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A protocol for the enrichment of different types of CFU-S from fetal mouse liver
A Corso1, M G Hogeweg-Platenburg, P De Vries
1Divisione di Ematologia, Policlinico San Matteo, Pavia, Italy.
Abstract:
A method is described for purifying hemopoietic stem cells from fetal mouse liver. It entails three steps. First, fetal liver cell obtained from 14- and 15- days-old fetuses are centrifuged on a discontinuous metrizamide gradient and the low density fraction is removed. These cells are then incubated with monoclonal antibodies directed against late differentiation antigens, and the positive cells are removed by immunomagnetic beads. The negative cells are labelled with fluorescein-conjugated pokeweed mitogen (FITC-PWM) and sorted by a fluorescence- activated cell sorter (FACS) on the basis of differences in fluorescence intensity. The number of stem cells is determined by spleen colony assay (CFU-S) for the various sorted fractions. We observed that, as shown for the bone marrow, the different cell fractions are responsible for CFU-S heterogeneity in the kinetics of spleen colony formation. The PWM dull day-12 CFU-S, which originate from cells with a high enrichment factor, would probably be a closer measure of pluripotent hemopoietic stem cells (PHSC), while the PWM bright day-8 and day-12 CFU-S likely originate from committed stem cells. Furthermore, the PWM dull sorted cells had a better capacity for protecting lethally irradiated mice than did the bright cells, although the latter yielded good numbers of day-8 and day-12 CFU-S that displayed, as in the bone marrow, a discrepancy between the enrichment for day-12 CFU-S and radioprotection.
Insights
This study purifies hemopoietic stem cells from fetal mouse liver using density gradients, antibody selection, and fluorescence-activated cell sorting. Results suggest distinct cell fractions correlate with pluripotent vs. committed stem cells and radioprotective capacity.
Area of Science:
- Hematology
- Stem Cell Biology
- Immunology
Background:
- Hemopoietic stem cells (HSCs) are crucial for blood formation and immune reconstitution.
- Understanding HSC heterogeneity is vital for regenerative medicine and disease treatment.
- Current methods for isolating HSCs from fetal sources require refinement.
Purpose of the Study:
- To develop and validate a method for purifying hemopoietic stem cells from fetal mouse liver.
- To characterize different HSC subpopulations based on differentiation markers and functional assays.
- To investigate the correlation between cell surface markers and stem cell potency.
Main Methods:
- Fetal mouse liver cells isolated from 14- and 15-day-old fetuses.
- Density gradient centrifugation using metrizamide.
- Immunomagnetic bead selection against late differentiation antigens.
- Fluorescence-activated cell sorting (FACS) using fluorescein-conjugated pokeweed mitogen (FITC-PWM).
- Spleen colony assay (CFU-S) to determine stem cell numbers and kinetics.
- Radioprotection assays in lethally irradiated mice.
Main Results:
- A three-step purification method successfully isolated distinct cell fractions from fetal mouse liver.
- FITC-PWM dull cells showed higher enrichment and better radioprotective capacity, suggesting they represent pluripotent hemopoietic stem cells (PHSC).
- FITC-PWM bright cells yielded more day-8 and day-12 CFU-S but had lower radioprotective potential, indicating committed stem cells.
- Heterogeneity in CFU-S formation kinetics was observed across different sorted cell fractions.
Conclusions:
- The developed method effectively purifies and distinguishes between pluripotent and committed hemopoietic stem cell populations in fetal mouse liver.
- FITC-PWM dull cells are proposed as a closer measure of PHSC due to their enrichment and radioprotective capabilities.
- The findings highlight the functional heterogeneity of HSCs and its implications for stem cell research and therapeutic applications.