Active mitochondria support osteogenic differentiation by stimulating β-catenin acetylation

Area of Science:

• Cell Biology
• Biochemistry
• Stem Cell Biology

Background:

• Bone marrow stromal cells (BMSCs), also known as mesenchymal stem cells, differentiate into osteoblasts, adipocytes, and chondrocytes.
• Osteogenic differentiation of BMSCs is associated with increased mitochondrial oxidative phosphorylation (OxPhos).

Purpose of the Study:

• To investigate the mechanisms linking mitochondrial OxPhos to osteoblast differentiation.
• To determine if mitochondria support osteogenesis through pathways independent of ATP production.

Main Methods:

• Used C3H10T1/2 cells, a BMSC-like cell line.
• Inhibited OxPhos using a chemical inhibitor.
• Stimulated OxPhos by replacing glucose with galactose in the cell culture media.
• Assessed osteogenic potential, ATP levels, and glycolysis.
• Investigated the role of β-catenin signaling and acetylation.
• Utilized ATP citrate lyase (ACLY) inhibition with SB204990.
• Performed immunoprecipitation to detect β-catenin acetylation.

Main Results:

• OxPhos inhibition reduced osteogenic potential without decreasing ATP levels, indicating glycolysis compensation.
• Galactose-induced OxPhos stimulation increased osteogenesis and β-catenin activity independently of osteoinducers.
• Inhibition of ACLY reversed galactose-induced β-catenin activity and osteoblast differentiation.
• Detected increased β-catenin acetylation, which correlated with increased OxPhos and osteoinduction.

Conclusions:

• Mitochondrial OxPhos supports osteoblast differentiation through mechanisms beyond ATP supply.
• Mitochondria promote osteogenesis by facilitating β-catenin acetylation and subsequent activity.
• This highlights a novel role for mitochondrial metabolic function in regulating stem cell differentiation pathways.