Structural alterations provoked by narrow-band ultraviolet B in immortalized keratinocytes: assessment by atomic force microscopy.

We applied atomic force microscopy (AFM) to visualize ultrastructural changes of the keratinocyte morphology after narrow-band ultraviolet B (NB-UVB) irradiation. Immortalized human keratinocytes were cultured under standard conditions, irradiated with NB-UVB light at doses ranging from 50 to 800 mJ/cm2 and imaged by AFM mounted on an inverted optical microscope. It was observed, that NB-UVB irradiation provoked dose-dependent alterations of the keratinocyte morphology. While the surface of non-irradiated cells exhibited homogenously distributed crest-like shaped protrusions (height 0.16 +/- 0.05 microm), cells irradiated with a dose of 800 mJ/cm2 in addition showed round shaped protrusions (height 0.14 +/- 0.06 microm) distributed predominantly around the nucleus and bleb-like protrusions irregularly distributed on the cell surface (height 0.95 +/- 0.29 microm). These irradiated cells easily detached from the supporting glass surface, showed impaired contact with adjacent keratinocytes and significantly rearranged their cytoskeleton network. We hypothesize that these structural and functional alterations reflect ongoing apoptosis in UVB treated cells.