The Changes Of Serum MMP-9 Relate To Cervical Ripening And Dilation At Term

BackgroundThe Mechanisms of the spontaneous onset of human labor are complex and not clear till now. In normal labor, there appears to be a time-dependent relationship among these factors: the biochemical connective tissue changes in the cervix usually precede uterine contractions that, in turn, precede cervical dilatation. The cervix is a metabolically active organ in pregnancy composed of extracellular matrix (ECM) components such as collagen, elastin, proteoglycans, hyaluronan in addition to stromal, epithelial, and smooth muscle cells. Matrix metalloproteinases (MMPs) play a major role in ECM turnover under both physiological and pathological conditions. The effects of MMPs on ECM degradation could result in significant collagen tissue remodeling and structural changes in the cervix, lead to cervical ripening and cervical dilation. Many studies proved that MMP-9 activity and protein, the 92-kd typeⅣcollagenase/gelatinase B , are increase with labor. In addition, some studies found that MMP-9 play an important role in the degradation of cervical collagen leading to softening of the cervix.ObjectiveThis study was conducted to investigate the relationship of MMP-9 in serum and cervical Bishop score in term pregnancy and assessed the labor-associate changes in the concentration of MMP-9 during cervical dilatation, and the relationship between MMP-9 with WBC.MethodsTerm pregnant women with a mean age of 28.57 yr (range: 25–34yr), a mean gestational age of 39 wk (range: 37–41+6wk), and nulliparty with singleton pregnancy were enrolled in the study (n = 51). These women were not in labor. 33 of them delivered vaginal successfully, the others were undergoing elective cesarean section. All women underwent cervical exame (Bishop score) and blood routine examination. Blood samples(2ml) were obtained soon after admission before any treatment was taken. Other 2ml blood samples were obtained at the end of the first stage of labor from women who had vaginal delivery. Serum was separated from blood sample and stored in refrigeration at -70℃until analysis.Results1. There was positive correlation between serum MMP-9 levels and the Bishop score before labor in term pregnancy. (r =0.285, P =0.045)2.The serum concentrations of MMP-9 significantly(P=0.000)increased at the end of the first stage of labor.3. There was positive correlation between serum MMP-9 concentration difference and the time interval during cervical dilatation. (r=0.486,P=0.004).4.There was positive correlation between serum MMP-9 levels and the leukocyte count of whole blood.(r=0.380,P =0.006)Conclusions1. The higher MMP-9 level of serum , the higher cervical Bishop score . MMP-9 level may influent the degradation of cervical collagen leading to ripening of the cervix.2. During cervical dilatation, the longer time interval, the greater the concentration difference of MMP-9. MMP-9 may play an important role in cervical dilatation.3. The positive correlation between concentration of MMP-9 in serum and blood WBC indicate that leukocytes may be main sources of MMP-9.