Inflammatory damage to the limbal stem cells after acute ocular injury: Protection with TNF-α inhibition

Abstract

Purpose : Limbal stem cell (LSC) deficiency is a frequent complication following ocular chemical injury. This study was designed to investigate the role of TNF-α mediated inflammation in LSC deficiency after corneal alkali burn and to explore a rescue therapy based on TNF-α inhibition.

Methods : Corneal alkali injuries were created in mice using a 2-mm in diameter filter paper soaked in 1N NaOH, applied to the central cornea for 20 seconds (peripheral cornea and limbus spared). Injured eyes received copious irrigation with sterile saline for 15 minutes. Immediately after lavage, mice were treated with an intraperitoneal injection of either IgG or TNF-α inhibitor (infliximab; 10mg/kg). Corneal tissues were collected at 24 hours, 7 days and 1.5 months after the injury and evaluated using qPCR, flow cytometry, immunofluorescence, and in situ hybridization. LSC damage was evaluated using in situ cell death detection assay. LCSs were identified using anti-ABCB5. Conjunctival epithelium was discriminated from corneal epithelium using anti-cytokeratin 13 (CK13) and anti-CK12 immunofluorescence.

Results : Corneal alkali injury caused rapid infiltration of peripheral CD45⁺CCR2⁺ (130-fold increase) and CD45⁺CX3CR1⁺ (22-fold) monocytes into the cornea and upregulation of TNF-α mRNA (12-fold) in the limbal, peri-limbal, and scleral region, which were spared the injury by alkali. Extensive LSC death was noted, however, within 24 hours. TNF-α inhibition after the injury significantly suppressed immune cell infiltration (49% reduction) and TNF-α expression (32%) at 24 hours (p<0.05, for both), which ameliorated LSC loss. The protective effect of TNF-α inhibition on LSCs was confirmed using TNF receptor 1&2 knock-out mice. Anti-TNF-α treated mice retained more normal corneal epithelial phenotype with reduced presence of conjunctival epithelial cells on the corneal surface, as compared to untreated mice; the latter exhibited complete corneal surface conjunctivalization 1.5 months after the injury.

Conclusions : Secondary inflammation can lead to LSC damage even in the absence of direct damage by the injury. Prompt inhibition of TNF-α can help salvage viable LSCs and promote normal corneal epithelium regeneration. Thus, TNF-α inhibition may be an important therapeutic intervention for ocular alkali injury

This is a 2020 ARVO Annual Meeting abstract.