Serum osteoprotegerin is markedly increased and may contribute to decreased blood T cell count in hemodialysis patients

Acquired immunity is impaired in hemodialysis (HD) patients, and decreased T cell number may contribute. Receptor activator of nuclear factor-kappa B ligand (RANKL) and osteoprotegerin (OPG) are expressed in cells of the immune system and affect T cell development, homeostasis and proliferation. Serum levels of RANKL and OPG and their relation to blood T cell number were evaluated in HD patients. Thirty-four HD patients and 20 healthy controls participated in the study. Serum RANKL and OPG were measured by ELISA and T cell number was assessed by flow cytometry. Median RANKL concentration did not differ between HD patients and healthy volunteers (300.00 pmol/L; range, 3,340.00 vs. 330.00 pmol/L; range, 440.00 pmol/L; p = 0.528). Median OPG was markedly higher in HD patients than in healthy volunteers (13.12 +/- A 4.71 vs. 4.71 +/- A 0.93 pmol/L, p < 0.001). The T cell count was significantly lower in HD patients than in healthy controls (1,177.00 +/- A 567.71 vs. 1,519.80 +/- A 594.96 cells/mm(3), p = 0.044). In HD patients, blood T cell number was correlated positively with serum RANKL (rho = 0.462, p = 0.007) and negatively to serum OPG (r = -0.449, p = 0.008). Serum OPG concentration is markedly increased in HD patients and may contribute to decreased blood T cell count and impaired acquired immunity that characterizes this population

5-Azacytidine facilitates osteogenic gene expression and differentiation of mesenchymal stem cells by alteration in DNA methylation

Mesenchymal stem cells (MSCs) are considered to be one of the most promising therapeutic cell sources as they encompass a plasticity of multiple cell lineages. The challenge in using these cells lies in developing well-defined protocols for directing cellular differentiation to generate a desired lineage. In this study, we investigated the effect of 5-azacytidine, a DNA demethylating agent, on osteogenic differentiation of MSCs. The cells were exposed to 5-azacytidine in culture medium for 24 h prior to osteogenic induction. Osteogenic differentiation was determined by several the appearance of a number of osteogenesis characteristics, including gene expression, ALP activity, and calcium mineralization. Pretreatment of MSCs with 5-azacytidine significantly facilitated osteogenic differentiation and was accompanied by hypomethylation of genomic DNA and increased osteogenic gene expression. Taking dlx5 as a representative, methylation alterations of the “CpG island shore” in the promoter caused by 5-azacytidine appeared to contribute to osteogenic differentiation