Nikolsky's sign: a novel way to evaluate damage at the dermal-epidermal junction

Background/aims: Sulfur mustard (2,2′‐dichlorodiethyl sulfide, HD) is a potent vesicating (blistering) agent. Cutaneous exposure causes the destruction of basal cells and leads to a separation at the dermal‐epidermal junction. To evaluate the efficacy of candidate antivesicant compounds, suitable animal models are needed. A tape stripping method and the Dermal Torque Meter (DTM) have been used in novel applications to evaluate for the Nikolsky's sign in the hairless guinea pig. The Nikolsky's sign is the separation and loss of the epidermis from the dermis when the skin is pressed with a sliding or twisting motion. The purpose of this study was to find an objective, reproducible, and quantitative method that could be used as an end‐point to evaluate the degree of damage at the dermal‐epidermal junction following cutaneous HD vapor exposure. Methods: Hairless guinea pigs were exposed to saturated HD vapor (1.4 mg/l) for time intervals between 2 and 9 min using 14‐mm vapor cups. At 24 h post‐exposure, both tape stripping (fabric carpet tape) and a DTM were used to produce the Nikolsky's sign in animals under anesthesia. Using the tape stripping method, 15‐mm disks of tape were applied to each skin site. After 5 s the tape was peeled off. The D T M was used to apply a horizontal twisting motion to the skin. The parameters included a 15‐mm center disk, a ring gap of 1 mm, a torque of 30 mNm, and a 5‐s cycle time. A cyanoacrylate adhesive was used to secure the center disk and guard ring to the skin. The loss of the epidermis was determined by visual observation and confirmed by histopathological examination. The standard D T M unit was modified to use multiple center disk/guard ring assemblies so that several sites on each animal could be evaluated at the same time. Results: The mean (±S E M) percent incidence of positive Nikolsky's sign observations using the tape stripping method for HD vapor exposures of 3,5,7, and 9 min was 0,50 (±16), 94 (±6.2), and 100, respectively. The mean (±S E M) percent incidence of positive Nikolsky's sign observations using the D T M method for HD vapor exposures of 2, 3, 4, and 5 min was 0, 25 (±7.1), 91 (±2.9), and 96 (±2.3), respectively. Conclusions: The Nikolsky's sign produced by the tape stripping method and the D T M were useful in evaluating damage at the dermal‐epidermal junction following cutaneous HD vapor exposures. These methods have the potential to replace histopathology as an end‐point for routine screening proce