Noonan K J, Stevens J W, Tammi R, Tammi M, Hernandez J A, Midura R J
Department of Orthopaedic Surgery, University of Iowa, College of Medicine, Iowa City 52242, USA.
J Orthop Res. 1996 Jul;14(4):573-81. doi: 10.1002/jor.1100140411.
CD44 has been described as a cell surface hyaluronan receptor present on a variety of different cells, and it is generally assumed to be prevalent in most connective tissues that contain hyaluronan. A major aim of this study was to test that presumption by localizing CD44 and hyaluronan within several tissues of the proximal tibia of the growing rat. Comparison of these profiles would reveal whether CD44 and hyaluronan co-localize with high fidelity, as would be expected if CD44 were a major hyaluronan binding protein. Using in situ hybridization and immunohistochemistry, CD44 was identified on osteoclasts, chondroclasts, osteocytes, hematopoietic marrow cells, synovial cells, and connective tissue fibroblasts (ligaments, tendons, and fascia). Although the majority of osteocytes expressed CD44, reduced expression was observed for osteoblasts and ostcoprogenitor cells. Additionally. CD44 was not detected on chondrocytes from epiphyseal and metaphyseal growth cartilages or in meniscal fibrocartilage. Using biotinylated G1 domain from aggrecan and link protein, hyaluronan was observed in the maturational and hypertrophic zones of all growth cartilages, the synovium and other fibroblastic connective tissues, regional areas of the periosteum and endosteum (around osteoblasts, osteoprogenitor cells, and osteoclasts), osteocyte lacunae, and surrounding blood vessels. In regions of co-localization for CD44 and hyaluronan, it seems that CD44 is a likely hyaluronan binding protein in several tissues of the proximal tibia. However, it does not appear to be the predominant hyaluronan binding protein in growing cartilages of the weanling rat.
CD44被描述为一种存在于多种不同细胞上的细胞表面透明质酸受体，通常认为它在大多数含有透明质酸的结缔组织中普遍存在。本研究的一个主要目的是通过在生长中大鼠胫骨近端的几种组织内定位CD44和透明质酸来验证这一推测。如果CD44是一种主要的透明质酸结合蛋白，那么比较这些分布图将揭示CD44和透明质酸是否以高保真度共定位。使用原位杂交和免疫组织化学方法，在破骨细胞、软骨破骨细胞、骨细胞、造血骨髓细胞、滑膜细胞和结缔组织成纤维细胞（韧带、肌腱和筋膜）上鉴定出了CD44。虽然大多数骨细胞表达CD44，但在成骨细胞和骨祖细胞中观察到表达降低。此外，在骨骺和干骺端生长软骨的软骨细胞或半月板纤维软骨中未检测到CD44。使用来自聚集蛋白聚糖和连接蛋白的生物素化G1结构域，在所有生长软骨的成熟和肥大区、滑膜和其他成纤维结缔组织、骨膜和骨内膜的局部区域（成骨细胞、骨祖细胞和破骨细胞周围）、骨细胞陷窝和周围血管中观察到了透明质酸。在CD44和透明质酸共定位的区域，CD44似乎是胫骨近端几种组织中一种可能的透明质酸结合蛋白。然而，它似乎并不是断乳大鼠生长软骨中主要的透明质酸结合蛋白。
