs） were isolated by enzymatic dissociation from hearts of 1-to 2-day-old Sprague-Dawley （SD） rats and differentially plated to remove fibroblasts. Mouse GFP-BMSCs were cocultured with neonatal rat CMs through direct and indirect contact

respectively. Cardiomyogenic differentiation of BMSCs was evaluated by immunostaining with anti -α-actin monoclonal antibody and observing synchronous contraction with adjacent CMs by phase contrast microphotography. Results: On day 7 of coculture

GFP-BMSCs （CMs : BMSCs = 4 : 1）attached to nonfluorescent contracting cells （rat-derived CMs） showed myotube-like formation and started to contract synchronously with adjacent cardiomyocytes. About 10% of the fluorescent GFP-BMSCs were cardiomy-ocyte-like cells as determined by cell morphology and positive actin staining. Conclusion:Direct cell-to-cell interaction with CMs is crucial for cardiomyogenic differentiation of BMSCs in heterogeneous CMs microenvironment in vitro. This provides a novel inducing pathway for directional differentiation of cardiovascular tissue engineering seed cells.