BMP‐9‐induced osteogenic differentiation of mesenchymal progenitors requires functional canonical Wnt/β‐catenin signalling

Abstract

Bone morphogenetic protein 9 (BMP‐9) is a member of the transforming growth factor (TGF)‐β/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/β‐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. β‐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, β‐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 β‐catenin to the osteocalcin promoter. Thus, we have demonstrated that canonical Wnt signalling, possibly through interactions between β‐catenin and Runx2, plays an important role in BMP‐9‐induced osteogenic differentiation of MSCs.

Ginsenoside Rg3 inhibits colorectal tumor growth through the down-regulation of Wnt/ß-catenin signaling

“…Firefly luciferase reporter assay was carried out as described previously (29,34,37,38,(42)(43)(44)(45)(46)(47)(48)(49). Briefly, HCT116 cells were seeded in 25 cm 2 culture flasks and transfected with 3.0 μg per flask of pTOP-Luc luciferase reporter (42,43,48,49) using Lipofectamine (Invitrogen).…”

“…Western blotting experiments were carried out essentially the same as described (45)(46)(47)(50)(51)(52). Briefly, HCT116 cells were seeded in 6-well plates (2x10 5 cells/well) and treated with 60 μM, or 100 μM Rg3 or solvent control for 24 h. Cells were first washed with ice-cold PBS and lysed in 300 μl cell lysis buffer.…”

Sclerostin and the regulation of bone formation: Effects in hip osteoarthritis and femoral neck fracture

“…Wnt signaling is required for bone morphogenetic proteins (BMPs) to stimulate ALP activity in several osteoblastic cell lines. (17,18) Inhibition of Wnt signaling by sclerostin therefore may account for the inhibitory effect of sclerostin on BMP-stimulated bone formation. Stimulation of the canonical Wnt signaling pathway results in the accumulation of b-catenin in the cytoplasm following the inactivation of GSK-3b.…”

Bisindoylmaleimide I enhances osteogenic differentiation

“…Conditional deletion of the β-catenin gene in osteoblasts leads to reduced bone mass, and osteocyte-specific β-catenin-deficient mice develop low bone mass phenotype (Glass et al, 2005;Kramer et al, 2010). Increasing evidences also indicate that autocrine Wnt signaling is required for BMP in inducing bone formation (Rawadi et al, 2003;Fujita and Janz, 2007;Qiang et al, 2008;Tang et al, 2009;Honda, et al, 2010).…”