Experimental study on gender difference in the recovery of nerve function after spinal cord injury in rats

Objective To explore the difference of the neural function and some reasons in male and female rats after spinal cord injury (SCI).Methods By the striking of the spinal cord at the level of T7 with Allen's device,acute SCI was induced in anesthetized rats.Sixty SCI model rats were divided into 2 groups by gender:group A (male group) and group B (female group),each with 30 SD rats.The changes of superoxide dismutase (SOD),malondialdehyde (MDA) and cell apotosis in the lesion site were observed in 1,2,3,4 and 7 days after SCI.The motor functional changes were evaluated by BBB scale in 1 day and 1,2,3,4 weeks after SCI.And at the same time point,the injuried spinal cord was made into frozen section,histomorphology change was observed by hematoxylin and eosin (HE) staining.Results The motor capacity of hind limb was some obvious recovery in every group in 2-4 w after modeling.The BBB scores were significantly higher in group B (8.25 ±1.658) than in group A (5.58 ±1.443) after 4 w (P＜0.01).The SOD activity was the minimum in both group A [(28.822±2.804) U/ml] and group B [(106.833 ±5.878) U/ml] in 2 d.To 7 d,it were (93.556 ±7.138) U/ml in group A and (106.833 ±5.878) U/ml in group.It was higher in group B than group A in 7 d (P ＜ 0.01).The evel of MDA was no difference in 2 d after SCI modeling.To 3,4 and 7 d,it was (28.822 ±2.804),(25.106 ± 1.911),(15.163 ±3.075) μnol/L in group A,and (24.224 ± 2.627),(18.377 ± 2.416),(10.959 ± 2.780) μmol/L in group A (P ＜ 0.05).The biggest number of apoptotic cells was (187.83 ± 18.30) cell/view in group A and (160.67 ± 8.34) cell/view in group B after 3 d.It was (84.00 ± 10.96) cell/view in group A and (56.00 ± 7.43) cell/view in group B in 7 d.It was less in goup B than in group A in 2,3,4,7 d (P ＜ 0.01).Group B was better than group A in pathological changes of spinal cord injury,incloud inflammatory,cavitation,white matter retained,scar formation.Condusion The recovery of motor capacity of hind limb is better after SCI in female rats than in male rats; the reason may be that there are more estrogen in female rat than in male rat,because estrogens can reduce oxygen free radicals and adip-peroxidation,decrease apoptosis of nerve cell in the injury site of spinal cord. Key words: Spinal cord injury;  Gender difference;  Rat;  Animal experiment