Pregnancy- and delivery-induced biomechanical changes in rat vagina persist postpartum

Alperin, Marianna; Feola, Andrew; Duerr, Robert; Moalli, Pamela; Abramowitch, Steven D.

doi:10.1007/s00192-010-1149-6

Cited by 41 publications

(41 citation statements)

References 10 publications

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“…These findings are in agreement with studies in mice [25] and rats [26] where the supportive perivaginal tissues decreased in stiffness and strength during pregnancy and returned to virgin levels four weeks after delivery [26]. However, another rat study showed increased vaginal distensibility during pregnancy compared to virgins, which did not return to virgin levels four weeks postpartum [27]. We also found a higher level of induced permanent strain following cyclic loading in pregnant vaginal tissue, indicating it was the least elastic by this measure and the least likely to return to its original dimensions.…”

Section: Discussionsupporting

confidence: 90%

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

Dirnagl¹,

Edwards²,

Su³

et al. 2014

Geburtshilfe Frauenheilkd

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Objective: To undertake a comprehensive analysis of the biochemical tissue composition and passive biomechanical properties of ovine vagina and relate this to the histo-architecture at different reproductive stages as part of the establishment of a large preclinical animal model for evaluating regenerative medicine approaches for surgical treatment of pelvic organ prolapse.Methods: Vaginal tissue was collected from virgin (n = 3), parous (n = 6) and pregnant sheep (n = 6; mean gestation; 132 d; term = 145 d). Tissue histology was analyzed using H+E and Masson's Trichrome staining. Biochemical analysis of the extracellular matrix proteins used a hydroxyproline assay to quantify total collagen, SDS PAGE to measure collagen III/I+III ratios, dimethylmethylene blue to quantify glycosaminoglycans and amino acid analysis to quantify elastin. Uniaxial tensiometry was used to determine the Young's modulus, maximum stress and strain, and permanent strain following cyclic loading.

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Section: Discussionsupporting

confidence: 90%

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

Dirnagl¹,

Edwards²,

Su³

et al. 2014

Geburtshilfe Frauenheilkd

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“…26 Rat has also been shown to be a reliable model for the study of pregnancy-related changes in cervix, vagina, and vaginal supportive structures. 14,27,28 In this study we quantified the structural adaptations that take place in the PFMs throughout pregnancy and determined the extent of recovery after vaginal delivery. Second, to determine whether these changes are specific to the PFMs or occur throughout the body, we examined a hind limb muscle, the tibialis anterior.…”

mentioning

confidence: 99%

Pregnancy-induced adaptations in the intrinsic structure of rat pelvic floor muscles

Alperin

Lawley

Esparza

et al. 2015

American Journal of Obstetrics and Gynecology

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OBJECTIVE Maternal birth trauma to the pelvic floor muscles (PFMs) is a major risk factor for pelvic floor disorders. Modeling and imaging studies suggest that demands placed on PFMs during childbirth exceed their physiologic limits; however many parous women do not sustain PFM injury. Here we determine whether pregnancy induces adaptations in PFM architecture, the strongest predictor of muscle function, and/or intramuscular extracellular matrix (ECM), responsible for load bearing. To establish if parallel changes occur in muscles outside of the PFM, we also examined a hind limb muscle. STUDY DESIGN Coccygeus, iliocaudalis, pubocaudalis, and tibialis anterior of 3-month-old Sprague-Dawley virgin, mid-pregnant, and late-pregnant; 6-month-old virgin; and 4- and 12-week postpartum rats (N = 10/group) were fixed in situ and harvested. Major architectural parameters determining muscle’s excursion and force-generating capacity were quantified, namely, normalized fiber length (Lfn), physiologic cross-sectional area, and sarcomere length. Hydroxyproline content was used as a surrogate for intramuscular ECM quantity. Analyses were performed by 2-way analysis of variance with Tukey post hoc testing at a significance level of .05. RESULTS Pregnancy induced a significant increase in Lfn in all PFMs by the end of gestation relative to virgin controls. Fibers were elongated by 37% in coccygeus (P < .0001), and by 21% in iliocaudalis and pubocaudalis (P < .0001). Importantly, no Lfn change was observed in the tibialis anterior. Physiologic cross-sectional area and sarcomere length were not affected by pregnancy. By 12 weeks’ postpartum, Lfn of all PFMs returned to the prepregnancy values. Relative to virgin controls, ECM increased by 140% in coccygeus, 52% in iliocaudalis, and 75% in pubocaudalis in late-pregnant group, but remained unchanged across time in the tibialis anterior. Postpartum, ECM collagen content returned to prepregnancy levels in iliocaudalis and pubocaudalis, but continued to be significantly elevated in coccygeus (P < .0001). CONCLUSION This study demonstrates that pregnancy induces unique adaptations in the structure of the PFMs, which adjust their architectural design by adding sarcomeres in series to increase fiber length as well as mounting a substantial synthesis of collagen in intramuscular ECM.

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“…We recognize that the difference in posture and small fetal size of the species we evaluated makes naturally occurring PFD a rare event in these animals. However, a rodent model has been a reliable exemplar for the study of pregnancy adaptations and effects of simulated birth injury [28, 29]. Pregnancy-induced adaptations in rat persist postpartum [29]; also, simulated birth injury in rodent induces stress urinary incontinence via injury of striated muscles [30].…”

Section: Discussionmentioning

confidence: 99%

“…However, a rodent model has been a reliable exemplar for the study of pregnancy adaptations and effects of simulated birth injury [28, 29]. Pregnancy-induced adaptations in rat persist postpartum [29]; also, simulated birth injury in rodent induces stress urinary incontinence via injury of striated muscles [30]. Despite the limitations listed above, our study provides prerequisite data on the structure of the pelvic skeletal muscle in mouse, rat, and rabbit, all of which are frequently used for studying PFD.…”

Section: Discussionmentioning

confidence: 99%

Comparison of pelvic muscle architecture between humans and commonly used laboratory species

et al. 2014

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Introduction and hypothesis Pelvic floor muscles (PFM) are deleteriously affected by vaginal birth, which contributes to the development of pelvic floor disorders. To mechanistically link these events, experiments using animal models are required, as access to human PFM tissue is challenging. In choosing an animal model, a comparative study of PFM design is necessary, since gross anatomy alone is insufficient to guide the selection. Methods Human PFM architecture was measured using micromechanical dissection and then compared with mouse (n=10), rat (n=10), and rabbit (n=10) using the Architectural Difference Index (ADI) (parameterizing a combined measure of sarcomere length-to-optimal-sarcomere ratio, fiber-to-muscle-length ratio, and fraction of total PFM mass and physiological cross-sectional area (PCSA) contributed by each muscle). Coccygeus (C), iliocaudalis (IC), and pubocaudalis (PC) were harvested and subjected to architectural measurements. Parameters within species were compared using repeated measures analysis of variance (ANOVA) with post hoc Tukey's tests. The scaling relationships of PFM across species were quantified using least-squares regression of log-10-transformed variables. Results Based on the ADI, rat was found to be the most similar to humans (ADI = 2.5), followed by mouse (ADI = 3.3). When animals' body mass was regressed against muscle mass, muscle length, fiber length, and PCSA scaling coefficients showed a negative allometric relationship or smaller increase than predicted by geometric scaling. Conclusion In terms of muscle design among commonly used laboratory animals, rat best approximates the human PFM, followed by mouse. Negative allometric scaling of PFM architectural parameters is likely due to the multifaceted function of these muscles.

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Pregnancy- and delivery-induced biomechanical changes in rat vagina persist postpartum

Abstract: Introduction and hypothesis-We sought to define changes in vaginal distensibility (VD) induced by pregnancy and vaginal delivery using a novel in vivo biomechanical testing protocol.

Cited by 41 publications

References 10 publications

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

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

Pregnancy-induced adaptations in the intrinsic structure of rat pelvic floor muscles

Comparison of pelvic muscle architecture between humans and commonly used laboratory species

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