Epigenetic changes during mechanically induced osteogenic lineage commitment

Osteogenic lineage commitment is often evaluated by analyzing gene expression. However, many genes are transiently expressed during differentiation. The availability of genes for expression is influenced by epigenetic state, which affects the heterochromatin structure. DNA methylation, a form of epi...

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Bibliographic Details
Published in:	Journal of biomechanical engineering Vol. 137; no. 2; p. 020902
Main Authors:	Chen, Julia C, Chua, Mardonn, Bellon, Raymond B, Jacobs, Christopher R
Format:	Journal Article
Language:	English
Published:	United States 01-02-2015
Subjects:	Adipogenesis - drug effects Adipogenesis - genetics Animals Biomarkers - metabolism Biomechanical Phenomena Cell Line, Tumor Culture Media, Conditioned - pharmacology DNA Methylation - drug effects Epigenesis, Genetic - drug effects Gene Expression Regulation - drug effects Mechanical Phenomena Mesenchymal Stem Cells - cytology Mesenchymal Stem Cells - drug effects Mesenchymal Stem Cells - metabolism Mice Osteogenesis - drug effects Osteogenesis - genetics RNA, Messenger - genetics RNA, Messenger - metabolism Sequence Analysis, DNA Stress, Mechanical
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Summary:	Osteogenic lineage commitment is often evaluated by analyzing gene expression. However, many genes are transiently expressed during differentiation. The availability of genes for expression is influenced by epigenetic state, which affects the heterochromatin structure. DNA methylation, a form of epigenetic regulation, is stable and heritable. Therefore, analyzing methylation status may be less temporally dependent and more informative for evaluating lineage commitment. Here we analyzed the effect of mechanical stimulation on osteogenic differentiation by applying fluid shear stress for 24 hr to osteocytes and then applying the osteocyte-conditioned medium (CM) to progenitor cells. We analyzed gene expression and changes in DNA methylation after 24 hr of exposure to the CM using quantitative real-time polymerase chain reaction and bisulfite sequencing. With fluid shear stress stimulation, methylation decreased for both adipogenic and osteogenic markers, which typically increases availability of genes for expression. After only 24 hr of exposure to CM, we also observed increases in expression of later osteogenic markers that are typically observed to increase after seven days or more with biochemical induction. However, we observed a decrease or no change in early osteogenic markers and decreases in adipogenic gene expression. Treatment of a demethylating agent produced an increase in all genes. The results indicate that fluid shear stress stimulation rapidly promotes the availability of genes for expression, but also specifically increases gene expression of later osteogenic markers.
ISSN:	1528-8951
DOI:	10.1115/1.4029551