Forkhead box O-1 regulates the biological behavior of BMP-2-induced human bone mesenchymal stem cells through mitochondrial dynamics and autophagy

This study explored the mechanism by which forkhead box O-1 (FoxO1) modulates the biological behaviors of bone mesenchymal stem cell (BMSC). Human BMSCs were cultured for seven days in Dulbecco's modified Eagle medium (DMEM) containing bone morphogenetic protein-2 (BMP-2) and treated with a short hairpin-FoxO1 plasmid. The study assessed cell proliferation, migration, apoptosis, adenosine triphosphate (ATP) levels, mitochondrial DNA (mtDNA) levels, membrane potential (MMP), autophagy, and the levels of FoxO1, apoptosis-associated proteins, osteogenic differentiation-associated proteins, mitochondrial fusion and fission proteins, and mitochondrial autophagy-related proteins. The cells were also treated with the mitochondrial fusion activator MASM7 and the mitochondrial autophagy activator carbonyl cyanide 3-chlorophenylhydrazone (CCCP). The study evaluated whether mitochondrial dynamics and autophagy activation could rescue the FoxO1 knockdown-induced changes in BMSC biological behaviors, mitochondrial dynamics, and mitochondrial autophagy. BMP-2-induced BMSCs exhibited upregulated FoxO1 expression, enhanced proliferation and migration, and induced osteogenic differentiation, while FoxO1 knockdown inhibited BMP-2-induced BMSC proliferation, migration and osteogenic differentiation, increased apoptosis, and affected mitochondrial dynamics and autophagy. Promoting mitochondrial fusion partially reversed the regulatory effects of FoxO1 downregulation on mitochondrial autophagy and the inhibitory effects of FoxO1 silencing on BMP-2-induced BMSC biological behaviors. Activated mitochondrial autophagy facilitated the homeostasis of mitochondrial dynamics and partially counteracted the inhibitory effects of FoxO1 knockdown on BMP-2-induced BMSC biological behaviors. In conclusion, FoxO1 regulates mitochondrial dynamics and autophagy to modulate the osteogenic differentiation of BMP-2-induced human BMSCs.