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Mammalian pregnancy requires gradual yet extreme remodeling of the reproductive organs to support the growth of the embryos and their birth. After delivery, the reproductive organs return to their non-pregnant state. As pregnancy has traditionally been understudied, there are many unknowns pertaining to the mechanisms behind this remarkable remodeling and repair process which, when not successful, can lead to pregnancy-related complications such as maternal trauma, pre-term birth, and pelvic floor disorders. This study presents the first longitudinal imaging data that focuses on revealing anatomical alterations of the vagina, cervix, and uterine horns during pregnancy and postpartum using the mouse model. By utilizing advanced magnetic resonance imaging (MRI) technology, T1-weighted and T2-weighted images of the reproductive organs of three mice in their in vivo environment were collected at five time points: non-pregnant, mid-pregnant (gestation day: 9–10), late pregnant (gestation day: 16–17), postpartum (24–72 h after delivery) and three weeks postpartum. Measurements of the vagina, cervix, and uterine horns were taken by analyzing MRI segmentations of these organs. The cross-sectional diameter, length, and volume of the vagina increased in late pregnancy and then returned to non-pregnant values three weeks after delivery. The cross-sectional diameter of the cervix decreased at mid-pregnancy before increasing in late pregnancy. The volume of the cervix peaked at late pregnancy before shortening by 24–72 h postpartum. As expected, the uterus increased in cross-sectional diameter, length, and volume during pregnancy. The uterine horns decreased in size postpartum, ultimately returning to their average non-pregnant size three weeks postpartum. The newly developed methods for acquiring longitudinal in vivo MRI scans of the murine reproductive system can be extended to future studies that evaluate functional and morphological alterations of this system due to patholog

Mammalian pregnancy requires gradual yet extreme remodeling of the reproductive organs to support the growth of the embryos and their birth. After delivery, the reproductive organs return to their non-pregnant state. As pregnancy has traditionally been understudied, there are many unknowns pertaining to the mechanisms behind this remarkable remodeling and repair process which, when not successful, can lead to pregnancy-related complications such as maternal trauma, pre-term birth, and pelvic floor disorders. This study presents the first longitudinal imaging data that focuses on revealing anatomical alterations of the vagina, cervix, and uterine horns during pregnancy and postpartum using the mouse model. By utilizing advanced magnetic resonance imaging (MRI) technology, T1-weighted and T2-weighted images of the reproductive organs of three mice in their in vivo environment were collected at five time points: non-pregnant, mid-pregnant (gestation day: 9–10), late pregnant (gestation day: 16–17), postpartum (24–72 h after delivery) and three weeks postpartum. Measurements of the vagina, cervix, and uterine horns were taken by analyzing MRI segmentations of these organs. The cross-sectional diameter, length, and volume of the vagina increased in late pregnancy and then returned to non-pregnant values three weeks after delivery. The cross-sectional diameter of the cervix decreased at mid-pregnancy before increasing in late pregnancy. The volume of the cervix peaked at late pregnancy before shortening by 24–72 h postpartum. As expected, the uterus increased in cross-sectional diameter, length, and volume during pregnancy. The uterine horns decreased in size postpartum, ultimately returning to their average non-pregnant size three weeks postpartum. The newly developed methods for acquiring longitudinal in vivo MRI scans of the murine reproductive system can be extended to future studies that evaluate functional and morphological alterations of this system due to patholog

Collagen fiber re-alignment and uncrimping are postulated mechanisms of structural response to load. It has been suggested that fibers re-orient in the direction of load and then "uncrimp" before collagen is tensioned and that in general, the structure is a result of the function tendons perform. However, little is known about how fiber re-alignment and uncrimping change in response to load, how this change relates to tendon mechanical properties, and if these changes are dependent on the underlying structure. Throughout postnatal development, dramatic structural and compositional changes occur in tendon. Postnatal tendons, with immature collagen networks, may respond to load in a different manner and timescale than mature collagen networks. Therefore, the overall objective of this study was to quantify the mechanical properties and structural response to load in a developmental mouse tendon model at 4, 10, 28 and 90 days old. Local collagen fiber re-alignment and crimp frequency were quantified throughout mechanical testing and local mechanical properties were measured. Throughout development, fiber re-alignment occurred at different points in the mechanical testing protocol. At early development, re-alignment was not identified until the linear (4 days) or toe-regions (10 days) of the mechanical test suggesting that fibers required a prolonged exposure to mechanical load before responding and that the immature collagen network present may delay re-alignment. The uncrimping of collagen fibers was identified during the toe-region of the mechanical test at all ages suggesting that crimp contributes to tendon nonlinear behavior. Additionally, results at 28 and 90 days suggested that collagen fiber crimp frequency decreased with increasing number of preconditioning cycles, which may affect toe-region properties. Mechanical properties and cross-sectional area increased throughout development. The insertion site demonstrated lower moduli values and a more disorganized fi