Growth factor regulation of chondrocyte integrins - Differential effects of insulin-like growth factor 1 and transforming growth factor beta on alpha 1 beta 1 integrin expression and chondrocyte adhesion to type VI collagen
Growth factor regulation of chondrocyte integrins - Differential effects of insulin-like growth factor 1 and transforming growth factor beta on alpha 1 beta 1 integrin expression and chondrocyte adhesion to type VI collagen
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DOI：
10.1002/art.1780400211
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发表时间：
1997-02-01
影响因子：
--
通讯作者：
Loeser, RF
中科院分区：
文献类型：
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作者：
Loeser, RF
目标。生长因子调节整合素表达的能力在组织修复和重塑过程中可能是重要的，本研究旨在确定转化生长因子β (TGF β)和胰岛素样生长因子1 （IGF-1）对软骨细胞β 1整合素表达和整合素介导的细胞外基质蛋白粘附的影响。从正常牛关节软骨中获得的软骨细胞分别在10%胎牛血清、100 pM IGF-1或100 pM TGF β中培养，通过免疫沉淀整合素蛋白印迹、Northern印迹分析和细胞粘附试验检测整合素的表达和功能。与无血清培养相比，使用血清可使α 1整合素亚基和代表α 3和α 5的条带平均增加10倍，α 3/ α 5条带平均增加12倍，IGF-1可使α 1和α 3/ α 5条带平均分别增加3倍和4倍。TGF β也增加了α 3/ α 5的5倍，但α 1的平均下降率为无血清对照组的24%，Northern blot分析显示，TGFP显著增加了α 5整合素亚基RNA水平，而IGF-1对α 5或α 1整合素亚基RNA水平没有显著影响，表明其对整合素的影响是转录后的。TGF β治疗导致软骨细胞对VI型胶原的粘附减少50%，而对II型胶原和纤维连接蛋白的粘附受到刺激，IGF-1刺激了对所有3种蛋白的粘附，α 1整合素阻断抗体抑制了高达75%的人软骨细胞对VI型胶原的粘附。IGF-1和TGF - β均刺激软骨细胞表面α 3/ α 5整合素亚基带的表达，刺激软骨细胞对纤维连接蛋白和II型胶原的粘附。这两种生长因子对α 1 - β 1的表达作用相反，IGF-1升高而TGF - β降低该整合素的细胞表面水平，TGF - β处理的细胞对VI型胶原的粘附也降低。IGF-1和TGF β对软骨细胞α 1 β 1表达和对VI型胶原粘附的相反作用表明α 1 β 1介导了软骨细胞对VI型胶原的粘附，这一点通过α 1整合素亚基抗体阻断软骨细胞对VI型胶原的粘附得到证实。
Objective. The ability of growth factors to modulate integrin expression may be important with regard to processes involved in tissue repair and remodeling, This study was undertaken to determine the effect of transforming growth factor beta (TGF beta) and insulin-like growth factor 1 (IGF-1) on chondrocyte beta 1 integrin expression and integrin-mediated adhesion to extracellular matrix proteins.Methods. Chondrocytes obtained from normal bovine articular cartilage were cultured in the presence or absence of 10% fetal bovine serum, 100 pM IGF-1, or 100 pM TGF beta, Integrin expression and function were measured by protein blotting of immunoprecipitated integrins, Northern blot analysis, and cell adhesion assays.Results. Immunoprecipitation with an anti-beta 1 integrin antibody coprecipitated the alpha 1 integrin subunit and a band representing alpha 3 and alpha 5, as previously reported, Compared with serum-free cultures, the use of serum resulted in an average 10-fold increase in the alpha 1 band and a 12-fold increase in the alpha 3/alpha 5 band, IGF-1 increased alpha 1 and alpha 3/alpha 5 by an average of 3-fold and 4-fold, respectively, TGF beta also increased alpha 3/alpha 5 by >5-fold but decreased alpha 1 to an average of 24% of that found in serum-free controls, Northern blot analysis revealed that TGFP significantly increased alpha 5 integrin subunit RNA levels, IGF-1 did not have a significant effect on alpha 5 or alpha 1 integrin subunit RNA levels, suggesting that its effects on integrins are posttranscriptional, In cell adhesion assays, TGF beta treatment resulted in a 50% decrease in the adhesion of chondrocytes to type VI collagen, while adhesion to type II collagen and fibronectin was stimulated, IGF-1 stimulated adhesion to all 3 proteins, An alpha 1 integrin blocking antibody inhibited up to 75% of the adhesion of human chondrocytes to type VI collagen.Conclusion. Both IGF-1 and TGF beta stimulate chondrocyte cell surface expression of the alpha 3/alpha 5 integrin subunit band and stimulate adhesion of chondrocytes to fibronectin and type II collagen, The 2 growth factors have opposite effects on expression of alpha 1 beta 1, with IGF-1 increasing and TGF beta decreasing cell surface levels of this integrin, TGF beta-treated cells also have decreased adhesion to type VI collagen, The opposing effects of IGF-1 and TGF beta on chondrocyte expression of alpha 1 beta 1 and on adhesion to type VI collagen suggest that alpha 1 beta 1 mediates chondrocyte adhesion to type VI collagen, This was confirmed by using an antibody to the alpha 1 integrin subunit to block adhesion of chondrocytes to type VI collagen.