Ocular Surface Microbiota-Derived Lipoteichoic Acid Promotes Dry Eye Disease by Inducing Corneal Inflammation.

Purpose: Ocular surface microbiota (OSM) dysbiosis is associated with dry eye disease (DED), but the underlying mechanisms remain poorly understood. This study investigated the role of lipoteichoic acid (LTA), a Gram-positive bacterial product, in DED pathogenesis. Methods: A cross-sectional study was conducted involving 277 participants to analyze OSM composition via 16S rRNA sequencing and quantify tear LTA levels. In vitro experiments using human corneal epithelial cells (HCE-T) and in vivo mouse models were used to explore LTA-induced inflammation. The involvement of Toll-like receptor 2 (TLR2) and platelet-activating factor receptor (PAFR) was assessed using siRNAs and the PAFR antagonist Apafant. Results: Patients with DED showed functional enrichment in LTA synthesis-related pathways in their OSM. Tear LTA levels were significantly elevated in patients with DED and correlated positively with disease risk and clinical severity. Mechanistically, LTA activated p38 MAPK and NF-κB signaling pathways via TLR2 and PAFR, upregulating pro-inflammatory cytokine expression. In mice, topical LTA administration induced corneal epithelial damage, reduced tear secretion, and caused histopathological changes. Treatment with Apafant significantly alleviated LTA-induced corneal inflammation, improved tear secretion, and preserved epithelial integrity. Conclusions: Our findings establish a mechanistic link between OSM-derived LTA and DED. LTA promotes ocular surface inflammation and dysfunction through TLR2 and PAFR signaling, suggesting that targeting microbial products or their receptors, such as PAFR, may offer a novel therapeutic strategy for DED.