The three objectives of this proposal will examine the regulation of both growth and softening of the cervix during pregnancy. In the rat, cervical growth is accompanied by an accumulation of epithelial and stromal cells. The first objective is to determine the influence of relaxin, estrogen and progesterone on the rates of apoptosis and proliferation of cervical cells. At three-day intervals throughout the second half of pregnancy, relaxin's action will be neutralized with a monoclonal antibody for rat relaxin, estrogen's action will be blocked with the estrogen antagonist ICI 182,780, and progesterone's action will be blocked with the progesterone antagonist RU 486. The rates of apoptosis will be determined immunohistochemically by employing the terminal deoxynucleotidyl transferase-mediated UTP end-labeling (TUNEL) method. Electron microscopy will be used to evaluate treatment effects on percent of cell types undergoing apoptosis, stromal collagen, and epithelium functional complexes. Light microscopy immunohistochemistry will be used also to evaluate treatment effects on epithelium functional complexes. Rates of cell proliferation will be determined immunohistochemically by measuring the rate of incorporation of 5-bromo-2-deoxyuridine (BrdU) into proliferating cells and also by measuring the expression of proliferating cell nuclear antigen (PCNA). RU 486 induces delivery and promotes cervical softening at term in women and other species. The second objective will test the hypothesis that relaxin is more effective than RU 486 in promoting cervical softening near term. To accomplish this, the effects of RU 486 and relaxin on cervical extensibility will be determined at term in relaxin-deficient rats in which endogenous relaxin is immunoneutralized throughout the second half of pregnancy. Morphometric analysis will also be done to compare the effects of RU 486 and relaxin on the histological characteristics of the cervix. This proposal will also examine a novel procedure for both inducing delivery and softening the cervix. Induction of labor more than doubled to 19% between 1989 and 1998. The success of labor induction is influenced by the state of the cervix. The active component of the two approved agents for cervical softening (Prepidil and Cervidil) is PGE2, and this prostaglandin causes uterine hyperstimulation in a significant percentage of patients. Relaxin has potential advantages over PGE2 because relaxin not only promotes rapid and marked growth and softening of the cervix, but also reduces uterine contractility. The third objective will test the hypothesis that the administration of RU 486 for induction of delivery in combination with relaxin for induction of cervical softening is more effective in promoting rapid and safe delivery in pregnant rats than is the administration of RU 486 alone. Treatment with RU 486 alone and in combination with exogenous relaxin will be done at term with relaxin-deficient rats.
