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Role of hypoxia in viability and endothelial differentiation potential of UC-MSCs and VEGF interference.

OBJECTIVE
To investigate the effect of hypoxia on cell viability and the endothelial differentiation potential in human umbilical cord derived mesenchymal stem cells (UC-MSCs), and to assess the in vitro protective role of VEGF under low oxygen tension.


METHODS
MSCs were isolated from human umbilical cords and cultured in vitro. The morphological and phenotypic characterizations of human UC-MSCs were analyzed. The hypoxia induction was performed with or without the presence of 50 ng/mL of VEGF for different lengths of time. The cell proliferation, apoptosis, and reactive oxygen species (ROS) generation were assessed. Meanwhile, the endothelial differentiation potential of the UC-MSCs was measured.


RESULTS
An increased apoptosis and ROS generation but reduced proliferation rate were observed at early stages (6, 12 h) after transferring the UC-MSCs from the atmospheric condition to the hypoxia condition. However, the UC-MSCs presented equal proliferation and apoptosis levels under hypoxic condition as compared with those under the atmospheric condition at the later stages (24, 72 h). A high concentration of exogenous VEGF (50 ng/mL) attenuated the increased apoptosis and inhibited the proliferation of UC-MSCs, induced by a short-term hypoxia treatment. After 14 days of exogenous VEGF induction under the hypoxia condition, the UC-MSCs acquired an early endothelial phenotype consisting of a mature endothelial molecule and some endothelial functions.


CONCLUSION
UC-MSCs progressively adapt to hypoxia in a step-by-step manner and maintain differentiation potential under hypoxia condition. VEGF can protect the UC-MSCs from cell damage and induce a differentiation of UC-MSCs toward endothelial lineage under hypoxic conditions.