Abstract
Purpose: :
Nitrogen mustard (NM) and ultraviolet B light (UVB) are vesicants that induce microbullae in the cornea. Severe exposures result in the loss of epithelial-stromal integrity. Physicians treat mustard wounds under the assumption that they heal more slowly than equivalent injuries with epithelial-stromal (or epidermal-dermal) separations. We set out to experimentally determine whether or not this presumption is true.
Methods: :
Rabbit corneas in air lifted organ cultures (Gordon et al., J. Ocul Pharmacol. Ther. 26:407-419, 2010) were exposed to different intensities of UVB and different exposures of NM. UVB exposures were 100, 400, 800, 1200 and 1600 mJ/cm2. For NM, corneas were exposed to 100 nmoles of the vesicant for 30, 60 or 120 min. Composites of overlapping micrographs of H&E stained sections covering the entire diameter of cornea were analyzed to determine what conditions resulted in equivalent phenotypes at 24 hr post exposure. Corneas with equivalent 24 hr injuries were allowed to heal for 1-10 days. The timing of re-epithelialization was determined and the appearance and removal of provisional matrix components SPARC and hevin were assessed by immunofluorescence.
Results: :
At 24 hours post exposure, a nearly equivalent epithelial-stromal separation was observed with 2000mJ/cm2 UVB (61.7% separation) and with a 60 min exposure to 100 nmol NM (58.3% separation). The UVB-exposed corneas re-epithelialized within 5 days, while the NM-exposed cornea took 7 days to re-epithelialize. Immunofluorescence analysis showed that provisional wound matrix components HEVIN and SPARC persisted at least 1 day longer in the NM-exposed corneas than in UVB-exposed corneas.
Conclusions: :
These data experimentally verify that mustard-induced corneal injuries heal more slowly than equivalent UVB injuries. Both re-epithelialization and removal of provisional matrix components require longer times in NM-exposed corneas.
Keywords: cornea: basic science • wound healing • extracellular matrix