Sympathetic Nerves Coordinate Corneal Epithelial Wound Healing by Controlling the Mobilization of Ly6C(hi) Monocytes From the Spleen to the Injured Cornea

PURPOSE: This study aims to investigate the potential involvement of spleen-derived monocytes in the repair process following corneal epithelial abrasion. METHODS: A corneal epithelial abrasion model was established in male C57BL/6J mice, and the dynamic changes of monocyte subpopulations in the injured cornea were analyzed using flow cytometry. The effects of Ly6C(hi) monocyte depletion and local adoptive transfer of purified Ly6C(hi) monocytes on wound closure and neutrophil recruitment to the injured cornea were observed. The effect of sympathetic nerves on the recruitment of spleen-derived Ly6C(hi) monocytes to the injured cornea was also investigated using multiple methods. The emigration of fluorescence-labeled monocytes to the injured cornea was validated through intravital microscopy. Finally, differential genes between different groups were identified through high-throughput RNA sequencing and analyzed for functional enrichment, followed by verification by quantitative PCR. RESULTS: Ly6C(hi) monocytes were present in large numbers in the injured cornea prior to neutrophil recruitment. Predepletion of Ly6C(hi) monocytes significantly inhibited neutrophil recruitment to the injured cornea. Furthermore, surgical removal of the spleen significantly reduced the number of Ly6C(hi) monocytes in the injured cornea. Further observations revealed that sympathetic blockade significantly reduced the number of Ly6C(hi) monocytes recruited to the injured cornea. In contrast, administration of the β2-adrenergic receptor agonist significantly increased the number of Ly6C(hi) monocytes recruited to the injured cornea in animals treated with sympathectomy and catecholamine synthesis inhibition. CONCLUSIONS: Our results suggest that spleen-derived Ly6C(hi) monocytes, under the control of the sympathetic nervous system, play a critical role in the inflammatory response following corneal injury.