Increased Level of Matrix Metalloproteinases 2 and 9 in the Ripening Process of the Human Cervix1

The human uterine cervix is a fibrous organ with a high connective tissue content. An extensive remodeling of the connective tissue prior to parturition, i.e., cervical ripening, requires the presence of proteolytic enzymes. The exact mechanism of cervical ripening has not been clarified. We evaluated in vivo distribution and expression of matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9) in the human cervix at term pregnancy and immediately after parturition compared with the nonpregnant state. Cervical biopsies were obtained from term pregnant, postpartum, and nonpregnant women. MMP-2 and MMP-9 proteins were localized by immunohistochemistry. Messenger RNA levels of MMP-2 and MMP-9 were evaluated by relative quantitative reverse transcription-polymerase chain reaction (RT-PCR) using an invariable internal standard. The mRNA levels of MMP-2 and MMP-9 were increased in the cervix at term pregnancy and postpartum compared with the nonpregnant state. Cervical stromal fibroblasts and smooth muscle cells were identified as main sources of MMP-2, whereas the MMP-9 protein was observed exclusively in invading leukocytes. These data indicate the involvement of MMP-2 and MMP-9 in the cervical ripening process.