c-Fos brain connectome in mouse with chronic corneal pain

Dry eye disease (DED) affects 30% of the adult population worldwide and causes corneal pain which remains a therapeutic challenge. Our study aimed to identify the first brain connectome associated with corneal pain by mapping c-Fos positive cells (an indirect marker of neuronal activation) in the whole mouse brain.Adult male C57BL/6 mice received unilateral topical instillation of 0.2% benzalkonium chloride twice/day for 7 days (DED model, n=5) and were compared to naive animals (n=5). Spontaneous ocular pain (eye closure ratio) and corneal mechanical sensitivity (von Frey test) were monitored at day 0 and day 7. Brain sections were immunostained with c-Fos antibody and imaged under NanoZoomer. Images were aligned to Allen Brain Atlas by ABBA (a FIJI plugin) followed by regional quantification of c-Fos positive cells. Data were analyzed with Python programming for network visualization in Cytoscape.Our results show that mice with persistent DED developed a spontaneous ocular pain and a mechanical hypersensitivity compared to control mice. In this study, we quantified expression of the activity-regulated gene c-Fos in 815 cerebral regions. Among them, 37 brain regions, that are pathways associated with pain transmission or modulation, exhibited significant increased c-Fos expression in DED mice. Furthermore, our study identified several cerebral hub regions in mice with persistent corneal pain. In conclusion, the whole brain network of corneal pain we constructed and our findings contribute to the identification of brain areas as targets for therapeutic approaches against corneal pain.