Mitochondrial function contributes to oxysterol-induced osteogenic differentiation in mouse embryonic stem cells

作者：Kwon Il Keun; Lee Sang Cheon; Hwang Yu Shik; Heo Jung Sun^*

来源：Biochimica et Biophysica Acta-Molecular Cell Research, 2015, 1853(3): 561-572.

DOI：10.1016/j.bbamcr.2014.12.011

• Embryonic stem cell
• Oxysterol
• Osteogenic differentiation
• Mitochondrion
• Hh signaling
• Wnt/beta-catenin

Oxysterols, oxidized derivatives of cholesterol, are biologically active molecules. Specific oxysterols have potent osteogenic properties that act on osteoprogenitor cells. However, the molecular mechanisms underlying these osteoinductive effects on embryonic stem cells (ESCs) are unknown. This study investigated the effect of an oxysterol combination of 22(S)-hydroxycholesterol and 20(S)-hydroxycholesterol (SS) on osteogenic differentiation of ESCs and the alterations to mitochondrial activity during differentiation. Osteogenic differentiation was assessed by alkaline phosphatase (ALP) activity, matrix mineralization, mRNA expression of osteogenic factors, runt-related transcription factor 2, osterix, and osteocalcin, and protein levels of collagen type IA (COLIA) and osteopontin (OPN). Treatment of cells with SS increased osteoinductive activity compared to the control group. Intracellular reactive oxygen species production, intracellular ATP content, mitochondrial membrane potential, mitochondrial mass, mitochondrial DNA copy number, and mRNA expression of peroxisome proliferator-activated receptor-gamma coactivators l alpha and beta, transcription factors involved in mitochondrial biogenesis, were significantly increased during osteogenesis, indicating upregulation of mitochondrial activity. Oxysterol combinations also increased protein levels of mitochondria(respiratory complexes I-V. We also found that SS treatment increased hedgehog signaling target genes, Smo and Gill expression. Inhibition of Hh signaling by cyclopamine suppressed mitochondrial biogenesis and ESC osteogenesis. Subsequently, oxysterolinduced Wnt/beta-catenin pathways were inhibited by repression of Hh signaling and mitochondrial biogenesis. Transfection of S-catenin specific siRNA decreased the protein levels of COLIA and OPN, as well as ALP activity. Collectively, these data suggest that lipid-based oxysterols enhance differentiation of ESCs toward the osteogenic lineage by regulating mitochondrial activity, canonical Hh/Gli, and Wnt/beta-catenin signaling.

• 出版日期2015-3