| [Objective] Inflammation, tumor and trauma are the main causes of spinal cord injury(SCI) which accompany with degeneration or necrosis of spinal cord neurons(SCNs), SCI is a serious disability injury that could lead to the related sensory, motor, sphincter and autonomic dysfunction of the injured spinal cord. In our country, the patients with paraplegia caused by SCI showed an increasing trend year by year. It is a heavy economic burden to the society and the family, it also bring long-term pressure to body and mind of patiets suffered from SCI. With the in-depth study of SCI, emphasis on SCI research would be how to protect SCNs in early stage of injury, how to delay the programmed death of SCNs and decrease the number of apoptosis cells. Recently studies showed that the level of varieties of micro RNA(mi RNA) have changed before and after SCI. These mi RNA are involved in the regulation of gene expression after neuronal injury, correspondingly, it deeply participate in a series of pathophysiological processes, such as inflammation, glial scar formation and neuronal necrosis after SCI. According to the literature and the results of our preliminary study, the expression of mi RNA-93 was increased after SCI, meanwhile, the increased expression of mi RNA-93 promoted the growth of SCNs processes. Therefore, we look forward to further explore the role of mi RNA-93 in SCNs, the impact of the growth of SCI processes and the mechanism of mi RNA-93 regulation of SCNs growth.[Methods] First of all, we have prepared a rat model of SCI, Real-time PCR was used to detect the expression changes of a series of micro RNA at different time points after SCI, according to the experimental results, the micro RNA molecules with different expression changes were selected to do the in vitro functional test. Then we observed the effect of micro RNA molecule on neurite outgrowth of SCNs in rat in vitro. The results showed that the overexpression of mi RNA-93 significantly promoted the growth of SCNs processes. Based on the above experimental results, we used the SCI model in vivo and in vitro, to observe the effects of mi RNA-93 on the growth and regeneration of SCNs, the effects of the proliferation and activation of astrocytes and microglia, the effects of demylination. After we clarifed the related function of mi RNA-93 after SCI, and dual-luciferase reporter assay verifed the target proteins of mi RNA-93, We used western-blot experiments to explore the related function and mechanism of mi RNA-93 in signaling pathway which regulate the growth of SCNs.[Results](1) The expression of mi RNA-93 was increased after spinal cord injury in rats;(2) Overexpression of mi RNA-93 in cultured rat SCNs promoted the growth of SCNs processes;(3) Overexpression of mi RNA-93 increased the number of tubulin-positive neurons, inhibited the proliferation of activation of GFAP-positive astrocytes, decreased the number of actived Iba-1-positive microglias and protected the oligodendrocytes in the rat SCI model;(4) Overexpression of mi RNA-93 inhibits the expression of protein Eph A4 associated with the growth and development of neurons in cultured rat SCNs, the data of dual-luciferase reporter assay showed that through binding to the Eph A4 3 ’ untranslated region(3’ UTR), mi RNA-93 could inhibit the expression of Eph A4 protein;(5) Mi RNA-93 promotes neurite outgrowth of neurons directly acts on Eph A4 to regulate the activity of p-ephexin and Rho A active.[Conclusions] SCI induced high expression of mi RNA-93 in spinal cord, the increased mi RNA-93 was able to inhibit the expression of Eph A4 through the 3 ’UTR region of Eph A4, thereby promoting the growth of SCNs in rats. At the same time, mi RNA-93 can protect the SCNs from secondary damage by inhibiting the activation of astrocytes and microglia, protecting the integrity of the myelin sheath and so on. Mi RNA-93 regulated the growth and regeneration of spinal cord neurons by modulating the Eph A4-ephexin-Rho A signaling pathway. |
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