Architectural and biochemical expressions of mustard gas keratopathy: preclinical indicators and pathogenic mechanisms.
A subset of victims of ocular sulfur mustard (SM) exposure develops an irreversible, idiotypic keratitis with associated secondary pathologies, collectively referred to as mustard gas keratopathy (MGK). MGK involves a progressive corneal degeneration resulting in chronic ocular discomfort and impaired vision for which clinical interventions have typically had poor outcomes. Using a rabbit corneal vapor exposure model, we previously demonstrated a clinical progression with acute and chronic sequelae similar to that observed in human casualties. However, a better understanding of the temporal changes that occur during the biphasic SM injury is crucial to mechanistic understanding and therapeutic development. Here we evaluate the histopathologic, biochemical and ultrastructural expressions of pathogenesis of the chronic SM injury over eight weeks. We confirm that MGK onset exhibits a biphasic trajectory involving corneal surface regeneration over the first two weeks, followed by the rapid development and progressive degeneration of corneal structure. Preclinical markers of corneal dysfunction were identified, including destabilization of the basal corneal epithelium, basement membrane zone abnormalities and stromal deformation. Clinical sequelae of MGK appeared abruptly three weeks after exposure, and included profound anterior edema, recurring corneal erosions, basement membrane disorganization, basal cell necrosis and stromal degeneration. Unlike resolved corneas, MGK corneas exhibited frustrated corneal wound repair, with significantly elevated histopathology scores. Increased lacrimation, disruption of the basement membrane and accumulation of pro-inflammatory mediators in the aqueous humor provide several mechanisms for corneal degeneration. These data suggest that the chronic injury is fundamentally distinct from the acute lesion, involving injury mechanisms that operate on different time scales and in different corneal tissues. Corneal edema appears to be the principal pathology of MGK, in part resulting from persistent necrosis of the basal corneal epithelium and deterioration of the basement membrane. The findings also provide a potential explanation as to why administration of anti-inflammatories transiently delays, but does not prevent, the development of MGK sequelae.
United States Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland, United States of America. patrick.mcnutt@us.army.mil
Patrick
P
McNutt
Megan
M
Lyman
Adam
A
Swartz
Kaylie
K
Tuznik
Denise
D
Kniffin
Kim
K
Whitten
Denise
D
Milhorn
Tracey
T
Hamilton
D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism; D001485:Basement Membrane / Q000648:ultrastructure; D003315:Cornea / Q000187:drug effects / Q000473:pathology / Q000648:ultrastructure; D018450:Disease Progression; D004847:Epithelial Cells / Q000473:pathology / Q000648:ultrastructure; D005260:Female; D018836:Inflammation Mediators / Q000378:metabolism; D007634:Keratitis / Q000139:chemically induced* / Q000378:metabolism / Q000473:pathology*; D009151:Mustard Gas / Q000633:toxicity*; D011817:Rabbits; D014945:Wound Healing
D018836:Inflammation Mediators; D009151:Mustard Gas