BACKGROUND: Transplantation of bone marrow mesenchymal stem cells (MSCs) has been used in the field of repair of nerve injury. Brain stereotactic transplantation and transvascular transplantation are two transplantation methods. OBJECTIVE: We infused MSCs into rat peripheral cerebral infarct focus, in order to investigate the improvement of rat neurological dysfunction by forelimb use asymmetry test and postural reflex test.DESIGN: A randomized controlled animal experiment. SETTING: Department of Neurology, First Hospital of Jilin University.MATERIALS: This study was performed at the Key Laboratory of Zoonosis, Ministry of Education, Institute of Zoonosis, Jilin University between October 2006 and April 2007. Healthy male Wistar rats of clean grade, weighing 250-280 g, were provided by the Laboratory Animal Center of Jilin University. The protocol was performed in accordance with ethical guidelines for the use and care of animals.METHODS: MSCs from healthy adult volunteers were in vitro cultured and proliferated by density gradient separation and adherence screening method. Their immunophenotypes were identified by a flow cytometer. The Wistar rats were randomized into 5 groups with 10 rats in each: normal control group, sham-operated group, model group, serum-free DMEM-treated group (DMEM group) and MSCs -treated group (MSCs group). Rat models of cerebral ischemia/reperfusion were developed by occluding rat right middle cerebral artery following suture occlusion method modified by Longa et al. Rats in the normal control group were untouched. In the sham-operated group, operation was not ended till cervical interior and exterior arteries were exposed and sutured, and the other disposals were the same as those in the model group. At ischemia 90 minutes reperfusion 1 hour, a stereotaxic apparatus was used to take rat right peripheral cerebral ischemic region as transplantation site: 3 mm lateral to, 1mm caudal to and 4 mm posterior to Bregma. Rats in the MSCs group were slowly injected 5 μL BrdU-labeled MSCs (4×1011 L-1) serum-free medium. Rats in the DMEM group were injected 5 μL serum-free medium. After perfusion, inserted needle was retained for 5 minutes and then slowly withdrawn in order to avoid the back flow of liquid from needle pole. The survival of MSCs in rats was detected by immunohistochemical technique, and rat behavioral changes of observed on days1, 3, 7 and 28 after transplantation by forelimb use asymmetry test and postural reflex test.MAIN OUTCOME MEASURES: ① The immunophenotype of MSCs were identified by a flow cytometer. ② The survival of transplanted MSCs in the rat brain. ③ Rat behavioral changes. RESULTS: All the 50 rats were included in the final analysis. ① High purity of MSCs were harvested in the experiment. Flow cytometer detection showed that both CD44 and CD29 were positive, while CD34, CD45 and CD31 were negative. ② MSCs transplanted into the brains of rats in the MSCs group gathered in the peripheral cerebral ischemic region and survived. ③ Behavioral scores of rats in the MSCs group were significantly lower than those in the other groups (P < 0.05). They were gradually decreased with time after transplantation, and reached the valley value on day 7 after transplantation (P < 0.01). CONCLUSION: Neurological function of rats recovers in all the groups except normal control group. But the recovery differs in different groups, and neurological function of rats in the MSCs group recovers better than that in other groups.