Sequential modulation of the cGAS-STING pathway promotes spinal cord injury repair.

INTRODUCTION The cGAS-STING pathway is a central innate immune sensor of cytosolic DNA. Spinal cord injury (SCI) triggers sterile inflammation, but the spatiotemporal role of this pathway in injured spinal cord repair remains unclear. Understanding its phase-dependent functions may enable precise immunomodulation to improve recovery.

Objectives

This study aimed to investigate the dynamic activation of the cGAS-STING pathway after SCI and to determine whether a time-sequenced pharmacological strategy, consisting of early activation followed by late inhibition, could enhance functional repair.

Methods

A mouse thoracic compressive SCI model was used. Pathway expression and cellular localization were assessed by western blot, immunofluorescence, and transcriptomics. Sustained or sequential modulation was performed using STING agonists and antagonists. Motor recovery was evaluated by the Basso Mouse Scale and footprint analysis. Axonal integrity, myelin preservation, and glial scarring were analyzed histologically. Myeloid cells (including microglia) were depleted with PLX5622, and neuron-microglia cocultures were established for mechanistic studies.

Results

cGAS-STING was significantly activated predominantly in myeloid cells (mainly microglia, with a smaller contribution from infiltrating macrophages) after SCI. Sustained activation or inhibition failed to improve recovery. Sequential treatment (ADU-S100 days 0-10 → C-176 days 11-28) markedly enhanced motor function, axonal integrity, and myelin preservation while reducing glial scarring. Mechanistically, early activation boosted microglial phagocytosis and clearance; late inhibition resolved inflammation and promoted the expression of anti-inflammatory and axon-associated genes. Myeloid cell depletion completely abolished these benefits.

Conclusion

The cGAS-STING pathway exerts phase‑dependent, biphasic functions in SCI. A precisely timed "activation followed by inhibition" strategy optimally harnesses myeloid cell dynamics to coordinate debris clearance and inflammation resolution, offering a novel immunomodulatory paradigm for central nervous system repair.