Enhancing Hematopoietic Stem Cell Transplantation Efficacy by Mitigating Oxygen Shock

Area of Science:

• Hematology
• Cell Biology
• Stem Cell Research

Background:

• Hematopoietic stem cells (HSCs) normally reside in hypoxic bone marrow and cord blood niches.
• Standard HSC isolation and processing occur in ambient air, a non-physiologic condition.

Purpose of the Study:

• To investigate the impact of ambient oxygen exposure on HSC recovery.
• To identify the mechanisms underlying oxygen-induced HSC damage.
• To explore strategies for mitigating this damage during cell collection.

Main Methods:

• Collection and manipulation of bone marrow and cord blood under native hypoxic conditions versus ambient air.
• Assessment of long-term repopulating HSCs and progenitor cell populations.
• Investigation of reactive oxygen species (ROS) production and mitochondrial permeability transition pore (MPTP) induction.
• Evaluation of the protective effect of the MPTP inhibitor cyclosporin A.

Main Results:

• Brief exposure to ambient oxygen significantly decreases the recovery of long-term repopulating HSCs.
• This extraphysiologic oxygen shock/stress (EPHOSS) phenomenon leads to an underestimation of true HSC numbers.
• ROS production and MPTP induction via cyclophilin D and p53 were identified as mechanisms of EPHOSS.
• Cyclosporin A treatment protected HSCs from EPHOSS, increasing the recovery of transplantable HSCs from both mouse bone marrow and human cord blood.

Conclusions:

• Ambient oxygen exposure during collection and processing causes significant loss of functional HSCs.
• Understanding and mitigating EPHOSS is crucial for accurate HSC quantification and successful transplantation.
• Pharmacological inhibition of MPTP may offer a clinical advantage for improving HSC transplantation outcomes.