Confocal Microscopic Analysis of Integrin Expression on the Microvasculature and its Sprouts in the Neonatal Foreskin

Members of the integrin family of adhesion receptors are essential participants in blood vessel growth and remodeling. It is not known which integrins are involved in the initial stages of angiogenesis in vivo. In this study we determined the location of integrins on the blood vessels of a growing tissue, the neonatal fore- skin, in which neovascularization is likely to occur. We used the confocal microscope to visually reconstruct vessels from the papillary dermis of the foreskin and to identify potential sprouts as narrow, tapering extensions from these vessels. Blood vessels were initially identified by their positive reaction with antibodies to von Willebrand factor or human platelet endothelial cell adhesion molecule and their negative response to anti-neurofilament antibodies. Later, vessels were identified by theft shape and location. We screened vessels with anti bodies to integrin subunits α1, α2, α3, α5, α6, αv, β1, β3 and β4. We found that integrin sub- units a6 and fl4 were consistently found along the whole length of capillary loops and extended to the distal ends of presumed sprouts. The α2 and αv integrin concentrations, which are normally low in the micro- vasculature, were increased on the sprouts. α5 was either absent from vessels entirely or more concentrated on the body than on the sprout. α1 was more commonly present on nerves than blood vessels. These studies suggest an important role for the α6β4 integrin in the initial stages of endothelial outmigration during new vessel growth.