The Critical Role of PI3K/AKT/mTOR Signaling in BCP Ceramic-Induced Osteogenesis

Abstract

Increasing studies demonstrate biphasic calcium phosphate (BCP) ceramics can induce bone regeneration. But the underlying molecular mechanisms involved are still poorly understood. This work was proposed to investigate how PI3k/AKT/mTOR signaling influenced the osteogenesis mediated by BCP ceramics. The results showed that a co-culture with BCP ceramics promoted the proliferation of murine bone marrow-derived mesenchymal stem cells (BMSCs) in a time-dependent manner. But the resulting cell proliferation was then suppressed by the selective inhibition of either PI3k, AKT, or mTOR by LY294002, MK2206, or RAP, respectively. Next, we confirmed that BCP ceramics up-regulated the phosphorylation levels of AKT and mTOR, suggesting the ability of BCP ceramics to drive the activation of PI3k/AKT/mTOR signaling in BMSCs. Further, the blockade of PI3k/AKT/mTOR signaling prevented the BCP ceramics from up-regulating the expression of genes encoding OPN and RUNX2 indicating osteogenic differentiation and VEGF referring to pro-angiogenesis by BMSCs, and suppressed the infiltration of stem cells and new bone formation in the implants following intra-muscular implantation of BCP ceramics in the mice. Therefore, our results suggested that PI3K/AKT/mTOR signaling played a critical regulatory role in BCP ceramic-induced osteogenesis.

Note:
Funding Information: This work is supported by Sichuan Science and Technology Program (grant No. 2020YFS0039), National Natural Science Foundation of China (Grant No. 32171333), and the Fundamental Research Funds for the Central Universities (grant No. YJ201915).

Declaration of Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Ethics Approval Statement: All animal experiments in the study were approved by the local Ethic Committee of Sichuan University (Chengdu, China), and the surgeries were carried out following the Guide for the Care and Use of Laboratory Animals published by the National Academy of Sciences.

Keywords: calcium phosphate ceramics, cell proliferation, PI3K/AKT/mTOR signaling, Osteogenesis, Angiogenesis, stem cell infiltration