Distribution and Activation of Uterine Mononuclear Phagocytes in Peripartum Endometrium and Myometrium of the Mouse

Abstract

The present study tested the hypothesis that macrophage distribution and activation are enhanced in the uterus before term. Mid-uterine horn tissue strips from mice on Days 15 and 18 of pregnancy, the day of birth (= Day 19), and one day postpartum were paraffin-embedded and then sectioned, stained with a monoclonal pan-macrophage marker (BM8), and processed for visualization and quantification of resident macrophages per nuclear area. Macrophages were dispersed throughout the endometrium and subluminal epithelium; cell numbers declined on the day before term, then increased postpartum. Within myometrium, macrophages congregated in stroma surrounding muscle bundles, and staining was enhanced near term. Macrophage numbers were similar in pregnant and postpartum uteri, enhanced more than 2-fold over those in nonpregnant controls. Uterine sections were also analyzed by laser-scanning cytometry to enumerate activated macrophages (i.e., those that express the intercellular adhesion molecule marker CD54+) and to determine cell cycle (propidium iodide fluorescence). Activated macrophages were directly proportional to cell numbers and, by cell cycle analysis, were not terminally differentiated. Highest cell numbers occurred on Day 15: 4-fold greater than those in nonpregnant controls and 2-fold higher than those at Day 18 or in postpartum groups. These findings indicate a decline in endometrial macrophage numbers at least one day before the onset of parturition and raise the possibility that trafficking of this immune cell may contribute to onset of labor.

Ultrastructural Changes in the Uterine Luminal and Glandular Epithelium during the Oestrous Cycle of the Marsupial <i>Monodelphis domestica</i> (Grey Short-Tailed Opossum)

“…These findings correspond with the observations made in the cycling eutherian uteri by Hunt and Pollard [1992], Miller and Hunt [1996] and Mackler et al [1999Mackler et al [ , 2000. During pro-oestrus, the number and size of macrophages in the Monodelphis endometrium are lowest.…”

Differentiation of the Endometrial Macrophage during Pregnancy in the Cow

“…Indeed, endometrial macrophages increase in number in the pregnant cow after experimental infection with Neospora caninum [9]. A role for macrophages in clearing bacteria after parturition or in the expulsion of the conceptus is also a possibility because macrophages accumulate with impending parturition [10], [11]. Activation of a local immune response in response to intrauterine infection can also turn macrophages into pregnancy foes that induce fetal resorption [12].…”

Structural Transformations of Myocytes during Gestation and Early Postpartum Involution of the Uterus

“…Therefore, recovery of the uterine weight on day 5 postpartum [12] does not mean that the involution processes are over in rats by this period. The study of the time course of numerical density (ND) of hematogenic ("inflammation") cells did not confirm the development of inflammatory processes in the uterus [9]. The lymphocyte ND decreased (p<0.01) during pregnancy and returned to the control level on day 3 postpartum (Fig.…”