201. Effects of relaxin deficiency on matrix metalloproteinase expression in the cervix and vagina of pregnant mice

Abstract

The major functions of relaxin are associated with female reproductive physiology, especially the regulation of biochemical processes involved in the remodelling of the reproductive tract at term. Studies in relaxin deficient mice (Rlx^–/–) demonstrate that although females give birth to live young without apparent dystocia, they have abnormal cervices and vaginae. This phenotype is attributed to an increase in stromal collagen, but the mechanism(s) by which relaxin regulates extracellular matrix (ECM) production in reproductive tissues is poorly understood. In this study, we assessed the expression of matrix metalloproteinases (MMPs) in the cervix and vagina of pregnant wild-type (Rlx^+/+) and Rlx^–/– mice. Tissues were obtained from adult C57/Blk6J Rlx^+/+ mice on days 7.5, 14.5, 17.5, 18.5 pc and Rlx^–/– littermates on days 7.5, 14.5 and 18.5 pc. Real-time PCR using dual-labelled fluorogenic probes was performed in an Opticon 2 cycler (MJ Research) to quantify MMP-2, -3, -7, -9 and -13 gene expression. In the cervix and vagina of Rlx^+/+ mice, only MMP-2 mRNA levels were significantly higher at term compared with earlier stages of gestation. There were significant decreases in MMP-7 and -13 expression at term, but no change in MMP-3 and -9. In contrast, MMP-3, -7, -9 and -13 mRNA levels were significantly higher in the cervix and vagina of late pregnant Rlx^–/– mice. The expression of MMP-2 did not differ between Rlx^+/+ and Rlx^–/– mice at term. Despite the higher expression of the majority of MMPs we examined in Rlx^–/– mice, there was no histological evidence of increased ECM degradation in the cervix and vagina in late gestation. Although previous in vitro studies suggest that relaxin positively regulates MMP activity, our data demonstrate that relaxin deficiency does not result in decreased MMP expression in the mouse cervix and vagina in vivo.