BACKGROUND; Under induction of retinoic acid (RA), bone marrow stromal cells (BMSCs) can differentiate into nerve cells or neuron-like cells, which do not survive for a long time, so those are restricted to an application. Other neurotrophic factors can also differentiate into neuronal cells through inducing BMSCs; especially, brain-derived neurotrophic factor (BDNF) can delay natural death of neurons and play a key role in survival and growth of neurons. The combination of them is beneficial for differentiation of BMSCs.OBJECTIVE: To investigate the effects of BDNF combining with RA on inducing differentiation of BMSCs to nerve cells of adult rats and compare the results between common medium group and single BDNF group.DESIGN: Randomized controlled animal study.SETTING : Department of Neurology, Affiliated Hospital of Xuzhou Medical College.MATERIALS: The experiment was carried out in the Clinical Neurological Laboratory of Xuzhou MedicalCollege from September 2003 to April 2005. A total of 24 SD rats, of either gender, 2 months old,weighing 130-150 g, were provided by Experimental Animal Center of Xuzhou Medical College [certification: SYXK (su) 2002-0038]. Materials and reagents: low-glucose DMEM medium, bovine serum, BDNF,RA, trypsin, separating medium of lymphocyte, monoclonal antibody of mouse-anti-nestin, neuro-specific enolase, glial fibrillary acidic protein (GFAP) antibody, SABC kit, and diaminobenzidine (DAB) color agent. All these mentioned above were mainly provided by SIGMA Company, GIBCO Company and Boshide Company.METHODS: Bone marrow of SD rats was selected for density gradient centrifugation. BMSCs were undertaken primary culture and subculture; and then, those cells were induced respectively in various mediums in total of 3 groups, including control group (primary culture), BDNF group (20 μg/L BDNF) and BDNF+RA group (20 μg/L BDNF plus 20 μg/L RA). On the 3rd and the 7th days after induction, BMSCs were stained immunocytochemically with nestin (sign of nerve stem cells), neuron-specific enolase (NSE, sign of diagnosing neurons) and GFAP (diagnosing astrocyte), and evaluated cellular property.MAIN OUTCOME MEASURES: Induction and differentiation in vitro of BMSCs in 3 groups.RESULTS: ① Induction and differentiation of BMSCs: Seven days after induction, cells having 2 or more apophyses were observed. Soma shaped like angle or erose form, which were similar to neurons and glial cells having strong refraction. ② Results of immunocytochemical detection: Three days after induction, rate of positive cells in BDNF+RA group was higher than that in BDNF group and control group [(86.15±4.58)%, (65.43±4.23)%, (4.18±1.09)%, P ＜ 0.01]. Seven days after induction, rate of positive cells was lower in BDNF group and BDNF+RA group than that in both groups at 3 days after induction [(31.12±3.18)%,(29.35±2.69)%, P ＜ 0.01]; however, amounts of positive cells of NSE and GFAP were higher than those at 3 days after induction (P＜0.01); meanwhile, the amount in BDNF+RA group was remarkably higher than that in BDNF group (P ＜ 0.01).CONCLUSION: Combination of BDNF and RA can cooperate differentiation of BMSCs into neurons and astrocyte, and the effect is superior to single usage of BDNF.