Bunge R P
Department of Anatomy and Neurobiology, Washington University School of Medicine, St Louis, MO 63110.
J Exp Biol. 1987 Sep;132:21-34. doi: 10.1242/jeb.132.1.21.
During peripheral nerve development the Schwann cell population is expanded so that adequate numbers are available for ensheathment of both nonmyelinated and myelinated nerve fibres. As ensheathment of these fibres progresses each axon--Schwann cell unit becomes surrounded by a basal lamina, providing a unique microtubular framework within the peripheral nerve trunk. Tissue culture studies of pure populations of neurones and Schwann cells cultured separately and in combination indicate that a surface component on the axon provides a mitogenic signal to Schwann cells requiring cell-cell contact. Biochemical, electron microscopic and immunocytochemical analyses of these cultures indicate that Schwann cells in contact with axons are able to generate a basal lamina (containing type IV collagen, laminin and heparan sulphate proteoglycan) and fibrous collagen, without the aid of other cells, and that axonal contact is required for deposition of the basal lamina. The role of Schwann cells and the extracellular matrix they synthesize and organize, as well as the role of the other known products of the Schwann cells in the process of peripheral nerve regeneration, are discussed. It is suggested that the large numbers and advantageous position of the Schwann cells, as well as their ability to provide their own surfaces, a basal lamina and multiple secretory products, may account for their extraordinary ability to foster nerve fibre regeneration.
在周围神经发育过程中，施万细胞数量增加，以便有足够数量的细胞来包裹无髓鞘和有髓鞘神经纤维。随着这些纤维的包裹过程推进，每个轴突 - 施万细胞单元被基膜包围，在周围神经干内形成独特的微管框架。对分别培养及联合培养的神经元和施万细胞纯群体进行的组织培养研究表明，轴突上的一种表面成分向需要细胞 - 细胞接触的施万细胞提供促有丝分裂信号。对这些培养物进行的生化、电子显微镜和免疫细胞化学分析表明，与轴突接触的施万细胞能够在没有其他细胞帮助的情况下生成基膜（包含IV型胶原、层粘连蛋白和硫酸乙酰肝素蛋白聚糖）和纤维状胶原，并且基膜的沉积需要轴突接触。文中讨论了施万细胞及其合成和组织的细胞外基质的作用，以及施万细胞的其他已知产物在周围神经再生过程中的作用。有人提出，施万细胞数量众多、位置优越，以及它们能够提供自身表面、基膜和多种分泌产物，可能解释了它们促进神经纤维再生的非凡能力。
