Extracellular acidosis inhibits the proangiogenic responses and the tissue regeneration capacity of endothelial progenitor cells

NEGROTTO S; FONDEVILA C; BOISSON-VIDAL C; SCHATTNER M

Congreso; International Congress of Thrombosis and Haemostasis; 2013

Background: We have previously demonstrated that extracellular acidosis, a characteristic feature of inflammation, induces apoptosis of hematopoietic progenitors (CD34+ cells). Endothelial progenitor cells (EPC) are a subpopulation within the CD34+ cells which are mobilized from the bone marrow after vascular damage to the site of injury and contribute to tissue revascularization. Aims: To study the impact of acidosis on the proangiogenic responses and the tissue regeneration capacity of EPC. Methods: EPC were seeded in EBM medium supplemented with fetal bovine serum, VEGF1, SDF1 and bFGF. The pH of the culture medium (normal value: 7.4) was adjusted at pH values of 7.0 and 6.6 by the addition of an isotonic solution of HCl (n=4-5. *P<0.05 vs. pH 7.4, ANOVA). Results: We found that while the survival of EPC was not affected by pH, the exposure to acidic medium for 24 h inhibited the proliferation (18±1 and 26±1*% of inhibition at pH 7 and 6.6 respectively, pNPP assay), migration (55±3* and 61±6*%, Boyden chamber), wound repair (9±1 and 69±4*%, mechanical damage of the monolayer) and tubule formation (58±2* and 77±5*%, Matrigel). We also evaluated how acidosis influences the EPC contribution to tissue regeneration in a murine model of hind limb ischemia induced by ligation of the femoral artery. To this end, EPC were previously incubated for 24 h at pH 7.4 or 6.5 and then transplanted intravenously (5 h post-surgery). After 7 days, the percentage of blood flow recovery within the ischemic area was analyzed (Doppler scanning). While the percentage of flow recovery in non-transplanted mice was 49±6%, in those transplanted with EPC grown at pH 7.4 the flow recovery was 78±10*%. However, when the EPC were exposed at pH 6.6, the flow recovery was similar to the non-transplanted animals (48±8%, n=4 nude mice per group). Summary/Conclusion: Our results suggest that extracellular acidosis inhibits EPC proangiogenic responses in vitro and the tissue regeneration capacity of EPC in a murine model of hind limb ischemia.