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Hematopoietic precursors in disease induced by the myeloproliferative sarcoma virus
Abstract:
Granulocyte and macrophage precursors (GM-CFU-C-), which differentiate in vitro without added granulocyte and macrophage colony stimulating factor (GM-CSF), can be detected in the hematopoietic organs of mice infected with myeloproliferative sarcoma virus (MPSV). Retransplantation experiments have shown that the GM-CFU-C- are incapable of autonomous growth and depend on a factor present in medium conditioned by MPSV spleen cells (MPSV-CM). This factor is not MPSV and is not produced by spleen cells of noninfected mice. Two classical sources of GM-CSF, lung GM-CSF and GM-CSF contained in the plasma of endotoxin-treated mice, cannot replace the MPSV factor. Inversely, MPSV-CM does not stimulate the growth of retransplanted clusters induced in normal bone marrow with lung GM-CSF, whereas lung GM-CSF does. Two conditioned media containing activity promoting the in vitro proliferation and differentiation of hematopoietic stem cells in the mixed colony assay stimulate the growth of MPSV clusters: one medium was conditioned by pokeweed-mitogen-stimulated spleen cells, the other by the WEHI 3 cell line. The implication of the results in the comprehension of MPSV disease is discussed.
Insights
Myeloproliferative sarcoma virus (MPSV) infection in mice leads to granulocyte and macrophage precursors (GM-CFU-C) that require a specific factor from MPSV-infected spleen cells for growth, distinct from standard GM-CSF.
Area of Science:
- Hematology
- Virology
- Cell Biology
Background:
- Granulocyte and macrophage precursors (GM-CFU-C) are key cells in hematopoiesis.
- Myeloproliferative sarcoma virus (MPSV) is known to cause hematopoietic abnormalities.
- The regulation of GM-CFU-C growth is crucial for understanding myeloproliferative disorders.
Purpose of the Study:
- To investigate the growth requirements of GM-CFU-C in mice infected with MPSV.
- To identify the specific factor supporting GM-CFU-C proliferation in MPSV infection.
- To differentiate this factor from known sources of granulocyte-macrophage colony-stimulating factor (GM-CSF).
Main Methods:
- Detection and isolation of GM-CFU-C from hematopoietic organs of MPSV-infected mice.
- Retransplantation experiments to assess the growth capacity of GM-CFU-C.
- In vitro culture assays using conditioned media from MPSV spleen cells (MPSV-CM) and other sources of GM-CSF.
- Comparative analysis of growth stimulation using different conditioned media.
Main Results:
- GM-CFU-C were detected in MPSV-infected mice and required a factor from MPSV-CM for growth.
- This factor is not MPSV itself and is not produced by non-infected spleen cells.
- Standard sources of GM-CSF (lung GM-CSF, endotoxin-induced plasma GM-CSF) could not substitute for the MPSV-CM factor.
- MPSV-CM did not stimulate normal bone marrow GM-CFU-C, while lung GM-CSF did, indicating factor specificity.
- Conditioned media from pokeweed-mitogen-stimulated spleen cells and WEHI 3 cell line also stimulated MPSV-induced GM-CFU-C growth.
Conclusions:
- MPSV infection induces a unique requirement for a specific growth factor for GM-CFU-C.
- This factor is distinct from classical GM-CSF and plays a critical role in MPSV-induced myeloproliferation.
- Understanding this factor may provide insights into the pathogenesis of MPSV disease.