Development and evaluation of a skin organ model for the analysis of radiation effects

The reaction of tissues to ionizing radiation involves alterations in cell-cell and cell-matrix interactions mediated by cellular adhesion molecules. The aim of this study was to develop and evaluate an artificial skin organ model for the analysis of radiation effects. A human co-culture system consisting of the spontaneously immortalized keratinocyte cell line HaCaT and primary HDFa fibroblasts embedded into a collagen sponge was established. This skin organ model has been characterized and evaluated for its suitability for radiobiological investigations. For that purpose, expression of beta(1)-integrin following irradiation was compared in the skin organ model and in HaCaT monolayer cells (FACScan and immunohistochemistry). Furthermore, the influence of ionizing radiation on DNA fragmentation was investigated in the skin organ model (TUNEL assay). The novel skin organ model showed characteristics of human skin as demonstrated by cytokeratin and Ki-67 immunoreactivity and by electron microscopy. A single dose of 5 Gy X-irradiation induced an upregulation of beta(1)-integrin expression both in the skin organ model and in HaCaT cells. Following irradiation, beta(1)-integrin immunoreactivity was intensified in the upper layers of the epidermis equivalent whereas it was almost absent in the deeper layers. Additionally, irradiation of the skin organ model also caused a marked increase of DNA fragmentation. These results demonstrate that the novel skin organ model is suitable to investigate cellular radiation effects under three-dimensional conditions. This allows to investigate radiation effects which cannot be demonstrated in monolayer cell cultures.