title: R-spondin 2 facilitates differentiation of proliferating chondrocytes into hypertrophic chondrocytes by enhancing Wnt/β-catenin signaling in endochondral ossification.
abstract: Endochondral ossification is a crucial process for longitudinal growth of bones. Differentiating chondrocytes in growth cartilage form four sequential zones of proliferation, alignment into column, hypertrophy, and substitution of chondrocytes with osteoblasts. Wnt/β-catenin signaling is essential for differentiation of proliferating chondrocytes into hypertrophic chondrocytes in growth cartilage. R-spondin 2 (Rspo2), a member of R-spondin family, is an agonist for Wnt signaling, but its role in chondrocyte differentiation remains unknown. Here we report that growth cartilage of Rspo2-knockout mice shows a decreased amount of β-catenin and increased amounts collagen type II (CII) and Sox9 in the abnormally extended proliferating zone. In contrast, expression of collagen type X (CX) in the hypertrophic zone remains unchanged. Differentiating chondrogenic ATDC5 cells, mimicking proliferating chondrocytes, upregulate Rspo2 and its putative receptor, Lgr5, in parallel. Addition of recombinant human Rspo2 to differentiating ATDC5 cells decreases expressions of Col2a1, Sox9, and Acan, as well as production of proteoglycans. In contrast, lentivirus-mediated knockdown of Rspo2 has the opposite effect. The effect of Rspo2 on chondrogenic differentiation is mediated by Wnt/β-catenin signaling, and not by Wnt/PCP or Wnt/Ca(2+) signaling. We propose that Rspo2 activates Wnt/β-catenin signaling to reduce Col2a1 and Sox9 and to facilitate differentiation of proliferating chondrocytes into hypertrophic chondrocytes in growth cartilage.
authors.affiliation: Division of Neurogenetics, Center of Neurological Disease and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan; Department of Orthopaedic Surgery, Nagoya University School of Medicine, Nagoya, Japan.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Takegami
authors.affiliation: Division of Neurogenetics, Center of Neurological Disease and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Bisei
authors.initials: B
authors.lastname: Ohkawara
authors.affiliation: Division of Neurogenetics, Center of Neurological Disease and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Mikako
authors.initials: M
authors.lastname: Ito
authors.affiliation: Division of Neurogenetics, Center of Neurological Disease and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Masuda
authors.affiliation: Department of Orthopaedic Surgery, Nagoya University School of Medicine, Nagoya, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Nakashima
authors.affiliation: Department of Orthopaedic Surgery, Nagoya University School of Medicine, Nagoya, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Ishiguro
authors.affiliation: Division of Neurogenetics, Center of Neurological Disease and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan. Electronic address: ohnok@med.nagoya-u.ac.jp.
authors.forename: Kinji
authors.initials: K
authors.lastname: Ohno
mesh_terms: D000818:Animals; D002356:Cartilage / Q000378:metabolism; D002454:Cell Differentiation; D049109:Cell Proliferation; D019902:Chondrocytes / Q000166:cytology*; D024043:Collagen Type II / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D055758:SOX9 Transcription Factor / Q000378:metabolism*; D019699:Thrombospondins / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D051153:Wnt Proteins / Q000378:metabolism; D060449:Wnt Signaling Pathway; D051176:beta Catenin / Q000378:metabolism; D000098907:R-Spondins
chemical_list: D024043:Collagen Type II; D036341:Intercellular Signaling Peptides and Proteins; D043562:Receptors, G-Protein-Coupled; D055758:SOX9 Transcription Factor; D019699:Thrombospondins; D014157:Transcription Factors; D051153:Wnt Proteins; D051176:beta Catenin; C447413:Col2a1 protein, mouse; C493597:Lgr5 protein, mouse; C518904:RSPO2 protein, mouse; D000098907:R-Spondins; C557408:Rspo2 protein, human; C527933:Sox9 protein, mouse; C550082:TRIM29 protein, mouse
keywords: Chondrocytes; Collagen type II; Endochondral ossification; R-spondin2 (Rspo2); Wnt/β-catenin signaling