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Resting and activated subsets of mouse multipotent hematopoietic stem cells
1Walter and Eliza Hall Institute for Medical Research, Melbourne, Victoria, Australia.
Summary
Resting hematopoietic stem cells (HSCs), identified by low rhodamine 123 (Rh-123) uptake, show greater long-term repopulation and differentiation potential than activated HSCs. This highlights the heterogeneity of HSC clonogenic capacity.
Area of Science:
- Hematology
- Stem Cell Biology
- Mitochondrial Biology
Background:
- Rhodamine 123 (Rh-123) is a fluorescent vital dye that accumulates in mitochondria, reflecting cellular activity.
- Hematopoietic stem cells (HSCs) are crucial for blood formation and are known to be heterogeneous.
Purpose of the Study:
- To investigate the functional differences between mouse bone marrow hematopoietic stem cell populations with varying rhodamine 123 (Rh-123) uptake.
- To determine if Rh-123 levels correlate with stem cell activity, proliferative potential, and differentiation capacity.
Main Methods:
- Mouse bone marrow hematopoietic stem cells were sorted into Rh-123lo, Rh-123med, and Rh-123hi populations based on dye uptake.
- Functional assays included proliferative potential assessment, splenic colony-forming unit (CFU-S) differentiation assays (in vivo and in vitro), and secondary recipient repopulation studies.
Main Results:
- The Rh-123lo (resting) population demonstrated a significantly higher proliferative potential and a 20-fold greater capacity for splenic colony-forming unit (CFU-S) differentiation compared to the Rh-123hi (activated) population.
- While the activated population had more day 13 CFU-S on primary transfer, only the resting population supported long-term hematopoietic repopulation in secondary recipients.
- Morphological differences in splenic colonies were observed between the two populations, but in vitro colony characteristics were similar.
Conclusions:
- Hematopoietic stem cells exhibit heterogeneity in their clonogenic capacities, as demonstrated by differences in proliferative potential and differentiation ability based on mitochondrial activity (Rh-123 uptake).
- The Rh-123lo population represents a more primitive, long-term repopulating stem cell pool, while the Rh-123hi population may represent more committed or activated progenitors.