Li Fu-Shu, Li Pei-Pei, Li Ling, Deng Yan, Hu Ying, He Bai-Cheng
Department of Pharmacology, School of Pharmacy, Chongqing Medical University, Chongqing, China.
Key Laboratory of Biochemistry and Molecular Pharmacology of Chongqing, Chongqing Medical University, Chongqing, China.
Front Cell Dev Biol. 2021 Feb 4;8:608544. doi: 10.3389/fcell.2020.608544. eCollection 2020.
Bone morphogenetic protein 9 (BMP9) is one of the most efficacious osteogenic cytokines. PTEN and Wnt10b are both implicated in regulating the osteogenic potential of BMP9, but the potential relationship between them is unknown. In this study, we determined whether PTEN could reduce the expression of Wnt10b during the osteogenic process initialized by BMP9 in mesenchymal stem cells (MSCs) and the possible molecular mechanism. We find that PTEN is inhibited by BMP9 in MSCs, but Wnt10b is increased simultaneously. The BMP9-induced osteogenic markers are reduced by PTEN but increased by silencing PTEN. The effects of knockdown PTEN on elevating BMP9-induced osteogenic markers are almost abolished by knockdown of Wnt10b. On the contrary, the BMP9-increased ALP activities and mineralization are both inhibited by PTEN but almost reversed by the combination of Wnt10b. Bone masses induced by BMP9 are enhanced by knockdown of PTEN, which is reduced by knockdown of Wnt10b. The BMP9-increased Wnt10b is decreased by PTEN but enhanced by knockdown of PTEN. Meanwhile, the BMP9-induced Wnt10b is also reduced by a PI3K-specific inhibitor (Ly294002) or rapamycin, respectively. The BMP9-induced phosphorylation of CREB or Smad1/5/9 is also reduced by PTEN, but enhanced by PTEN knockdown. In addition, p-CREB interacts with p-Smad1/5/9 in MSCs, and p-CREB or p-Smad1/5/9 are both enriched at the promoter region of Wnt10b. Our findings indicate that inhibitory effects of PTEN on BMP9's osteogenic potential may be partially mediated through decreasing the expression of Wnt10b via the disturbance of interaction between CREB and BMP/Smad signaling.
骨形态发生蛋白9（BMP9）是最有效的成骨细胞因子之一。PTEN和Wnt10b均参与调节BMP9的成骨潜能，但它们之间的潜在关系尚不清楚。在本研究中，我们确定了PTEN是否能在间充质干细胞（MSC）中由BMP9启动的成骨过程中降低Wnt10b的表达以及可能的分子机制。我们发现，在MSC中PTEN被BMP9抑制，但Wnt10b同时增加。PTEN可降低BMP9诱导的成骨标志物，但沉默PTEN则使其增加。敲低Wnt10b几乎消除了敲低PTEN对提高BMP9诱导的成骨标志物的作用。相反，PTEN抑制了BMP9增加的碱性磷酸酶（ALP）活性和矿化，但Wnt10b的联合作用几乎使其逆转。敲低PTEN增强了BMP9诱导的骨量，而敲低Wnt10b则使其减少。PTEN可降低BMP9增加的Wnt10b，但敲低PTEN则使其增强。同时，BMP9诱导的Wnt10b也分别被PI3K特异性抑制剂（Ly294002）或雷帕霉素降低。PTEN还降低了BMP9诱导的CREB或Smad1/5/9的磷酸化，但敲低PTEN则使其增强。此外，p-CREB在MSC中与p-Smad1/�/9相互作用，且p-CREB或p-Smad1/5/9均在Wnt10b的启动子区域富集。我们的研究结果表明，PTEN对BMP9成骨潜能的抑制作用可能部分是通过干扰CREB与BMP/Smad信号之间的相互作用来降低Wnt10b的表达介导的。
