Depilatory double-disc mouse model for evaluation of vesicant dermal injury pharmacotherapy countermeasures

Background:Sulfur mustard(SM)is a chemical warfare vesicant that severely injures exposed eyes,lungs,and skin.Mechlorethamine hydrochloride(NM)is widely used as an SM surrogate.This study aimed to develop a depilatory double-disc(DDD)NM skin burn model for investigating vesicant pharmacotherapy countermeasures.Methods:Hair removal method(clipping only versus clipping followed by a depilatory),the effect of acetone in the vesicant administration vehicle,NM dose(0.5-20μmol),vehicle volume(5-20μl),and time course(0.5-21 days)were investigated using male and female CD-1 mice.Edema,an indicator of burn response,was assessed by biopsy skin weight.The ideal NM dose to induce partial-thickness burns was assessed by edema and histopathologic evaluation.The optimized DDD model was validated using an established reagent,NDH-4338,a cyclooxygenase,inducible nitric oxide synthase,and acetylcholinesterase inhibitor prodrug.Results:Clipping/depilatory resulted in a 5-fold higher skin edematous response and was highly reproducible(18-fold lower%CV)compared to clipping alone.Acetone did not affect edema formation.Peak edema occurred 24-48 h after NM administra-tion using optimized dosing methods and volume.Ideal partial-thickness burns were achieved with 5μmol of NM and responded to treatment with NDH-4338.No dif-ferences in burn edematous responses were observed between males and females.Conclusion:A highly reproducible and sensitive partial-thickness skin burn model was developed for assessing vesicant pharmacotherapy countermeasures.This model pro-vides clinically relevant wound severity and eliminates the need for organic solvents that induce changes to the skin barrier function.