Influence of reproductive status on tissue composition and biomechanical properties of ovine vagina

Dirnagl, Ulrich; Edwards, SL; Su, Kai; White, JF; Werkmeister, JA; Gargett, Caroline E.

doi:10.1055/s-0034-1374740

Cited by 8 publications

(12 citation statements)

References 18 publications

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“…We and others have recently become interested in sheep for pelvic floor research and experimental surgery [13][14][15]. For that purpose, we previously compared the pelvic floor anatomy and tissue composition of reproductive, pregnant, and postpartum ewes to that of women [11,12,[16][17][18]. Herein, we further explore the impact of key moments in the lifespan of women on the ovine pelvic floor, using gross anatomical and biomechanical readouts.…”

Section: Introductionmentioning

confidence: 99%

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

Hympánová

Rynkevic

Urbánková

et al. 2019

Gynecol Obstet Invest

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Background/Aims: 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. Methods: 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. Results: 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. Conclusion: The changes in the ovine vaginal wall during representative moments of her lifespan parallel those observed in women.

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Section: Introductionmentioning

confidence: 99%

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

Hympánová

Rynkevic

Urbánková

et al. 2019

Gynecol Obstet Invest

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“…Some previous models of soft tissue injury have selected purely strain-based criteria (Li W., 2016). However, we note that literature values for soft tissue failure do show a dependence on both stress and strain (Chiba & Komatsu, 1993; Panjabi, Crisco, Lydon, & Dvorak, 1998; Ulrich, et al, 2014; Bonner, et al, 2015), hence our choice of failure criterion seems reasonable.…”

Section: Discussionmentioning

confidence: 91%

“…The soft tissue injury criterion was assumed to be the product of stress*strain. This was based on literature available for ligament failures (Chiba & Komatsu, 1993; Panjabi, Crisco, Lydon, & Dvorak, 1998; Bonner, et al, 2015), while the exact value of 2.7 MPa was based on the measured conditions for the ultimate failure of pregnant ovine tissue estimated graphically from Ulrich et al (Ulrich, et al, 2014).…”

Section: Methodsmentioning

confidence: 99%

On the variation in maternal birth canal in vivo viscoelastic properties and their effect on the predicted length of active second stage and levator ani tears

Tracy

Wadhwani

Triebwasser

et al. 2018

Journal of Biomechanics

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The pubovisceral muscles (PVM) help form the distal maternal birth canal. It is not known why 13% of vaginal deliveries end in PVM tears, so insights are needed to better prevent them because their sequelae can lead to pelvic organ prolapse later in life. In this paper we provide the first quantification of the variation in in vivo viscoelastic properties of the intact distal birth canal in healthy nulliparous women using Fung's Quasilinear Viscoelastic Theory and a secondary analysis of data from a clinical trial of constant force birth canal dilation to 8 cm diameter in the first stage of labor in 26 nullipara. We hypothesized that no significant inter-individual variation would be found in the long time constant, τ which characterizes how long it takes the birth canal to be dilated by the fetal head. That hypothesis was rejected because τ values ranged 20-fold above and below the median value. These data were input to a biomechanical model to calculate how such variations affect the predicted length of the active second stage of labor as well as PVM tear risk. The results show there was a 100-fold change in the predicted length of active second stage for the shortest and longest τ values, with a noticeable increase for τ values over 1000 s. The correlation coefficent between predicted and observed second stage durations was 0.51. We conclude that τ is a strong theoretical contributor to the time a mother has to push in order to deliver a fetal head larger than her birth canal, and a weak predictor of PVM tear risk.

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“…Sheep are cheap, easily accessible, and there are less ethical constraints than with non-human primates. Consequently, we and others have started to use this model for vaginal surgery and biomechanics [10,11,24,25].…”

Section: Resultsmentioning

confidence: 99%

Comparative Anatomy of the Ovine and Female Pelvis

Urbánková

Vdoviaková²,

Rynkevic³

et al. 2017

Gynecol Obstet Invest

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Background: Pelvic organ prolapse affects half of vaginally parous women. Several animal models are used to study its pathophysiology and treatment. Sheep are interesting because they develop spontaneously prolapse with similar risk factors as women and can be used for vaginal surgery. This study describes ovine pelvis anatomy and compares it to women's pelvis to provide anatomical tools for translational researchers. Methods: MRI, pelvic dissections, and histology were used for detailed macro- and microscopic analysis of relevant anatomical structures in 6 nulliparous ewes. Results: Although sheep are quadrupeds, the gross and microscopic anatomies are similar to the female pelvis. Principal differences are the shape and its orientation, the absence of the sacrospinous ligament and the internal obturator. The levator ani (except for the puborectalis) and the coccygeus muscle are present, yet the latter is more developed - coinciding with the tail. The dimensions and morphology of the ovine vagina is comparable. The retropubic and the rectovaginal space are accessible transvaginally. There is a wide expression of estrogen receptors with low or absent immunoreactivity in the urethral epithelium, bladder, anus and internal anal sphincter. Conclusion: The ovine pelvic floor has many anatomical and ultrastructural similarities to the female pelvic floor.

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Influence of reproductive status on tissue composition and biomechanical properties of ovine vagina

Cited by 8 publications

References 18 publications

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

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

On the variation in maternal birth canal in vivo viscoelastic properties and their effect on the predicted length of active second stage and levator ani tears

Comparative Anatomy of the Ovine and Female Pelvis

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