Iwanaga T, Shikichi M, Kitamura H, Yanase H, Nozawa-Inoue K
Laboratory of Anatomy, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
Arch Histol Cytol. 2000 Mar;63(1):17-31. doi: 10.1679/aohc.63.17.
The joint capsule exhibits a unique cellular lining in the luminal surface of the synovial membrane. The synovial intimal cells, termed synoviocytes, are believed to be responsible for the production of synovial fluid components, for absorption from the joint cavity, and for blood/synovial fluid exchanges, but their detailed structure and function as well as pathological changes remain unclear. Two types of synoviocytes, macrophagic cells (type A cells) and fibroblast-like cells (type B cells) have been identified. Type A synoviocytes are non-fixed cells that can phagocytose actively cell debris and wastes in the joint cavity, and possess an antigen-presenting ability. These type A cells, derived from blood-borne mononuclear cells, can be considered resident macrophages (tissue macrophages) like hepatic Kupffer cells. Type B synoviocytes are characterized by the rich existence of rough endoplasmic reticulum, and dendritic processes which form a regular network in the luminal surface of the synovial membrane. Their complex three-dimensional architecture was first revealed by our recent scanning electron microscopy of macerated samples. The type B cells, which are proper synoviocytes, are involved in production of specialized matrix constituents including hyaluronan, collagens and fibronectin for the intimal interstitium and synovial fluid. The proliferative potentials of type B cells in loco are much higher than type A cells, although the transformation of subintimal fibroblasts into type B cells can not be excluded. In some mammals, type B cells show features suggesting endocrine and sensory functions, but these are not recognized in other species. The synoviocytes, which form a discontinuous cell layer, develop both fragmented basement membranes around the cells and junctional apparatus such as desmosomes and gap junctions. For an exact understanding of the mechanism of arthritis, we need to establish the morphological background of synoviocytes as well as their functions under normal conditions.
关节囊在滑膜腔表面呈现出独特的细胞内衬。滑膜内膜细胞，即滑膜细胞，被认为负责滑液成分的产生、关节腔的吸收以及血液/滑液交换，但其详细结构、功能以及病理变化仍不清楚。已鉴定出两种类型的滑膜细胞，即巨噬细胞（A型细胞）和成纤维细胞样细胞（B型细胞）。A型滑膜细胞是不固定的细胞，能够主动吞噬关节腔内的细胞碎片和废物，并具有抗原呈递能力。这些源自血源性单核细胞的A型细胞可被视为驻留巨噬细胞（组织巨噬细胞），类似于肝库普弗细胞。B型滑膜细胞的特征是粗面内质网丰富，且其树突状突起在滑膜腔表面形成规则网络。我们最近对浸软样本的扫描电子显微镜观察首次揭示了它们复杂的三维结构。B型细胞是真正的滑膜细胞，参与为内膜间质和滑液产生包括透明质酸、胶原蛋白和纤连蛋白在内的特殊基质成分。尽管不能排除内膜下成纤维细胞向B型细胞的转化，但B型细胞在局部的增殖潜能远高于A型细胞。在一些哺乳动物中，B型细胞表现出提示内分泌和感觉功能的特征，但在其他物种中未观察到这些特征。形成不连续细胞层的滑膜细胞在细胞周围形成碎片化的基底膜以及诸如桥粒和缝隙连接等连接装置。为了准确理解关节炎的发病机制，我们需要建立滑膜细胞在正常条件下的形态学背景及其功能。
