Baehr M, Bunge R P
Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110.
Exp Neurol. 1989 Oct;106(1):27-40. doi: 10.1016/0014-4886(89)90141-6.
Properties of Schwann cells (SC) within the environment of the peripheral nerve can differ depending on their state of differentiation (e.g., quiescent, proliferating or mature SCs). In the present study we have tested the efficacy of SCs in different functional states to promote adult rat retinal ganglion cell (RGC) survival and neurite growth. We have used culture conditions which allowed regenerating retinal axons to contact SCs (1) as quiescent SCs that had not been in contact with axons, (2) as SCs that had been proliferating in contact with neurites, and (3) as mature SCs which had myelinated axons and deposited basal lamina around the axon-SC unit. Both proliferating and mature SCs were activated, i.e., were removed from axonal contact by inducing Wallerian degeneration, 2-3 days prior to testing their ability to support neuronal survival and neurite growth. Activated SCs, (derived from either proliferating or mature SCs) supported adult rat RGC survival and axonal regrowth significantly better than quiescent SC monolayers. Conditioned media (CM) derived from corresponding SC preparations (quiescent, proliferating, or mature SCs) supported short-term survival of RGCs and neurite outgrowth on defined substrata. A dissociation of substrate adsorbable neurite-promoting and nonadsorbable neurotrophic factors could be observed. The neurite-promoting activities found in CM were trypsin and heat sensitive, suggesting that the active component(s) is protein(s). None of the CM tested was able to support adult rat RGC survival and axonal growth as effectively as activated SCs (either proliferating or mature SCs). Long-term survival (greater than 4 days) of RGCs in explant cultures were especially dependent on RGC-neurite contact with preactivated SCs; CM derived from corresponding SCs (mature and proliferating SC-CM) were significantly less effective in supporting long-term survival. From these data we conclude that consideration must be given to the functional state of the SCs in experiments designed to utilize SCs in promoting CNS regeneration.
在周围神经环境中，施万细胞（SC）的特性会因其分化状态（如静止、增殖或成熟的施万细胞）而有所不同。在本研究中，我们测试了不同功能状态的施万细胞促进成年大鼠视网膜神经节细胞（RGC）存活和神经突生长的功效。我们采用了培养条件，使再生的视网膜轴突能够接触到施万细胞：（1）作为未与轴突接触的静止施万细胞；（2）作为与神经突接触并增殖的施万细胞；（3）作为已使轴突髓鞘化并在轴突 - 施万细胞单元周围沉积基膜的成熟施万细胞。在测试其支持神经元存活和神经突生长能力的2 - 3天前，增殖型和成熟型施万细胞均被激活，即通过诱导华勒氏变性使其与轴突脱离接触。激活后的施万细胞（源自增殖型或成熟型施万细胞）在支持成年大鼠视网膜神经节细胞存活和轴突再生方面，明显优于静止的施万细胞单层。源自相应施万细胞制剂（静止、增殖或成熟的施万细胞）的条件培养基（CM）能支持视网膜神经节细胞的短期存活以及在特定基质上的神经突生长。可以观察到底物可吸附的神经突促进因子和不可吸附的神经营养因子的分离。在条件培养基中发现的神经突促进活性对胰蛋白酶和热敏感，这表明活性成分是蛋白质。所测试的任何一种条件培养基在支持成年大鼠视网膜神经节细胞存活和轴突生长方面，都不如激活后的施万细胞（增殖型或成熟型施万细胞）有效。外植体培养中视网膜神经节细胞的长期存活（超过4天）尤其依赖于视网膜神经节细胞神经突与预先激活的施万细胞的接触；源自相应施万细胞（成熟型和增殖型施万细胞 - CM）的条件培养基在支持长期存活方面效果明显较差。从这些数据我们得出结论，在设计利用施万细胞促进中枢神经系统再生的实验时，必须考虑施万细胞的功能状态。
