Concentrations of matrix metalloproteinase 8 and 9 and tissue inhibitor of metalloproteinases-1 in the uterus during preterm delivery

Objective: We studied concentrations of the matrix metalloproteinases 8 and 9 (MMP-8 and MMP-9) and tissue inhibitor of metalloproteinases-1 (TIMP-1) in the lower uterine segment in women with preterm labor. Methods: Tissue samples from the lower uterine segment were obtained from 32 patients undergoing secondary cesarean delivery of a singleton infant before term. Patients were stratified according to cervical dilatation ( 6-12 hours, n = 6; > 12 hours, n = 10). Concentrations of MMP-8, MMP-9 and TIMP-1 were measured in protein extracts with enzyme-linked immunosorbent assays. Multiple linear regression analysis was used to assess associations with cervical dilatation and duration of labor. Results: The median concentration of MMP-8 increased from 59.1 ng/mg protein at a cervical dilatation of 4 cm than at < 2 cm (55.9 vs. 20.9 ng/mg protein, p < 0.05). The TIMP-1 concentration was not associated with cervical dilatation. None of the parameters showed an association with the duration of labor. The concentrations of MMP-9 and TIMP-1 had the closest association with cervical dilatation. Conclusion: Increased release of matrix metalloproteinases in the lower uterine segment may be an important mechanism in preterm parturition.