| Objective Transplantation of peripheral nerve or Schwann cells can enhance neuronal survival,axonal regeneration and functional recovery after spinal cord injury (SCI). Barium-alginate microcapsules, which develop an immunoisolation effect, make the xenotransplantation be possible. Here, the pretreated sciatic nerve tissue/cells from rabbit were microencapsulated and transplanted into the injured site of spinal cord in rats. Then the effects of transplantation of microencapsulated sciatic nerve tissue/cells from rabbits on the changes of Calcitonin Gene-related Peptide (CGRP) expression and the regeneration of Motor Endplate (MEP) in adult rats with hemisected spinal cord were observed.And the possible mechanism of repair that the transplantation of the microencapsulated xeno-sciatic nerve tissue/cells treated SCI and the relationship between CGRP expression and the regeneration of MEP were discussed.Method Experiments were performed in 8 adult rabbits and 80 adult Sprague-Dawley (SD) rats of either sex, weighing 3200-3600 g and 200-250 g, respectively. Then all of the rats were randomly divided into four groups: Group A (transplantation of microencapsulated sciatic nerve tissue/cells, n=24), Group B (transplantation of tissue/cells suspension, n=24), Group C (single injury control, n=24), Group D (sham control, n=8). After dividing, BBB score was enforced on right hindlimb of rats. Bilateral sciatic nerves pretreated from rabbits were dissected under sterile conditions and made into nerve tissue/cells suspension. Following centrifugation at a low speed, the tissue/cells were mixed with 1.5% sodium alginate solution, which was then extruded into 20mmol/L barium chloride solution by using a droplet generation device, forming microencapsulated sciatic nerve tissue/cells suspension. Group A, B and C were performed a right hemisection injury of spinal cord at T10 level, where were transplanted with the gelatin sponge sticking 10μl microencapsulated nerve tissue/cells suspension, the gelatin sponge sticking 10μl tissue/cells suspension and the gelatin sponge, respectively. Group D was only removed the vertebrae, not injured the spinal cord of and implanted. At 1w, 2w, 4w, 8w after SCI, six rats of each group (two rats in Group D) were anesthetized and perfused transcardially with 4% paraformaldehyde (pH7.4), following BBB score on right hindlimb. The tissue of 8mm spinal cord below the lesion site and corresponding segment of sham group were taken out. After the tissues got were performed the paraffin sections, which were dealed with Hematoxylin-eosin (HE) staining and anti-CGRP immunohistochemistry. In addition, the gastrocnemius of right hindlimb were extracted and then were carried out HE staining and auric chloride staining of MEP.Result The number of CGRP-positive cells in the ventral horn of right spinal cord in rats reduced remarkably in each group after SCI, but it gradually recovered to a different extent 1w later.The difference of the number of CGRP-positive cells between Group A and B was not remarkable, but both of them existed the distinction to compare with Group C (P <0.05). At 2w, 4w, 8w after SCI, comparing to Group B and C, the number of CGRP-positive cells of Group A increased obviously (P <0.01) , which was less than the normal level. while the variance between Group B and C was no sense (P >0.05). Under the observation of light microscopy, the muscle fiber of sham group arrayed orderly, the volume of normal MEP was intact, showing a elliptical or oval shape. The terminals of axon formed many branches, winding round muscle fiber. And many endplate nuclei could be seen. At the first 2w after SCI, the difference of MEP in the pigmentation and number was not significant among every group. At 4w, the MEP along the muscle fiber started to degenerate, its pigmentation grew weak, the branches of axonal terminals decreased and the nuclei of endplate reduced. Comparing to Group B and C, the extent of degeneration in Group A was very faint (P <0.05). At 8w, the MEP of Group B and C degenerated apparently, taking on a big blank area in staining;its number reduced, even disappeared, showing obscure profile. But Group A changed weakly and the difference was notable to compare to Group B and C, displaying the trend of regeneration. BBB score of locomotive function of sham control was normal at every time, while that of other groups was also normal before surgery, but it was low and no difference among every group at 1w after SCI. After that, it was gradually ascending. The comparison between Group A and Group B or C existed the difference at 2w (P <0.05). The score of Group A was significantly superior to that of Group B and C at 4w and 8w, whose difference was remarkable (P <0.01), but it didn't reach the normal level. The locomotive function of right hindlimbs in rats got recovered to a greater or less extent, but Group A was the best one.Conclusion The xenotransplantation of microencapsulated sciatic nerve tissue/cells can improve the recovery of injured neuron, promote the regeneration of MEP and enhance CGRP expression;The changes of CGRP expression in ventral horn of spinal cord are in parallel with the MEP remodeling.
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