title: Glucocorticoids impair bone formation of bone marrow stromal stem cells by reciprocally regulating microRNA-34a-5p.
abstract: The inhibitory effects of glucocorticoids (GCs) on bone marrow stromal stem cell (BMSC) proliferation and osteoblastic differentiation are an important pathway through which GCs decrease bone formation. We found that microRNA-34a-5p was a critical player in dexamethasone (Dex)-inhibited BMSC proliferation and osteogenic differentiation. MicroRNA-34a-5p might be used as a therapeutic target for GC-impaired bone formation.
  
  
  BACKGROUND
  The inhibitory effects of glucocorticoids (GCs) on bone marrow stromal stem cell (BMSC) proliferation and osteoblastic differentiation are an important pathway through which GCs decrease bone formation. The mechanisms of this process are still not completely understood. Recent studies implicated an important role of microRNAs in GC-mediated responses in various cellular processes, including cell proliferation and differentiation. Therefore, we hypothesized that these regulatory molecules might be implicated in the process of GC-decreased BMSC proliferation and osteoblastic differentiation.
  
  
  METHODS
  Western blot, quantitative real-time PCR, and cell proliferation and osteoblastic differentiation assays were employed to investigate the role of microRNAs in GC-inhibited BMSC proliferation and osteoblastic differentiation.
  
  
  RESULTS
  We found that microRNA-34a-5p was reciprocally regulated by Dex during the process of BMSC proliferation and osteoblastic differentiation. Furthermore, we confirmed that microRNA-34a-5p was a critical player in Dex-inhibited BMSC proliferation and osteogenic differentiation. Mechanistic studies showed that Dex inhibited BMSC proliferation by microRNA-34a-5p targeting cell cycle factors, including CDK4, CDK6, and Cyclin D1. Furthermore, downregulation of microRNA-34a-5p by Dex leads to Notch signaling activation, resulting in inhibition of BMSC osteogenic differentiation.
  
  
  CONCLUSIONS
  These results showed that microRNA-34a-5p, a crucial regulator for BMSC proliferation and osteogenic differentiation, might be used as a therapeutic target for GC-impaired bone formation.
authors.affiliation: Shanghai Key Laboratory for Bone and Joint Diseases, Shanghai Institute of Orthopaedics and Traumatology, Shanghai Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
authors.forename: H
authors.initials: H
authors.lastname: Kang
authors.affiliation: Shanghai Key Laboratory for Bone and Joint Diseases, Shanghai Institute of Orthopaedics and Traumatology, Shanghai Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
authors.forename: H
authors.initials: H
authors.lastname: Chen
authors.affiliation: Shanghai Key Laboratory for Bone and Joint Diseases, Shanghai Institute of Orthopaedics and Traumatology, Shanghai Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
authors.forename: P
authors.initials: P
authors.lastname: Huang
authors.affiliation: Shanghai Key Laboratory for Bone and Joint Diseases, Shanghai Institute of Orthopaedics and Traumatology, Shanghai Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
authors.forename: J
authors.initials: J
authors.lastname: Qi
authors.affiliation: Shanghai Key Laboratory for Bone and Joint Diseases, Shanghai Institute of Orthopaedics and Traumatology, Shanghai Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
authors.forename: N
authors.initials: N
authors.lastname: Qian
authors.affiliation: Shanghai Key Laboratory for Bone and Joint Diseases, Shanghai Institute of Orthopaedics and Traumatology, Shanghai Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China. lfdeng@msn.com.|Ruijin Hospital, Shanghai Jiaotong University School of Medicine, No. 197, The Second Ruijin Road, Luwan District, Shanghai, 200025, People's Republic of China. lfdeng@msn.com.
authors.forename: L
authors.initials: L
authors.lastname: Deng
authors.affiliation: Shanghai Key Laboratory for Bone and Joint Diseases, Shanghai Institute of Orthopaedics and Traumatology, Shanghai Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China. guolei607@126.com.|Ruijin Hospital, Shanghai Jiaotong University School of Medicine, No. 197, The Second Ruijin Road, Luwan District, Shanghai, 200025, People's Republic of China. guolei607@126.com.
authors.forename: L
authors.initials: L
authors.lastname: Guo
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D049109:Cell Proliferation / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology*; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects*; D008810:Mice, Inbred C57BL; D035683:MicroRNAs / Q000235:genetics*; D058990:Molecular Targeted Therapy / Q000379:methods; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects; D010012:Osteogenesis / Q000187:drug effects* / Q000235:genetics
chemical_list: D005938:Glucocorticoids; C551848:MIRN34a microRNA, mouse; D035683:MicroRNAs; D003907:Dexamethasone
keywords: Glucocorticoid; Marrow stromal stem cell; MicroRNA-34a-5p; Osteoblastic differentiation; Proliferation