title: Epidermal growth factor receptor (EGFR) signaling regulates epiphyseal cartilage development through β-catenin-dependent and -independent pathways.
abstract: 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.
authors.affiliation: From the Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104,; the Department of Physiology, School of Basic Medical Science, Wuhan University, Wuhan 430072, Hubei Province, China.
authors.forename: Xianrong
authors.initials: X
authors.lastname: Zhang
authors.affiliation: From the Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
authors.forename: Ji
authors.initials: J
authors.lastname: Zhu
authors.affiliation: From the Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104,; the Shanghai Municipal Hospital of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China.
authors.forename: Yumei
authors.initials: Y
authors.lastname: Li
authors.affiliation: From the Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104,; the Department of Orthopaedic Surgery, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, Zhejiang Province, China.
authors.forename: Tiao
authors.initials: T
authors.lastname: Lin
authors.affiliation: From the Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
authors.forename: Valerie A
authors.initials: VA
authors.lastname: Siclari
authors.affiliation: From the Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Chandra
authors.affiliation: the Department of Orthopaedic Surgery, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, Zhejiang Province, China.
authors.forename: Elena M
authors.initials: EM
authors.lastname: Candela
authors.affiliation: From the Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104,; the Department of Surgery, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104.
authors.forename: Eiki
authors.initials: E
authors.lastname: Koyama
authors.affiliation: From the Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104,; the Department of Surgery, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104.
authors.forename: Motomi
authors.initials: M
authors.lastname: Enomoto-Iwamoto
authors.affiliation: From the Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104,. Electronic address: qinling@mail.med.upenn.edu.
authors.forename: Ling
authors.initials: L
authors.lastname: Qin
mesh_terms: D000818:Animals; D019902:Chondrocytes / Q000378:metabolism*; D017364:Collagenases / Q000096:biosynthesis / Q000235:genetics; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D005109:Extracellular Matrix / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D006132:Growth Plate / Q000196:embryology* / Q000378:metabolism; D060488:Low Density Lipoprotein Receptor-Related Protein-6 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D010766:Phosphorylation / Q000502:physiology; D053245:RANK Ligand / Q000235:genetics / Q000378:metabolism; D060449:Wnt Signaling Pathway / Q000502:physiology*; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
chemical_list: D060488:Low Density Lipoprotein Receptor-Related Protein-6; C555476:Lrp6 protein, mouse; D053245:RANK Ligand; C505689:Tnfsf11 protein, mouse; D051176:beta Catenin; C541485:EGFR protein, mouse; D066246:ErbB Receptors; D017364:Collagenases
keywords: Beta-Catenin; Cartilage Biology; Cartilage Matrix Degradation; Epidermal Growth Factor Receptor (EGFR); Extracellular Matrix; Matrix Metalloproteinase (MMP); Secondary Ossification Center
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