Hematopoietic Stem Cell States, Function, and Molecular Identity: From Quantitative Assays to Modern Multi-Omics

Area of Science:

• Hematology
• Stem Cell Biology
• Cellular Assays

Background:

• Hematopoietic stem and progenitor cells (HSPCs) are crucial for maintaining blood cell production.
• Understanding HSPC function requires robust quantitative and qualitative measurement methods.
• Key characteristics include proliferation, differentiation, self-renewal, and hematopoietic system repopulation.

Purpose of the Study:

• To review and evaluate historical and current functional assays for HSPCs.
• To emphasize the principles of functional definition for stem and progenitor cells.
• To discuss discoveries regarding clonal origin and functional heterogeneity in HSPC populations.

Main Methods:

• Review of established and novel functional assays for HSPCs.
• Historical perspective on assay development.
• Evaluation of assay utilities and limitations.
• Focus on in vitro and in vivo models, including single-cell platforms.

Main Results:

• Comprehensive overview of transplantation, CFU, long-term culture, xenotransplantation, and single-cell assays.
• Analysis of the strengths and weaknesses of each method.
• Demonstration of how assays have revealed clonal origin and heterogeneity within HSPCs.

Conclusions:

• Functional assays are essential for defining and understanding HSPCs.
• Assay development has significantly advanced the field of hematopoiesis research.
• Phenotypically defined HSPC populations exhibit functional heterogeneity and clonal origins.