ABSTRACT. We examined whether erythropoietin (EPO) can inhibit adipogenic differentiation of mesenchymal stem cells (MSCs) in the mouse bone marrow and its underlying mechanism. We separated and extracted mouse bone marrow MSCs and induced adipogenic differentiation using 3-isobutyl-1-methylxanthine, insulin, and dexamethasone. Different concentrations of EPO were added to the cells and observed by Oil Red O staining on the 20th day to quantitatively analyze the degree of cell differentiation. mRNA expression levels of peroxysome proliferator-activated receptor g (PPARg), CCAAT enhancer binding protein a, and adiponectin were analyzed by real-time quantitative polymerase chain reaction, and the activity of PPARg, extracellular signal-regulated kinase (ERK), and p38 mitogen-activated protein kinase (p38 MAPK) were determined by western blotting. EPO significantly inhibited adipogenic differentiation of MSCs after 20 days and reduced absorbance values by Oil Red O staining without affecting proliferation (2015) activity. EPO downregulated the mRNA expression of PPARg, CCAAT enhancer binding protein a, fatty acid binding protein 4, and adiponectin during adipogenesis and increased protein phosphorylation of ERK, p38 MAPK, and PPARg during differentiation. EPO downregulated the mRNA expression of PPARg, CCAAT enhancer binding protein a, fatty acid binding protein 4, and adiponectin by increasing protein phosphorylation of ERK, p38 MAPK, and PPARg during differentiation, which inhibited adipogenic differentiation of MSCs.
SummaryTo explore the protective effects of 1,25-dihydroxy vitamin D3 (1,25-(OH)2D3) on the bone marrow microenvironment in mice after irradiation and the underlying molecular mechanisms, a total of 150 7-wk-old male BALB/c mice were randomly divided into a normal group, an irradiation (IR) group and an irradiationϩ1,25-(OH)2D3 (IRϩVD3) group. The mice in the IRϩVD3 group were treated with 6.0 Gy 60 Co␥ rays, and 1,25-(OH)2D3 (dissolved in DMSO, 2.5 g/kg) was administered once per day from 2 d before to 8 d after irradiation. Mice in the IR group were treated with the same dose of ␥ rays and an equal volume of DMSO. Subsequently, the body weights and the numbers of peripheral white blood cells (WBCs) were measured. Histological analysis of femur bone marrow was conducted to determine the proportion of adipose area as well. Finally, the expression of peroxisome proliferator-activated receptor-gamma (PPAR␥) in bone marrow was detected by immunohistochemistry. After irradiation, the percentage of adipose area in the bone marrow was significantly increased, and the WBC number and body weight were markedly reduced. Compared with irradiation alone, the co-administration of 1,25-(OH)2D3 with irradiation markedly attenuated radiation-induced adipogenesis in bone marrow, resulted in fewer bone marrow stromal cells expressing PPAR␥ and enhanced the recovery of body weight and WBCs. These results indicate that 1,25-(OH)2D3 could accelerate the recovery of body weight and WBCs in irradiated mice and protect the bone marrow by inhibiting radiation-induced adipogenesis via the down-regulation of PPAR␥ expression.
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