Background: The purpose of this study was to examine whether EP4 as prostaglandin (PG) E2 receptor is involved in lipopolysaccharide (LPS)-induced cervical ripening.
Methods: New Zealand White non-pregnant rabbits were randomly allocated to 4 equal groups and treated with vaginal suppositories containing LPS with various concentrations of EP4-selective antagonist once daily for 3 days, and then sacrificed for analysis. Analysis was performed in order to examine the inhibitory effect of EP4 antagonist on LPS-induced cervical ripening. The expression of EP4 in a cervix treated with LPS was examined immunohistochemically. The percent of cervical extensibility in the segment of cervix as the tensile strength was determined with 5.8 g of constant perpendicular stretching. The ripening area of the cervix with edematous changes in H&E sections was calculated by a microscopic system with a computer-assisted digital analyser. Type-1 collagenase activity was determined in cervical tissue using FITC-labelled type-1 collagen.
Results: Immunohistochemical study shows the positive staining of EP4 at the interstitial cells in the cervix treated with LPS. The extensibility, cervical edematous area and type-1 collagenase activity are significantly reduced in the cervix treated with LPS in the presence of EP4 antagonist compared with that treated with LPS alone.
Conclusions: These data implicates the EP4 as the PGE2 receptor involved in LPS-induced cervical ripening.