The mTOR/ULK1 signaling pathway mediates the autophagy-promoting and osteogenic effects of dicalcium silicate nanoparticles

Abstract

A novel bioactive inorganic material containing silicon, calcium and oxygen, calcium silicate (Ca 2 SiO 4 , C 2 S) with a CaO-SiO 2 ingredient, has been identified as a potential candidate for artificial bone. Autophagy has an essential function in adult tissue homoeostasis and tumorigenesis. However, little is known about whether silicate nanoparticles (C 2 S NPs) promote osteoblastic differentiation by inducing autophagy. Here we investigated the effects of C 2 S NPs on bone marrow mesenchymal stem cell differentiation (BMSCs) in osteoblasts. Furthermore, we identified the osteogenic gene and protein expression in BMSCs treated with C 2 S NPs. We found that autophagy is important for the ability of C 2 S NPs to induce osteoblastic differentiation of BMSCs. Our results showed that treatment with C 2 S NPs upregulated the expression of BMP2, UNX2, and OSX in BMSCs, and significantly promoted the expression of LC3 and Beclin, while P62 (an autophagy substrate) was downregulated. C 2 S NP treatment could also enhance Alizarin red S dye (ARS), although alkaline phosphatase (ALP) activity was not significantly changed. However, all these effects could be partially reversed by 3-MA. We then detected potential signaling pathways involved in this biological effect and found that C 2 S NPs could activate autophagy by suppressing mTOR and facilitating ULK1 expression. Autophagy further activated β-catenin expression and promoted osteogenic differentiation. In conclusion, C 2 S NPs promote bone formation and osteogenic differentiation in BMSCs by activating autophagy. They achieve this effect by activating mTOR/ ULK1, inducing autophagy, and subsequently triggering the WNT/β-catenin pathway to boost the differentiation and biomineralization of osteoblasts.

c-MYC-induced long noncoding RNA MEG3 aggravates kidney ischemia–reperfusion injury through activating mitophagy by upregulation of RTKN to trigger the Wnt/β-catenin pathway

“…The Wnt/β-catenin pathway is activated in AKI 43 , 44 and can promote apoptosis of HK-2 cells 45 , 46 . The Wnt/β-catenin pathway can activate autophagy 47 – 49 or be triggered by autophagy 50 . Moreover, MEG3 downregulates miR-183 to activate BRI3 and thus triggers the Wnt/β-Catenin pathway in BON1 cells 51 .…”

Silicified collagen scaffold induces semaphorin 3A secretion by sensory nerves to improve in-situ bone regeneration

“…Western blot assay was used to identify the expression or phosphorylation of DRG tissues derived from the SCS and the blank groups that were sacrificed on week 6 (n = 6). Previous studies have shown that Si activates Wnt/β-catenin [ 25 ], MAPK/p38 [ 26 ] and PI3K/Akt/mTOR signaling pathways [ 27 ]. Freshly separated tissues were homogenized and lysed in radio-immunoprecipitation assay lysis containing 1x phosphatase inhibitor cocktail (Roche, Mannheim, Germany).…”

High PPT1 expression predicts poor clinical outcome and PPT1 inhibitor DC661 enhances sorafenib sensitivity in hepatocellular carcinoma

“…The autophagy process can basically be divided into an early and late stage [ 9 ]. The early autophagy stage includes the initiation, nucleation, and elongation of autophagosomes [ 10 ], while lysosomes fuse with autophagosomes, hydrolyze damaged organelles, and recycle them during the late stage of autophagy [ 10 , 19 ]. Because both normative and non-normative autophagies depend on lysosomal degradation, lysosomes provide the best targets for autophagy inhibition [ 9 ].…”