Morphological variation and cell adhesion of terminal Schwann cells-- a study by three-dimensional microanatomy and immunohistochemistry.

通过基于扫描和电子显微镜联合观察的三维显微解剖和利用针对雪旺细胞标记物S100β蛋白的抗体的免疫组织化学，分析与各种感觉末梢相关的终末雪旺细胞的形态和发育。比较观察大鼠牙周Ruffini末梢和触须披针形末梢以及猴手掌皮肤中的Meissner小体，发现这些机械感受器中的终末雪旺氏细胞始终发出主要的板层突起来包裹轴突末梢。主突具有与受体类型相对应的细小附属突起。末端雪旺氏细胞的附属突起以不同的方式将不同的机械感受器与周围组织联系起来，这表明由外力引起的组织变形通过细锚传递到轴突末端的感受器部位。在2 ~ 3周龄大鼠触须披针形末梢观察到终末雪旺细胞的成熟。未成熟的许旺细胞，这是星状的，从细胞体放射状的细突起，发生在披针形末梢周围的结缔组织中。这些细胞逐渐转变为终末雪旺氏细胞，沿轴突终末沿着延伸主突起。在成熟的过程中，绝大多数的细放射状突起的雪旺氏肌退化，而成锚，附属突起。这些结果表明，终端许旺细胞的形态发生诱导接触轴突终端。参与细胞相互作用的信号物质和细胞粘附分子仍有待阐明。

Morphology and development of terminal Schwann cells associated with various sensory endings were analyzed both by three-dimensional microanatomy based on combined observation by scanning and electron microscopy, and by immunohistochemistry utilizing an antibody against the Schwann cell marker, S100β protein. Comparative observation of periodontal Ruffini endings and vibrissal lanceolate endings in rats and Meissner corpuscles in monkey palmar skn showed that terminal Schwann cells in these mechanoreceptors consistently issued main, lamellar processes to envelope axon endings. The main processes were provided with fine accessory projections specific to receptor types in morphology. The accessory projections of the terminal Schwann cells linked the different mechanoreceptors with surrounding tissues in distinct manners, suggesting that tissue deformations induced by external forces are transmitted to receptor sites of the axon terminals via the fine anchors. Maturation of terminal Schwann cells was observed in vibrissal lanceolate endings of 2 to 3 week-old rats. Immature Schwann cells, which were stellate in shape with fine processes radiating from the cell body, occurred in connective tissue surrounding lanceolate endings. These cells were gradually transformed into terminal Schwann cells, extending main processes along axon terminals. In the process of maturation, the great majority of the fine radial processes of the Schwann cels regressed, while the remainders became the anchoring, accessory projections. These findings indicate that the morphogenesis of terminal Schwann cells is induced by contact with axon terminals. Signaling substances and cell adhesion molecules involved in the cell interaction remain to be elucidated.