Density of Stromal Cells and Macrophages Associated with Collagen Remodeling in the Human Cervix in Preterm and Term Birth

Remodeling of the cervix occurs in advance of labor both at term and at preterm birth. Morphological characteristics associated with remodeling in rodents were assessed in cervix biopsies from women at term (39 weeks' gestation) and preterm (<33 weeks' gestation). Collagen I and III messenger RNA and hydroxyproline concentrations declined in cervix biopsies from women in labor at term and preterm compared to that in the cervix from nonlaboring women. Extracellular collagen was more degraded in sections of cervix from women at term, based on optical density of picrosirius red stain, versus that in biopsies from nonpregnant women. However, collagen structure was unchanged in the cervix from women at preterm labor versus the nonpregnant group. As an indication of inflammation, cell nuclei density was decreased in cervix biopsies from pregnant women irrespective of labor compared to the nonpregnant group. Moreover, CD68-stained macrophages increased to an equivalent extent in cervix subepithelium and stroma from groups in labor, both at term and preterm, as well as in women not in labor at term. Evidence for a similar inflammatory process in the remodeled cervix of women at term and preterm birth parallels results in rodent models. Thus, a conserved final common mechanism involving macrophages and inflammation may characterize the transition to a ripe cervix before birth at term and in advance of premature birth.