Abstract： Objective To explore the potential neurotrophic effect of bone marrow-derived mesenchymal stem cells (BMSCs) on the proliferation and differentiation of ventral mesencephalic precursors (VMPs).Methods VMPs from E 11 inbred rat embryos and BMSCs from adult rats were cultured in 2 separate groups.Moreover,a co-cultured group was also established.Afterwards,the 3 different differentiation mediums obtained from these 3 defined groups were used to influence the differentiation procedures of normal VMPs that had amplification in vitro for 7 d.The growth of cells was observed;immunocytochemical staining was performed on these cells at the late differentiation phase.Relative yields of TH+ cells were calculated and compared.Results Seven d after the inducing differentiation,the total cell numbers multiplied about 44.13±4.75,60.63±5.25 and 64.00±7.63 folds in the VMP control group,the BMSCs group and the VMP+BMSCs co-cultured group,respectively,as compared with those before the differentiation.Correspondingly, the ratios of TH+ cells in the total cell population were (18.76±5.20)%, (23.49±4.10)% and (28.08±5.42)% in the VMP control group,the BMSCs group and the VMP+BMSCs co-cultured group,respectively; significant differences betwwen each 2 groups were found (P<0.05).Conclusion BMSCs can secret nutritional factors to promote the proliferation and committed differentiation of VMPs into dopaminergic neurons.