Lesion-remote astrocytes govern microglia-mediated white matter repair.
Publication Year:
2026
PubMed ID:
41407858
Funding Grants:
Public Summary:
When the spinal cord is injured, the healthy tissue surrounding the damage plays a surprisingly active role in the healing process. Researchers recently discovered that special support cells in these uninjured areas completely change their behavior to help manage the crisis. These support cells release a specific chemical messenger that acts as an instruction manual for the nervous system's local immune cells, telling them exactly how to safely digest and clear away the greasy nerve debris left behind by the injury. When scientists blocked this chemical messenger, the immune cells became overwhelmed and essentially "choked" on the waste, preventing the spinal cord from repairing itself and recovering lost physical functions. Importantly, this exact same cellular teamwork also appears naturally in human nerve diseases, meaning that finding ways to boost these helpful support cells could eventually lead to powerful new treatments that help patients recover from devastating spinal cord injuries.
Scientific Abstract:
Spared regions of the damaged central nervous system undergo dynamic remodelling and exhibit a remarkable potential for therapeutic exploitation(1). Lesion-remote astrocytes (LRAs), which interact with viable neurons and glia, undergo reactive transformations whose molecular and functional properties are poorly understood(2). Here, using multiple transcriptional profiling methods, we investigated LRAs from spared regions of mouse spinal cord following traumatic spinal cord injury. We show that LRAs acquire a spectrum of molecularly distinct, neuroanatomically restricted reactivity states that evolve after spinal cord injury. We identify transcriptionally unique reactive LRAs in degenerating white matter that direct the specification and function of local microglia that clear lipid-rich myelin debris to promote tissue repair. Fuelling this LRA functional adaptation is the secreted matricellular protein CCN1. Loss of astrocyte-derived CCN1 results in excessive, aberrant activation of local microglia, characterized by abnormal molecular specification, impaired debris processing reflected by the intracellular accumulation of myelin and axon debris, and dysregulated lipid metabolism with distinctive attenuation in lipid droplet accumulation. Mechanistically, we find that CCN1 binds microglial SDC4 to augment lipid storage, linking this signalling axis to a vital repair-associated lipid buffering response in debris-clearing microglia. Accordingly, microglial deficits resulting from astrocyte CCN1 depletion culminate in blunted clearance of white matter debris and impaired neurological recovery from spinal cord injury. Ccn1-expressing white matter astrocytes are induced by local myelin damage and are generated in diverse demyelinating disorders in mice and humans, pointing to their fundamental, evolutionarily conserved role in white matter repair. Our findings show that context-specific cues shape regionally distinct LRA reactivity states with functional adaptations that orchestrate multicellular processes underlying neural repair and influence disease outcome.