Impact of Micropillar-Induced Mechanical Confinement of the Cell Nucleus on DNA Damage Response to UV Irradiation

DNA damage induced by ultraviolet (UV) radiation adversely affects genome stability and contributes to various diseases. Therefore, biochemical or biomechanical methods for protecting DNA from such damage are highly important. In this study, we investigated the effects of mechanical factors, specifically the deformation of the cell nucleus using polydimethylsiloxane (PDMS)-based microfabricated arrays of micropillars with circular and elliptical cross-sections, on the UV resistance of DNA in cultured mammalian vascular smooth muscle cells. The cells spread normally within the spaces between the micropillars, where their nuclei exhibited significant deformation and appeared mechanically “trapped” between the pillars. This entrapment was accompanied by a decrease in nuclear volume and enhanced Hoechst fluorescence intensity, indicating increased DNA density within the nucleus. Evaluation of UV-induced DNA damage via the fluorescent intensity of phospho-histone γ-H2AX revealed that damage was significantly inhibited in the nuclei deformed between the pillars. These inhibitory effects were particularly pronounced on substrates with circular cross-section micropillars compared to elliptical cross-sections. Our results suggest that the suppression of UV-induced DNA damage may be associated with reduced cell motility and increased intranuclear DNA density induced by mechanical confinement of the cell nucleus by the micropillars.