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Microglia in colony-stimulating factor 1-deficient op/op mice
1Canadian Network of Centres of Excellence, Department of Anatomy, College of Medicine, University of Saskatchewan, Saskatoon, Canada.
Abstract:
Mice that are homozygous for the autosomal recessive mutation osteopetrosis (op) suffer from a general skeletal sclerosis, and the numbers of macrophages in various tissues are significantly decreased. We report that microglia in op/op mice are not affected by the mutation. They have normal morphology and are present in the CNS in normal frequency. In cultures, disaggregated cells of neopallia can form microglia, but such cells from neopallia of op/op mice form microglia only when colony-stimulating factor 1 (CSF-1) is added to the culture medium. The addition of granulocyte/macrophage (GM)-CSF or interleukin (IL)-3 to the culture medium does not stimulate production of microglia. Microglia that form in op/op neopallial cell cultures, in the presence of CSF-1, are capable of Fc-receptor-mediated phagocytosis. Based on our experiments, it seems that microglia are CSF-1 dependent but in op/op mice (in which CSF-1 is absent) microglia may use other locally produced factors.
Insights
Osteopetrosis (op) mice lack colony-stimulating factor 1 (CSF-1), impacting macrophages but not microglia. Microglia in these mice require CSF-1 for development, suggesting alternative local factors support their function in vivo.
Area of Science:
- Neuroimmunology
- Developmental Biology
- Genetics
Background:
- Osteopetrosis (op) mutation in mice leads to skeletal defects and reduced macrophage populations.
- Microglia, the resident immune cells of the central nervous system (CNS), are crucial for brain homeostasis.
- The role of colony-stimulating factor 1 (CSF-1) in microglia development and function is well-established.
Purpose of the Study:
- To investigate the impact of the osteopetrosis (op) mutation on microglia development and function.
- To determine the dependence of microglia on CSF-1 in the context of the op/op mouse model.
- To explore potential alternative factors supporting microglia in CSF-1 deficient environments.
Main Methods:
- Culturing disaggregated neopallial cells from wild-type and op/op mice.
- Supplementing culture media with colony-stimulating factor 1 (CSF-1), granulocyte/macrophage (GM)-CSF, or interleukin (IL)-3.
- Assessing microglia morphology, frequency, and Fc-receptor-mediated phagocytosis.
Main Results:
- Microglia in op/op mice exhibit normal morphology and frequency within the CNS.
- Neopallial cells from op/op mice require exogenous CSF-1 to differentiate into microglia in culture.
- CSF-1, but not GM-CSF or IL-3, stimulates microglia production from op/op cells.
- Cultured microglia from op/op mice demonstrate Fc-receptor-mediated phagocytosis when supported by CSF-1.
Conclusions:
- Microglia development is dependent on CSF-1.
- Despite the absence of CSF-1 in op/op mice, microglia are present in the CNS, suggesting the involvement of other locally produced factors.
- These findings highlight the complex regulation of microglia homeostasis and potential compensatory mechanisms in the CNS.
