Inflammatory Myeloid Cell Resurgence and Impaired Pro-Resolution Macrophage Maintenance Characterize Chronic Corneal...

To investigate longitudinal cellular and molecular immune remodeling during the transition from acute injury to chronic immunopathology after severe corneal alkali burn.

Corneal alkali burns were induced in BALB/c mice using 1-M NaOH for 30 seconds. Corneal opacity and neovascularization (NV) were clinically assessed, and excised corneas were analyzed for flow cytometric myeloid profiles and gene expression at baseline and at 1, 2, 4, and 8 weeks post-injury. Gene expression analyses included transcripts related to monocyte recruitment, cytokine responses, innate immune sensing, and inflammasome pathways. Late-phase C-C motif chemokine receptor 2 (CCR2) inhibition was performed from week 4 to week 8, followed by clinical, flow cytometric, and cleaved caspase-1 immunohistochemical analyses.

Alkali burn caused persistent corneal opacity, NV, and stromal and vascular remodeling. Leukocyte infiltration showed biphasic kinetics, with an early surge, transient decline at 4 weeks, and resurgence at 8 weeks. This chronic resurgence involved CD45+CD206⁻Ly6Chi inflammatory myeloid cells and antigen-presenting cell (APC)-like subsets, accompanied by recurrent Tlr4-Myd88-Ccl2 expression. In contrast, CD206+ and CD163+ pro-resolution macrophage-related subsets expanded transiently at 2 weeks but failed to persist chronically. Despite attenuation of Il1b and Il6 and progressive Il1rn upregulation, inflammasome-related transcripts remained elevated or resurged at 8 weeks. Late-phase CCR2 inhibition reduced recruited and APC-like inflammatory myeloid cells and modestly attenuated opacity and NV but was associated with sustained cleaved caspase-1-positive stromal signals.

Chronic alkali burn is characterized by secondary CCR2-sensitive inflammatory and APC-like myeloid resurgence, loss of pro-resolution macrophage-related subset maintenance, and inflammasome-related signaling that is temporally decoupled from acute cytokine responses.