The low viability of human CD34+ cells under acidic conditions is improved by exposure to TPO, SCF, IL-3 or increased cAMP levels.

D'ATRI LP; ETULAIN J; ROMANIUK MA; TORRES O; NEGROTTO S; SCHATTNER M

TRANSFUSION

WILEY-BLACKWELL PUBLISHING, INC

Año: 2010 vol. 8 p. 1784 - 1795

0041-1132

Background: Transplanted hematopoietic progenitor cells (CD34+) have shown great promise in regenerative medicine. However, the therapeutic potential of transplanted cells is limited by their poor viability. It is well known that the microenvironment in which progenitors reside substantially affects their behavior. Because extracellular acidosis is a common feature of injured tissues or the tumor microenvironment and is a critical regulator of cell survival and activation, we evaluated the impact of acidosis on CD34+ cell biology. Study design and methods: Apoptosis was evaluated by fluorescence microscopy and binding of annexin-V, hypodiploid cells, Bcl-xL expression, active caspase-3, mithocondrial potential were determined by flow cytometry. Colony-forming units were studied by clonogenic assays and cell cycle was evaluated by flow cytometry. Results: Exposure of CD34+ cells to low pH (7.0-6.5) caused intracellular acidification, decreased cell proliferation and triggered apoptosis via the mitochondrial pathway. Whereas exposure to TPO, SCF, IL-3, or increases in cAMP levels prevented, CD34+ cell death induced by acidic conditions, GM-CSF, Flt3-L, EPO, and VEGF had no effect. Despite their cytoprotective effect, CD34+ cell expansion triggered by TPO, SCF or IL-3 was significantly impaired at low pH. However, a cocktail of these three cytokines synergistically supported proliferation, cell cycle progression and colony formation. Discussion: Our findings indicate that an acidic milieu is deleterious for CD34+ cells and that a combination of certain cytokines and cAMP donors may improve cell viability and function. These data may be useful to develop new therapeutic strategies or to optimize protocols for regenerative medicine.