Akihiro Aioi
Development Laboratory, SEPTEM-SOKEN Co., Ltd.,
Jun-ichi Kashiwakura
Department of Life Science, Faculty of Pharmaceutical Sciences, Hokkaido University of Sciences
Tomozumi Imamichi
Frederick National Laboratory for Cancer Research, Applied and Developmental Research Directorate
Emiko Okuda-Ashitaka
Department of Biomedical Engineering, Osaka Institute of Technology

[Abstract]
NUMB, which is an antagonist for Notch signaling pathway, is supposed to control the fate of keratinocytes where the activity of senescence associated-β-galactosidase (SA-β-Gal) was expressed. Here we evaluated the involvement of NUMB in passage-dependent keratinocyte senescence in normal human epidermal keratinocytes derived from new born foreskin. While the ratio of SA-β-Gal activity psitive cells increased from 9.9±0.7％ in third passage to 53.3±6.7% in sixth passage, the expression of NUMB significanty upregulated in both mRNA level and protein level. Where the expression of integrin β1 , a basal keratinocyte marker was unchanged, the expression of involucrin, a differentiated keratinocyte marker was upregulated. To evaluate whether the upregulation of NUMB expression is depended on keratinocyte differentiation, the NUMB expression was examined in Ca2+-induced differentiated keratinocytes. While involucrin expression was enhanced in Ca2+-induced differentiated keratinocytes as well-known, NUMB expression levels were unchanged. Three-D analysis of Immunofluorescence cytochemistry in sixth pasasge keratinocytes indicated that involucrin negative/ NUMB positive keratinocytes existed. These results suggest that NUMB can be a candidate for a nove cellular senescence marker in passage-dependent keratinocyte senescencs.