Effect of intermittent hyperoxia on stem cell mobilization and cytokine expression

Abstract

Introduction Modern medicine has made enormous progress in the past 150 years including the development of vaccines and pharmaceutical therapies. However, to date there is little progress in developing therapies that speed the healing of injured tissues. Hyperbaric oxygen therapy (HBOT) is a FDA approved therapy for non‐healing wounds consisting of daily intermittent doses of elevated partial pressure of oxygen (PO2) above 1520 torr. The hypothetical mechanism is its influence on mobilizing stem cells via cell signaling and gene transcription at effector tissues. Preclinical research showed a regimen of HBOT resulted in mobilization of stem cells and increased vasculogenesis in a wound healing model. Our study sought to determine if partial pressures of oxygen less than 760 torr would also mobilize stem cells. Methods Twelve, 10‐week‐old Sprague Dawley rats were randomly divided into two groups. The treatment group was exposed to a hyperoxic environment with a PO2 = 319 torr. The control group was exposed to room air (PO2 = 159 torr). Treatments were performed 5 days per week for 2 hours daily for a total of 10 treatment days (20 hours). Animals were sacrificed and approximately 8 ml of venous blood was harvested from the inferior vena cava. Red blood cells were lysed and plasma was drawn off and frozen. Remaining cells were prepared for flow cytometry by exposing them to cell surface marker antibodies for CD34+and CD 133+. These cells were then analyzed on a BD LSRII flow cytometer using DIVA software. Analysis was completed using FlowJo software. Statistics were performed using an unpaired t‐test with a p<.05 to indicate significance. Results Animals treated with a PO2 = 319 torr showed an increase (p = 0.045) in mobilized CD133+/34 endothelial progenitor cells (EPC's), while no differences were seen in CD133−/34+ hematopoietic stem progenitor cells (HSPC's) when compared to the control group. Discussion We hypothesized that there would be an increase in the CD133+/34− EPC's and an increase in CD133−/34+ HSPC's. Although our hypothesis was correct regarding the EPC's we did not see an increase in HSPC's as expected. CD133+/34− EPC's are considered more primitive stem cells than the CD133−/34+ HSPC's. CD133+/34− EPC's are capable of differentiation into CD133−/34+ HSPC's as they progress along the oligopotent path to maturation. Future research should include a pathological condition to test for changes in stem cell populations and the effects of pathology on stem cell differentiation. Our data suggest that low doses of daily intermittent hyperoxia mobilize the population of CD133+/34− EPC's. These EPC's have been shown in vivo to increase vascular density in a skin graft model. Further study is needed to determine what amount of intermittent hyperoxia treatment results in the most efficacious treatment in an injury model (increased stem cell mobilization, vasculogenesis and functional recovery). Support or Funding Information DOD Navy ‐ N00024‐17‐C‐4318 This abstract is from the Experimental Biology 2018 Meetin...

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