Representative immunofluorescent staining of VEGFRs and NRPs in human healthy skin epidermis. The presence of VEGFRs and NRPs is indicated by green fluorescence staining. Red indicates PI nuclear staining. Column 1, normal human skin from a 19-year-old male donor; column 2, human umbilical cord vein; column 3, negative staining by mouse IgG. The letters in the figures refer to epidermis (e), dermis (d), and basal layer of epidermis (b) in skin sections. The luminal side of the human umbilical cord vein is indicated by capital letter L. Scale bar, 50 µm. VEGFR-1 (A1) and VEGFR-2 (B1) are strongly detected at the stratum basal and spinosum adjacent to the basal of epidermis (arrows). VEGFR-3 (C1) is detected uniformly at all layers of the epidermis except for the horny cell layer (arrow). NRP-1 (D1) and NRP-2 (E1) are distributed uniformly among all layers of the epidermis except for the horny cell layer (arrows). Positive controls of human umbilical cord vein showed strong staining for HUVECs and smooth muscle cells for all 5 antibodies for VEGFRs and NRPs (arrows). Negative staining controls of human skin by using mouse IgG are unstained in all experiments (arrowheads refer to the outer edge of skin).