Hyperbaric oxygen treatment effects on in vitro cultured umbilical cord blood CD34⁺ cells

Umbilical cord blood (UCB) provides an alternative source for hematopoietic stem/progenitor cells (HSPCs) in the treatment of hematological malignancies. However, clinical usage is limited due to the low quantity of HSPCs in each unit of cord blood and defects in bone marrow homing. Hyperbaric oxygen (HBO) is among the more recently explored methods used to improve UCB homing and engraftment. HBO works by lowering the host erythropoietin before UCB infusion to facilitate UCB HSPC homing, because such UCB cells are not directly exposed to HBO. In this study, we examined how direct treatment of UCB-CD34⁺ cells with HBO influences their differentiation, proliferation and in vitro transmigration.

Using a locally designed HBO chamber, freshly enriched UCB-CD34⁺ cells were exposed to 100% oxygen at 2.5 atmospheres absolute pressure for 2 h before evaluation of proliferative capacity, migration toward a stromal cell-derived factor 1 gradient and lineage differentiation.

Our results showed that HBO treatment diminishes proliferation and in vitro transmigration of UCB-CD34⁺ cells. Treatment was also shown to limit the ultimate differentiation of these cells toward an erythrocyte lineage. As a potential mechanism for these findings, we also investigated HBO effects on the relative concentration of cytoplasmic and nucleic reactive oxygen species (ROS) and on erythropoietin receptor (Epo-R) and CXCR4 expression. HBO-treated cells showed a relative increase in nucleic ROS but no detectable differences in the level of Epo-R nor CXCR4 expression were established compared with non-treated cells.

In summary, HBO amplifies the formation of ROS in DNA of UCB-CD34⁺ cells, potentially explaining their reduced proliferation, migration and erythrocytic differentiation.