Costa Silvia, Planchenault Thierry, Charriere-Bertrand Cecile, Mouchel Yann, Fages Christiane, Juliano Sharon, Lefrançois Thierry, Barlovatz-Meimon Georgia, Tardy Marcienne
INSERM U-421, Medical Faculty, Creteil, France.
Glia. 2002 Feb;37(2):105-13. doi: 10.1002/glia.10015.
The molecular determinants underlying the failure of axons to regenerate in the CNS after injury were studied in an in vitro model of astrogliosis and neuronal coculture. Mechanically lesioned neuron-astrocyte mouse cortical cocultures were treated with antisense glial fibrillary acidic protein (GFAP)-mRNA in order to inhibit the formation of gliofilaments that occurs in response to injury. This inhibition relieves the blockage of neuron migration and neuritic outgrowth observed after lesion, and migrating neurons reappeared, supported by a laminin-labeled extracellular network (permissive conditions). We then questioned the relationship between this permissivity and laminin production. Follow-up studies on the concentration of laminin indicated that, after antisense treatment, the laminin level was increased in the cocultures and was under the control of astrocyte-neuron interactions. The addition of exogenous laminin favored neuronal migration and neurite outgrowth, whereas neutralizing laminin bioavailability with antibodies recognizing the astroglial laminin resulted in an inhibition of both neuronal access to the lesion site and neurite outgrowth, suggesting an active role for laminin in the permissive process. This permissive process could be associated with modulation of extracellular matrix (ECM) molecule degradation by proteinases. Among the latter, matrix metalloproteinases (MMPs) are involved in the breakdown of the ECM component. Our investigation showed a net decrease of the matrix metalloproteinase MMP-2 expression and activity and an increase of its endogenous inhibitor TIMP-2 expression. Both proteins associated with permissivity should be involved in the laminin stabilization and cell-matrix interactions. High levels of laminin and laminin bioavailability, consequent to a reduction in astrogliosis, may be important permissive elements for neuronal migration and neurite outgrowth postlesion.
在星形胶质细胞增生和神经元共培养的体外模型中，研究了中枢神经系统损伤后轴突再生失败的分子决定因素。对机械损伤的神经元 - 星形胶质细胞小鼠皮质共培养物用反义胶质纤维酸性蛋白（GFAP） - mRNA进行处理，以抑制损伤后发生的胶质丝形成。这种抑制解除了损伤后观察到的神经元迁移和神经突生长的阻滞，迁移的神经元重新出现，并由层粘连蛋白标记的细胞外网络支持（许可条件）。然后，我们质疑这种许可性与层粘连蛋白产生之间的关系。对层粘连蛋白浓度的后续研究表明，反义处理后，共培养物中层粘连蛋白水平升高，并且受星形胶质细胞 - 神经元相互作用的控制。添加外源性层粘连蛋白有利于神经元迁移和神经突生长，而用识别星形胶质层粘连蛋白的抗体中和层粘连蛋白的生物利用度会导致神经元进入损伤部位和神经突生长均受到抑制，这表明层粘连蛋白在许可过程中起积极作用。这种许可过程可能与蛋白酶对细胞外基质（ECM）分子降解的调节有关。在这些蛋白酶中，基质金属蛋白酶（MMPs）参与ECM成分的分解。我们的研究表明，基质金属蛋白酶MMP - 2的表达和活性净下降，其内源性抑制剂TIMP - 2的表达增加。与许可性相关的这两种蛋白质都应参与层粘连蛋白的稳定和细胞 - 基质相互作用。星形胶质细胞增生减少导致的高水平层粘连蛋白和层粘连蛋白生物利用度，可能是损伤后神经元迁移和神经突生长的重要许可因素。
