Dexamethasone shifts bone marrow stromal cells from osteoblasts to adipocytes by C/EBPalpha promoter methylation

Abstract

Dexamethasone (Dex)-induced osteoporosis has been described as the most severe side effect in long-term glucocorticoid therapy. The decreased bone mass and the increased marrow fat suggest that Dex possibly shifts the differentiation of bone marrow stromal cells (BMSCs) to favor adipocyte over osteoblast, but the underlying mechanisms are still unknown. In this paper, we established a Dex-induced osteoporotic mouse model, and found that BMSCs from Dex-treated mice are more likely to differentiate into adipocyte than those from control mice, even under the induction of bone morphogenetic protein-2 (BMP2). We also discovered both in vitro and in vivo that the expression level of adipocyte regulator CCAAT/enhancer-binding protein alpha (C/EBPalpha) is significantly upregulated in Dex-induced osteoporotic BMSCs during osteoblastogenesis by a mechanism that involves inhibited DNA hypermethylation of its promoter. Knockdown of C/EBPalpha in Dex-induced osteoporotic cells rescues their differentiation potential, suggesting that Dex shifts BMSC differentiation by inhibiting C/EBPalpha promoter methylation and upregulating its expression level. We further found that the Wnt/beta-catenin pathway is involved in Dex-induced osteoporosis and C/EBPalpha promoter methylation, and its activation by LiCl rescues the effect of Dex on C/EBPalpha promoter methylation and osteoblast/adipocyte balance. This study revealed the C/EBPalpha promoter methylation mechanism and evaluated the function of Wnt/beta-catenin pathway in Dex-induced osteoporosis, providing a useful therapeutic target for this type of osteoporosis.

miR-216a rescues dexamethasone suppression of osteogenesis, promotes osteoblast differentiation and enhances bone formation, by regulating c-Cbl-mediated PI3K/AKT pathway

“…36,47 We found that when the concentration is higher than 10 nM, the osteogenic differentiation of hAMSCs can be significantly inhibited by DEX. In all, 10 nM of DEX was then used as the minimum effective concentration in vitro system to investigate protective factors for osteoporosis.…”

“…36 To clarify the effect of glucocorticoids on osteogenic differentiation, we used different concentrations of DEX to treat hAMSCs in the process of osteogenic differentiation. Using ALP staining, Alizarin red staining and qRT-PCR, we demonstrated that DEX suppressed the osteogenic differentiation of hAMSCs in a dose-dependent manner.…”

“…DEX, a widely used glucocorticoid, was shown to inhibit osteogenic differentiation and bone formation, 36,46 and DEX redirects the differentiation of bone marrow stromal cells from the osteoblastic lineage to the adipocyte lineage. 36,47 We found that when the concentration is higher than 10 nM, the osteogenic differentiation of hAMSCs can be significantly inhibited by DEX.…”

IL-12p40 impairs mesenchymal stem cell-mediated bone regeneration via CD4+ T cells

“…Western blot analysis was performed as previously described. 38 In brief, cells were ruptured with ice-cold lysis buffer (50 mM Tris-HCl, pH 7.4, 150 mM NaCl, 1% NP-40, and 0.1% sodium dodecyl sulfate) supplemented with protease inhibitors (Millipore). Cell extracts were centrifuged at 12 000 r.p.m.…”

Obesity is associated with depot-specific alterations in adipocyte DNA methylation and gene expression

“…Thus, dexamethasone treatment of mice leads to decreased DNA methylation at the Cebpa promoter inducing a shift in the preference of bone marrow stromal cells to favor adipocyte over osteoblast development. 5 Moreover, methylation of the cAMP response elements in the Ucp1 promoter has been suggested to repress expression of Ucp1 in white adipocytes. 6 Intake of high fat diet has been shown to increase methylation of the leptin promoter in retroperitoneal adipocytes in rats, and this was associated with lower circulating leptin levels.…”