USE OF DERMAL EQUIVALENT AND SKIN EQUIVALENT MODELS FOR IDENTIFYING PHOTOTOXIC COMPOUNDS IN-VITRO

Phototoxicity inducing in vivo photoirritation, a reversible inflammat ory reaction of the skin after chemical contact and UVA radiation expo sure, is increasingly observed as a side effect associated with the us e of both cosmetics and systemic drugs. In order to systematically scr een for the phototoxic potential of new compounds, we propose two thre e-dimensional models suitable for in vitro testing: a dermal equivalen t (DE) and a skin equivalent (SE) model, The DE model includes a colla gen-glycosaminoglycans-chitosan porous matrix populated by normal huma n fibroblasts. The SE model is made by seeding normal human keratinocy tes onto the DE, leading to a fully differentiated epidermis, The obje ctives of this pilot study are: 1) to compare the deleterious effects of UVA radiation on the two models and 2) to evaluate to what extent t he in vitro results can predict the in who phototoxicity caused by wel l-known photoirritant compounds, included in the COLIPA validation pho totoxicity reference chemical list. Dilutions of thiourea, sulisobenzo ne, promethazine, chlorpromazine and tetracycline were applied (20 mu l) onto DEs and SEs (n=6) and incubated for 1 h (or 15 h) at 37 degree s C. Irradiated samples received 3 J/cm(2) UVA. The 24 h post-irradiat ion residual cellular viability was measured using the MTT test on tre ated and untreated tissues and IL-la release measurement in collected SE culture media, A concordance in terms of photoirritant/non-photoirr itant was obtained between the in vivo data and the in vitro results, suggesting that the DE and the SE models could be integrated, after a complete validation study, into a protocol for in vitro testing of the photoirritant potential of new molecules.