Effect Of Function Trainiring On Rsconstructin Of Corticospinal Tract Projection Pathway And Its Related Mechanism

[Objective]In this study,we established the rat unilateral CST injury model.through observedthe morphology change of uninjuryed CST collateral sprout and axon elongation tocompare the recovery of rat foreleg function in different time point.Analyse the effectof functional training to rat CST plasticity.Detection the GAP-43,Bcl-2,Bax andcaspase-3 protein expression in rat cervical enlargement.Analyse the mechanism ofthe effect of function training to rat plasticity after SCI,provided the experimentalevidence for repair for central nervous system injury.[Methods]In the present study, pyramidotomy model that resulted in rats with unilateralCST injury was used.Used"Single pellet reaching task"and"Horizontal ladder walking"grade themotor function in different time point.Used BDA trace rats CST,and observed the morphology change of CST .Countthe quantity of axon in denervation .Used immunohistochemistry and western blot method detection theBcl-2,Bax,GAP-43 and caspase-3 protein expression in uninjury spinal cord indifferent time point.Used the TUNEL method label apoptotic cells in denervation.[Result]On the basis of rat CST anatomy,used the pyramidotomy injure the unilateralCST to establish a small sector CST injury model which is more reliable andconvenience to research the central nervous system injury.In this experiment we found that within three weeks after injury, Pyt ratsforelimb and forepaw recovered obviously,which is a gradually increase trend .But therecover of Pyt rats is weak than SHAM.That suggests the function of injury rats is notrecover completely.Pyu rats have certain degree recover,but the level is worse than Pyt rats.we found that though the rats are trained after postoperative three weeks ,butthe fuunction is not further recovery,and the level is same to the three weeks timepoint.It suggests that it is a key time window within postoperative three weeks toimprove rats function.We found that the quantity of axon increase obviously within postoperative threeweeks.After three weeks ,the quantity of axon is stable.The functional Pyt ratsquantity of axon is more than Pyu rats ,P＜0.05.Density scanner analysis revealed that spinal cord of SHAM group rats contain alittle GAP-43 protein expression .There are positive expression in Pyt rats denervatespinal cord after pyramidotomy .The expression of GAP-43 protein peaked at twoweeks ,and dropped gradually.The expression of Pyt rats GAP-43 protein afterpyramidotomy four weeks are close to the SHAM group ,and the expression of Pytrats GAP-43 protein increased obviously than Pyu group rats after pyramidotomy oneweek ,two weeks and three weeks. GAP-43 positive product positioning mainlydistributed in the nuclear, the product is pale brown.There are some positive cellexpression in ventral horn of SHAM group rats spinal cord. There are positive cellexpression in Pyt rats denervate spinal cord after pyramidotomy one week.Theexpression of GAP-43 protein positive cell peaked at two weeks ,and droppedgradually.The expression of Pyt rats GAP-43 protein positive cell after pyramidotomyfour weeks are close to the SHAM group. Interestingly, the expression of Pyt ratsGAP-43 protein positive cell increased obviously than Pyu group rats afterpyramidotomy one week ,two weeks and three weeks P＜0.05.Density scanner analysis revealed that spinal cord of SHAM group rats contain alittle Bcl-2 protein expression .There are positive expression in Pyt rats denervatespinal cord after pyramidotomy one week.The expression of Bcl-2 protein droppedgradually.The expression of function training rats Bcl-2 protein after pyramidotomyfour weeks are close to the SHAM group ,and the expression of Pyt rats Bcl-2 proteinincreased obviously than Pyu group rats after pyramidotomy one week ,two weeksand three weeks.Density scanner analysis revealed that spinal cord of SHAM group rats contain alittle Bax protein expression .There are positive expression in Pyt rats denervate spinalcord after pyramidotomy one week.The expression of Bax protein droppedgradually.The expression of function training rats Bax protein after pyramidotomy four weeks are close to the SHAM group ,and the expression of Pyt rats Bax protein isclose to the Pyu group rats after pyramidotomy one week ,two weeks ,three weeks andfour weeks.Density scanner analysis revealed that spinal cord of SHAM group rats contain alittle Cleaved caspase-3 protein expression .There are positive expression in Pyt ratsdenervate spinal cord after pyramidotomy one week.The expression of Cleavedcaspase-3 protein dropped gradually.The expression of Pyt rats Cleaved caspase-3protein after pyramidotomy four weeks are close to the expression of Pyu rats afterpyramidotomy four weeks,and the expression of Pyt rats Cleaved caspase-3 proteinincreased obviously than Pyu group rats after pyramidotomy one week ,two weeksand three weeks.TUNEL labled positive cell positioning distributed in the nucleus,its boundary isclear. Experiment results show that there are only a little apoptotic cells in SHAMgroup rats spinal cord. There are positive apoptotic cell obviously expression in Pytrats after pyramidotomy one week.The Pyt group rats expression of positive cellreduced obviously than Pyu group rats, and dropped gradually.The expression of Pytrats positive cell after pyramidotomy four weeks are close to the Pyu group rats afterpyramidotomy four weeks P＞0.05.[Conclusion]1. Through the morphological observation of the lesion site of pyramidal tractand behavioral assessment of the forelimb and forepaw, it is accurate and reliable toestablish the model of CST injury of rats, by selectively abscinding the pyramidaltract.2. Pyt rats after spinal cord injury, especially some targeted strengtheningpractice, helps the change of central nervous plasticity. Meantime, we also find thatwithin 3 weeks after spinal cord injury is the key time window to improve andamplify the change of neural function plasticity, which may provide the experimentalevidence for the detailed mechanism of cortical spinal cord axon collateralgermination, extending process and neural plasticity in the future study.3. GAP-43 is found to up-regulate expression after spinal cord injury, whoseexpression quantity can be further enhanced by functional training, which willstrengthen the growth and extension of the axon, providing the experimental evidencefor the thesis that functional training may improve the change of the central nervous plasticity.4. Antiapoptotic protein Bcl-2 is found to up-regulated expression after ratcortical spinal cord injury with the help of functional training, which will inhibit theexpression of Cleaved caspase-3, a promoting apoptosis protein. At the same time,apoptosis neurons in the side of lesion from rats of Pyt group, comparing with the Pyugroup, markedly decrease in quantity, which may be one of the mechanismsunderlying that functional training is protective to the central nervous neurons afterSCI.