Endothelial growth factor receptors in human fetal heart

Background-Endothelial receptor tyrosine kinases include 3 members of the v ascular endothelial growth factor receptor (VEGFR) family and 2 members of the angiopoietin receptor (Tie) family. In addition, the VEGF(165) isoform binds to neuropilin-1 (NP-1), a receptor for collapsins/semaphorins. The im portance of these receptors for vasculogenesis and angiogenesis has been sh own in gene-targeted mice, but so far, little is known about their exact ex pression patterns in the human vasculature. Methods and Results-Frozen sections of human fetal heart were stained immun ohistochemically with receptor-specific monoclonal (VEGFR, Tie) or polyclon al (NP-1) antibodies. The following patterns were observed: The endocardium was positive for VEGFR-1, VEGFR-2, NP-I, Tie-1, and Tie-2 but negative for VECFR-3. The coronary vessels were positive for Tie-1, Tie-2, VEGFR-1, and NP-1 and negative for VEGFR-2 and VEGFR-3. Myocardial capillaries and epic ardial blood vessels stained for VEGFR-1, VEGFR-2, NP-1, and Tie-1; myocard ial capillaries and epicardial veins weakly for Tie-2; and epicardial lymph atic vessels for VEGFR-2 and VEGFR-3, weakly for Tie-1 and Tie-2, but not f or VEGFR-1 or NP-1. Conclusions-The results demonstrate differential expression of the endothel ial growth factor receptors in distinct types of vessels in the human heart . This information is useful for the understanding of their roles in physio logical and pathological processes and for their diagnostic and therapeutic application in cardiovascular medicine.