Pregnancy-Induced Dynamical and Structural Changes of Reproductive Tract Collagen

The tissues and organs of the female reproductive tract and pelvic floor undergo significant remodeling and alterations to allow for fetal growth and birth. In this work, we report on a study of the alterations of murine reproductive tract collagen resulting from pregnancy and parturition by spectrophotometry, histology, and ¹³C, ²H nuclear magnetic resonance (NMR). Four different cohorts of rats were investigated that included virgin, multiparous, two- and fourteen-day postpartum primiparous rats. ¹³C CPMAS NMR revealed small chemical shift differences across the cohorts. The measured H-C internuclear correlation times indicated differences in dynamics of some motifs. However, the dynamics of the major amino acids, e.g., Gly, remained unaltered with respect to parity. ²H NMR relaxation measurements revealed an additional water reservoir in the postpartum and multiparous cohorts pointing to redistribution of water due to pregnancy and/or parturition. Spectrophotometric measurements indicated that the collagen content in virgin rats was highest. Histological analysis of the upper vaginal wall indicated a signature of collagen fiber dissociation with smooth muscle and a change in the density of collagen fibers in multiparous rats.