Leukocytes infiltrate the myometrium during human parturition: further evidence that labour is an inflammatory process

Abstract

Inflammatory mediators in the cervix, placenta and fetal membranes play a crucial role in human parturition. The aim of this study was to determine whether the upper and lower segments of the myometrium are infiltrated by inflammatory cells during pregnancy and parturition. Myometrial biopsies were obtained from non-pregnant women, and pregnant women at term before and after the onset of spontaneous labour. Subpopulations of inflammatory cells were identified using immunocytochemistry. The intercellular adhesion molecules, 1 and 2, platelet endothelial cell adhesion molecule, vascular cell adhesion molecule and E-selectin were immunolocalized to investigate their involvement in leukocyte accumulation. Histological analysis demonstrated that inflammatory cells, predominantly neutrophils and macrophages, infiltrate human myometrium during spontaneous labour at term. The infiltrate is predominant in the lower uterine segment but is also present in the upper segment. Increased expression of E-selectin was found on the vascular endothelium of biopsies obtained during labour, suggesting a role for this molecule in the accumulation of leukocytes. These results suggest that inflammatory cell infiltration is part of the physiological mechanisms that occur in the myometrium during parturition. Further understanding of this process may suggest new strategies aimed at preventing preterm delivery.

Critical Paracrine Interactions Between TNF-α and IL-10 Regulate Lipopolysaccharide-Stimulated Human Choriodecidual Cytokine and Prostaglandin E2 Production

“…Previous studies have characterized cytokine production by chorion and decidual cells and also identified the localization of cytokine receptors present (7,47,50,59). Apart from resident cells of these tissues, other potential sources of cytokine production are the lymphocytes that infiltrate as the onset of labor approaches (65)(66)(67). All the placentas used in this study were from patients undergoing elective Cesarean sections at term.…”

Embryo implantation evolved from an ancestral inflammatory attachment reaction

“…Inflammation is an important component of the parturition process in eutherian mammals, and infection can cause preterm labor (68,69). In wallabies, inflammatory prostaglandins are sufficient to induce parturition behavior, and blocking prostaglandin activity late in gestation results in the extension of pregnancy (70,71).…”

“…Given that eutherian parturition, like implantation, is an inflammatory process (11,68), and the attachment reaction in the opossum is inflammatory, an interesting hypothesis is that both implantation and parturition are proinflammatory reactions because they are both derived forms of the therian attachment reaction (Fig. 8).…”

Endocrine immune interactions in human parturition

“…At its most basic level, this concept is supported by the demonstration that leukocytes, (largely neutrophils and macrophages, and also T cells) invade the myometrium, cervix and fetal membranes at or immediately after the onset of labour (Osman et al, 2003, Thomson et al, 1999, attracted by increased tissue expression of chemokines and cell adhesion molecules (Ledingham et al, 2001, Winkler et al, 1998. In parallel, leukocytes circulating in the peripheral blood increase their expression of cell adhesion molecule ligands such as CD11a and CD11b (Yuan et al, 2009), facilitating leukocyte emigration into the myometrium and cervix.…”