Uterine distension differentially affects remodeling and distensibility of the uterine vasculature in non-pregnant rats

The mechanisms that mediate uterine vascular growth during pregnancy are poorly defined, though local rather than systemic influences predominate. By using a novel surgical model, the aim of this study was to determine the effect of stretch on the remodeling of the uterine vasculature in the rat, in the absence of both the hormonal changes of pregnancy and fetal/placental influences. Silicone gel was injected into alternating uterine horns of virgin cycling non-pregnant Sprague-Dawley rats (n=9) and animals were sacrificed three weeks post surgery. Measurements of length and diameter were made for the main and radial uterine artery, in association with rates size of the smooth muscle cell division. As a result of the surgical procedure, we saw significant increases of 30-75% in vessel length and 20-60% in vessel diameter, depending on vessel type. A significant increase in rates of cell division (hyperplasia) was seen only in radial arteries. The results show that myometrial stretch alone is sufficient to affect both axial and circumferential remodeling, to varying degrees, implicating differential regulation of these growth processes and supporting a role for this local mechanism in gestational vascular remodeling.