Dual SP/ALDH functionalities refine the human hematopoietic Lin-CD34+CD38- stem/progenitor cell compartment

Area of Science:

• Hematology
• Stem Cell Biology
• Cellular Immunology

Background:

• Traditional hematopoietic stem/progenitor cell (HSPC) purification relies on CD34 and CD38 antigens, but their variable expression presents limitations.
• Independent methods like side population (SP) phenotype (drug efflux via ABCG2 pump) and aldehyde dehydrogenase (ALDH) activity detection distinguish primitive cell subsets.
• These SP and ALDH(Bright) (ALDH(Br)) subsets offer insights into cell phenotype and proliferative capacity.

Purpose of the Study:

• To develop a multiparametric flow cytometry method combining SP and ALDH activities for human HSPC analysis.
• To refine the purification of primitive HSPCs by leveraging the coexpression of SP and ALDH markers.
• To identify a specific HSPC subset with enhanced primitive characteristics.

Main Methods:

• Developed a multiparametric flow cytometry approach integrating SP and ALDH activity assays.
• Analyzed human lineage-negative (Lin(-)) bone marrow cells.
• Sorted distinct cell fractions based on combined SP/ALDH activity levels.

Main Results:

• Lin(-)CD34(+)CD38(Low/-) cells were observed across the ALDH spectrum, enriched in ALDH(Br) when associated with SP functionality (SP/ALDH(Br) fraction).
• The SP marker identified quiescent (G(0)) cells irrespective of ALDH activity.
• Within the Lin(-)CD34(+)CD38(-)ALDH(Br) population, the SP marker identified cells with superior stemness gene expression and proliferative potential.

Conclusions:

• Coexpression of SP and ALDH markers refines the Lin(-)CD34(+)CD38(-) hematopoietic compartment.
• An SP/ALDH(Br) cell subset enriched in quiescent primitive HSPCs was identified.
• This combined marker approach offers improved purification of highly primitive HSPCs.