Cell-cell contacts between young and senescent HUVECs are disrupted in co-cultures. (a) Immunofluorescent labeling of VE-cadherin and claudin-5 in co-cultures of senescent and non-senescent HUVECs (bar 25 μm). Bottom row shows the corresponding DAPI labeling. The white arrows in the upper row indicate lipofuscin autofluorescence; the white stars in the lower row indicate the nucleus of senescent cells. (b) Fluorescence intensity of claudin-5 at cell-cell contacts, normalized against the mean intensity at position 4. Numbers at the x-axis correspond to the positions indicated in the schematic representation (inset) showing the senescent cell in white and the non-senescent cells in gray.