Using mitochondrial activity to select for potent human hematopoietic stem cells.

Area of Science:

• Cell Biology
• Hematology
• Stem Cell Biology

Background:

• Hematopoietic cell transplantation is crucial for treating blood disorders.
• Challenges exist in obtaining sufficient potent hematopoietic stem cells (HSCs) for long-term engraftment due to metabolic limitations.
• Mitochondrial function is implicated in HSC potency and behavior.

Purpose of the Study:

• To investigate the heterogeneity of mitochondrial activity within purified human HSCs.
• To determine the correlation between mitochondrial activity and HSC potency.
• To identify a method for isolating highly potent HSCs for clinical applications.

Main Methods:

• Purification of human CD34+CD38-CD45RA-CD90+CD49f+ HSCs.
• Assessment of mitochondrial membrane potential (MMP) to measure mitochondrial activity.
• In vitro long-term culture initiating cell assays.
• In vivo transplantation studies in immunodeficient mice.

Main Results:

• Human HSCs exhibit heterogeneous mitochondrial activity (MMP).
• HSCs with the lowest MMP (MMP-low) demonstrated significantly higher potency and long-term repopulating capacity in vivo compared to MMP-high HSCs.
• MMP-low HSCs showed fragmented mitochondria and a delayed cell-cycle priming profile, suggesting quiescence.

Conclusions:

• Lowest MMP identifies highly potent, likely dormant, human HSCs within purified populations.
• Mitochondrial activity and morphology are critical intrinsic regulators of HSC quiescence and potency.
• This finding offers a novel strategy for isolating superior HSCs for hematopoietic cell transplantation.