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Hypercapnia slows down proliferation and apoptosis of human bone marrow promyeloblasts

Hamad, Mouna, Irhimeh, Mohammad R., Abbas, Ali
Bioprocess and biosystems engineering 2016 v.39 no.9 pp. 1465-1475
apoptosis, bone marrow, carbon dioxide, cell proliferation, cultured cells, flow cytometry, hematopoietic stem cells, humans, hypercapnia, surface antigens, therapeutics, viability
Stem cells are being applied in increasingly diverse fields of research and therapy; as such, growing and culturing them in scalable quantities would be a huge advantage for all concerned. Gas mixtures containing 5 % CO₂ are a typical concentration for the in vitro culturing of cells. The effect of varying the CO₂ concentration on promyeloblast KG-1a cells was investigated in this paper. KG-1a cells are characterized by high expression of CD34 surface antigen, which is an important clinical surface marker for human hematopoietic stem cells (HSCs) transplantation. KG-1a cells were cultured in three CO₂ concentrations (1, 5 and 15 %). Cells were batch-cultured and analyzed daily for viability, size, morphology, proliferation, and apoptosis using flow cytometry. No considerable differences were noted in KG-1a cell morphological properties at all three CO₂ levels as they retained their myeloblast appearance. Calculated population doubling time increased with an increase in CO₂ concentration. Enhanced cell proliferation was seen in cells cultured in hypercapnic conditions, in contrast to significantly decreased proliferation in hypocapnic populations. Flow cytometry analysis revealed that apoptosis was significantly (p = 0.0032) delayed in hypercapnic cultures, in parallel to accelerated apoptosis in hypocapnic ones. These results, which to the best of our knowledge are novel, suggest that elevated levels of CO₂ are favored for the enhanced proliferation of bone marrow (BM) progenitor cells such as HSCs.