Hormonal regulation of matrix metalloproteinase 9 gelatinase B gene expression in rabbit uterine cervical fibroblasts

Since the degradation of uterine cervical extracellular matrix is an essential process in cervical ripening and dilatation at term, we examined the effect of pregnancy on the level of pro-matrix metalloproteinase 9 (proMMP-9)/progelatinase B in the rabbit uterine cervix and its regulation in uterine cervical fibroblasts. Uterine cervices shortly before term parturition contained high levels of proMMP-9 compared with those of nonpregnant rabbits. Uterine cervical fibroblasts prepared from rabbits at 23 days of gestation did not produce proMMP-9; in contrast, interleukin (IL)-1 alpha, IL-1 beta, or phorbol 12-myristate 13-acetate (PMA) induced proMMP-9 production along with an increase of proMMP-9 mRNA, and the IL-1-mediated induction of proMMP-9 was synergistically enhanced by PMA. On the other hand, physiological concentrations of progesterone suppressed IL-1-and/or PMA-mediated production of proMMP-9 in a dose-dependent manner. This suppressive effect of progesterone on proMMP-9 production was accompanied by a decrease in matrix metalloproteinase 9 (MMP-9) mRNA, indicating that progesterone down-regulates the production of proMMP-9 at the transcriptional level. These results indicate that in the rabbit uterine cervix, IL-1 alpha and IL-1 beta are effective inducers of the proMMP-9 production, and progesterone is a physiological suppressor. Thus, MMP-9 and progesterone are very likely to play essential roles in cervical ripening and dilatation in the rabbit, and the production of MMP-9 in the cervix is finely regulated during pregnancy.