title: Absence of OX-43 antigen expression in invasive capillary sprouts: identification of a capillary sprout-specific endothelial phenotype.
abstract: Endothelial cells exhibit a number of unique phenotypes, some of which are angiogenesis dependent. To identify a capillary sprout-specific endothelial phenotype, we labeled angiogenic rat mesentery tissue using a microvessel and capillary sprout marker (laminin), selected endothelial cell markers (CD31, tie-2, and BS-I lectin), and the OX-43 monoclonal antibody, which recognizes a 90-kDa membrane glycoprotein of unknown function. In tissues that were stimulated through wound healing and compound 48/80 application, double-immunolabeling experiments with an anti-laminin antibody revealed that the OX-43 antigen was expressed strongly in all microvessels. However, the OX-43 antigen was completely absent from a large percentage (>85%) of the capillary sprouts that were invading the avascular tissue space. In contrast, sprouts that were introverting back into the previously vascularized tissue retained high levels of OX-43 antigen expression. Double-labeling experiments with endothelial markers indicated that the OX-43 antigen was expressed by microvessel endothelium but was absent from virtually all invasive capillary sprout endothelial cells. We conclude that the absence of OX-43 antigen expression marks a novel, capillary sprout-specific, endothelial cell phenotype. Endothelial cells of this phenotype are particularly abundant in capillary sprouts that invade avascular tissue during angiogenesis.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism*; D002196:Capillaries / Q000378:metabolism / Q000502:physiology*; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D008833:Microcirculation / Q000502:physiology; D018919:Neovascularization, Physiologic / Q000502:physiology*; D010641:Phenotype; D051381:Rats; D013152:Splanchnic Circulation / Q000502:physiology; D014945:Wound Healing / Q000502:physiology; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D003189:p-Methoxy-N-methylphenethylamine