Astrocytes: The Unsung Architects of Synaptic Integration and Their Role in Brain Health and Disease

Astrocytes, long viewed as passive support cells, are now recognized as dynamic regulators of synaptic function. This mini review summarizes recent findings revealing that astrocyte leaflets, thin peripheral processes of astrocyte, form gap junction interconnected domains containing tiny endoplasmic reticulum saccules. Interestingly, the astrocyte leaflets directly contact and enwrap 90% of neuron synapses in clusters. Furthermore, neuronal circuit activity could trigger local Ca²⁺ dynamics in astrocyte leaflets mediated by inositol 1,4,5-trisphosphate receptor type 1 (IP₃R1), while leaflet Ca²⁺ signals could integrate neuronal circuits active at different spatiotemporal scales. These findings uncover the novel glial-synapse interactions and highlight the pathophysiological roles of astrocyte leaflets in neuron circuit computation, relevant to human neurological diseases (NDs). In addition, therapeutic opportunities, such as targeting leaflet calcium signaling for neuroprotection, alongside challenges in imaging and modeling are discussed. Future perspectives emphasize advanced tools like optogenetics and artificial intelligence to unravel astrocyte contributions, paving the way for glial-centric interventions in NDs.