Immunohistochemical characterization of developing and mature primate retinal blood vessels.

PURPOSE To characterize developing retinal blood vessels with vascular markers and to relate the histochemical profile of maturing vessels to morphologic stages in retinal vascular development. METHODS Vessels were examined in frozen and paraffin-embedded retinas and in wholemounts of Macaca monkeys ranging in age from fetal day 75 (F75) to adulthood. Endothelial cells were visualized immunohistochemically using antisera to von Willebrand's factor and CD31 with lectins Ulex europaeus, Bandeiraea simplicifolia, peanut agglutinin, Ricinis communis, and wheat germ agglutinin, and by ATPase and ADPase enzymatic histochemistry. Antibodies to vascular basement membrane and matrix markers laminin, fibronectin, and collagen types I and VIII, and antisera recognizing cell cycle-specific nuclear proteins (cyclin, Ki-67, Mib-1) also were used. RESULTS Newly formed and mature vessels were reactive with reagents specific for CD31, von Willebrand's factor, types I and VIII collagens, laminin, fibronectin, U. europaeus, R. communis, and peanut agglutinin. Wheat germ agglutinin labeled vessels only after pretreatment with neuraminidase. All vascular markers appeared simultaneously, but some were distributed differentially between capillaries and larger vessels, along the central-peripheral extent of a vascular plexus, and among different vascular laminae. Markers of vessels failed to label spindle-shaped presumed vascular precursor cells lying peripheral to the advancing vessels during development. Spindle cells exhibited cyclin, Ki-67, and Mib-1 immunoreactivity. CONCLUSIONS Immature and mature vitread and sclerad vessels displayed histochemical profiles that were qualitatively similar but that had subtle quantitative differences. Results do not support identification of spindle-shaped cells as vascular precursors in the developing monkey retina and are discussed in relation to mechanisms of retinal vascularization.