The importance of extracellular matrix in the induction of preterm delivery

Evidence suggests that in the lower uterine segment at term an increased production of tumor necrosis factor (TNF) alpha and interleukin (IL)-1 beta induces an increase in the expression of adhesion molecules by the endothelium. The expression of endothelial-leukocyte adhesion molecule-1 and vascular cell adhesion molecule-1 were found to increase from a cervical dilatation of 2-3 cm and reaches a maximum at cervical dilatation of more than 6 cm. Increased adhesiveness of the endothelium leads to extravasation of neutrophils into the cervical stroma. The chemotaxis and degranulation of these cells is triggered by a rise in the concentration of IL-8 found in the lower uterine segment when cervical dilatation progresses. A significant increase in stroma invasion by neutrophils with progressive cervical dilatation was observed. This finding coincides with a rise in the granulocytic matrix metalloproteinases (MMP)-8 and MMP-9 concentrations up to complete cervical dilatation. We found similar patterns of cytokine concentrations in the lower uterine segment of patients with preterm delivery: at 2-3 cm dilatation the concentrations of IL-1 beta, IL-6- und IL-8 were significantly higher than at less than 2 cm. Concomitantly, we also found an increase in MMP-8, MMP-9 and tissue inhibitor of metalloproteinases-1 concentrations from less than 2 cm to 2-3 cm cervical dilatation. These findings suggest that the changes in the lower uterine segment during preterm parturition seem to be similar to those at term and both resemble an inflammatory process.