Stem cell membrane transplantation for treatment of spinal cord injury

BACKGROUND: Adult stem cell (ASC) transplantation is commonly used presently. However, the present transplanted method could result in injury again, and efficiency of neuron differentiation in vivo was low. OBJECTIVE: Based on the previous study of neuron precursor cell collection by step-by-step induction and differentiation, to design stem cell membrane, and to observe functional recovery after attachment transplantation for treating spinal cord injury. DESIGN, TIME AND SETTING: The randomized, controlled, animal study was performed at the Experimental Center, Medical College, Zhengzhou University from May to October 2008. MATERIALS: Membrane-like matrix was established by enzyme and chemical method. Amnion-derived mesenchymal stem cells (ADMSCs) were isolated, cultured and amplified, and then labeled by BrdU. Cells at 1×10¹¹/L were used for further use. The remaining cells were induced and prepared into stem cell membrane. METHODS: Totally 88 healthy adult male Sprague Dawley rats, weighing 220-250 g, were used to create acute spinal cord injury models by self-designed shape-suitable impinge. 6 hours after modeling, rats was equally and randomly divided into 4 groups. Rats in the stem cell membrane group received laminectomy at T₁₁. The dura mater was opened to fully expose damaged spinal cord and to stop bleeding. The stem cell membrane was covered on the damaged spinal cord, which was then fixed on the dura mater under a microscope. Muscle and skin were sutured. In the stem cell transplantation group, 5 μ L cell suspension (1×10¹¹/L) was infused into the damaged spinal cord. The following procedures were the same as above mentioned. In the matrix group, membrane-like matrix was coated on the damaged spinal cord. The following procedures were the same as above mentioned. Rats in the control group only underwent laminectomy, and the dura mater was opened. MAIN OUTCOME MEASURES: One day postinjury and weekly thereafter for 10 weeks, behavioral analysis was performed by Basso-Beattie-Bresnahan (BBB) scale, the ability to maintain body position on an inclined plane. 2, 4, 6 week postinjury, cell survival and morphology were observed. Immunocytochemistry was performed employing the following antibodies: glial fibrillary acidic protein (GFAP), synaptophysin and neurone specific enolase (NSE). RESULTS: BBB gradually stabilized from 4 weeks after injury in each group. BBB scoring over 12 points was important recovery index at 10 weeks, and 100% in the stem cell membrane group, 33% in the stem cell transplantation group, 17% in the matrix group, and 17% in the control group. During inclined plane test, when facing upwards, the angle in the stem cell membrane group was significantly improved at 10 weeks compared with that at 4 weeks (P = 0.027), and no significant difference in BBB score was detected at the same time point in the same group (P = 0.286). BrdU-positive cells did not show statistically significant different between the stem cell membrane and stem cell transplantation groups (P=0.089). The cells was neuron-like in the stem cell membrane group and microglia-like in the stem cell transplantation group. Synaptophysin, GFAP expression enhanced and NSE expression decreased gradually in each group. Synaptophysin and NSE expression was higher, but GFAP expression was lower in the stem cell membrane group than other groups at each interval (P < 0.05). GFAP expression was gradually increased in the stem cell membrane, matrix and control groups at various time points (P < 0.05). CONCLUSION: Neuronic precursor cells on stem cell membrane could integrate into injured cord and survive for a long time, and have a property to differentiate into neuron high-efficiency in vivo. Stem cell membrane transplantation on the injured cord contributes to synaptophysin expression, neural network reconstruction and neural functional recovery in the damaged cord. Stem cell membrane transplantation can show better functional recovery compared with stem cell transplantation alone.