Morphological and Functional Changes in the Vagina following Critical Lifespan Events in the Ewe

The ewe is increasingly being used as an animal model for pelvic floor disorders. The aim was to further characterize changes in the vaginal properties during its entire lifespan.

Vaginal tissues were collected at different stages of reproductive life (neonatal, prepubescence, nulliparous, primiparous, multiparous, and menopausal; ≥6 ewes/group). Vaginal size, as well as active and passive biomechanics, was measured. Microscopy included thickness of glycogen, epithelium, lamina propria and muscularis thickness, densities of collagen, elastin, smooth muscle, and nerves.

Vaginal dimensions increase during adolescence, peak at reproductive levels, and decrease sharply after ovariectomy. One year after first delivery, the distal vagina gets more compliant, yet this is reversed later in life. The thickness of glycogen staining epithelial layers changed with puberty and menopause. The epithelium was markedly thicker after multiple deliveries. The thickness of lamina propria and muscularis increased in puberty and in nulliparous. Semi-quantitative collagen assessment demonstrated a lower collagen and higher elastin content after first and multiple deliveries.

The changes in the ovine vaginal wall during representative moments of her lifespan parallel those observed in women.