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.

ABSTRACT. The aim of this study was to explore methods by which the ERK signaling pathway inhibitor PD98059 (PD) could be used in long-term in vivo experiments. Forty healthy New Zealand rabbits were randomly divided into blank control, model control, PD low-dose, PD high-dose, PD blank, dimethyl sulfoxide (DMSO) control, DMSO blank, and positive control groups. The corresponding treatments were administered to each experimental group over the course of four weeks, after which, total ERK1/2 and ERK5 protein levels, protein phosphorylation, and gene expression were measured in myocardial tissues. Treatment of rabbits with Adriamycin (doxorubicin) resulted in the significant overall differences in ERK1/2 and ERK5 phosphorylation (P < 0.05). Compared with the model control group, changes in phosphorylated ERK1/2 and phosphorylated ERK5 were lowest in the PD high-dose group (P < 0.05). No significant differences in total protein and mRNA levels of myocardial ERK1/2 and ERK5 were detected between the groups after four weeks (P > 0.05). Continuous intravenous injection of PD98059 significantly reduced phosphorylation of ERK1/2 X.Y. Chen et al. 18326©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 14 (4): 18325-18333 (2015) and that of ERK5. In conclusion, Adriamycin-induced myocardiopathy and abnormal ERK signaling might constitute a valuable model foruse in long-term experiments. These methods may provide a theoretical basis for related in vivo studies of long duration.