Increase of integrin α6+p63+ cells after ultraviolet B irradiation in normal human keratinocytes

Abstract

Epidermal stem cells (SC) are believed to be resistant to environmental damage for the purpose of self renewal. Most promising SC markers include integrin α6 and p63. The aim of our study was to determine whether the integrin α6+p63+ cell fraction representative of the epidermal progenitor or SC is increased after ultraviolet B (UVB) irradiation and to clarify the hypothesis that epidermal SC are resistant to high-dose UVB damage. We irradiated early passage normal human keratinocytes (NHK) with 0, 25, 50, and 100 mJ/cm2 UVB. The percentage of cell death was calculated. Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and western blotting analyses were performed to identify integrin α6 and p63, and flow cytometry analysis with integrin α6 and p63 antibodies was done. After 50 and 100 mJ/cm2 UVB, integrin α6+p63+ cells were found to be much increased by fluorescence-activated cell sorting. Expression of integrin α6 and p63 was increased in NHK after UVB irradiation, which was shown with real-time RT-PCR and western blotting analyses. We concluded that an increase of integrin α6+p63+ cells after high-dose UVB may suggest that the putative progenitor or SC are resistant to UVB irradiation.

Keratinocyte stem cells are more resistant to UVA radiation than their direct progeny

“…Note that for each studied parameter, both suspensions enriched for KSCs and TAs were irradiated before entering into their cell cycle to approximate physiological conditions. These results are consistent with other studies where KSCs were more resistant to various genotoxic stressors such as UVB [ 41 , 42 ] and ionizing radiation [ 44 , 45 ].…”

“…Actually, an alpha6 + /CD44 + cell population sharing similar characteristics to KSCs displayed resistance to apoptosis following UVB radiation or other genotoxic stressors [ 41 ]. Moreover, 24 h post-UVB radiation, the proportion of the alpha6 + /p63 + cell population, considered to be stem cells, increased at the expense of the other populations, which decreased in proportion [ 42 ]. Interestingly, rapid adherent cells (10 min on collagen I) extracted from irradiated skin are photosensitive [ 43 ] but not in comparison to non-adherent cells.…”

α6 Integrin (α6high)/Transferrin Receptor (CD71)low Keratinocyte Stem Cells Are More Potent for Generating Reconstructed Skin Epidermis Than Rapid Adherent Cells

“…As KSC are protected in their niche, they are more resistant to Ultraviolet B radiation (UVB) [ 18 ] and ionizing radiation [ 19 , 20 ] than TA being in proliferation state. Thus, since mutations can lead to their deregulation and skin cancer, it is important to be able to isolate this cell population from others (TA and DC) in order to perform biochemical, pharmaceutical and toxicological studies.…”