409 Corneoptosis, functional keratinocyte cell death, is tightly associated with spaciotemporal dynamics of epidermal tight junctions

Epidermis has two physical barrier components, stratum corneum (SC) and tight junction (TJ). Formation of SC or cornification is initiated by the cell death top layer (SG1) granulosum, termed ‘corneoptosis’ after prolonged intracellular Ca2+([Ca2+]i) elevation (∼60min), followed rapid acidification. However, exact timing onset corneoptorsis remains to be clarified. In this study, we aimed determine spatiotemporal relationship between turnover TJs corneoptosis. We performed intravital confocal microscopic imaging mouse ear co-expressing ZO-1-Venus (TJ strand marker) GCaMP3 (intracellular Ca2+ marker). Hoechst 33342 was intradermally injected monitor change nuclear pH. Consistent with our previous observation, signals showed TJ strand-pattens in upper SG. According turnover, three phases are observed; TJ-phase 1 which shows single old formed SG2 cells; 2 double strands; 3 new strand. Time lapse analysis revealed that signal observed only TJs, but not other TJ-phases. The [Ca2+]i lasted for approximately 60min. Subsequently, acidification induced these SG1 cells as detected both decrease increase signals. Simultaneously, ‘upper larger strand’ double-TJ disappeared, resulting from 3. These findings indicated corneoptosis tightly associated spaciotemporal dynamics TJs.