Epidermal Growth Factor Receptor (EGFR) Signaling Regulates Epiphyseal Cartilage Development through β-Catenin-dependent and -independent Pathways*
Epidermal Growth Factor Receptor (EGFR) Signaling Regulates Epiphyseal Cartilage Development through β-Catenin-dependent and -independent Pathways*
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DOI：
10.1074/jbc.m113.463554
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发表时间：
2013-09
期刊：
影响因子：
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通讯作者：
Xianrong Zhang;Ji Zhu;Yumei Li;Tiao Lin;Valerie A. Siclari;Abhishek Chandra;Elena M Candela
中科院分区：
文献类型：
--
作者：
Xianrong Zhang;Ji Zhu;Yumei Li;Tiao Lin;Valerie A. Siclari;Abhishek Chandra;Elena M Candela
Background: EGFR is an important player in endochondral ossification. Results: Mice with EGFR deficiency in chondrocytes have delayed secondary ossification center formation due to reduced cartilage degradation, and EGFR regulates MMPs and RANKL expression in chondrocytes partially via Wnt/β-catenin. Conclusion: EGFR regulates epiphyseal cartilage development. Significance: The cross-talk between EGFR and Wnt/β-catenin signaling in chondrocytes shed new light on studying cartilage development and diseases. The epidermal growth factor receptor (EGFR) is an essential player in the development of multiple organs during embryonic and postnatal stages. To understand its role in epiphyseal cartilage development, we generated transgenic mice with conditionally inactivated EGFR in chondrocytes. Postnatally, these mice exhibited a normal initiation of cartilage canals at the perichondrium, but the excavation of these canals into the cartilage was strongly suppressed, resulting in a delay in the formation of the secondary ossification center (SOC). This delay was accompanied by normal chondrocyte hypertrophy but decreased mineralization and apoptosis of hypertrophic chondrocytes and reduced osteoclast number at the border of marrow space. Immunohistochemical analyses demonstrated that inactivation of chondrocyte-specific EGFR signaling reduced the amounts of matrix metalloproteinases (MMP9, -13, and -14) and RANKL (receptor activator of NF-κB ligand) in the hypertrophic chondrocytes close to the marrow space and decreased the cartilage matrix degradation in the SOC. Analyses of EGFR downstream signaling pathways in primary epiphyseal chondrocytes revealed that up-regulation of MMP9 and RANKL by EGFR signaling was partially mediated by the canonical Wnt/β-catenin pathway, whereas EGFR-enhanced MMP13 expression was not. Further biochemical studies suggested that EGFR signaling stimulates the phosphorylation of LRP6, increases active β-catenin level, and induces its nuclear translocation. In line with these in vitro studies, deficiency in chondrocyte-specific EGFR activity reduced β-catenin amount in hypertrophic chondrocytes in vivo. In conclusion, our work demonstrates that chondrocyte-specific EGFR signaling is an important regulator of cartilage matrix degradation during SOC formation and epiphyseal cartilage development and that its actions are partially mediated by activating the β-catenin pathway.
