轴突影响施万细胞分化与整合素α_6β_4表达

Axonal regulation of Schwann cell differentiation and integrin α_6β_4 expression

目的 :探讨轴突对施万细胞 (Schwanncells,SC)分化成熟与髓鞘形成的影响 ,及在SC的极向分化过程中整合素α6β4 的表达。方法 :用Wistar乳鼠坐骨神经分离SC ,用其脊髓分离神经细胞。经纯化后分别培养及共同培养。用扫描电镜观察二者的形态及髓鞘形成情况 ;分别用髓鞘碱性蛋白 (myelinbasicprotein ,MBP)、神经微丝 (neu rofilament ,NF)抗体进行免疫标记 ;采用原位杂交技术检测整合素α6β4 mRNA的表达。结果 :单独培养的SCMBP抗原表达阴性 ;原位杂交检测α6β4 表达阴性。SC与神经细胞共同培养时其MBP阳性 (说明其已转变为髓鞘形成细胞 ) ,在神经突起周围表达阳性 ;扫描电镜可见SC与神经细胞贴附、融合、包绕轴突形成髓鞘 ;原位杂交显示α6β4在SC与神经轴突相贴附处呈线状阳性表达。结论 :SC的分化成熟及髓鞘形成呈轴突依赖性 ,仅在与神经细胞共同培养时 ,才开始形成髓鞘。它在包绕轴突形成髓鞘时 ,α6β4 在SC表面沿基膜呈方向性表达 ,在SC与基膜、细胞外基质之间起信号传导作用 ,使增生的SC具有极性并发生形态结构的改变。在SC的分化成熟及髓鞘形成的过程中 。

SUMMARY Objective: To study the axonal effect and the expression of integrin α 6β 4 during Schwann cell(SC) differentiation and myelination. Methods: Schwann cells were dissociated from the sciatic nerve of neonatal Waster rats and neurons dissociated from spinal cord. Singal cultures and purified populations of SC were cocultured with NC. Four methods (contrast microscope, scanning electron microscopy(SEM), immunocytochemistry method and in situ hybridization ) were used. Results: The separately cultured Schwann cells showed MBP negetive by immunocytochemistry method. But cocultured SC were shown positive. SEM showed that Schwann cells' membrane loop progressively circumnavigated around the axon during myelination, which suggested that the non myelinating SC(nMSC) transformed to myelinating SC (MSC). In situ hybridization showed integrin α 6β 4 positive signals only on the outer surface of the Schwann cell axon unit in SC coculture with NC. Conclusion: The differentiation and maturation of SC depend on axon, and the activity of integrins is expressed by axon. Axonal contact induces the expression of α 6β 4 during SC myelination, which suggests that integrin α 6β 4 is an important mediator of interactions of myelinating SC with the basal limina.