Relaxin and porcine uterine growth and remodeling

Abstract

Uterine growth is the result of mitogenic activity of uterine cells, as well as remodeling of the connective tissue framework of the uterus, to facilitate uterine expansion. The stimulation of uterine growth during pregnancy is critical to accommodate growing fetuses. Among the causes of early embryo loss is competition for limited maternal resources, due to insufficient uterine accommodation, which reduces uterine capacity. Relaxin stimulates uterine growth and remodeling in prepubertal [1], pregnant [2] and ovariectomized, steroid-treated animals [3]. While the uterotropic effects of relaxin have been documented, the mechanism of relaxin action in promoting uterine growth is less clear. In our laboratory we are studying the ability of relaxin to stimulate uterine growth, independently of estradiol, using an in vivo, prepubertal gilt model in which the uterotropic actions of relaxin were first reported by Hall et al. [1]. Studies from our laboratory indicate that relaxin interacts with the IGF-I system in promoting uterine growth [4]. In addition, our working hypothesis is that relaxin acts as a growth factor in the uterus by increasing expression of elements that enhance remodeling and cell communication such as connective tissue proteases, connexin gap junction proteins and vascular endothelial growth factor (VEGF).