Cell proliferation and vascular morphology in the marmoset corpus luteum

Luteal formation is associated with angiogenesis and low progesterone produ ction. Maximal mid-luteal phase progesterone production is concurrent with extensive vascularization, and luteolysis occurs when steroidogenesis decre ases. Angiogenic cell proliferation and vascular changes have not been exam ined in the marmoset, The aim of this study was to examine vascular morphol ogy throughout the luteal phase by identifying: (i) von Willebrand factor V III antigen (vW)-immunopositive endothelial cells; (ii) Ki67-positive proli ferating cells; and (iii) bromodeoxyuridine-positive proliferating cells.:M armoset corpora lutea were examined thoughout the cycle, and natural regres sion was compared with induced luteolysis after administration of a prostag landin F-2 alpha analogue or gonadotrophin-releasing hormone (GnRH) antagon ist, Steroidogenic and endothelial cells were positive for proliferation ma rkers. Endothelial cell proliferation was highest during luteal formation, then decreased and remained low during the luteal phase and functional regr ession, however endothelial cell proliferation increased during structural regression, Endothelial cell proliferation was unchanged by induced regress ion. The area of vW immunostaining was highest during luteal formation, dec reased thereafter and remained constant during the luteal phase and regress ion. Distribution of immunostaining indicated the presence of an extensive capillary network, but during structural regression the numbers of capillar ies decreased and numbers of microvessels increased. These results suggest that vascular changes are concurrent with changes in the functional status of the marmoset corpus luteum.