| Numerous studies now show that anatomical regeration and functional recovery are possible if given proper conditions in injuried CNS, and the axon regeneration is decided by both the instinct properties of neurons and the environment cues abround them. It is becoming increasingly evident that several factors are implicated in the failure of central nervous system neurons to regenerate their axons after injury,these factors are often conceptualized as being either intrinsic or extrinsic.The instrinc factors is pointed to the factors that related to the native gene expression response to the axotomized CNS neuron. The extrinsic ones are ,for example, the factors that related to molecules and/or physical barriers in the CNS environment that inhibit axonal growth in nature. In fact, extrinsic factors such as molecules that influence growth cone motility/ guidance may also induce intrinsic factors such as neuronal gene expression. It was proved that cell body treatment of axotomized neurons with neurotrophins reversed atrophy, increased GAP-43 and Tα-1 tubulin mRNA expression, and promoted axonal regeneration into peripheral nerve grafts. With regarding to the extrinsic factors, the gene expression variety in CNS are qualitatively and/or quantitatively different from that in PNS. Seeking for the key genes associating with regeneration and strengthening their expression in CNS to promote the axonal regeneration and/or neuritis sprouting is an very essential direction in neuroscience research.It has been proved that the CNS of newborn rats have more strengthened regeneration ability compared with the adult rats, and the newborn injured rats accepted fetal spinal cord transplantation have more strengthened regeneration ability compared with the newborn rats without fetal spinal cord transplantation. It is suggested the newborn rats accepted the fetal spinal cord transplantation may express novel genes associating with regeneration that maybe have more stronger regeneration ability. To explore the variational gene expression in cerebral cortical neurons of newborn rats during their stage of regeneration after injury, to grope for the related regeneration mechanism ,and to ask for more efficiently therapeutic methods, our experimentsprepared the spinal cord hemisection model, transplanted the fetal spinal cord immediately after the injury at the local injuried position, constructed the differential expression cDNA library combining the methods of SMART and SSH, analysised the positive clones and BLASTN the EST sequences, in silico cloned one gene from the library and BLASTP the putatively protein, also we considered that the protein may play important roles in axonal regeneration of CNS.The main results and conclusions are as below:1. We constructed the spinal cord hemisection model in newborn 1-2 days rats, transplanted fetal spinal cord into the local injuried place immediately. The model can impersonally reflect the unilateral and cross characteristic in structure and function of CST, it is easy investigated and repeated, with identical causative factors in same environment, it is an ideal model for the study of regeneration after spinal cord injury .2. Using in situ hybridization methods, we observed that the injuried spinal cord express GAP-43 mRNA extensively 5 days after fetal spinal cord transplantation, it implied that the time point of 5 days after injury is proper. Otherwise, the transplantation group express strengthened GAP-43 efficiently compared with the untreated and uninjuried groups, so we concluded that the model we constructed is perfect for our experiment.3. Combining the techniques of SMART with SSH, we constructed the differential expression cDNA library of the cortical neurons of newborn rats 5 days after the spinal cord injury and fetal spinal cord transplantation. After BLASTNing the genes we screened from the library, we found the genes on the highest identities with them are involved in many biological processings, including synthesis of energy and protein, cell prolifer... |
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