Morphotype-specific calcium signaling in human microglia

Area of Science:

• Neuroscience
• Cell Biology
• Neuroimmunology

Background:

• Microglia, the brain's immune cells, use calcium (Ca2+) signaling to monitor neural activity and detect damage.
• Ca2+ dyshomeostasis is implicated in neurological disorders in mice, but human microglial Ca2+ signaling remains uncharacterized.

Purpose of the Study:

• To investigate the in situ Ca2+ signaling properties of human microglia within their native microenvironment.
• To characterize the differences in Ca2+ signal compartmentalization and properties across human microglial morphotypes.

Main Methods:

• Development of a novel genetically-encoded ratiometric Ca2+ indicator for human microglia.
• Analysis of Ca2+ signaling in freshly resected human brain tissue and organotypic slice cultures.
• In situ monitoring of Ca2+ signaling in aged human microglia.

Main Results:

• Human microglial Ca2+ signals are compartmentalized, with distinct properties in different cellular compartments and morphotypes.
• Basal Ca2+ levels are lower in ramified microglia and higher in ameboid microglia.
• Signal dynamics (fraction of active cells, signal amplitude/duration) vary significantly across microglial morphotypes (ramified, hypertrophic, ameboid).

Conclusions:

• Human microglia display unique, compartmentalized Ca2+ signaling patterns not previously observed.
• Differences in Ca2+ signaling across morphotypes suggest functional specialization within the human microglia population.
• These findings provide a foundation for understanding human microglial roles in health and disease.