title: Retinoic acids potentiate BMP9-induced osteogenic differentiation of mesenchymal progenitor cells.
abstract: BACKGROUND
  As one of the least studied bone morphogenetic proteins (BMPs), BMP9 is one of the most osteogenic BMPs. Retinoic acid (RA) signaling is known to play an important role in development, differentiation and bone metabolism. In this study, we investigate the effect of RA signaling on BMP9-induced osteogenic differentiation of mesenchymal progenitor cells (MPCs).
  
  
  RESULTS
  Both primary MPCs and MPC line are used for BMP9 and RA stimulation. Recombinant adenoviruses are used to deliver BMP9, RARalpha and RXRalpha into MPCs. The in vitro osteogenic differentiation is monitored by determining the early and late osteogenic markers and matrix mineralization. Mouse perinatal limb explants and in vivo MPC implantation experiments are carried out to assess bone formation. We find that both 9CRA and ATRA effectively induce early osteogenic marker, such as alkaline phosphatase (ALP), and late osteogenic markers, such as osteopontin (OPN) and osteocalcin (OC). BMP9-induced osteogenic differentiation and mineralization is synergistically enhanced by 9CRA and ATRA in vitro. 9CRA and ATRA are shown to induce BMP9 expression and activate BMPR Smad-mediated transcription activity. Using mouse perinatal limb explants, we find that BMP9 and RAs act together to promote the expansion of hypertrophic chondrocyte zone at growth plate. Progenitor cell implantation studies reveal that co-expression of BMP9 and RXRalpha or RARalpha significantly increases trabecular bone and osteoid matrix formation.
  
  
  CONCLUSIONS
  Our results strongly suggest that retinoid signaling may synergize with BMP9 activity in promoting osteogenic differentiation of MPCs. This knowledge should expand our understanding about how BMP9 cross-talks with other signaling pathways. Furthermore, a combination of BMP9 and retinoic acid (or its agonists) may be explored as effective bone regeneration therapeutics to treat large segmental bony defects, non-union fracture, and/or osteoporotic fracture.
authors.affiliation: Department of Orthopaedic Surgery, West China Hospital, Sichuan University, Chengdu, Sichuan, China.
authors.forename: Wenli
authors.initials: W
authors.lastname: Zhang
authors.forename: Zhong-Liang
authors.initials: ZL
authors.lastname: Deng
authors.forename: Liang
authors.initials: L
authors.lastname: Chen
authors.forename: Guo-Wei
authors.initials: GW
authors.lastname: Zuo
authors.forename: Qing
authors.initials: Q
authors.lastname: Luo
authors.forename: Qiong
authors.initials: Q
authors.lastname: Shi
authors.forename: Bing-Qiang
authors.initials: BQ
authors.lastname: Zhang
authors.forename: Eric R
authors.initials: ER
authors.lastname: Wagner
authors.forename: Farbod
authors.initials: F
authors.lastname: Rastegar
authors.forename: Stephanie H
authors.initials: SH
authors.lastname: Kim
authors.forename: Wei
authors.initials: W
authors.lastname: Jiang
authors.forename: Jikun
authors.initials: J
authors.lastname: Shen
authors.forename: Enyi
authors.initials: E
authors.lastname: Huang
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Gao
authors.forename: Jian-Li
authors.initials: JL
authors.lastname: Gao
authors.forename: Jian-Zhong
authors.initials: JZ
authors.lastname: Zhou
authors.forename: Jinyong
authors.initials: J
authors.lastname: Luo
authors.forename: Jiayi
authors.initials: J
authors.lastname: Huang
authors.forename: Xiaoji
authors.initials: X
authors.lastname: Luo
authors.forename: Yang
authors.initials: Y
authors.lastname: Bi
authors.forename: Yuxi
authors.initials: Y
authors.lastname: Su
authors.forename: Ke
authors.initials: K
authors.lastname: Yang
authors.forename: Hao
authors.initials: H
authors.lastname: Liu
authors.forename: Hue H
authors.initials: HH
authors.lastname: Luu
authors.forename: Rex C
authors.initials: RC
authors.lastname: Haydon
authors.forename: Tong-Chuan
authors.initials: TC
authors.lastname: He
authors.forename: Bai-Cheng
authors.initials: BC
authors.lastname: He
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D002460:Cell Line; D002478:Cells, Cultured; D055427:Growth Differentiation Factor 2 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D009924:Organ Culture Techniques; D010012:Osteogenesis / Q000187:drug effects / Q000235:genetics; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism; D000072482:Retinoic Acid Receptor alpha; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014212:Tretinoin / Q000494:pharmacology*
chemical_list: D055427:Growth Differentiation Factor 2; C000607071:RARA protein, human; C000607072:Rara protein, mouse; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D014212:Tretinoin