Kleitman N, Wood P, Johnson M I, Bunge R P
Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110.
J Neurosci. 1988 Feb;8(2):653-63. doi: 10.1523/JNEUROSCI.08-02-00653.1988.
Despite evidence that glial cell surfaces and components of the extracellular matrix (ECM) support neurite outgrowth in many culture systems, the relative contributions of these factors have rarely been compared directly. Specifically, it remains to be determined which components of peripheral nerve support growth of central nerve fibers. We have directly compared neurite outgrowth from embryonic day 15 rat retinal explants placed onto beds of (1) Schwann cells without ECM, (2) Schwann cells expressing ECM (including a basal lamina), (3) cell-free ECM prepared from neuron-Schwann cell cultures, (4) nonglial cells (fibroblasts), and (5) 2 isolated ECM components, laminin and type I collagen. From the first day in culture, retinal explants extended neurites when placed on Schwann cells without ECM. Outgrowth on Schwann cells expressing ECM was also extensive, but not obviously different form that on Schwann cells alone. Ultrastructural study revealed that 95% of retinal neurites in ECM-containing cultures contacted other neurites and Schwann cell surfaces exclusively. On cell-free ECM prepared from neuron-Schwann cell cultures, neurite extension was poor to nonexistent. No neurite outgrowth occurred on fibroblasts. Retinal explants also failed to extend neurites onto purified laminin and ammoniated type I collagen substrata; however, growth was rapid and extensive on air-dried type I collagen. In cultures containing islands of air-dried type I collagen on a laminin-coated coverslip, retinal explants attached and extended neurites on collagen, but these neurites did not extend off the island onto the laminin substratum. We conclude from these experiments that neurite extension from embryonic rat retina is supported by a factor found on the surface of Schwann cells and that neither organized nor isolated ECM components provide this neurite promotion. These findings are discussed in relation to possible species differences in growth requirements for retinal ganglion cell neurites and to the specificity of response of different CNS neurites to ECM substrata.
尽管有证据表明，在许多培养系统中，神经胶质细胞表面和细胞外基质（ECM）的成分可支持神经突生长，但这些因素的相对作用很少被直接比较。具体而言，外周神经的哪些成分支持中枢神经纤维的生长仍有待确定。我们直接比较了将胚胎第15天大鼠视网膜外植体置于以下几种基质上时的神经突生长情况：（1）无ECM的雪旺细胞；（2）表达ECM（包括基膜）的雪旺细胞；（3）从神经元 - 雪旺细胞培养物中制备的无细胞ECM；（4）非神经胶质细胞（成纤维细胞）；（5）两种分离的ECM成分，层粘连蛋白和I型胶原蛋白。从培养的第一天起，当视网膜外植体置于无ECM的雪旺细胞上时，就会伸出神经突。置于表达ECM的雪旺细胞上时，神经突生长也很广泛，但与仅置于雪旺细胞上的情况没有明显差异。超微结构研究表明，含ECM培养物中95%的视网膜神经突仅与其他神经突和雪旺细胞表面接触。在从神经元 - 雪旺细胞培养物中制备的无细胞ECM上，神经突延伸很少或几乎没有。在成纤维细胞上没有神经突生长。视网膜外植体在纯化的层粘连蛋白和氨化I型胶原蛋白基质上也未能伸出神经突；然而，在风干的I型胶原蛋白上生长迅速且广泛。在层粘连蛋白包被的盖玻片上含有风干I型胶原蛋白岛的培养物中，视网膜外植体附着在胶原蛋白上并伸出神经突，但这些神经突并未延伸到岛外的层粘连蛋白基质上。我们从这些实验中得出结论，胚胎大鼠视网膜的神经突延伸由雪旺细胞表面发现的一种因子支持，并且无论是有组织的还是分离的ECM成分都不能提供这种促进神经突生长的作用。这些发现将结合视网膜神经节细胞神经突生长需求可能存在的物种差异以及不同中枢神经系统神经突对ECM基质反应的特异性进行讨论。
