title: MicroRNA-29a mitigates glucocorticoid induction of bone loss and fatty marrow by rescuing Runx2 acetylation.
abstract: Glucocorticoid treatment reportedly increases the morbidity of osteoporotic or osteonecrotic disorders. Exacerbated bone acquisition and escalated marrow adipogenesis are prominent pathological features of glucocorticoid-mediated skeletal disorders. MicroRNAs reportedly modulate tissue metabolism and remodeling. This study was undertaken to investigate the biological roles of microRNA-29a (miR-29a) in skeletal and fat metabolism in the pathogenesis of glucocorticoid-induced osteoporosis. Transgenic mice overexpressing miR-29a precursor or wild-type mice were given methylprednisolone. Bone mass, microarchitecture and histology were assessed by dual energy X-ray absorptiometry, μCT and histomorphometry. Differential gene expression and signaling components were delineated by quantitative RT-PCR and immunoblotting. Glucocorticoid treatment accelerated bone loss and marrow fat accumulation in association with decreased miR-29a expression. The miR-29a transgenic mice had high bone mineral density, trabecular microarchitecture and cortical thickness. miR-29a overexpression mitigated the glucocorticoid-induced impediment of bone mass, skeletal microstructure integrity and mineralization reaction and attenuated fatty marrow histopathology. Ex vivo, miR-29a increased osteogenic differentiation capacity and alleviated the glucocorticoid-induced promotion of adipocyte formation in primary bone-marrow mesenchymal progenitor cell cultures. Through inhibition of histone deacetylase 4 (HDAC4) expression, miR-29a restored acetylated Runx2 and β-catenin abundances and reduced RANKL, leptin and glucocorticoid receptor expression in glucocorticoid-mediated osteoporosis bone tissues. Taken together, glucocorticoid suppression of miR-29a signaling disturbed the balances between osteogenic and adipogenic activities, and thereby interrupted bone formation and skeletal homeostasis. miR-29a inhibition of HDAC4 stabilized the acetylation state of Runx2 and β-catenin that ameliorated the detrimental effects of glucocorticoid on mineralization and lipogenesis reactions in bone tissue microenvironments. This study highlighted emerging skeletal-anabolic actions of miR-29a signaling in the progression of glucocorticoid-induced bone tissue destruction. Sustaining miR-29a actions is beneficial in protecting against glucocorticoid-mediated osteoporosis.
authors.affiliation: Departments of Orthopedic Surgery, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan; Graduate Institute of Clinical Medical Sciences, Chang Gung University College of Medicine, Kaohsiung, Taiwan.
authors.forename: Jih-Yang
authors.initials: JY
authors.lastname: Ko
authors.affiliation: Department of Medical Research, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan; Core Laboratory for Phenomics and Diagnostics, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan.
authors.forename: Pei-Chin
authors.initials: PC
authors.lastname: Chuang
authors.affiliation: Department of Medical Research, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan; Core Laboratory for Phenomics and Diagnostics, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan.
authors.forename: Huei-Jin
authors.initials: HJ
authors.lastname: Ke
authors.affiliation: Department of Medical Research, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan; Core Laboratory for Phenomics and Diagnostics, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan.
authors.forename: Yu-Shan
authors.initials: YS
authors.lastname: Chen
authors.affiliation: Department of Medical Research, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan; Core Laboratory for Phenomics and Diagnostics, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan.
authors.forename: Yi-Chih
authors.initials: YC
authors.lastname: Sun
authors.affiliation: Department of Medical Research, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan; Centre for Translational Research in Biomedical Sciences, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan; Core Laboratory for Phenomics and Diagnostics, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan; Graduate Institute of Clinical Medical Sciences, Chang Gung University College of Medicine, Kaohsiung, Taiwan. Electronic address: wangfs@ms33.hinet.net.
authors.forename: Feng-Sheng
authors.initials: FS
authors.lastname: Wang
mesh_terms: D015502:Absorptiometry, Photon; D000107:Acetylation; D050156:Adipogenesis / Q000187:drug effects / Q000235:genetics; D000818:Animals; D001853:Bone Marrow / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D001842:Bone and Bones / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D050659:Core Binding Factor Alpha 1 Subunit / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005938:Glucocorticoids / Q000633:toxicity*; D015151:Immunoblotting; D017403:In Situ Hybridization; D008775:Methylprednisolone / Q000633:toxicity; D051379:Mice; D008822:Mice, Transgenic; D035683:MicroRNAs / Q000378:metabolism*; D010012:Osteogenesis / Q000187:drug effects / Q000235:genetics; D010024:Osteoporosis / Q000139:chemically induced / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055114:X-Ray Microtomography
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; D005938:Glucocorticoids; C547014:MIRN29 microRNA, mouse; D035683:MicroRNAs; C493716:Runx2 protein, mouse; D008775:Methylprednisolone
keywords: Bone loss; HDAC4; Marrow fat; Runx2 acetylation; miR-29a