Hypoxia improves migration and limits the differentiation of rat cardiac stem cells

Abstract

Abstract The heart harbors a population of resident cardiac stem cells (CSC) that maintain tissue homeostasis. These cells also find application in cell-based therapy, where cardiac stem cells are transplanted as cardiospheres or cardiosphere-derived cells (CDCs) for myocardial regeneration. Cardiac stem cells are expanded in culture to obtain sufficient numbers for transplantation. On transplantation, cells home into the site of injury and mediate myocardial regeneration. Conventionally, cell cultures are carried out in ambient O2 (21% O2). Stem cells reside in niches where the O2 level is close to 3%. Assuming that maintenance of cells in a milieu that simulates the in-situ conditions will help in the preservation of stem cell attributes, CDCs isolated from adult Wistar rats was cultured in 3% O2 (hypoxia) and compared with CDCs maintained in 20% O2 (normoxia). Expression of c-kit and Nkx 2.5 was higher and cardiac troponin lower in hypoxia, indicating the maintenance of an undifferentiated state. Expression of von Willebrand factor and angiogenic differentiation was higher in cultures maintained in 3% O2 suggesting enhanced vasculogenic potential. Cellular senescence and intracellular reactive oxygen generation (ROS) were lower, and the proliferation rate was higher in CSCs maintained in 3% O2. Enhanced migration, proliferation, and preservation of undifferentiated state lead to the inference that, culture in low oxygen tension can increase the yield of healthy cardiac stem cells for myocardial regeneration.