Sciatic Nerve Injury And Regeneration Of Neurons Of Gap-43 Mrna In Expression And Protein Synthesis

A study of the expression of GAP-43 mRNA and protein in ratneurons during sciatic nerve lesion and regenerationAbstractObjective:The main objective of this experiment is to provide systmatic dada for further study about the relationship between growthassociated protein(GAP-43) changes and peripheral nerve regeneration.Methods:We set up an adult rat model in that the right sciatic nerve (ScN) was crushed. During the process of nerve regeneration from 1 day to 60 days after injury, the changes of GAP-43 expression and histological examination in dorsal root ganglion (DRG), in ScN and in motor neurons of spinal cord were investigated by methods of in situ hybridization, immunocytochemistry and electron-micoscopy.Results:I .Two days after ScN lesion, GAP-43 mRNA hybridization signals appeared in motor neurons of lumbar spinal cord and primary sensory neurons of DRG. During the nerve regeneration, the number of GAP-43 mRNA positive cells and the intensity of signals increased continuously and peaked at 7 days after axotomy, then went down at 30 days. 2.Four days after nerve crush, GAP-43 up-regulated remarkably in DRG, gray matter of spinal cord and ScN. Interestingly, small-sized neurons in DRG showed much stronger staining than large-sized neurons. 3 .In the histological examination, the axons of SeN were completely axotomized with crush at the injury site. 14 days after operation, there were many new sprouts around the injury site. At 30 days, the new axons had passed through the injury and extended in the distal SeN. The experiment showed that the nerve regeneration is closely related to the changes of GAP-43 mRNA expression and protein transportation. 4.Electronmicroscopy examination: The rough endoplasmic reticulum(RER) was reduced in the motor neurons or migrated to the cellular membrane in the DRG neurons following sciatic nerve injury. New sprouts were found 30 days after the lesion.Conclusion:1. Expression of GAP-43 mRNA was induced by axotomy and associated with the regeneration state of the neurons. 2.High level of GAP-43 regulate intrinsic events in neurons, might have significant effect on promoting axon regeneration. 3.In vivo, both transcriptional and posttranscriptional mechanisms operate synergistically to determine overall levels of GAP-43mRNA. 4.Tbe changes of cell ultrastructure is in accordance with the expression of GAP-43mRNA and synthesis of the protein.