Nakamura S, Kamihagi K, Satakeda H, Katayama M, Pan H, Okamoto H, Noshiro M, Takahashi K, Yoshihara Y, Shimmei M, Okada Y, Kato Y
Hiroshima University, Japan.
Arthritis Rheum. 1996 Apr;39(4):539-51. doi: 10.1002/art.1780390402.
To investigate the roles of SPARC (secreted protein, acidic and rich in cysteine) (osteonectin) in arthritis, using cartilage and synovium specimens and synovial fluids (SF) from patients with rheumatoid arthritis (RA) or osteoarthritis (OA), and to examine the effects of cytokines, growth factors, and hormones on SPARC synthesis by chondrocytes in culture.
SPARC in cartilage and synovium was immunostained with monoclonal antibodies. SPARC synthesis by cultured chondrocytes was measured by Northern blot analysis, immunoblotting, and sandwich enzyme-linked immunosorbent assay.
SPARC was identified in numerous chondrocytes in the superficial and middle zones and in regenerating chondrocytes of RA and OA joints, whereas such staining was absent in these zones of normal cartilage, except for weak signals from a few chondrocytes in the deep zone. In addition, SPARC synthesis was enhanced in synovial cells of RA and OA joints. The average SPARC level in SF was 10-fold higher in the RA than in the OA population. In rabbit articular chondrocyte cultures, administration of transforming growth factor beta 1 (TGF beta 1) and bone morphogenetic protein 2 increased SPARC levels at 24-48 hours, whereas interleukin-lbeta (IL-1 beta), IL-1 alpha, tumor necrosis factor alpha, lipopolysaccharide, phorbol myristate acetate, basic fibroblast growth factor, and dexamethasone decreased SPARC levels at 24-72 hours. TGF beta increased SPARC messenger RNA (mRNA) levels at 24 hours, whereas IL-1 beta caused a marked decrease in SPARC mRNA levels at 24 hours. Furthermore, IL-1 decreased the glycosylation of SPARC.
These findings suggest that various growth factors and cytokines, including TGF beta 1 and IL-1 beta, regulate the production of SPARC by chondrocytes at pre- and posttranslational levels, and that SPARC synthesis is markedly enhanced in arthritic joints.
利用类风湿关节炎（RA）或骨关节炎（OA）患者的软骨、滑膜标本及滑液（SF），研究富含半胱氨酸的酸性分泌蛋白（SPARC）（骨连接素）在关节炎中的作用，并检测细胞因子、生长因子和激素对培养的软骨细胞合成SPARC的影响。
用单克隆抗体对软骨和滑膜中的SPARC进行免疫染色。通过Northern印迹分析、免疫印迹和夹心酶联免疫吸附测定法检测培养的软骨细胞合成SPARC的情况。
在RA和OA关节的表层和中层众多软骨细胞以及再生软骨细胞中发现了SPARC，而在正常软骨的这些区域未发现此类染色，除了深层少数软骨细胞有微弱信号。此外，RA和OA关节的滑膜细胞中SPARC合成增强。RA患者滑液中的SPARC平均水平比OA患者高10倍。在兔关节软骨细胞培养中，给予转化生长因子β1（TGFβ1）和骨形态发生蛋白2可在24 - 48小时提高SPARC水平，而白细胞介素-1β（IL-1β）、IL-1α、肿瘤坏死因子α、脂多糖、佛波酯、碱性成纤维细胞生长因子和地塞米松在24 - 72小时降低SPARC水平。TGFβ在24小时时增加SPARC信使核糖核酸（mRNA）水平，而IL-1β在24小时时导致SPARC mRNA水平显著降低。此外，IL-1降低了SPARC的糖基化。
这些发现表明，包括TGFβ1和IL-1β在内的多种生长因子和细胞因子在翻译前和翻译后水平调节软骨细胞合成SPARC，且关节炎关节中SPARC合成明显增强。
