Work

ADGRG1 blockade drives astrocytes into the extracellular matrix to reduce glial scar size

Year: 2026

Type: preprint

Abstract: Background After wide range of traumatic damage to the spinal cord, reactive astrocytes migrate toward the lesion but stop at the edge of the fibrotic extracellular matrix (ECM) core. There, the reactive astrocytes accumulate and form the glial scar border that prevents the regenerating axons from passing through. Why these astrocytes stop at this border rather than entering the ECM remains unknown. We reasoned that this stop signal comes from the fibrotic ECM. Among its components, we focused on type III collagen, which is abundant in the core but whose role in scar formation is unknown. Methods We analyzed single-nucleus RNA-sequencing and spatial transcriptomic datasets of mouse spinal cords. Using cell-cell interaction analysis, we searched for the astrocyte receptor that binds type III collagen. We then tested the candidate pathway in primary astrocytes in vitro , in vivo using pharmacological and genetic inhibition, and in human induced pluripotent stem cell (hiPSC)-derived astrocytes. Results We found six astrocyte subclusters that changed over time. Among them, reactive astrocytes showed a strong interaction between type III collagen, encoded by Col3a1 , and adhesion G protein-coupled receptor G1 (ADGRG1). Col3a1 -expressing vascular leptomeningeal cells (VLMCs) and arachnoid barrier cells (ABCs) sat next to ADGRG1-expressing astrocytes at the fibrotic border. In vitro , type III collagen activated RhoA-GTP loading through ADGRG1 and suppressed astrocyte migration. This effect was specific to type III collagen and was reversed by the ADGRG1 antagonist Dihydromunduletone (DHM). In vivo , both pharmacological inhibition of ADGRG1 and astrocyte-specific Adgrg1 knockdown let astrocytes enter the type III collagen-rich matrix. This produced smaller glial scars, enhanced corticospinal tract (CST) regeneration, and improved motor recovery. The same response occurred in hiPSC-derived astrocytes. Conclusions Type III collagen keeps astrocytes at the edge of the fibrotic ECM and stops them from entering it, acting through ADGRG1–RhoA signaling. This sets the position of the glial scar border. The type III collagen–ADGRG1 axis may be a new therapeutic target for controlling maladaptive scarring after CNS injury.

Source: Research Square

DOI: 10.21203/rs.3.rs-10546825/v1