Sca+CD34- murine side population cells are highly enriched for primitive stem cells

Area of Science:

• Hematology
• Stem Cell Biology
• Cellular Immunology

Background:

• Side population (SP) cells possess unique properties due to their ability to efflux Hoechst dye.
• Understanding the stem cell capacity of SP cells and their subpopulations is crucial for regenerative medicine and disease research.

Purpose of the Study:

• To characterize murine side population (SP) stem cells and their subpopulations.
• To determine the primitive stem cell capacity of these cells using cobblestone area-forming cell (CAFC) frequencies.

Main Methods:

• Isolation of SP cells from murine adult whole bone marrow (WBM) using flow cytometry based on Hoechst dye efflux.
• Subpopulation isolation using anti-Sca and anti-CD34 antibodies.
• Assessment of primitive stem cell content via CAFC assay.

Main Results:

• SP cells are significantly enriched for primitive (day-28-35 CAFC) and more mature (day-14-21 CAFC) hematopoietic stem cells compared to WBM.
• SP(+)Sca(+)CD34(-) cells demonstrated the highest day-28-35 CAFC activity, approximately 2200 times that of normal bone marrow.
• SP cells with the greatest Hoechst dye efflux exhibited the highest day-35 CAFC frequencies, nearly 6000 times that of normal marrow.

Conclusions:

• Murine SP cells encompass both progenitor and primitive hematopoietic stem cell populations.
• The most primitive stem cells are characterized as Sca(+)CD34(-) with high Hoechst dye efflux capacity.
• Isolation of these specific SP cells may facilitate the study of primitive stem cell damage mechanisms.