Distribution and fine structure of macrophages in the human ovary during the menstrual cycle, pregnancy and menopause

We evaluated the distribution and ultrastructural characteristics of macrophages in the ovaries of women of reproductive ages, during pregnancy, and after menopause, by immunohistochemistry and transmission electron microscopy. Macrophages appeared around the ovarian follicle with its development. Their organelles were poorly developed, and no vacuoles or granules were observed in the cytoplasm. Macrophages were also present in the cavity of the atretic follicle, being larger in size than those in the developing follicle and characterized by cytoplasmic vacuoles and granules of a lysosomal nature. With the luteinization of the follicle, macrophages were seen to be distributed inside and outside the corpus luteum, but constituted only a minor population as compared with other kinds of leukocytes. The intracellular organelles were well-developed, including the lysosomal granules. In early pregnancy, the number of macrophages was noticeably increased in the corpus luteum. They were observed mainly outside the corpus luteum, and stained strongly with hCG immunohistochemically. Macrophages were present in the regressing corpus luteum and in the corpus albicans. Numerous lipid droplets and elongated cholesterol crystals were seen in the cytoplasm. Macrophages therefore appeared to be present throughout the ovarian cycle and may be involved in the development and atresia of the follicles and the progression and the regression of luteal tissues.