SCA-1 Expression Level Identifies Quiescent Hematopoietic Stem and Progenitor Cells

Area of Science:

• Hematology
• Stem Cell Biology
• Immunology

Background:

• Blood cell generation relies on hematopoietic stem cells (HSCs) and progenitors.
• These cells exist in quiescent and actively cycling states.
• Hematopoietic stem and progenitor cells (HSPCs) express Stem cell antigen 1 (SCA-1).

Purpose of the Study:

• To investigate the role of SCA-1 expression levels in identifying quiescent HSPCs.
• To determine if SCA-1 expression correlates with self-renewal capacity.
• To assess the influence of type I interferon signaling on SCA-1 expression and cell function.

Main Methods:

• Utilized histone 2B-red fluorescent fusion protein label retention.
• Employed cell-cycle reporter mice.
• Analyzed SCA-1 expression levels on lineage-SCA-1+KIT+ (LSK) populations.
• Performed transplantation assays to evaluate self-renewal potential.

Main Results:

• High SCA-1 expression (SCA-1hi) identified quiescent cells at all hierarchical levels within the LSK population.
• Transplanted SCA-1hi HSPC populations demonstrated superior self-renewal potential compared to SCA-1lo populations.
• Quiescence and self-renewal capacity of SCA-1hi cells were independent of type I interferon signaling at steady state.

Conclusions:

• SCA-1 expression levels can prospectively isolate functionally heterogeneous HSPC subpopulations.
• SCA-1hi identifies quiescent HSPCs with high self-renewal capacity.
• Type I interferon signaling is not required for maintaining quiescence and self-renewal in SCA-1hi cells under steady-state conditions.