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BMP-9-induced osteogenic differentiation of mesenchymal progenitors requires functional canonical Wnt/beta-catenin signalling.

Tang N, Song WX, Luo J, Luo X, Chen J, Sharff KA, Bi Y, He BC, Huang JY, Zhu GH, Su YX, Jiang W, Tang M, He Y, Wang Y, Chen L, Zuo GW, Shen J, Pan X, Reid RR, Luu HH, Haydon RC, He TC - J. Cell. Mol. Med. (2008)

Bottom Line: Wnt3A and BMP-9 enhanced each other's ability to induce alkaline phosphatase (ALP) in MSCs and mouse embryonic fibroblasts (MEFs).Wnt antagonist FrzB was shown to inhibit BMP-9-induced ALP activity more effectively than Dkk1, whereas a secreted form of LPR-5 or low-density lipoprotein receptor-related protein (LRP)-6 exerted no inhibitory effect on BMP-9-induced ALP activity. beta-Catenin knockdown in MSCs and MEFs diminished BMP-9-induced ALP activity, and led to a decrease in BMP-9-induced osteocalcin reporter activity and BMP-9-induced expression of late osteogenic markers.Furthermore, beta-catenin knockdown or FrzB overexpression inhibited BMP-9-induced mineralization in vitro and ectopic bone formation in vivo, resulting in immature osteogenesis and the formation of chondrogenic matrix.

View Article: PubMed Central - PubMed

Affiliation: The Second Affiliated Hospital and the Key Laboratory of Diagnostic Medicine designated by the Chinese Ministry of Education, Chongqing Medical University, Chongqing, China.

ABSTRACT
Bone morphogenetic protein 9 (BMP-9) is a member of the transforming growth factor (TGF)-beta/BMP superfamily, and we have demonstrated that it is one of the most potent BMPs to induce osteoblast differentiation of mesenchymal stem cells (MSCs). Here, we sought to investigate if canonical Wnt/beta-catenin signalling plays an important role in BMP-9-induced osteogenic differentiation of MSCs. Wnt3A and BMP-9 enhanced each other's ability to induce alkaline phosphatase (ALP) in MSCs and mouse embryonic fibroblasts (MEFs). Wnt antagonist FrzB was shown to inhibit BMP-9-induced ALP activity more effectively than Dkk1, whereas a secreted form of LPR-5 or low-density lipoprotein receptor-related protein (LRP)-6 exerted no inhibitory effect on BMP-9-induced ALP activity. beta-Catenin knockdown in MSCs and MEFs diminished BMP-9-induced ALP activity, and led to a decrease in BMP-9-induced osteocalcin reporter activity and BMP-9-induced expression of late osteogenic markers. Furthermore, beta-catenin knockdown or FrzB overexpression inhibited BMP-9-induced mineralization in vitro and ectopic bone formation in vivo, resulting in immature osteogenesis and the formation of chondrogenic matrix. Chromatin immunoprecipitation (ChIP) analysis indicated that BMP-9 induced recruitment of both Runx2 and beta-catenin to the osteocalcin promoter. Thus, we have demonstrated that canonical Wnt signalling, possibly through interactions between beta-catenin and Runx2, plays an important role in BMP-9-induced osteogenic differentiation of MSCs.

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A model depicting the mechanistic basis of β‐catenin function in BMP‐9‐induced osteocalcin (OC) expression. (A) BMP‐9 is less effective in inducing osteocalcin expression when the canonical Wnt/β‐catenin signalling is inhibited by FrzB or silenced by β‐catenin siRNA (e.g. simBC). (B) β‐Catenin directly interacts with Runx2 and acts synergistically on regulating osteocalcin expression. The filled circles represent putative Runx2 binding sites, while the open circle represents the putative LEF1/Tcf4 binding site. The open and filled boxes represent the exons and the coding region of mouse osteocalcin gene, respectively.
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f8: A model depicting the mechanistic basis of β‐catenin function in BMP‐9‐induced osteocalcin (OC) expression. (A) BMP‐9 is less effective in inducing osteocalcin expression when the canonical Wnt/β‐catenin signalling is inhibited by FrzB or silenced by β‐catenin siRNA (e.g. simBC). (B) β‐Catenin directly interacts with Runx2 and acts synergistically on regulating osteocalcin expression. The filled circles represent putative Runx2 binding sites, while the open circle represents the putative LEF1/Tcf4 binding site. The open and filled boxes represent the exons and the coding region of mouse osteocalcin gene, respectively.

Mentions: Based on our findings, we propose a working model as illustrated in Fig. 8, which depicts that canonical Wnt signalling, through a cooperative interaction between β‐catenin and Runx2, plays an important role in BMP‐9‐induced osteogenic differentiation of MSCs. As depicted in Fig. 8A, BMP‐9 regulates Runx2 and subsequent downstream osteogenic factors (such as osteocalcin) with a low efficiency in the absence of canonical Wnt signal, the presence of Wnt antagonist FrzB, or silencing of β‐catenin expression. In the presence of canonical Wnt signal β‐catenin acts cooperatively with BMP‐9‐induced Runx2 to effectively regulate osteogenic factors (Fig. 8B). This model underscores an important role of canonical Wnt signalling in BMP‐9‐induced osteogenic differentiation of MSCs.


BMP-9-induced osteogenic differentiation of mesenchymal progenitors requires functional canonical Wnt/beta-catenin signalling.

Tang N, Song WX, Luo J, Luo X, Chen J, Sharff KA, Bi Y, He BC, Huang JY, Zhu GH, Su YX, Jiang W, Tang M, He Y, Wang Y, Chen L, Zuo GW, Shen J, Pan X, Reid RR, Luu HH, Haydon RC, He TC - J. Cell. Mol. Med. (2008)

A model depicting the mechanistic basis of β‐catenin function in BMP‐9‐induced osteocalcin (OC) expression. (A) BMP‐9 is less effective in inducing osteocalcin expression when the canonical Wnt/β‐catenin signalling is inhibited by FrzB or silenced by β‐catenin siRNA (e.g. simBC). (B) β‐Catenin directly interacts with Runx2 and acts synergistically on regulating osteocalcin expression. The filled circles represent putative Runx2 binding sites, while the open circle represents the putative LEF1/Tcf4 binding site. The open and filled boxes represent the exons and the coding region of mouse osteocalcin gene, respectively.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4940786&req=5

f8: A model depicting the mechanistic basis of β‐catenin function in BMP‐9‐induced osteocalcin (OC) expression. (A) BMP‐9 is less effective in inducing osteocalcin expression when the canonical Wnt/β‐catenin signalling is inhibited by FrzB or silenced by β‐catenin siRNA (e.g. simBC). (B) β‐Catenin directly interacts with Runx2 and acts synergistically on regulating osteocalcin expression. The filled circles represent putative Runx2 binding sites, while the open circle represents the putative LEF1/Tcf4 binding site. The open and filled boxes represent the exons and the coding region of mouse osteocalcin gene, respectively.
Mentions: Based on our findings, we propose a working model as illustrated in Fig. 8, which depicts that canonical Wnt signalling, through a cooperative interaction between β‐catenin and Runx2, plays an important role in BMP‐9‐induced osteogenic differentiation of MSCs. As depicted in Fig. 8A, BMP‐9 regulates Runx2 and subsequent downstream osteogenic factors (such as osteocalcin) with a low efficiency in the absence of canonical Wnt signal, the presence of Wnt antagonist FrzB, or silencing of β‐catenin expression. In the presence of canonical Wnt signal β‐catenin acts cooperatively with BMP‐9‐induced Runx2 to effectively regulate osteogenic factors (Fig. 8B). This model underscores an important role of canonical Wnt signalling in BMP‐9‐induced osteogenic differentiation of MSCs.

Bottom Line: Wnt3A and BMP-9 enhanced each other's ability to induce alkaline phosphatase (ALP) in MSCs and mouse embryonic fibroblasts (MEFs).Wnt antagonist FrzB was shown to inhibit BMP-9-induced ALP activity more effectively than Dkk1, whereas a secreted form of LPR-5 or low-density lipoprotein receptor-related protein (LRP)-6 exerted no inhibitory effect on BMP-9-induced ALP activity. beta-Catenin knockdown in MSCs and MEFs diminished BMP-9-induced ALP activity, and led to a decrease in BMP-9-induced osteocalcin reporter activity and BMP-9-induced expression of late osteogenic markers.Furthermore, beta-catenin knockdown or FrzB overexpression inhibited BMP-9-induced mineralization in vitro and ectopic bone formation in vivo, resulting in immature osteogenesis and the formation of chondrogenic matrix.

View Article: PubMed Central - PubMed

Affiliation: The Second Affiliated Hospital and the Key Laboratory of Diagnostic Medicine designated by the Chinese Ministry of Education, Chongqing Medical University, Chongqing, China.

ABSTRACT
Bone morphogenetic protein 9 (BMP-9) is a member of the transforming growth factor (TGF)-beta/BMP superfamily, and we have demonstrated that it is one of the most potent BMPs to induce osteoblast differentiation of mesenchymal stem cells (MSCs). Here, we sought to investigate if canonical Wnt/beta-catenin signalling plays an important role in BMP-9-induced osteogenic differentiation of MSCs. Wnt3A and BMP-9 enhanced each other's ability to induce alkaline phosphatase (ALP) in MSCs and mouse embryonic fibroblasts (MEFs). Wnt antagonist FrzB was shown to inhibit BMP-9-induced ALP activity more effectively than Dkk1, whereas a secreted form of LPR-5 or low-density lipoprotein receptor-related protein (LRP)-6 exerted no inhibitory effect on BMP-9-induced ALP activity. beta-Catenin knockdown in MSCs and MEFs diminished BMP-9-induced ALP activity, and led to a decrease in BMP-9-induced osteocalcin reporter activity and BMP-9-induced expression of late osteogenic markers. Furthermore, beta-catenin knockdown or FrzB overexpression inhibited BMP-9-induced mineralization in vitro and ectopic bone formation in vivo, resulting in immature osteogenesis and the formation of chondrogenic matrix. Chromatin immunoprecipitation (ChIP) analysis indicated that BMP-9 induced recruitment of both Runx2 and beta-catenin to the osteocalcin promoter. Thus, we have demonstrated that canonical Wnt signalling, possibly through interactions between beta-catenin and Runx2, plays an important role in BMP-9-induced osteogenic differentiation of MSCs.

Show MeSH
Related in: MedlinePlus