Appraisal of an alternative skin model for the study of epidermal restoration following exposure to various environmental stress agents
Muriel Isoir, Doctorate thesis of the Versailles Saint-Quentin en Yvelines (France), speciality Cutaneous Biology and Pharmacology, 227p, defended on the 7th June 2006
Human skin is a major target tissue for ionising radiation (IR) and UVB. We developed a skin explant model and used 2 types of keratinocytes to study survival and oxydative stress induced by these radiations. We examined oxidative damages by measuring ROS produced and cellular anti-oxidant defences induced. We observed into skin exposed to IR a modulation of genes expression implied in the control of oxidative stress, confirmed by the decrease of catalase, glutathione peroxidase and superoxide dismutase enzymatic activities. The imbalance observed between anti- and pro-apoptotic genes expression shows that keratinocytes apoptosis may be partly dependent on radiation-induced ROS production. We showed the difference of radiosensitivity between NHEK and HaCaT, which may be linked to their differential oxidative responses. In addition, during reepithelization, we demonstrated that activated NHEK after IR express keratin 6, release pro-inflammatory cytokines and proliferate, without modification of their differentiation. Treatment of NHEK with geranylgeranylacetone (GGA) has a beneficial effect on their radio-induced activation by increasing IL-1 release, their migration in scrapped area and their survival. GGA has an anti-apoptotic ability (induction of Hsp70-caspase3 pathway) and migratory properties (P38/RhoA activation) on NHEK, but after IR, only caspase-3 pathway is induced. This work thus contributes to the understanding of cutaneous damages after IR and GGA mechanism of action which accelerates reepithelization.