BACKGROUND: Transplantation of fetal cell suspension or blocks of fetal tissue can ameliorate the nerve function after the injury or disease in the central nervous system,and it has been used to treat neurodegenerative disorders induced by Parkinson disease.OBJECTIVE:To observe the effects of the transplantation of neuron-like cells derived from bone marrow stromal cells (rMSCs) into the brain in restoring the dysfunctions of muscle strength and balance as well as leing and memory in rat models of cerebral infarction.DESIGN : A randomized controlled experiment.SETTING: Department of Pathophysiology, Zhongshan Medical College of Sun Yat-sen University.MATERIALS: Twenty-four male SD rats (3-4 weeks of age, weighing 200-220 g) were used in this study (Certification number:2001A027).METHODS:The experiments were carried out in Zhongshan Medical College of Sun Yat-sen University be tween December 2003 and December 2004.① Twenty-four male SD rats randomized into three groups with 8 rats in each: experimental group, control group and sham-operated group. Rats in the experiment al group and control group were induced into models of middle cerebral artery occlusion (MCAO). After in vitro cultured, purified and identified with digestion, the Fischer344 rMSCs were induced to differentiate by tanshinone IIA, which was locally injected into the striate cortex (18 area) of rats in the experimental group, and the rats in the control group were injected by L-DMEM basic culture media (without serum) of the same volume to the corresponding brain area.In the sham-operated group, only muscle and vessel of neck were separated.② At 2 and 8 weeks after the transplantation,the rats were given the screen test,prehensile-traction test,balance beam test and Morris water-maze test. ③ The survival and distribution of the induced cells in corresponding brain area were observed with Nissl stained with toluidine blue and hematoxylin and eosin (HE) staining in the groups.MAIN OUTCOME MEASURES:① Results of the behavioral tests (time of the Morris water-maze test screen test, prehensile-traction test, balance beam test); ② Survival and distribution of the induced cells.RESULTS: All the 24 rats were involved in the analysis of results. ① Two weeks after transplantation, rats with neuron-like cells grafts in the experimental group had significant improvement on their general muscle strength than those in the control group [screen test: (9.4±1.7), (4.7±1.0) s, P ＜ 0.01]; forelimb muscle strength [prehensile-traction test: (7.6±1.4), (5.2±1.2) s,P ＜ 0.01], ability to keep balance [balance beam test: (7.9±0.74), (6.1 ±0.91) s, P ＜ 0.01] and abilities of leing and memory [latency to find the platform:(35.8±5.9), (117.5±11.6) s, P ＜ 0.01; distance: (623.1 ±43.4), (1 902.3±98.6) cm, P ＜ 0.01] as compared with those in the control group.The functional performances in the experimental group at 8 weeks were better than those at two weeks, which were still obviously different from those in the sham-operated group (P ＜ 0.05). ② The HE and Nissl stained brain tissue section showed that there was nerve cell proliferation at the infarcted cortex in the experiment group, the density was higher than that in the control group, plenty of aggregative or scattered cells could be observed at the site where needle was inserted for transplantation, the cells migrated directively towards the area around them, the cerebral vascular walls were wrapped by plenty of cells;In the control group, most of the cortices were destroyed, karyopyknosis and necrosis of neurons were observed, normal nervous tissue structure disappeared induced by edema, only some nerve fibers and glial cells remained.CONCLUSION: The rMSCs transplantation can obviously enhance the motor function and the abilities of leing and memory in rat models of cerebral infarction.