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Conditioned medium from renal tubular epithelial cells stimulated by hypoxia influences rat bone marrow-derived endothelial progenitor cells

Background and aims: It has been well documented that endothelial progenitor cells (EPCs) participate in neovascularization in adults and that rarefaction of peritubular capillaries (PTCs) is closely associated with progressive kidney disease. Therefore, we investigated whether EPCs were influenced by conditioned medium (CM) of renal tubular epithelial cells (RTECs) stimulated by hypoxia, to provide evidence for EPCs transplantation in vivo in the future. Methods: Mononuclear cells of rat bone marrow were isolated by density gradient centrifugation and were cultured according to previously described techniques. RTECs were cultured primarily with routine tissue block adhering wall method. In addition, CM was harvested from RTECs cultivated for 48 h in 5% O2. EPCs proliferation and migration were evaluated by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and transwell. The protein and mRNA expression of stromal cell-derived factor (SDF-1), vascular endothelial growth factor (VEGF), angiogenin 1 (Ang-1), and C-X-C chemokine receptor 4 (CXCR4) was separately assessed by Western blot, enzyme-linked immunosorbent assay (ELISA), and reverse transcriptase-polymerase chain reaction (RT-PCR) methods. Results: We showed that hypoxia increased the expression of SDF-1 and VEGF in RTEC. In addition, hypoxic CM improved proliferation, migration, and expression of VEGF, Ang-1, and CXCR4 of EPCs. Conclusions: These results suggest that hypoxic CM improves neovascularization of EPCs and may also be considered as therapeutic agents to supply the potent origin of reconstituion of PTCs of progressive kidney disease.