During osteoporosis, the shift of mesenchymal stem cell (MSC) lineage commitment

During osteoporosis, the shift of mesenchymal stem cell (MSC) lineage commitment to adipocyte prospects to the imbalance between bone mass and fat, which increases the risk of fracture. redundant EZH2 shifted MSC cell lineage commitment to adipocyte, which contributed to the development of osteoporosis. We also offered EZH2 Slc2a2 like a novel therapeutic target for improving bone formation during osteoporosis. Intro Osteoporosis is one of the most common and severe skeletal disorders in aged human population. It is definitely characterized by low bone mineral denseness and damage of bone structure, leading to improved risk of fragility fractures.1 In osteoporosis, adipogenesis in bone marrow is increased at the expense of bone formation, resulting in bone mass loss and fat increase in bone marrow.2,3 Bone marrowCderived mesenchymal stem cells (BMSCs) are common precursors of osteoblasts GANT 58 and adipocytes in bone.4,5 It is widely approved that aberrant differentiation of BMSCs results in the imbalance between osteogenesis and adipogenesis during osteoporosis.6,7,8 Repairing BMSC cell lineage commitment is an appealing therapeutic strategy for osteoporosis. But the molecular mechanism of irregular BMSC fate dedication remains elusive, which hinders the progress of osteoporosis treatment. The fate of BMSCs is definitely governed by a number of signaling pathways. Notably, Wnt pathway takes on a critical part in BMSC differentiation and bone development. Wnt3a, Wnt5b, and Wnt10b activate Wnt canonical pathway to promote the transcription of Runt-related transcription element 2 (RUNX2), a dominating transcription element for osteogenic differentiation.9 Moreover, Wnt canonical pathway suppresses peroxisome proliferator-activated receptor- transcription to inhibit adipogenic differentiation of GANT 58 BMSCs.10 Wnt signaling is suppressed during osteoporosis, which contributes to stem cell dysfunction.11 However, the underlying mechanism of Wnt signaling disruption is largely unfamiliar. Epigenetic rules emerges as a key conductor of cell differentiation.12,13 Epigenetic modification, which determines gene expression, responds to cues from the environment to guide cell lineage commitment. Epigenetic modifications that determine cell lineage commitment are called as epigenetic signatures.14,15,16 Trimethylated histone 3 lysine 27 (H3K27me3), a key marker of gene repression, is one of the dominant epigenetic signatures. Relating to genome-wide chromatin studies, H3K27me3 is definitely a marker to distinguish pluripotent stem cells from differentiated cells. Enrichment of H3K27me3 across the genome is definitely improved during embryonic stem cell (Sera cell) differentiation.17 Recently, H3K27me3 was reported to be a negative signature of Wnt signaling. H3K27me3 enrichment in promoter regions of Wnt ligands represses Wnt/-catenin signaling,18 suggesting epigenetic regulation is definitely important in Wnt signaling activation. Histone methylation is definitely generated and managed by histone methyltransferases. Enhancer of Zeste homology 2 (EZH2), the catalytic component of polycomb repressive complexes 2 (PRC2), catalyzes the trimethylation on Histone 3 lysine 27 (H3K27me3). Notably, EZH2 is essential for stem cell maintenance and differentiation. Genome-wide chromatin immunoprecipitation (ChIP) sequencing in Sera cells identifies that ~20% genes occupied by PRC2 and H3K27me3 are involved in cell differentiation and cell-fate dedication. These genes includes dominant transcription factors (such as Hox, Fox, Sox family) and signaling pathway proteins (such as Wnt, BMP, Notch) that closely related with stem cell differentiation.19 Launch of PRC2-mediated repression is pivotal to initiate pathway-specific gene expression programs during stem cell differentiation.20,21 EZH2 raises H3K27me3 levels to regulate epidermal cell differentiation.22 EZH2 also regulates skeletal muscle mass differentiation by repressing MyoD and SRF manifestation through H3K27me3.23 Moreover, EZH2 is recently reported as an epigenetic switch controlling osteogenic and adipogenic differentiation of BMSCs.18,24 Disruption of EZH2 methyltransferase activity on H3K27 encourages osteoblast differentiation.25 EZH2 represses Wnt expression to facilitate adipogenesis in preadipocytes.18 However, whether EZH2 contributes to the disorder of BMSC differentiation during osteoporosis is largely unknown. In this study, we found EZH2, which was improved in osteoporotic BMSCs, mediated the shift of BMSC lineage commitment to adipocyte during osteoporosis. Knockdown of EZH2 restored osteoporotic BMSC cell lineage commitment by reducing H3K27me3 levels on promoters of Wnt genes. Moreover, by using 3-deazaneplanocin GANT 58 A (DZNep), the inhibitor of H3K27me3, we efficiently recovered the balance between osteogenesis and adipogenesis of osteoporotic BMSCs. We shown that EZH2-mediated epigenetic mechanism participated in the etiology of osteoporosis and offered an epigenetic target for osteoporosis treatment..

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