The Effect of Hypoxic Preconditioning on the Biological Function of Bone Marrow-Derived Endothelial Progenitor Cells

Objective To investigate the effect of hypoxic preconditioning on the biological function of bone mar-row-derived endothelial progenitor cells(BM-EPCs). Methods Mononuclear cells were collected by density gradient cen-trifugation from the bone marrow of rats. The isolated cells were cultivated in dishes coated with the vitronectin from rat plas-ma,filled with the endothelial cell basal medium-2. Cells were then cultured under the conventional culture conditions(37 ℃ and 5% CO2). The cultured cells were divided into control group and hypoxia training group after four-day culture.Cells of the control group were cultured in previous conditions for another three days. However, cells of the hypoxia traininggroups were cultured in previous conditions for 0, 1 and 2 days,and then under the hypoxic condition(1% O2+5% CO2+94%N2) for another 72 hours, 48 hours and 24 hours, respectively. After seven days,cells in all of groups were collected for thefollowing study. The immunofluorescence labeling and cell analyzer were used to indentify BM-EPCs. The tube formation ofBM-EPCs was tested by Matrigel assay. Annexin V/PI antiapoptotic assay was used to detect the apoptotic rate of BM-EPCs.Results The early apoptotic rate of BM-EPCs was increased obviously with extended hypoxia. There was no significant dif-ference in the early apoptotic rate of BM-EPCs between control group(0.89±0.20)% and hypoxic 24-h group(1.33±0.07) %(P 0.05). There was significant increase in the early apoptotic rate of BM-EPCs in hypoxic 48-h group(3.25±0.12)% andhypoxic 72-h group(7.48±1.53)%(P 0.05). Compare with control group, the tube formation ability was significantly in-creased in hypoxic 24-h group(P 0.01), but the tube formation ability was significantly decreased in hypoxic 48-h groupand hypoxic 72-h group(P 0.01). Conclusion After hypoxic preconditioning for 24 hours, the apoptotic rate was not obvi-ous in BM-EPCs, but the tube formation ability was markedly increased.