| Background and objectiveBrachial plexus injury(BPI) was a disease of high incidence and always caused afunction of upper limb, especially the injury of the spinal nerve roots which resulted in considerable motoneurons'loss. Although the peripheral nerve had powerful regenerative capacity following injuries, the functional recovery was deficient. The pathway of the regenerative axons was crucial to the functional recovery after injuries. Within the research of femoral nerve model, it was concluded that the regenerative motor axons always trended to reinnervate motor branch preferentially after injuries, that was preferential motor reinnervation (PMR). Our objective was to research: (1) the survival of spinal motoneurons, the pathway of regenerative axons and the recovery of motor function following the injury of the spinal nerve roots which constituted the brachial plexus. (2) the pathway of regenerative axons and the expression of heat shock protein 70 (Hsp70), heat shock protein 27 (Hsp27) and neuronal nitric oxide synthase (nNOS) in the spinal motoneurons following injuries of distal brachial plexus.Materials and methods1 Experimental animals: adult male SD rats.2 Fluorescence tracing: fluorogold labled regenerative motoneurons retrogradely.3 Neutral red stain: counterstain, to number the regenerative motoneurons.4 grooming test: to observe locomotion of experimental anterior limb of the SD rats, and in order to judge the recovery of motor function after BPI.5 Immunohistochemistry: SABC method was performed in the study. The expression of Hsp70, Hsp27 and nNOS protein in the spinal cord was tested.Results1 Neutral red counterstainConsiderable spinal motoneurons died following different injuries of the spinal nerve roots. The number of survival motoneurons after cut, crush and avulsion was 1126±25, 1005±89, 881±76, respectively. There was disparity among these three groups (P<0.01). Comparison between these three groups and the control group(1900±39) was significant (P<0.01). In the crush and cut groups, the number of survival motoneurons of C6(494±50, 506±36) was much more than that of C5(311±31, 299±21) and C7(200±49, 322±34) (P<0.01). In the avulsion group, the number of survival motoneurons of C6(340±53) was similar to that of C5(293±34) , but much more than that of C7(248±24) (P<0.01). In the control group, the number of survival motoneurons of C7 (759±36) was the most.2 Fluorescence trackingWhen injuried with the roots, the number of regenerative motoneurons reinnervated sensory branch of the four groups was all 10 to 20, but the number of regenerative motoneurons reinnervated motor branch after crush, avulsion and cut was 355±75, 300±51, 272±48, respectively. In the control group, the number was 611±40. Significant differences were found among these four groups (P<0.01). Of all the labled motoneurons, the percentage of C6 segment in the four groups was all larger than 50%, and comparison of the percentage of C5 and C7 segment between the three injured groups and the control group was significant(P<0.01). When injuried with the distal brachial plexus, the number of regenerative motoneurons reinnervated motor branch after crush and cut was 533±45,609±21, respectively, while the number of regenerative motoneurons reinnervated sensory branch was 18±5,162±45, respectively. The regenerative motoneurons reinnervated motor branch were much more than that sensory branch after these two different injuries(P<0.01).3 The recovery of motor functionEach animal had functional recovery with differential extent. When injury with the roots, the functional grade in the crush group(3.42) was much higher than the avulsion(1.75) and cut(1.75) group (P<0.01). But there was no dofference between the later two groups (P>0.05). In the control group, the functional grade was 5. Comparison between the three experimental groups and the control group was significant(P<0.01). When injuried with distal brachial plexus, the functional recovery after crush or cut was all significant. Moreover, the percentage of above grading 4 in the crush group(75%)was better than the cut group(50%)(P<0.01). 4 ImmunohistochemistryCompared to the control group, the expression of all the three protains in the motoneurons of experimental side in the two experimental groups was incressed significantly. The number of the Hsp70 and Hsp27 positive motoneurons in the cut group(143±7,145±6)was more than the crush group(129±5,137±3)(P<0.01), but the number of nNOS positive motoneurons in the crush group(103±4)was more than the cut group(67±6)(P<0.01).Conclusion:(1) Regenerative axons of spinal motoneurons reinnervate the motor branch after BPI. The site and the nature of the injury has no effect on the pathway of regenerative axons.(2) Different injuries upon the roots has different impact upon the survival, but no impact on the regeneration of spinal motoneurons.(3) Reestablishment of nerve promotes survival of the spinal motoneurons after injuries upon the roots.(4) Following injuries upon the roots, the regenerative neurons of the musculocutaneous nerve predominantly origin from C6. C7 participates in the reestablishmental process, too.(5) The extent of motor functional recovery is different after different injuries upon the roots.(6) The expression of Hsp70, Hsp27 and nNOS protein in the spinal motoneurons following different injuries with distal brachial plexus is different, and these three proteins may promote the survival and regeneration of the spinal motoneurons following injuries. |
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