Shangguan Lei, Ning Guangzhi, Luo Zhuojing, Zhou Yue
The Department of Orthopedics, Xinqiao Hospital, the Third Military Medical University, Chongqing 400037, PR China; The Department of Orthopedics, Xijing Hospital, the Fourth Military Medical University, Xi'an 710032, Shaanxi, PR China.
The Department of Orthopedics, Xinqiao Hospital, the Third Military Medical University, Chongqing 400037, PR China.
Int J Biol Macromol. 2017 Jun;99:293-299. doi: 10.1016/j.ijbiomac.2017.02.087. Epub 2017 Feb 24.
Fibulin-4 is an extracellular matrix (ECM) protein implicated in connective tissue development and elastic fiber formation. However, little is known about the underlying function of Fibulin-4 in cartilage development. The aim of this study was to investigate the role and probable mechanism of Fibulin-4 stimulation in ECM production and chondrocyte differentiation. Fibulin-4 has been observed to be abnormally elevated and matrix metalloproteinases 13 (MMP13) level was highly expressed in human osteoarthritis (OA) chondrocytes. In the chondrogenic cell line ATDC5, Fibulin-4 stimulation profoundly inhibited the expression of ECM gene type II collagen (Col2a1), aggrecan (Acan), and type X collagen (Col10a1). Overexpression of Fibulin-4 attenuated the expression of master transcription factors Sox6, Sox9 and Runx2, but had no effect on the expression of Sox5. Additionally, Fibulin-4 stimulation activated canonical Wnt pathway by reducing the expression of Wnt inhibitor DKK1 but not Sost. Moreover, Fibulin-4 augmented the expression of Wnt/β-catenin signaling target genes like β-catenin and Wnt-3a as well as diminished GSK-3β activation, and DKK1 abolished the effect of Fibulin-4 on chondrocyte differentiation, suggesting that Fibulin-4 is an important regulator of ECM production and chondrocyte differentiation through DKK1-mediated Wnt/β-catenin signaling. Our study provides evidence of a previously unknown link between Fibulin-4 and the canonical Wnt/β-catenin pathway that may contribute to our understanding of the molecular mechanisms of OA.
纤连蛋白-4是一种细胞外基质（ECM）蛋白，与结缔组织发育和弹性纤维形成有关。然而，关于纤连蛋白-4在软骨发育中的潜在功能知之甚少。本研究的目的是探讨纤连蛋白-4刺激在ECM产生和软骨细胞分化中的作用及可能机制。在人类骨关节炎（OA）软骨细胞中，已观察到纤连蛋白-4异常升高，且基质金属蛋白酶13（MMP13）水平高表达。在软骨形成细胞系ATDC5中，纤连蛋白-4刺激显著抑制了ECM基因II型胶原（Col2a1）、聚集蛋白聚糖（Acan）和X型胶原（Col10a1）的表达。纤连蛋白-4的过表达减弱了主要转录因子Sox6、Sox9和Runx2的表达，但对Sox5的表达没有影响。此外，纤连蛋白-4刺激通过降低Wnt抑制剂DKK1的表达而非Sost的表达来激活经典Wnt通路。而且，纤连蛋白-4增强了Wnt/β-连环蛋白信号靶基因如β-连环蛋白和Wnt-3a的表达，并减少了GSK-3β的激活，并且DKK1消除了纤连蛋白-4对软骨细胞分化的影响，这表明纤连蛋白-4是通过DKK1介导的Wnt/β-连环蛋白信号对ECM产生和软骨细胞分化的重要调节因子。我们的研究提供了纤连蛋白-4与经典Wnt/β-连环蛋白通路之间以前未知联系的证据，这可能有助于我们理解OA的分子机制。
