Astrocyte coordinated remodelling of the dorsal horn endothelium and pain hypersensitivity

Pain perception relies not only on sensory neurons but also on the interplay of a heterogeneous cell population, including endothelial cells, microglia, and astrocytes. Blood-spinal cord barrier dysfunction can alter nociceptive processing and lead to pain hypersensitivity. A component of this capillary network is the astrocytic foot processes that encapsulate the blood-brain barrier, providing critical nutritional support and protection. Astrocytes are a fundamental modulator of nervous system health as well as a regulator of capillary function, with reactive astrocytes a pathological hallmark of persistent pain. However, it remains unknown whether astrocytes influence angiogenic processes in the dorsal horn to induce persistent pain. In this study, we elucidate, using spatiotemporally delivered chemogenetic astrocyte activation, the role of astrocytes in the modulation of the blood-spinal cord barrier and nociception. Adult male and female mice were intrathecally administered AAV consisting of either GFAP-hM3D(Gq)-mCherry (GFAP-hM3D(Gq)) or GFAP-mCherry. mCherry-labelled GFAP-positive astrocytes were identified in the lumbar dorsal horn following AAV injection. DREADD-induced astrogliosis in the dorsal horn was indicated by increased astrocyte number and GFAP immunoreactivity, which occurred alongside mechanical and heat hypersensitivity in GFAP-hM3D(Gq) mice. In CNO-treated GFAP-hM3D(Gq) mice, astrocyte-endothelium interactions were increased in the dorsal horn compared with vehicle-treated rodents. The capillary network (reduced CD31) and angiogenic proteome were reduced in the dorsal horn of CNO-treated GFAP-hM3D(Gq) mice. Diminished angiogenesis and pain hypersensitivity were ameliorated by VEGF-A165b supplementation. This demonstrates that astrocytes in the dorsal horn modulate the blood-spinal cord barrier, impacting upon nociceptive processing and pain hypersensitivity.