Cartilage-specific constitutive expression of TSG-6 protein (product of tumor necrosis factor α-stimulated gene 6) provides a chondroprotective, but not antiinflammatory, effect in antigen-induced arthritis
Cartilage-specific constitutive expression of TSG-6 protein (product of tumor necrosis factor α-stimulated gene 6) provides a chondroprotective, but not antiinflammatory, effect in antigen-induced arthritis
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DOI：
10.1002/art.10555
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发表时间：
2002-08-01
影响因子：
--
通讯作者：
Mikecz, K
中科院分区：
文献类型：
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作者：
Glant, TT;Kamath, RV;Mikecz, K
Objective.采用抗原诱导关节炎（antigen induced arthritis，AIA）模型，研究组成型表达的TSG-6蛋白（tumor necrosis factor alpha-induced protein 6，Tnfip 6）对小鼠关节软骨的保护作用。产生在软骨中组成型表达TSG-6蛋白的转基因小鼠。TSG-6蛋白的软骨特异性组成型表达通过原位杂交、Western印迹分析和免疫组织化学证实。用甲基化牛血清白蛋白（mBSA）免疫对照和转基因小鼠，并通过关节内注射mBSA诱导关节炎。监测小鼠直至攻击后第35天，并使用番红0染色和针对由各种金属蛋白酶（MP）产生的新表位的抗体检查膝关节切片的软骨蛋白聚糖（聚集蛋白聚糖）损失。通过形态计量学方法定量分析番红O染色切片中聚集蛋白聚糖的损失。Tsg 6/tnfip 6转基因小鼠组成型表达tsg 6/tnfip 6信使RNA和相应的TSG-6蛋白在软骨从胚胎期到成年期，没有任何表型异常。这些小鼠用于AIA研究。关节内注射mBSA在对照（野生型和不相关的转基因系）小鼠和tsg 6/tnfip 6转基因小鼠中均诱导严重炎症。与从第5天起严重受损的对照动物的注射mBSA的膝关节相反，组成型表达TSG-6蛋白的转基因小鼠的软骨保持完整至少1周，并且随后是相对减少的聚集蛋白聚糖损失。伴随着聚集蛋白聚糖的丢失，MP产生的新表位在未受保护的关节中积累。到第35天，tsg 6/tnfip 6转基因小鼠的蛋白多糖含量恢复到接近正常水平，而对照小鼠的MP损伤膝关节软骨中的蛋白多糖含量仍然较低。已知TSG-6蛋白与α间抑制剂（IalphaI）（一种有效的丝氨酸蛋白酶抑制剂）形成复合物，其可以通过TSG-6蛋白的透明质酸（HA）结合结构域固定在软骨的富含HA的细胞外基质中。因此，TSG-6蛋白和TSG-6蛋白结合的IalphaI在tsg 6/tnfip 6转基因小鼠中的局部积累可能抑制丝氨酸蛋白酶和随后的NIPS活化。这表明，这种机制可能会保护软骨广泛的降解，即使在急性炎症的存在。
Objective. To study the chondroprotective effect of constitutively expressed TSG-6 protein (tumor necrosis factor alpha-induced protein 6; Tnfip6) in cartilage, using antigen-induced arthritis (AIA) in mice.Methods. Transgenic mice constitutively expressing TSG-6 protein in cartilage were generated. Cartilage-specific constitutive expression of TSG-6 protein was confirmed by in situ hybridization, Western blot analysis, and immunohistochemistry. Control and transgenic mice were immunized with methylated bovine serum albumin (mBSA), and arthritis was induced by the intraarticular injection of mBSA. Mice were monitored up to day 35 after the challenge, and knee joint sections were examined for loss of cartilage proteoglycan (aggrecan) using Safranin 0 staining and antibodies to neoepitopes generated by various metalloproteinases (MPs). The loss of aggrecan in Safranin O-stained sections was quantified by morphometric methods.Results. Tsg6/tnfip6 transgenic mice constitutively expressed tsg6/tnfip6 messenger RNA and corresponding TSG-6 protein in cartilage from embryonic life through adulthood, without any phenotypic abnormalities. These mice were used for AIA, studies. Intraarticular injection of mBSA uniformly induced severe inflammation both in control (wild-type and an irrelevant transgenic line) mice and in tsg6/tnfip6 transgenic mice. In contrast to the mBSA-injected knee joints of control animals that were heavily damaged from day 5, the cartilage of transgenic mice that constitutively expressed TSG-6 protein remained intact for at least 1 week, and this was followed by a relatively reduced loss of aggrecan. Concomitant with the loss of aggrecan, MP-generated neoepitopes accumulated in unprotected joints. By day 35, the proteoglycan content returned to nearly normal levels in tsg6/tnfip6 transgenic mice, whereas it remained low in MP-damaged knee cartilage of control mice.Conclusion. TSG-6 protein is known to form a complex with inter-alpha-inhibitor (IalphaI), a potent serine protease inhibitor, which may be immobilized via the hyaluronan (HA)-binding domain of TSG-6 protein in the HA-rich extracellular matrix of cartilage. Thus, the local accumulation of TSG-6 protein and TSG-6 protein-bound IalphaI in tsg6/tnfip6 transgenic mice may inhibit serine proteases and subsequent activation of NIPS. It is suggested that this mechanism might protect cartilage from extensive degradation even in the presence of acute inflammation.