Experimental Study Of Changes Of Schwann Cells Of Proximal Stumps In Transected Sciatic Nerves

The regeneration of peripheral nerve ,which does not occur in isolation,is the process of outgrowth of axon from the proximal stump to distal one.As a general tissue response to injury,local cells,infiltrating cells and extracellular matrix are all involved. Schwann cell(SC) which includes bionomics such as proliferation,migration,excreting many types of active masses is a kind of characteristic glial cell in peripheral nerve system(PNS). In microenvironment for regeneration, SC can regulate myelinization,myelination and formation of extracellular matrix by contacting axon.When peripheral nerve injuries, SC which is very important for regeneration of peripheral nerve proliferates and cleans degeneration product with macrophage. The study of environment for regeneration is focused on SC. After peripheral nerve injuries, changes of quantity,morphology and bionomics of SC can directly effect enviroment for regeneration.Proximal stumps of transected nerves have had less attention. Especially for quantity,morphology and bionomics of SC of proximal stump after peripheral nerve injury. We designed experiment in which changes of pathology,immunohistochemistry and indirect immunofluorescene of proximal stump of transected peripheral nerve to discuss relationship between environment for regeneration and peripheral nerve regeneration. Thus we can provide theoretical basis for applying SC in clinic.We studied changes of pathology of proximal stump of transected peripheral nerve, we found that transection of nerve fibers was a little irregular and swollen than normal ones at 1 day, inflammatory cells infiltrated and myelin sheath began to deform at 2 day, myelin sheath dissolved and degenerated, axons ruptured and dissolved with obvious cell proliferation at 3~7 day, above-mentioned conditions were aggravated obviously, especially for gross fibers at 14 day, after 28 day, regenerative thinner fibers with fibroblast cell proliferation were observed, some pettyy fibers were considered like-unmyelinated fibers. We concluded that the proximal stump degenerated at limited circumscription associated with extent of injury and diameter of nerve fibers unlike distal one which degenerated in total length because of connection with neuron body, there were both degeneration and regeneration.There is S-100 protein in peripheral nerves. The reduction of quantity of SC and content of S-100 protein led to decrease of S-100, not degeneration of axon. We studied changes of S-100 protein of proximal stump of transected peripheral nerve, we found that expression of S-100 attenuated at 1 day, obviously at 3 day, almost no expression at 7 day, increased a little at 14 day, as was considered with regeneration of peripheral nerve, S-100 was expressed invariably after 21 day. In normal situation, S-100 distributes conditionedly in peripheral nerves, there is dynamic balance among synthesis,excretion and transport, destruction of balance induces decrease of S-100 necessarily.We concluded that there was S-100 in cytoplasm and axilemma of mature SC, decrease of S-100 proved that mature SC decreased , as there was morphological changes of SC (from mature to immature) associated with disruption of signals after rupture of axons.GFAP which was important reconstituent of frame protein in cells was intimately correlated with early development of nerve system. We found that expression of GFAP increased at 1day, increased obviously at 3 day and grew at most at 5~7 day, after 14day, expression decreased and was tendent tobe constant, as was related to apotosis. The phenotypic changes of proximal stumps because of interruption of signals proved that MSC and NMSC retro-differentiated, especially for MSC, there was plasticity of phenotype of SC, different phenotypes of SC changed into each other in some condition. We also found that volume and quantity of nucelus of SC increased obviously, at most at 5~7 day, as proved that SC proliferated with active functions, all these changes provided that cellular basis for regeneration of peripheral nerve.There was changes of permebility in axolemma after peripheral nerve injury, as led to inflow of Ca2+ and activated neuroprotein enzyme to breakdown neurofilament. We found that expression of NF-200 of proximal stumps decreased gradully, increased after 7 day, at most at 14 day. We concluded that degeneration of axons led to decrease of NF-200 after peripheral nerve injury, expression increased with regeneration of peripheral nerves because ability of neuron synthetizing NF-200 increased.We studied indirect immunofluorescence of Anti-S-100 and Anti-GFAP﹑Anti-NF-200 and Anti-GFAP to confirm phenotypic changes of SC. There was almost no co-expression of different protein normally, there was co-expression in Anti-S-100 and Anti-GFAP﹑Anti-NF-200 and Anti-GFAP after peripheral nerve injury.We concluded that NMSC was expressed in MSC, as proved that MSC turned into NMSC.As above-mentioned, we concluded that the proximal stump degenerated at limited circumscription associated with extent of injury and diameter of nerve fibers unlike distal one which degenerated in total length because of connection with neuron body, there were both degeneration and regeneration.There was morphological changes of SC of proximal stumps(from mature to immature) after peripheral nerve injury, immature SC increased, MSC and NMSC retro-differentiated, especially for MSC. Volume and quantity of nucelus of SC increased obviously, at most at 5~7 day, as proved that SC proliferated with active functions, all these changes provided that cellular basis for regeneration of peripheral nerve.We concluded that the changes of proximal stumps provided not only eligible microenviroment for regeneration and cellular basis, but also therotical basis for plasticity of regeneration of peripheral nerve and functional regeneration of different qualitative nerves...