title: Expression of vascular endothelial growth factor receptors 1, 2, and 3 in quiescent endothelia.
abstract: The vascular endothelial growth factor (VEGF) family is involved in angiogenesis, and therefore VEGFs are considered as targets for anti-angiogenic therapeutic strategies against cancer. However, the physiological functions of VEGFs in quiescent tissues are unclear and may interfere with such systemic therapies. In pathological conditions, increased levels of expression of the VEGF receptors VEGFR-1, VEGFR-2, and VEGFR-3 accompany VEGF activity. In this study we investigated normal human and monkey tissues for expression patterns of these receptors. Immunohistochemical staining methods at the light and electron microscopic level were applied to normal human and monkey tissue samples, using monoclonal antibodies (MAbs) against the three VEGFRs and anti-endothelial MAbs PAL-E and anti-CD31 to identify blood and lymph vessels. In human and monkey, similar distribution patterns of the three VEGFRs were found. Co-expression of VEGFR-1, -2, and -3 was observed in microvessels adjacent to epithelia in the eye, gastrointestinal mucosa, liver, kidney, and hair follicles, which is in line with the reported preferential expression of VEGF-A in some of these epithelia. VEGFR-1, -2, and -3 expression was also observed in blood vessels and sinusoids of lymphoid tissues. Furthermore, VEGFR-1, but not VEGFR-2 and -3, was present in microvessels in brain and retina. Electron microscopy showed that VEGFR-1 expression was restricted to pericytes and VEGFR-2 to endothelial cells in normal vasculature of tonsils. These findings indicate that VEGFRs have specific distribution patterns in normal tissues, suggesting physiological functions of VEGFs that may be disturbed by systemic anti-VEGF therapy. One of these functions may be involvement of VEGF in paracrine relations between epithelia and adjacent capillaries.
authors.affiliation: Ocular Angiogenesis Group, Department of Ophthalmology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Antonella N
authors.initials: AN
authors.lastname: Witmer
authors.forename: Jiapei
authors.initials: J
authors.lastname: Dai
authors.forename: Herbert A
authors.initials: HA
authors.lastname: Weich
authors.forename: Gijs F J M
authors.initials: GF
authors.lastname: Vrensen
authors.forename: Reinier O
authors.initials: RO
authors.lastname: Schlingemann
mesh_terms: D000818:Animals; D004730:Endothelium, Vascular / Q000378:metabolism*; D004848:Epithelium; D006801:Humans; D007150:Immunohistochemistry; D008221:Lymphoid Tissue / Q000098:blood supply; D008252:Macaca fascicularis; D008833:Microcirculation; D009928:Organ Specificity; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D017978:Receptors, Growth Factor / Q000378:metabolism*; D040262:Receptors, Vascular Endothelial Growth Factor; D013045:Species Specificity; D040281:Vascular Endothelial Growth Factor Receptor-1; D040321:Vascular Endothelial Growth Factor Receptor-3
chemical_list: D011518:Proto-Oncogene Proteins; D017978:Receptors, Growth Factor; D020794:Receptor Protein-Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor; D040281:Vascular Endothelial Growth Factor Receptor-1; D040321:Vascular Endothelial Growth Factor Receptor-3