Novel role of 1,25(OH)(2)D(3) in induction of erythroid progenitor cell proliferation.

OBJECTIVE: Burst-forming unit erythroid and colony-forming unit erythroid growth in vitro is lower in studies of continuous ambulatory peritoneal dialysis patients than healthy controls. Burst-forming unit erythroid growth was potentiated by addition of 1alpha,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] and normalized by erythropoietin (Epo) therapy, suggesting an interaction between Epo and 1,25(OH)(2)D(3) at the stem cell level. The objective of this study was to determine the mechanism by which 1,25(OH)(2)D(3) enhances the stimulatory effect of Epo on the growth of erythroid precursor cells. MATERIALS AND METHODS: We examined the effect of 1,25(OH)(2)D(3) and Epo on stem cell proliferation. Proliferation of TF1 cells of erythroid origin was measured by the XTT method, 3[H] thymidine incorporation, and cell counting by trypan blue exclusion; cord blood (CB) stem cells were counted. Epo receptor (EpoR) quantitation was evaluated by 125I-Epo binding and Scatchard analysis, immunoprecipitation, and Western blotting. Expression of EpoR mRNA was measured by reverse transcriptase polymerase chain reaction. RESULTS: The stem cell factor-dependent CB stem cells and the TF1 cells responded to Epo and 1,25(OH)(2)D(3) by increased proliferation, while their simultaneous addition potentiated cell proliferation in a synergistic manner (25.67% +/- 4.8% of Epo proliferation at day 10 for CB cells; p < 0.005). 1,25(OH)(2)D(3) produced an up-regulation of EpoR number in TF1 cells and increased the expression of EpoR mRNA (p < 0.01). CONCLUSIONS: The increase in EpoR expression induced by 1,25(OH)(2)D(3) might explain the synergistic interaction between Epo and 1,25(OH)(2)D(3) in stem cells.

Potential link between C3a, C3b and endothelial progenitor cells in resistant hypertension.

INTRODUCTION: Endothelial progenitor cells (EPC) and complement C3 are involved in the pathophysiology of arterial hypertension. C3a is the negative regulator of progenitor cells egress during their mobilization from bone marrow. Previously, higher plasma concentration of C3 was observed in resistant arterial hypertension (RAH) than in controlled arterial hypertension (CAH). Thus, we hypothesized that RAH would be associated with complement C3 activation and reduced number of circulating EPCs. OBJECTIVE: To compare C3a, C3b and their correlation with circulating EPC in subjects with RAH and CAH. METHODS: Blood pressure was measured by electronic sphygmomanometer. EPCs were identified as CD34+/CD133+/KDR+ cells by flow cytometry. C3a and C3b were determined using enzyme-linked immunosorbent assay (Quidel, CA). RESULTS: : RAH group (n = 20) and CAH group (n = 20) and 17 healthy individuals (control group) were recruited. In the RAH group, C3a (858.1 +/- 70.6 microg/dL) was higher than in the CAH group (816.1 +/- 123.3 microg/dL; P < 0.001), and in the control group (751.3 +/- 98.8; P < 0.001), C3b (564.1 +/- 54.7 microg/dL) was higher than in the CAH group (490.2 +/- 58.5 microg/dL; P < 0.001). In control group (456.3 +/- 98.8; P < 0.001), statistically significant negative correlation was observed between C3a and blood levels of EPC (r = -0.523, P = 0.018); statistically significant positive correlation was observed between systolic blood pressure and blood levels of C3a (r = 0.52, P = 0.02) and between systolic blood pressure and blood levels of C3b (r = 0.57, P = 0.009). CONCLUSION: RAH is characterized by higher levels of C3 component fragments and a negative correlation between circulating C3a and EPCs.

Circulating endothelial progenitor cells, Th1/Th2/Th17-related cytokines, and endothelial dysfunction in resistant hypertension.

INTRODUCTION: A possible link between chronic vascular inflammation and arterial hypertension is now an object of intensive studies. OBJECTIVE: To compare Th1/Th2/Th17 cells-related cytokines, circulating endothelial progenitor cells (EPC), and endothelial function in subjects with resistant arterial hypertension (RAH) and controlled arterial hypertension (CAH). METHODS: Blood pressure was measured by electronic sphygmomanometer. EPC were identified as CD34+/CD133+/kinase insert domain receptor (KDR)+ cells by flow cytometry. Th1/Th2/Th17 cells-related cytokines were identified using the Human Th1/Th2/Th17 Cytokines MultiAnalyte ELISArray Kit. Endothelium-dependent (FMD) vasodilatation of brachial artery was measured by Doppler ultrasound scanning. RESULTS: RAH group (n = 20) and CAH group (n = 20) and 17 healthy individuals (control group) were recruited. In the RAH group, lower blood levels of EPC number (42.4 +/- 16.7 cells/mL) and EPC% (0.19 +/- 0.08%) were observed than in the CAH group (93.1 +/- 88.7 cells/mL; P = 0.017; 0.27 +/- 0.17; P = 0.036) and control group (68.5 +/- 63.6 cells/mL; P < 0.001; 0.28 +/- 0.17%; P = 0.003), respectively. Plasma transforming growth factor-beta1 levels were significantly higher in the RAH group (1767 +/- 364 pg/mL) than in the CAH group (1292 +/- 349; P < 0.001) and in control group (1203 +/- 419 pg/mL; P < 0.001). In the RAH group, statistically significant negative correlation was observed between systolic blood pressure and EPC% (r = -0.72, P < 0.01). FMD in the RAH group was significantly lower (5.5 +/- 0.8%) than in the CAH group (9.2 +/- 1.4; P < 0.001) and in healthy controls (10.1 +/- 1.1%; P < 0.001). CONCLUSION: RAH is characterized by reduced circulating EPC, substantial endothelial dysfunction, and increased plasma transforming growth factor-beta1 levels.