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Tan Z, Kong M, Wen S, Tsang KY, Niu B, Hartmann C, Chan D, Hui CC, Cheah KSE. IRX3 and IRX5 Inhibit Adipogenic Differentiation of Hypertrophic Chondrocytes and Promote Osteogenesis. J Bone Miner Res 2020; 35:2444-2457. [PMID: 32662900 DOI: 10.1002/jbmr.4132] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 06/19/2020] [Accepted: 07/14/2020] [Indexed: 12/12/2022]
Abstract
Maintaining the correct proportions of different cell types in the bone marrow is critical for bone function. Hypertrophic chondrocytes (HCs) and osteoblasts are a lineage continuum with a minor contribution to adipocytes, but the regulatory network is unclear. Mutations in transcription factors, IRX3 and IRX5, result in skeletal patterning defects in humans and mice. We found coexpression of Irx3 and Irx5 in late-stage HCs and osteoblasts in cortical and trabecular bone. Irx3 and Irx5 null mutants display severe bone deficiency in newborn and adult stages. Quantitative analyses of bone with different combinations of functional alleles of Irx3 and Irx5 suggest these two factors function in a dosage-dependent manner. In Irx3 and Irx5 nulls, the amount of bone marrow adipocytes was increased. In Irx5 nulls, lineage tracing revealed that removal of Irx3 specifically in HCs exacerbated reduction of HC-derived osteoblasts and increased the frequency of HC-derived marrow adipocytes. β-catenin loss of function and gain of function specifically in HCs affects the expression of Irx3 and Irx5, suggesting IRX3 and IRX5 function downstream of WNT signaling. Our study shows that IRX3 and IRX5 regulate fate decisions in the transition of HCs to osteoblasts and to marrow adipocytes, implicating their potential roles in human skeletal homeostasis and disorders.
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Affiliation(s)
- Zhijia Tan
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pok Fu Lam, Hong Kong, HKSAR, China
| | - Mingpeng Kong
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pok Fu Lam, Hong Kong, HKSAR, China
| | - Songjia Wen
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pok Fu Lam, Hong Kong, HKSAR, China
| | - Kwok Yeung Tsang
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pok Fu Lam, Hong Kong, HKSAR, China
| | - Ben Niu
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pok Fu Lam, Hong Kong, HKSAR, China
| | - Christine Hartmann
- Institute of Musculoskeletal Medicine, Department of Bone and Skeletal Research, Faculty of Medicine, University of Münster, Münster, Germany
| | - Danny Chan
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pok Fu Lam, Hong Kong, HKSAR, China
| | - Chi-Chung Hui
- Program in Developmental & Stem Cell Biology, The Hospital for Sick Children and Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Kathryn S E Cheah
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pok Fu Lam, Hong Kong, HKSAR, China
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