Senescence is associated with increased endothelial permeability. (A) Representative light microscopy images of non-senescent, co-cultured and senescent HUVECs on transwell filters (bar 100 μm). The cells were fixed after the permeability assay was performed and stained with toluidine blue. (B) Normalized values of transport through cultured non-senescent, co-culture or senescent HUVECs one hour after addition of LY or 24 hours after addition of PO. The values are normalized against the mean value of the non-senescent cultures. p < 0.01 in all cases.