Objective:To investigate the effects of environment in vitro and in vivo on the differentiation of bone mesenchymal stem cells (MSCs) into neural cells.Methods:①MSCs were labeled with 4,6-diamidino-2-phenylindole (DAPI) and injected into the right brain of the rats(n=6),which had suffered from middle cerebral artery occlusion(MACO) a day before.Two weeks later,immunofluorescent staining was used to detect the expression of nestin,microtubule-associated protein 2 (MAP-2) and glial fibrillary acidic protein (GFAP).②In vitro,MSCs were cultured with modified neuronal medium(MNM)for 18 hours after being pretreated with 0.5umol/L all-trans retinoid acid (ATRA) for 24 hours.Immunocytochemistry was used to detect the expression of nestin,MAP-2 and GFAP.Results:①After being injected into rats for 2 weeks,MSCs survived in the ischemic areas and a few cells expressed nestin,MAP-2 and GFAP respectively.②In vitro,after ATRA and MNM treatment,the positive percentage of nestin and MAP-2 were (92.3?3.4)% and (89.6?3.3)% respectively,but no expression of GFAP was detected.Conclusion:The different ratio of MSCs differentiating into neural cells suggests that there is difference in the process and mechanism between environment in vitro and in vivo.

Objective:To investigate the effect of all-trans retinoic acid (ATRA) on the differentiation of marrow stromal stem cells(MSCs)into neurons. Methods: Rat MSCs were expanded as undifferentiated cells in culture for 5-7 passages and pretreated with ATRA for 24 h, then induced by modified neuronal medium (MNM) for 18 h. The control cells were directly cultured in MNM without ATRA pretreatment. Immunocytochemistry was used to detect the expression of nestin, neuron-specific enolase (NSE), neuron-specific nuclear protein (NeuN) and microtuble-associated protein (MAP-2) in the experimental groups and the control cells. The change of cell proliferative cycles and the expression of retinoic acid receptor beta (RAR?) were detected before and after ATRA treatment. Results: 1. The expression of nestin, NSE, NeuN and MAP-2 was much higher than that of the control group. 2. No changes were found in the cell proliferative cycles before and after ATRA treatment. 3. No expression of RAR? was found in MSCs; but positive expression of RAR? was detected afer 24 h of ATRA treatment and it was (20.3?4.2)%. Conclusion: ATRA can activate gene transcription via nuclear receptor RAR? and promote MSCs transdifferentiation into neurons.