| Axotomy resulting either from direct axonal transection or from indirect tissue reactions to injury is an important consequence of clinical conditions such as trauma, compression and ischemia. Experimental studies on the neural responses to axotomy have a long history and were among the first attempts to investigate at the cellular level the effects of injury to the nervous system. Retrograde changes in neuronal cell bodies after axotomy were first recognized over 100 years ago (Nissl, 1892), and many of the basic degenerative and regenerative responses of neuronal peikarya and their axons to axotomy were well documented at the light microscopic level by the early part of this century. Neurons in the central and peripheral nervous system show various responses to axotomy, ranging from cell death or severe atrophy without axon regeneration to recovery with axon. For example, motor neurons survive axtomy and regenerate, Purkinje cells survive but do not regenerate, and retinal ganglion cells die. The cellular and molecular mechanisms that underlie these responses and determine these differences are not well understood. Current hypotheses regarding signals that mediate the neuronal response to axotomy include both the loss and the introduction of large molecules derived from muscle or schwann cell that signal via retrograde transport along the axon to the perikaryon. Molecules that derive from glial cells around neuronal perikarya, and retrograde signals along the axon mediated by the influx of ions through membrane damage at the site of axonal injury. Moreover, motoneurons can secrete some molecules by it self. When facial nerve was cutted off, Schwann cell, motoneuron and glia cell response to injury, such as becoming proliferates and changing of expression of gene promotes the regeneration of facial nerve occurred. Recent study show that neurotrophic factor have important roles in it.The facial nerve was cut off and suture. Research show that are ideal animal model of axotomy of facial nerve. With the analysis of immunohistochemstry, in situ hybridization, reverse transcript polymerase chain reaction (RT-PCR) to investigate the relation of gene and nerve regeneration. The present study include the followings:1. The expression of injury/regeneration-relation gene in the axotomy of facialnerveA new model of facial nerve in rat was established on the bases of previous experiments. We detected the expression of PMP-22, GAP-43, Bcl-2, HSP-70, c-fos with aid of in situ hybridization in facial nucleus and CNTF, CNTFR,GDNF, GDNFR with immunohistochemstry in nerve axon. The result shows that the level is vary great in different times, c-fos participate in gene transcript level, HSP-70 is related to nerve injury response, Bcl-2 have the role of anti-apoptosis, PMP-22 take part in axon remyelinization and GAP-43 is relative to axon re generation. The different expression of neurotrophic factor after injury verify that in different type nerve, different neurotrophic factor have different roles. For example, the expression of CNTF is rapid decrease after injury, wherease, posive signal of GDNF upregulate during regeneration.2. The role of TGF- ft 1 and rhBMP-2 in facial nerve regenerationTo elucidate the effects of TGF- P 1 and BMPs in the nerve regeneration, the levels of TGF- {3 1,2,3 and BMP-2,4,6,7 mRNA were detected using in situ hybridization and image analysis. The results show that some member of TGF- P superfamily such as BMP-2, 7 and TGF- & act as indirect neurotrophic factor in facial nerve injury. Therefore, we inject the TGF- 3 1 (400ng/ml)and rhBMP-2(200ng/ml) to the facial nerve adjacent region. We found TGF- 3 1 and rhBMP-2 could promote the nerve regeneration in different extent. TGF- 0 1 could increase the expression of CNTF and CNTFR, it may interacct with other neurotrophic factors to promote facial nerve outgrow.3. Construction of full length small GTP-binding protein(TClO) expressionplasmidThe full-length cDNA containing small GTP-binding protein (TC10) was deri... |
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