Endoglin differentially regulates TGF-β-induced Smad2/3 and Smad1/5 signalling and its expression correlates with extracellular matrix production and cellular differentiation state in human chondrocytes
Endoglin differentially regulates TGF-β-induced Smad2/3 and Smad1/5 signalling and its expression correlates with extracellular matrix production and cellular differentiation state in human chondrocytes
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DOI：
10.1016/j.joca.2010.09.002
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发表时间：
2010-11-01
影响因子：
7
通讯作者：
Philip, A.
中科院分区：
文献类型：
--
作者：
Finnson, K. W.;Parker, W. L.;Philip, A.
目的：转化生长因子-β (TGF-β) 在软骨稳态中发挥关键作用，其信号传导失调与骨关节炎 (OA) 有关。 TGF-β 同种型通过一对跨膜丝氨酸/苏氨酸激酶（称为 I 型和 II 型 TGF-β 受体）发出信号。内皮糖蛋白是一种 TGF-β 共受体，在 II 型 TGF-β 受体存在的情况下以高亲和力结合 TGF-β。我们之前已经证明内皮糖蛋白在人软骨细胞中表达，并且它与 TGF-β 信号受体形成复合物。然而，软骨细胞中内皮糖蛋白表达的功能意义尚不清楚。我们的目的是确定内皮糖蛋白是否调节人软骨细胞中的 TGF-β/Smad 信号传导和细胞外基质 (ECM) 产生，以及其表达是否随软骨细胞分化状态而变化。方法：通过人软骨细胞中内皮糖蛋白的过表达或反义吗啉代/siRNA 敲低，并测量 TGF-β 诱导的 Smad 磷酸化、转录活性和 ECM 产生来确定内皮糖蛋白功能。在人软骨细胞继代培养诱导的去分化过程中以及在正常与 OA 软骨样本中测定内皮糖蛋白表达水平的变化。结果：内皮糖蛋白增强人软骨细胞中 TGF-β 1 诱导的 Smad1/5 磷酸化并抑制 TGF-β 1 诱导的 Smad2 磷酸化、Smad3 驱动的转录活性和 ECM 产生。此外，内皮糖蛋白 siRNA 敲低对 TGF-β1 诱导的 Smad3 驱动转录的增强作用会被 ALK1 过表达逆转。此外，与正常软骨相比，传代诱导去分化后的软骨细胞和 OA 软骨中的内皮糖蛋白水平有所增加。结论：总的来说，我们的结果表明内皮糖蛋白调节人软骨细胞中 TGF-β/ALK1/Smad1/5 和 ALK5/Smad2/3 信号传导以及 ECM 产生之间的平衡，并且内皮糖蛋白可能代表软骨细胞表型的标志物。 (C) 2010 年国际骨关节炎研究协会。由爱思唯尔有限公司出版。保留所有权利。
Objective: Transforming growth factor-beta (TGF-beta) plays a critical role in cartilage homeostasis and deregulation of its signalling is implicated in osteoarthritis (OA). TGF-beta isoforms signal through a pair of transmembrane serine/threonine kinases known as the type I and type II TGF-beta receptors. Endoglin is a TGF-beta co-receptor that binds TGF-beta with high affinity in the presence of the type II TGF-beta receptor. We have previously shown that endoglin is expressed in human chondrocytes and that it forms a complex with the TGF-beta signalling receptors. However, the functional significance of endoglin expression in chondrocytes is unknown. Our objective was to determine whether endoglin regulates TGF-beta/Smad signalling and extracellular matrix (ECM) production in human chondrocytes and whether its expression varies with chondrocyte differentiation state.Method: Endoglin function was determined by overexpression or antisense morpholino/siRNA knockdown of endoglin in human chondrocytes and measuring TGF-beta-induced Smad phosphorylation, transcriptional activity and ECM production. Alterations in endoglin expression levels were determined during subculture-induced dedifferentiation of human chondrocytes and in normal vs OA cartilage samples.Results: Endoglin enhances TGF-beta 1-induced Smad1/5 phosphorylation and inhibits TGF-beta 1-induced Smad2 phosphorylation, Smad3-driven transcriptional activity and ECM production in human chondrocytes. In addition, the enhancing effect of endoglin siRNA knockdown on TGF-beta 1-induced Smad3-driven transcription is reversed by ALK1 overexpression. Furthermore, endoglin levels are increased in chondrocytes following subculture-induced dedifferentiation and in OA cartilage as compared to normal cartilage.Conclusion: Together, our results suggest that endoglin regulates the balance between TGF-beta/ALK1/Smad1/5 and ALK5/Smad2/3 signalling and ECM production in human chondrocytes and that endoglin may represent a marker for chondrocyte phenotype. (C) 2010 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.