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Haemopoietic stem cell proliferation in the bone marrow of S1/S1d mice
1Department of Anatomy and Experimental Pathology, University of St Andrews, Scotland.
Abstract:
In marrow from Sl/Sld mice (but not +/+ mice) day 7 and day 8 CFU-S proliferate whilst day 10 and day 12 CFU-S exhibit negligible proliferation. Media conditioned by both +/+ and Sl/Sld marrow contains an inhibitor of CFU-S proliferation but day 8 CFU-S in +/+ and Sl/Sld marrow show marked dose-response differences to this factor. To inhibit the proliferation of Sl/Sld CFU-S required approximately ten times the concentration of inhibitor that inhibited the proliferation of +/+ CFU-S. Thus abnormally responsive day 8-CFU-S were shown to proliferate in an inhibitory environment. Abnormalities in Sl/Sld CFU-S function were also demonstrated in heterotopic transplantation experiments using +/+ and Sl/Sld donors and hosts to obtain ectopic bone marrow with various stromal (donor) and haemopoietic (host) combinations. Day 8 Sl/Sld CFU-S were seen to proliferate, irrespective of whether the stromal environment was derived from Sl/Sld or +/+ marrow. Sl/Sld mice are generally regarded as animals in which there is a genetically determined defect in haemopoiesis due to an abnormality in the haemopoietic environment. It is difficult, however, to attribute the abnormal CFU-S behaviour in these experiments to environmental factors and the results are consistent with mutation at the Sl locus affecting the responses of CFU-S to regulatory signals, i.e. the genetic defect is not confined to the stromal environment.
Insights
Colony-forming unit-spleen (CFU-S) in Sl/Sld mice show abnormal proliferation in response to inhibitory factors. This suggests a genetic mutation affecting CFU-S regulation, not just the bone marrow environment.
Area of Science:
- Hematology
- Developmental Biology
- Genetics
Background:
- The Sl/Sld mouse model is characterized by defects in hematopoiesis, typically attributed to an abnormal hematopoietic environment.
- Colony-forming unit-spleen (CFU-S) are critical progenitor cells in hematopoiesis, and their proliferation is tightly regulated.
Purpose of the Study:
- To investigate the proliferative behavior of CFU-S in Sl/Sld mice compared to wild-type (+/+) mice.
- To determine if the observed abnormalities in CFU-S are due to environmental factors or intrinsic cellular defects.
Main Methods:
- Assessing CFU-S proliferation in marrow from Sl/Sld and +/+ mice at different developmental days (7, 8, 10, 12).
- Analyzing the response of CFU-S to proliferation inhibitors present in conditioned media from both genotypes.
- Conducting heterotopic transplantation experiments with varying donor and host combinations.
Main Results:
- Day 7 and 8 CFU-S from Sl/Sld mice exhibited proliferation, unlike in +/+ mice, while day 10 and 12 CFU-S showed negligible proliferation in both.
- Sl/Sld day 8 CFU-S required ten times more inhibitor to suppress proliferation compared to +/+ CFU-S, indicating abnormal responsiveness.
- Day 8 Sl/Sld CFU-S proliferated regardless of the stromal environment (Sl/Sld or +/+), suggesting intrinsic defects.
Conclusions:
- The abnormal behavior of Sl/Sld CFU-S is not solely due to environmental factors.
- Results strongly suggest a mutation at the Sl locus directly affects the response of CFU-S to regulatory signals.
- The genetic defect in Sl/Sld mice impacts CFU-S function intrinsically, extending beyond the stromal environment.