CHARACTERIZATION OF ULTRAVIOLET RADIATION-INDUCED DAMAGE TO KERATINOCYTES IN A SKIN EQUIVALENT IN-VITRO

The human skin equivalent (HSE) provides a convenient model for studyi ng the dermatological effects of exposure to ultraviolet (UV) radiatio n. HSEs, constructed by overlaying a collagen-fibroblast matrix with e pidermal cells, were maintained submerged for 1 week after the additio n of epidermal cells and then raised to the air-liquid interface for a n additional 3 weeks. HSEs were exposed to sublethal doses of UV radia tion ranging from 0 to 500 J/m2, incubated up to 48 h in medium contai ning H-3-thymidine and fixed for ultrastructural and autoradiographic analysis. Exposure to radiation doses greater than 50J/m2 led to vacuo lation of the cornified envelopes and enlargement of intercellular spa ces. These doses also led to the formation of dense cytoplasmic bodies , and separation and vesiculation of the nuclear envelope in the basal cells. DNA synthesis in the basal cells was analyzed autoradiographic ally. Maximal numbers of labeled basal cells were observed 24 h after exposure to UV radiation at 50 J/m2. Although the proportions of label ed cells varied among different epidermal donors, the maximal response s and time-course of H-3-thymidine incorporation remained consistent, supporting the usefulness of the HSE in studying the effects of UV irr adiation on human skin.