Transforming growth factor-β (TGF-β) induces the expression of chondrogenesis-related genes through TGF-β receptor II (TGFRII)-AKT-mTOR signaling in primary cultured mouse precartilaginous stem cells.

Precartilaginous stem cells (PSCs) are adult stem cells which could initiate chondrocytes and bone growth. In the current study, we purified PSCs from the neonate mice' perichondrial mesenchyme through immunomagnetic beads with the fibroblast growth factor receptor-3 (FGFR-3) antibody. Mouse PSCs were seeded and cultured, and their phenotype was confirmed by FGFR-3 over-expression. Transforming growth factor-β (TGF-β) was added to induce PSCs differentiation. TGF-β increased mRNA expression of chondrogenesis-related genes (collagen type II, Sox 9, and aggrecan) in the cultured PSCs, which was abolished by TGF-β receptor II (TGFRII) lentiviral shRNA depletion. TGF-β induced AKT activation in mouse PSCs, while the PI3K/AKT inhibitor (LY294002) and the AKT specific inhibitors (perifosine and MK-2206) largely suppressed TGF-β-induced collagen II, Sox 9, and aggrecan mRNA expression. Meanwhile, the mTOR complex 1 (mTORC1) blocker RAD001 or the mTORC1/2 dual inhibitor AZD-2014 also alleviated TGF-β-induced chondrogenesis-associated genes expression. Further, lentiviral shRNA depletion of SIN1 (a mTORC2 component) or mTOR inhibited TGF-β's effect in the mouse PSCs. In conclusion, our evidence suggests that TGF-β induces the expression of chondrogenesis-related genes through TGFRII-AKT-mTOR signaling in cultured mouse PSCs.