Suppression of AKT-mTOR signal pathway enhances osteogenic/dentinogenic capacity of stem cells from apical papilla

Abstract

BackgroundStem cells from apical papilla (SCAP) are a subpopulation of mesenchymal stem cells (MSCs) isolated from the apical papilla of the developing tooth root apex of human teeth. Because of their osteogenic/dentinogenic capacity, SCAP are considered as a source for bone and dentin regeneration. However, little is understood about the molecular mechanism of osteogenic/dentinogenic differentiation of SCAP. Phosphoinositide 3 kinase (PI3K)-AKT-mammalian target of rapamycin (mTOR) signal pathway participates in regulating the differentiation of various cell types, such as MSCs. In this study, we examined the role of the PI3K-AKT-mTOR signal pathway in the osteogenic/dentinogenic differentiation of SCAP. Moreover, we challenge to fabricate scaffold-free SCAP-based spheroidal calcified constructs.MethodsSCAP were pretreated with or without small interfering RNA for AKT (AKT siRNA), PI3K inhibitor LY294402, and mTOR inhibitor rapamycin and were cultured under osteogenic/dentinogenic differentiation to examine in vitro and in vivo calcified tissue formation. Moreover, SCAP-based cell aggregates were pretreated with or without LY294402 and rapamycin. The cell aggregates were cultured under osteogenic/dentinogenic condition and were analyzed the calcification of the aggregates.ResultsPretreatment with AKT siRNA, LY294402, and rapamycin enhances the in vitro and in vivo calcified tissue-forming capacity of SCAP. SCAP were fabricated as scaffold-free spheroids and were induced into forming calcified 3D constructs. The calcified density of the spheroidal constructs was enhanced when the spheroids were pretreated with LY294402 and rapamycin.ConclusionsOur findings indicate that the suppression of PI3K-AKT-mTOR signal pathway plays a role in not only enhancing the in vivo and in vitro osteogenic/dentinogenic differentiation of SCAP, but also promoting the calcification of scaffold-free SCAP-based calcified constructs. These findings suggest that a suppressive regulation of PI3K-AKT-mTOR signal pathway is a novel approach for SCAP-based bone and dentin regeneration.Electronic supplementary materialThe online version of this article (10.1186/s13287-018-1077-9) contains supplementary material, which is available to authorized users.

Activation of cannabinoid receptor type 2-induced osteogenic differentiation involves autophagy induction and p62-mediated Nrf2 deactivation

“…mTOR, a serine/threonine protein kinase, is a core component of mTOR complex 1 (mTORC1), the activation of which potently inhibits autophagy [26,27]. Administration of mTOR inhibitor (rapamycin) or genetic ablation of mTOR has been reported to preserve the function of osteoblasts and osteocytes, and prevent bone loss [28,29]. In addition to initiating autophagy, we also found that both CNR2 agonists suppressed mTOR signaling transduction.…”

Shikonin induces odontoblastic differentiation of dental pulp stem cells via AKT–mTOR signaling in the presence of CD44

“…The AKT signaling pathway is reportedly involved in osteogenic differentiation of human mesenchymal stem cells, human dental follicle cells, and rat bone marrow stromal cells [27–29]. However, AKT reportedly inhibits odontogenic differentiation of stem cells from the apical papilla [30,31]; thus, there is controversy regarding the function of AKT–mTOR signaling. The results of our study suggest that the AKT–mTOR signaling pathway is involved in the shikonin-induced odontoblastic differentiation of DPSCs.…”

Pulp Innate Immune Defense: Translational Opportunities

“…Of the compounds that were shown to exert an inhibitory effect on NETosis, including lapatinib, carmustine, erlotinib, bosutinib, rapamycin, and nilotinib 62 , to our knowledge, only rapamycin has been studied in dentin-pulp biology. Indeed, data from one recent study indicated that this compound was able to enhance the dentinogenic capacity of stem cells in culture 63 . Clearly, further studies on the relevance of NETs and their components in pulpal inflammation are still required along with assay of the effects of novel therapeutics, which may modulate inflammatory processes and enhance dental tissue repair.…”