[The precursor hematopoietic cell: its origin in ontogeny, proliferative activity and proliferative potential]

Area of Science:

• Hematopoiesis
• Stem Cell Biology
• Developmental Biology

Context:

• Primitive hematopoietic stem cells (P-HSC) are crucial for repopulating irradiated bone marrow cultures.
• P-HSC numbers and distribution change significantly during murine embryonic development and in adult tissues.
• Existing methods could not detect P-HSC proliferation during late gestation.

Purpose:

• To quantify primitive hematopoietic stem cells (P-HSC) during mouse development and in adult tissues.
• To investigate the proliferative capacity and self-maintenance potential of P-HSC.
• To assess the impact of cell dose on P-HSC numbers after bone marrow reconstitution.

Summary:

• P-HSC first appear in embryonic mouse liver around 12-13 days gestation, increasing tenfold by day 17-18.
• Adult mouse bone marrow contains approximately 100 P-HSC per femur, with lower concentrations in the spleen.
• In vivo treatments with 5-fluorouracil or hydroxyurea did not significantly alter P-HSC numbers, despite reducing CFU by 99%.
• Mice reconstituted with a low dose of bone marrow cells showed reduced P-HSC numbers compared to those receiving a high dose, suggesting limited self-renewal capacity.

Impact:

• These findings suggest that primitive hematopoietic stem cells have a limited proliferative potential and are incapable of self-maintenance.
• This has significant implications for understanding stem cell dynamics and developing regenerative medicine strategies.
• The study provides critical data for models of hematopoiesis and stem cell transplantation.