SPARC and Hevin in Corneal Healing after Nitrogen Mustard and UVB Injury

Nitrogen mustard (NM) and ultraviolet B (UVB) are vesicants, and exposures induce corneal microbullae due to the basal epithelial cells losing contact with the stroma. Our goal was to determine whether NM‐induced injury heals more slowly than an equivalent UVB‐induced injury by evaluating healing time and expression and clearance of provisional matrix components in the wound. Rabbit corneal organ cultures were exposed to levels of NM or UVB that produced about the same amount of epithelial‐stromal separation 24 hr after exposure: A 60 min exposure to 100 nmol NM resulted in 58.3% epithelium‐stromal separation, and a 2000 mJ/cm2 UVB (100 min) exposure resulted in 61.7% separation. This was assessed by making composites from micrographs of H&E stained sections to cover the entire diameter of the cornea. Repair of the epithelial‐stromal interface was followed for 10 days, and showed that UVB injury healed after 3 days, while the NM injury required 4 days. During the healing process, provisional matrix components SPARC and hevin were deposited into the healing tissue and cleared from it. The clearing occurred faster in UVB‐exposed samples than in NM‐exposed corneas. These data experimentally demonstrate that the healing of mustard vesicant injuries is delayed as compared to comparable injuries from other agents that affect the epithelial‐stromal junction. Grant Funding Source : RO1 EY009056 , U54 AR055073 , and P30 ES005022