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Fluorescent dye prelabelled microglial cells migrate into organotypic hippocampal slice cultures and ramify
N P Hailer1, F L Heppner, D Haas
1Department of Cell Biology and Neurobiology, Institute of Anatomy, Humboldt University Clinic Charité, Berlin, Germany.
Abstract:
Microglial cells with their characteristic ramified morphology are exclusively found in healthy CNS tissue, whereas various pathologies are associated with the occurrence of amoeboid, macrophage-like cells. It is still a matter of discussion whether amoeboid cells are blood-derived macrophages, or whether a characteristic change in morphology, reflecting activation of previously ramified microglia, takes place. Cells in dissociated microglia culture obtained from healthy rat brains, inevitably developing this amoeboid morphology, were labelled with a fluorescent dye and transferred onto organotypic hippocampal slice cultures. Prelabelled cells with amoeboid morphology invaded these slice cultures and had, after 9 days in vitro, gradually transformed into highly ramified cells. Our findings strengthen the hypothesis that the observed amoeboid and ramified cells belong to a single population of microglia, appearing with different morphologies depending on the presence of stimuli provided by the CNS microenvironment. Microglial cells obviously appear in different shapes and can switch from immunologically resting to activated modes and vice versa.
Insights
Microglia, the brain's immune cells, can change shape from ramified to amoeboid and back. This study shows amoeboid microglia can transform into ramified cells, suggesting a single cell population with dynamic morphology.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglial cells in the central nervous system (CNS) exhibit distinct morphologies: ramified in healthy tissue and amoeboid during pathology.
- The origin of amoeboid cells (blood-derived macrophages or activated microglia) remains debated.
Purpose of the Study:
- To investigate the dynamic morphological changes of microglial cells.
- To determine if amoeboid microglia can revert to a ramified state.
Main Methods:
- Primary microglia cultures from healthy rat brains were established and induced to adopt amoeboid morphology.
- Fluorescently labeled amoeboid microglia were transplanted into organotypic hippocampal slice cultures.
- Cellular morphology and behavior were observed over 9 days in vitro.
Main Results:
- Transplanted amoeboid microglia successfully invaded the hippocampal slice cultures.
- Over 9 days, these amoeboid cells gradually transformed into highly ramified microglial cells.
- This demonstrates a reversible morphological transformation within the microglial population.
Conclusions:
- The findings support the hypothesis that amoeboid and ramified cells represent a single microglial population with environmentally responsive morphology.
- Microglial cells possess the capacity to dynamically switch between resting (ramified) and activated (amoeboid) states.
- This plasticity is crucial for microglial function within the CNS microenvironment.