Hyc A, Osiecka-Iwan A, Jóźwiak J, Moskalewski S
Zakład Histologii i Embriologii Centrum Biostruktury, Akademia Medyczna, Warszawa.
Ortop Traumatol Rehabil. 2001 Apr 30;3(2):151-62.
The purpose of this article is to present the current state of knowledge regarding the structure and functions of articular cartilage. Articular cartilage is constructed with hyaline cartilage tissue. It is composed of chondrocytes located in lacunae and the extracellular matrix. The chondrial matrix contains water, collagen, proteglycans, non-collagenous matrix proteins, and lipids. Articular cartilage is devided into four zones - superficial, intermediate, deep, and calcified - on the basic of morphology, the orientation of collagen fiber, and the proteoglycan content. The dominant collagen of this tissue is Type II collagen, which, together with smaller quantities of other collagens (i.e. Types IX and XII), forms a network of fibers, with large, aggregating proteoglycans and smaller, non-aggregating proteoglycans. Proteoglycans are proteins that contain covalently attached glycosaminoglycans (GAGs), with water between them. The large aggregating proteoglycans, called "aggrecans", form aggregates that bind hyaluronic acid, and together with collagen they are responsible for the mechanical properties of cartilage. The smallnonaggregating proteoglycans, decorin and fibromodulin, limit the formation of collagen fibres. Other proteins in the cartilage matrix - chondrocalcin and the N-propetide of Type II collagen - participate in fiber formation. Yet other proteins - chondronectin, fibronectin, vitronectin and thrombospondin - take part in the interaction between the chondrocytes and the matrix. Cartilage oligomeric matrix protein (COMP) prevents the vascularization of the cartilage and, perhaps, is responsible for the repair process. The proteins known as Cart-1 and CEP-68 participate in chondrogenesis, while tenascin and Mgp are considered to be cartilage calcification inhibitors. Apart from the structural elements, chondrocytes produce substances that fulfill purely physiological functions: enzymes and cytokines. The enzymes - which include metalloproteinases, adamalysins, serine and cysteine proteases and their inhibitors - participate in cartilage matrix reconstruction. The cytokines - IL-1, TNF-alfa, IL-6, IL-8, and LIF - stimulate the chondrocytes to produce an increased amount of enzymes, while IL-4 inhibits this process. Human articular chondrocytes exibit the constitutive expression of class I molecules of the major histocompatibility complex (MHC), molecules regulating the activation of the complement, and after activation (e.g. under the influence of IFN-alfa, IL-1, TNF-a or in the course of arthritis), also MHC class II and ICAM-1 intracellular adhesion molecules. Numerous studies have shown that chondrocytes also have tissue-specific antigens, which induce the production of antibodies in patients with cartilage grafts, as well as those with rheumatoid arthritis and osteoarthritis. Some of these antibodies react with type II collagen, others are directed against other proteins i.e. anchorin CII and CH65. the role of these diverse molecules, which are present in cartilage cells and separated from the immune system by the matrix, remains unclear.
本文的目的是介绍有关关节软骨结构和功能的当前知识状态。关节软骨由透明软骨组织构成。它由位于腔隙中的软骨细胞和细胞外基质组成。软骨基质包含水、胶原蛋白、蛋白聚糖、非胶原蛋白基质蛋白和脂质。根据形态、胶原纤维方向和蛋白聚糖含量，关节软骨可分为四个区域——表层、中间层、深层和钙化层。该组织的主要胶原蛋白是II型胶原蛋白，它与少量其他胶原蛋白（即IX型和XII型）一起形成纤维网络，还有大型聚集蛋白聚糖和小型非聚集蛋白聚糖。蛋白聚糖是含有共价连接的糖胺聚糖（GAGs）的蛋白质，它们之间有水。大型聚集蛋白聚糖，称为“聚集蛋白聚糖”，形成与透明质酸结合的聚集体，它们与胶原蛋白一起负责软骨的力学性能。小型非聚集蛋白聚糖，饰胶蛋白聚糖和纤调蛋白聚糖，限制胶原纤维的形成。软骨基质中的其他蛋白质——软骨钙素和II型胶原蛋白的N-前肽——参与纤维形成。还有其他蛋白质——软骨粘连蛋白、纤连蛋白、玻连蛋白和血小板反应蛋白——参与软骨细胞与基质之间的相互作用。软骨寡聚基质蛋白（COMP）可防止软骨血管化，也许还负责修复过程。称为Cart-1和CEP-68的蛋白质参与软骨形成，而腱生蛋白和Mgp被认为是软骨钙化抑制剂。除了结构成分外，软骨细胞还产生具有纯粹生理功能的物质：酶和细胞因子。这些酶——包括金属蛋白酶、解聚素、丝氨酸和半胱氨酸蛋白酶及其抑制剂——参与软骨基质重建。细胞因子——IL-1、TNF-α、IL-6、IL-8和LIF——刺激软骨细胞产生更多的酶，而IL-4抑制这一过程。人关节软骨细胞表现出主要组织相容性复合体（MHC）I类分子的组成性表达，这些分子调节补体的激活，并且在激活后（例如在IFN-α、IL-1、TNF-α的影响下或在关节炎过程中），还表达MHC II类和细胞间黏附分子1（ICAM-1）。大量研究表明，软骨细胞也有组织特异性抗原，这些抗原在接受软骨移植的患者以及类风湿性关节炎和骨关节炎患者中诱导抗体产生。其中一些抗体与II型胶原蛋白反应，其他抗体则针对其他蛋白质，即锚定蛋白CII和CH65。这些存在于软骨细胞中并被基质与免疫系统隔开的各种分子的作用仍不清楚。
