Harvey A R, Plant G W
Department of Anatomy and Human Biology, University of Western Australia, Nedlands, Perth.
Exp Neurol. 1995 Aug;134(2):179-91. doi: 10.1006/exnr.1995.1047.
Schwann cells transplanted into the adult central nervous system (CNS) can exert powerful growth-promoting effects on damaged axons. An important issue is whether central axons induced to regrow by Schwann cells retain the capacity to recognize and selectively innervate their appropriate target cells. To examine how Schwann cells may influence the specificity of neuron-neuron interactions in CNS neuropil, we cultured neonatal rat Schwann cells and mixed them with dissociated fetal tectal cells. In some instances, Schwann cells were prelabeled with Hoechst dye 33342. Schwann cells comprised between 2.5 and 15% of the combined cell population. After reaggregation, cografts were injected onto the midbrain of newborn rats. One to 6 months later, grafts were examined for the presence of Schwann cells and the pattern and density of host retinal innervation of the cografts was assessed. Immunohistochemical studies showed that areas of the transplants containing large numbers of surviving Hoechst-labeled Schwann cells were strongly immunoreactive for the low-affinity nerve growth factor receptor (p75), S-100, GFAP, and laminin. Very little peripheral (Po positive) myelin was seen. As in pure fetal tectal grafts, host retinal axons were sometimes observed to innervate superficial, localized areas in the cografts known to be homologous to the retinorecipient layers of the superior colliculus. Unlike pure tectal grafts, however, optic axons were not confined to these regions and fibers were often dispersed within the cograft neuropil. Dense growth was seen in association with Hoechst-labeled Schwann cells and, in some cases, optic axons were observed to grow toward Schwann cells and away from nearby target areas. These observations suggest that, under certain circumstances, Schwann cells can stimulate retinal axons to grow into inappropriate (nontarget) regions in the CNS, presumably by producing growth promoting factors which mask or compete with signals released from the target neurons themselves.
移植到成年中枢神经系统（CNS）的施万细胞可对受损轴突发挥强大的促生长作用。一个重要问题是，由施万细胞诱导再生的中枢轴突是否保留识别并选择性支配其合适靶细胞的能力。为了研究施万细胞如何影响中枢神经系统神经毡中神经元 - 神经元相互作用的特异性，我们培养了新生大鼠的施万细胞，并将其与解离的胎脑顶盖细胞混合。在某些情况下，施万细胞用Hoechst染料33342预先标记。施万细胞占混合细胞群体的2.5%至15%。重新聚集后，将共移植体注射到新生大鼠的中脑。1至6个月后，检查移植体中施万细胞的存在情况，并评估宿主视网膜对共移植体的神经支配模式和密度。免疫组织化学研究表明，移植体中含有大量存活的Hoechst标记施万细胞的区域，对低亲和力神经生长因子受体（p75）、S - 100、GFAP和层粘连蛋白具有强烈免疫反应性。可见极少量的外周（Po阳性）髓磷脂。与纯胎脑顶盖移植体一样，有时可观察到宿主视网膜轴突支配共移植体中已知与上丘视网膜接受层同源的浅表局部区域。然而，与纯顶盖移植体不同的是，视神经轴突并不局限于这些区域，纤维常常分散在共移植体的神经毡内。在Hoechst标记的施万细胞周围可见密集生长，在某些情况下，观察到视神经轴突朝着施万细胞生长并远离附近的靶区域。这些观察结果表明，在某些情况下，施万细胞可刺激视网膜轴突生长到中枢神经系统的不适当（非靶）区域，大概是通过产生促进生长的因子，这些因子掩盖或与靶神经元自身释放的信号竞争。
