MACROPHAGES, CELL-PROLIFERATION, AND CELL-DEATH IN THE HUMAN MENSTRUAL CORPUS-LUTEUM

We studied the presence and numbers of macrophages in the different co mpartments of the human menstrual corpus luteum (CL) in relation to th e proliferative activity and apoptosis in luteal cells. Macrophages we re recognized by immunohistochemical demonstration of the lysosome-ass ociated glycoprotein CD68, and proliferating cells by immunohistochemi cal detection of the cell cycle-related protein Ki67 and by counting m itotic cells. In general, changes in the number of macrophages were pa rallel to the functional activity of the CL. Macrophage numbers increa sed up to the end of the early luteal phase, remained relatively uncha nged during the midluteal phase, and decreased at the late luteal phas e. Furthermore, macrophages showed prominent morphological changes dur ing the cycle. They showed round or elongated cytoplasm during the ear ly and late luteal phases, and dendritic features in the midluteal pha se. Proliferating cells were very abundant on Days 15-16 and showed a significant decrease thereafter. Most proliferating cells corresponded to stromal (mainly vascular) cells. However, about 5% of granulosa-lu tein cells and about 15% of theca-lutein cells were proliferating duri ng the early and midluteal phases. Regression of the CL at the late lu teal phase was associated with both a decrease in the number of prolif erating cells and an increase in the number of apoptotic cells, which were highly increased on Days 25-27 of the cycle. The number of macrop hages was not related to cell proliferation nor to cell death during t he luteal phase. The observed changes in both macrophage number and mo rphology suggest the existence of a bidirectional communication betwee n macrophages and steroidogenic cells in the human CL, or regulation o f both cell populations by similar mechanisms.