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Morphological studies on neuroglia. III. Macrophage response and "microgliocytosis" in kainic acid-induced lesions
Abstract:
Light- and electron-microscopic investigations of kainic acid-induced lesions revealed a marked macrophage response and "microgliocytosis". The hematogenous origin of reactive elements, such as brain macrophages and "'microglia-like reactive cells", was demonstrated when blood phagocytes were labeled with carbon particles or horseradish peroxidase prior to induction of the kainic acid-lesion. The induced lesion showed a proliferation of microglial cells, which led to a state of "microgliocytosis" in the later stage of lesioning. Since it is now generally accepted that microglial cells in the state of "microgliocytosis" are derived from the "microglia-like reactive cells", proliferated microglial cells in the brain lesions are probably of hematogenous origin. The relationships among the brain macrophages, the "microglia-like reactive cells" and the intrinsic microglial cells are discussed.
Insights
Kainic acid lesions trigger a significant macrophage response in the brain. Studies suggest these reactive brain cells, including microglia, originate from blood phagocytes, indicating a hematogenous origin for brain macrophages.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Kainic acid (KA) induces excitotoxic brain lesions.
- Lesions are characterized by inflammatory and cellular responses.
- The origin of reactive glial cells, particularly microglia, is debated.
Purpose of the Study:
- To investigate the origin of reactive cells in kainic acid-induced brain lesions.
- To determine if brain macrophages and microglia in lesions are derived from blood cells.
Main Methods:
- Light and electron microscopy were used to examine KA-induced lesions.
- Blood phagocytes were labeled with carbon particles or horseradish peroxidase.
- Labeled phagocytes were tracked after KA lesion induction.
Main Results:
- A marked macrophage response and microgliocytosis were observed in KA lesions.
- Labeled blood phagocytes infiltrated the lesion site.
- Proliferation of microglia-like cells was evident, suggesting hematogenous origin.
Conclusions:
- Reactive brain macrophages and microglia in KA lesions are likely of hematogenous origin.
- The study supports the concept that microglia can arise from circulating monocytes.
- Understanding glial cell origins is crucial for neuroinflammatory research.