CHANGES IN THE MORPHOLOGY AND DIFFERENTIATION OF HUMAN SKIN AFTER IRRADIATION

The use of charged particles in radiotherapy has several advan-tages e.g. sparing of healthy tissue. The application is increasingconstantly during the last years and more and more differenttypes of cancer can be treated succesfully. But in most radiationtreatments the skin can not be spared completely and is exposedto low or moderate doses. Therefore, a deeper understanding ofearly and late side effects occuring in skin is requiered. Wemeasured cellular and molecular changes related to the earlyinflammatory response of human skin irradiated with carbo-nions, in particular induction of cell death, as well as changes indifferentiation and proliferation of epidermal cells during thefirst days after exposure. Model systems for human skin of dif-ferent complexity, i.e., keratinocytes, coculture of skin cells, 3Dskin equivalents, and skin explants, were used to investigate thealterations induced by carbonions (spread-out Bragg peak, dose-averaged LET 100 keV/μm) in comparison to X-ray and UV-Bexposure. Whereas in none of the model systems apoptosis or necrosis wasobserved after ionizing irradiation, changes in proliferation anddifferentiation were detected. High doses of carbonions weremore effective than X-rays in reducing proliferation and induc-ing abnormal differentiation. In contrast, changes identified fol-lowing low-dose exposure (≤0.5 Gy), i.e., enhanced proliferationand change in the polarity of basal cells, were induced moreeffectively after X-ray exposure.