Effects Of Treadmill Exercise On The Expression Of RGMa,GAP-43 And The Neural Function After Middle Cerebral Artery Occlusion/Reperfusion In Rats.

Objective Ischemic stroke threatens human health and life safety , because it has high morbidity, high disability, high mortality. The related problem refering neurological rehabilitation has received extensive attention, then it becomes the focus of the research. Regeneration of impaired axons is mighty difficult in adult central nervous systerm(CNS), because there are plenty of neurite growth inhibitors in it,such as myelin associated glycoprotein(MAG), oligodendrocyte-myelin glycoprotein(OMgp), and so on. Researches found that axon impaired by mechanical factors or deprivation of oxygen and blood, could regrow and promote impaired functional recovery after some special intervention[1,2].Repulsive guidance molecule a (RGMa) is a axonal guidance molecule, a new discoverable neurite growth inhibitors.A research found that intrathecal administration of a neutralizing antibody to block function of RGMa could significantly enhance axonal growth and promote neurological function recovery after spinal cord injury in rats[3].As a kind of intrinsic gorwth associated factor, growth associated protein-43(GAP-43) plays an important role in the development and the reconstruction of neuroplasticity in the central nervous systerm[4,5].As we all know that exercise could promote the impaired function to recovery partly.So we planned to investagate the effects of treadmill exercise on the expression of RGMa,GAP-43 and the neural function after middle cerebral artery occlusion(MCAo)/reperfusion in rats.Then we further to investigate the relationship between treadmill exercise and neurite growth inhibitors. It can offer a theory evidence for interpretation on the mechanism of rehabilitation with physical exercise.It also provided an important clue for the rehabilitation of clinical cerebral ischemia.Methods 1. 120 healthy Sprague Dawley rats were randomly divided into normal group, sham group, model(MCAo/reperfusion) 7d,14d and 28d group. Each of above group was randomly divided into non-exercise, exercise of low-intensity, moderate-intensity and high-intensity group. And bebavior tests were used to evaluate neurological function recovery of the rats after focal cerebral ischemia.Reverse transcription quantitative polymerase chain reaction (RT-qPCR) was used to determine the changes of RGMa mRNA expression in the ischemic side of cortex and hippocampus. And immunohistochemistry was adopted to detect the expression of RGMa protein in the ischemic side of cortex and hippocampus.2.60 healthy adult Sprague Dawley(SD) rats were randomly divided into 5 groups, including normal group, sham group, model(MCAo/reperfusion) 7d,14d and 28d group.There were 12 rats in each group. Each group was randomly divided into non-exercise, exercise of low-intensity, moderate-intensity and high-intensity group.The protein expression of GAP-43 in the cortex and hippocampus of ischemic side was detected by immunohistochemistry.Results 1. There were drastic increment of expression of RGMa mRNA in ischemic cortex and hippocampus in each non-exercise MCAo group, compared with each normal and sham non-exercise group (p<0.05).As days passed, there was down-regulation of RGMa mRNA in each non-exercise MCAo group. There was no significant differences between each low-intensity exercise MCAo group and corresponding to each non-exercise MCAo group(P<0.05).There was down-regulation of it in each moderate-intensity treadmill exercise MCAo group(p<0.05), except at 7d(p>0.05), compared with each non-exercise MCAo group. But there was up-regulation in high-intensity treadmill exercise MCAo group, compared with each non-exercise MCAo group (p<0.05).2. There was significant reduction of the expression of RGMa protein in the ischemic cortex and hippocampus in each moderate-exercise MCAo group, compared with each non-exercise MCAo group in corresponding(p<0.05),except at 7d.There was no significant differences between moderate-intensity treadmill exercise 7d MCAO group and non-exercise 7d MCAo group(p>0.05).But the opposite result was got in high-intensity treadmill exercise MCAo group (p<0.05).There was no significant differences in low-intensity treadmill exercise MCAo group for the expression of protein RGMa, compared with non-exercise MCAo group(p>0.05). Neurological deficit scores test showed moderate-intensity treadmill exercise improved neurological function(p<0.05).The low-intensity treadmill exercise could not promote recovery of neural function compared to non-exercise MCAo group(p>0.05).But the high-intensity treadmill exercise may impair neural function after focal cerebral ischemia injury compared to non-exercise group(p<0.05).3. The expression of protein GAP-43 was the highest in the ischemic cortex and hippocampus in 7d MCAo non-exercise group. There was no significant differences between each non-exercise MCAo group and each low-intensity treadmill exercise MCAo group(p>0.05).The expression of GAP-43 was up-regulated in moderate-intensity treadmill exercise MCAo group, except at 7d(p>0.05), compared with each non-exercise MCAo group(p<0.05).But the opposite result was got in high-intensity treadmill exercise MCAo group (p<0.05).Conclusions Moderate-interate treadmill exercise decreased the expression of RGMa in the ischemic cortex and hippocampus of MCAo rats. What's more, moderate-intensity treadmill exercise also increased the expression of GAP-43 in the peri-ischemia cortex and hippocampus after ischemia stroke. Moderate-interate treadmill exercise can promote the recovery of neural function, which maybe related to the expression changes of GAP-43, RGMa, related to the regeneration of impaired axons in the central nervous systerm.