EFFECTS OF ACUTE AND CHRONIC ARSENIC EXPOSURE OF HUMAN-DERIVED KERATINOCYTES IN AN IN-VITRO HUMAN SKIN EQUIVALENT SYSTEM - A NOVEL MODEL OFHUMAN ARSENICISM

An organotypic culture (OTC) of a human keratinocyte cell line (HaCaT) over a human fibroblast-embedded collagen gel was used to model human epidermis in arsenicism, a syndrome that currently lacks valid experi mental models. Keratinocytes were exposed acutely or chronically to a mixture of arsenate (0.5 mu M), monomethylarsonic acid (MMA; 0.5 mu M) and dimethylarsinic acid (DMA; 1.5 mu M), or to the individual compon ents of the mixture. OTCs were assayed for microscopic morphology, the proliferating cell marker, Ki-67, labelling and cytokeratin expressio n. Acute exposures resulted in an epidermal phenotype that accurately modelled early human lesions, including hyperkeratosis, acanthosis and keratin 16 induction. Chronic exposures resulted in a de-differentiat ed epidermal phenotype with focal nests of keratinocytes growing into the collagen gel. The keratin 8/18 pair was induced by either acute or chronic arsenic exposure, as was the proliferating cell marker, Ki-67 . Exposure of keratinocytes to individual arsenic compounds demonstrat ed that all arsenic mixture-induced changes could be duplicated by exp osure to arsenate alone. In contrast, MMA and DMA were inactive. This study establishes OTC as a useful model of arsenicism, and implicates inorganic arsenic as the ultimate carcinogen. (C) 1997 Elsevier Scienc e Ltd.