OBJECTIVE:To investigate the influences of Schwann cells-alginic acid sodium hydrogel transplantation on cellular apoptosis,Bcl-2 expression,and lower limb locomotor function in a rat model of spinal cord injury.METHODS:SD rats of clean grade were randomly divided into 4 groups:normal control,simple injury,Schwann cells,and Schwann cells-alginic acid sodium hydrogel.Spinal cord transaction model was established in the latter 3 groups.Gelatin sponge blocks containing Schwann cells suspension were transplanted into the Schwann cells group.Schwann cells-alginic acid sodium hydrogel was transplanted into Schwann cells-alginic acid sodium hydrogel group.No treatments were performed in the normal control and simple injury groups.At 12 hours,1,3,7,and 21 days after surgery,animals were assessed using Basso,Beattie and Bresnahan (BBB) locomotor rating scale and were sacrificed.The spinal cord-transected segments were taken to prepare paraffin sections for TUNEL and Bcl-2 staining to quantitate apoptotic cells and Bcl-2 cells in the injured spinal cord and to investigate their distributions.RESULTS:A small number of slightly stained Bcl-2 positive cells were observed in the normal control group.In the simple injury group,Bcl-2 immunoreactive cells peaked at 3 days after surgery,and the expression level was close to normal level at 14 days.Following Schwann cells-alginic acid sodium hydrogel transplantation,Bcl-2 immunoreactive cells in the spinal cord-transected segments were significantly increased till 7 days (P＜0.05) and remained this level for more than 14 days.In the simple injury group,apoptotic cells were most as compared with the remaining 3 groups,and peaked at 1 and 7 days following spinal cord injury,and they were mostly distributed in the white matter.BBB scores were significantly higher in the Schwann cells-alginic acid sodium hydrogel transplantation group than in the simple injury and Schwann cells groups (P＜0.05).CONCLUSION:Schwann cells-alginic acid sodium hydrogel transplantation could inhibit cellular apoptosis and enhance Bcl-2 expression in the spinal cord-transected segments,and thereby promote the recovery of locomotor function after spinal cord injury but did not reach normal levels.

BACKGROUND: Schwann cells play an important role in axonal growth and myelin sheath formation of the peripheral nerve. Whether Schwann cells play the same role in the spinal cord had attracted considerable attention. Microencapsulation technology as an effective immune isolation technique can effectively keep Schwann cell activity to play the repair effect of Schwann cell in the spinal cord.OBJECTIVE: To observe the changes of myelin sheath in the injured transection of rats after transplantation of the alginic acid microencapsulated Schwann cells.DESIGN, TIME AND SETTING: The randomized controlled animal experiment was performed at the Basic Medical School of Nanchang University from March 2005 to February 2008.MATERIALS: Sciatic nerve trunk was obtained from adult rabbits to harvest Schwann cells in vitro using repeatedly differential velocity adherent technique, and to prepare Schwann cell suspension and microencapsulated Schwann cell suspension.METHODS: A total of 146 adult Sprague Dawley rats were used to establish models of right hemi-transection damage at T_(10) level and randomly assigned to four groups: simple injury group (n=44), cell transplantation group (n=44), microencapsulated cell transplantation group (n=44) and normal control group (n=14). At 1, 3, 7,14 and 28 days following surgery, 8 rats were selected from each group at each time point (2 from the normal control group) for perfusion and fixation. Spinal cord tissue was collected to make paraffin section, and then subjected to hematoxylin-eosin staining and Loyez myelin staining. In addition, 2 rats were selected from each group at 2 and 8 weeks. The spinal cord tissue was fixed, embedded in Epon816, stained using uranyl acetate and aluminum citrate, and then observed using an electron microscope.MAIN OUTCOME MEASURES: Neuron number and survival were observed surrounding the damaged region. Structural changes in the myelin sheath from spinal cord white substance at the damage site were measured.RESULTS: At 1 and 3 days following spinal cord injury, spinal neurons were degenerated and necrotic at damaged site, with reduced number of myelin sheath, loose structure, but above-mentioned was rare in the cell transplantation and microencapsulated cell transplantation groups. At 7 days, the reduced number of myelin sheath, with damaged structure was seen. The microencapsulated cell transplantation group was light. At 14 days, number of neurons was increased, with increased cell body, especially in the microencapsulated cell transplantation group. At 28 days, neurons gradually recovered, myelin sheath was gradually complete, with increased number in the microencapsulated cell transplantation group. There were significant differences compared with the simple injury and cell transplantation groups (P < 0.01). At 8 weeks, abundant myelin sheath was repaired, with new myelin sheath in the microencapsulated cell transplantation group.CONCLUSION: Microcapsule has immune isolation effects. Microencapsulated rabbit Schwann cells can promote the repair of rat spinal cord neurons and axonal myelinization.