Use of human skin equivalent Apligraf for in vitro assessment of cumulative skin irritation potential of topical products

The main goal of the present study was to investigate the response of the h uman skin equivalent Apligraf in vitro to the application of irritant subst ances and its predictivity as a screening tool for cumulative skin irritant potential in humans. Vaseline, calcipotriol, trans-retinoic acid, and sodi um lauryl sulfate were applied to Apligraf in vitro for 24 h. Cell viabilit y (lactate dehydrogenase leakage), release and mRNA expression of the proin flammatory cytokines IL-1 alpha and IL-8, and morphological changes were as sessed. The same products were applied to 30 healthy volunteers in a double -blind, randomized, vehicle-controlled within-subject study. The skin react ions after repeated 24-h applications over 3 weeks under Finn chamber patch es were monitored by visual scoring and biophysical methods (trans-epiderma l water loss, chromametry, and blood flow). Sodium lauryl sulfate was cytot oxic to Apligraf, and increased the release and expression of cytokines at low (0.2%, 0.4%), but not at high (0.8%, 1%) concentrations. It induced sev ere irritancy in vivo. Trans-retinoic acid increased the expression and rel ease of cytokines with no detectable cytotoxicity and showed moderate irrit ancy in humans. Although calcipotriol did neither affect cell viability nor the production of cytokines, it induced morphological signs of irritation and was mildly irritant for healthy volunteers. Vaseline was innocuous in v ivo and induced no changes in Apligraf. In conclusion, the cumulative skin irritation potential of the tested products could be predicted with Apligra f in a sensitive and specific manner, by monitoring cytotoxicity, proinflam matory cytokines, and morphological changes. (C) 2000 Academic Press.