Hopkins J M, Bunge R P
Miami Project to Cure Paralysis, University of Miami School of Medicine, Florida 33136.
Glia. 1991;4(1):46-55. doi: 10.1002/glia.440040106.
The ability of sciatic nerve grafts to support in vivo regeneration of retinal ganglion cell axons in the adult rat raises the question of which peripheral nerve constituents may be required to promote this unexpected central regenerative response. Prime candidates for this role include the surface of the Schwann cell and components of extracellular matrix present in peripheral nerve trunks. To determine the relative importance of Schwann cells and their basal lamina in promoting retinal ganglion cell axon regeneration in the mammalian visual system, we have used an in vitro model. This approach allowed analysis of the abilities of defined peripheral nerve constituents to promote in vitro outgrowth of neurites from explants of adult rat retina harvested 7 to 10 days after in vivo optic nerve crush. Neurite outgrowth was assessed by neurofilament immunofluorescence after 3 to 20 days in vitro. Culture substrata, consisting of isolated Schwann cells (SC), Schwann cells with their assembled extracellular matrix (SC + ECM), or isolated extracellular matrix from which the Schwann cells had been removed (ECM), were prepared by first co-culturing rat Schwann cells with embryonic dorsal root ganglion neurites on a layer of type I collagen, and then manipulating the cultures to produce the desired substrata. Type I collagen alone did not support neurite growth from adult rat retina. SC and SC + ECM supported regeneration of axons from retinal explants at average growth rates of 18 and 30 microns/h, respectively. Isolated ECM was a poor substrate for retinal neurite growth; the few neurites that gained access to this material grew at rates averaging less than 3 microns/h. These observations suggest that regeneration of adult mammalian retinal ganglion cell axons through peripheral nerve grafts (in vivo) is primarily dependent on neurite-promoting factors present on the surface of Schwann cells and does not require organized extracellular matrix.
坐骨神经移植物支持成年大鼠视网膜神经节细胞轴突在体内再生的能力，引发了一个问题：促进这种意外的中枢再生反应可能需要哪些周围神经成分？担任这一角色的主要候选者包括施万细胞表面和周围神经干中存在的细胞外基质成分。为了确定施万细胞及其基膜在促进哺乳动物视觉系统中视网膜神经节细胞轴突再生方面的相对重要性，我们使用了一种体外模型。这种方法能够分析特定周围神经成分促进成年大鼠视网膜外植体神经突体外生长的能力，这些外植体是在体内视神经挤压7至10天后获取的。体外培养3至20天后，通过神经丝免疫荧光评估神经突生长情况。培养底物由分离的施万细胞（SC）、带有组装好的细胞外基质的施万细胞（SC + ECM）或去除了施万细胞的分离细胞外基质（ECM）组成，制备方法是先将大鼠施万细胞与胚胎背根神经节神经突在I型胶原层上共培养，然后对培养物进行处理以产生所需的底物。单独的I型胶原不支持成年大鼠视网膜神经突生长。SC和SC + ECM分别以平均18和30微米/小时的生长速度支持视网膜外植体轴突的再生。分离的ECM是视网膜神经突生长的不良底物；少数接触到这种材料的神经突生长速度平均低于3微米/小时。这些观察结果表明，成年哺乳动物视网膜神经节细胞轴突通过周围神经移植物（在体内）的再生主要依赖于施万细胞表面存在的神经突促进因子，并不需要有组织的细胞外基质。
