title: TGFbeta/BMP type I receptors ALK1 and ALK2 are essential for BMP9-induced osteogenic signaling in mesenchymal stem cells.
abstract: Mesenchymal stem cells (MSCs) are bone marrow stromal cells that can differentiate into multiple lineages. We previously demonstrated that BMP9 is one of the most potent BMPs to induce osteogenic differentiation of MSCs. BMP9 is one of the least studied BMPs. Whereas ALK1, ALK5, and/or endoglin have recently been reported as potential BMP9 type I receptors in endothelial cells, little is known about type I receptor involvement in BMP9-induced osteogenic differentiation in MSCs. Here, we conduct a comprehensive analysis of the functional role of seven type I receptors in BMP9-induced osteogenic signaling in MSCs. We have found that most of the seven type I receptors are expressed in MSCs. However, using dominant-negative mutants for the seven type I receptors, we demonstrate that only ALK1 and ALK2 mutants effectively inhibit BMP9-induced osteogenic differentiation in vitro and ectopic ossification in MSC implantation assays. Protein fragment complementation assays demonstrate that ALK1 and ALK2 directly interact with BMP9. Likewise, RNAi silencing of ALK1 and ALK2 expression inhibits BMP9-induced BMPR-Smad activity and osteogenic differentiation in MSCs both in vitro and in vivo. Therefore, our results strongly suggest that ALK1 and ALK2 may play an important role in mediating BMP9-induced osteogenic differentiation. These findings should further aid us in understanding the molecular mechanism through which BMP9 regulates osteogenic differentiation of MSCs.
authors.affiliation: Key Laboratory of Diagnostic Medicine designated by Chinese Ministry of Education, The Affiliated Hospitals of Chongqing Medical University, Chongqing 400016, China.
authors.forename: Jinyong
authors.initials: J
authors.lastname: Luo
authors.forename: Min
authors.initials: M
authors.lastname: Tang
authors.forename: Jiayi
authors.initials: J
authors.lastname: Huang
authors.forename: Bai-Cheng
authors.initials: BC
authors.lastname: He
authors.forename: Jian-Li
authors.initials: JL
authors.lastname: Gao
authors.forename: Liang
authors.initials: L
authors.lastname: Chen
authors.forename: Guo-Wei
authors.initials: GW
authors.lastname: Zuo
authors.forename: Wenli
authors.initials: W
authors.lastname: Zhang
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: Yang
authors.initials: Y
authors.lastname: Bi
authors.forename: Xiaoji
authors.initials: X
authors.lastname: Luo
authors.forename: Wei
authors.initials: W
authors.lastname: Jiang
authors.forename: Yuxi
authors.initials: Y
authors.lastname: Su
authors.forename: Jikun
authors.initials: J
authors.lastname: Shen
authors.forename: Stephanie H
authors.initials: SH
authors.lastname: Kim
authors.forename: Enyi
authors.initials: E
authors.lastname: Huang
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Gao
authors.forename: Jian-Zhong
authors.initials: JZ
authors.lastname: Zhou
authors.forename: Ke
authors.initials: K
authors.lastname: Yang
authors.forename: Hue H
authors.initials: HH
authors.lastname: Luu
authors.forename: Xiaochuan
authors.initials: X
authors.lastname: Pan
authors.forename: Rex C
authors.initials: RC
authors.lastname: Haydon
authors.forename: Zhong-Liang
authors.initials: ZL
authors.lastname: Deng
authors.forename: Tong-Chuan
authors.initials: TC
authors.lastname: He
mesh_terms: D030201:Activin Receptors, Type I / Q000235:genetics / Q000378:metabolism*; D030301:Activin Receptors, Type II; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D055427:Growth Differentiation Factor 2 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D010012:Osteogenesis / Q000187:drug effects* / Q000235:genetics; D011485:Protein Binding; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055114:X-Ray Microtomography
chemical_list: D017077:Culture Media, Conditioned; D055427:Growth Differentiation Factor 2; D034741:RNA, Small Interfering; D030201:Activin Receptors, Type I; D030301:Activin Receptors, Type II; C498943:Acvr1 protein, mouse; C498931:Acvrl1 protein, mouse; D000469:Alkaline Phosphatase