immunohistochemical study of spinal motor neurons following sciatic nerve repair in adult rat

introduction: epineural suture and autologous graft are two routine techniques in peripheral nerve surgery. however, their efficiency can be highly limited depending on the type of lesion and the gap between two nerve stumps and because of deficient proper nerve donors. so much interest has been focused on the development of alternative instruments for bridging the nerve gaps. in the present study, we have used charged polyvinelidene fluoride (pvdf) tube filled with nerve growth factor (ngf) and collagen gel as a substitute for nerve autograft and compared the results with other current surgical techniques. we studied the changes of spinal motoneurons to evaluate the effect of repairing techniques. material and methods: in this study, 30 male wistar rats weighing 200-250 g were divided randomly in five groups: axotomy, epineural suture, autograft, nerve guidance channel, and sham operation. in all experimental groups, the left sciatic nerve was transected at mid-thigh level. the nerve was not repaired in axotomy group. in epineural suture group, it was sutured end-toend. in autograft group, a 10 mm piece of nerve was rotated 180° and sutured again in the nerve gap. finally, in nerve guidance channel group, a piece of pvdf tube containing ngf7s (100 ng/ml) and collagen gel (1.28 mg/ml) was replaced in the gap. after one week, one month, and two months, l4-6 segments of spinal cord were removed and 5 μm paraffin sections were prepared for bax immunohistochemical study. in all groups contralateral spinal cord was used as the control. the proportion of baxpositive apoptotic motoneurons was studied in all groups to evaluate the efficiency of different repairing techniques. results: mean percentage of bax-positive neurons to the total number of motor neurons in left side was analyzed. one way anova showed significant difference after two months. lsd post hoc test showed that mean percentage of bax-positive neurons in axotomized group was significantly higher compared to other surgical groups (p<0.05). the number of apoptotic neurons after one week, one month and two months in each type of surgical approach showed no significant difference between one week and one month and between one month and two months. comparison of motoneuron population in left side (experimental) with right side (control) showed no significant differences after one week, but significant differences were seen (p<0.01) after one month and two months. in sham group, no bax-positive neuron was found after one week, one month, and two months. conclusion: a pvdf tube filled with ngf and collagen gel can be used as a proper substitute for autografts and protect motoneurons following peripheral nerve injury.