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Impact of parity on ewe vaginal mechanical properties relative to the nonhuman primate and rodent

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Abstract

Introduction and hypothesis

Parity is the leading risk factor for the development of pelvic organ prolapse. To assess the impact of pregnancy and delivery on vaginal tissue, researchers commonly use nonhuman primate (NHP) and rodent models. The purpose of this study was to evaluate the ewe as an alternative model by investigating the impact of parity on the ewe vaginal mechanical properties and collagen structure.

Methods

Mechanical properties of 15 nulliparous and parous ewe vaginas were determined via uniaxial tensile tests. Collagen content was determined by hydroxyproline assay and collagen fiber thickness was analyzed using picrosirius red staining. Outcome measures were compared using Independent samples t or Mann–Whitney U tests. ANOVA (Gabriel’s pairwise post-hoc test) or the Welch Alternative for the F-ratio (Games Howell post-hoc test) was used to compare data with previously published NHP and rodent data.

Results

Vaginal tissue from the nulliparous ewe had a higher tangent modulus and tensile strength compared with the parous ewe (p < 0.025). The parous ewe vagina elongated 42 % more than the nulliparous ewe vagina (p = 0.015). No significant differences were observed in collagen structure among ewe vaginas. The tangent modulus of the nulliparous ewe vagina was not different from that of the NHP or rodent (p = 0.290). Additionally, the tangent moduli of the parous ewe and NHP vaginas did not differ (p = 0.773).

Conclusions

Parity has a negative impact on the mechanical properties of the ewe vagina, as also observed in the NHP. The ewe may serve as an alternative model for studying parity and ultimately prolapse development.

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Acknowledgements

We are grateful to the National Institutes of Health for funding support R01 HD-061811. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1247842. The assistance of Matthew Falcioni from the University of Pittsburgh, Department of Statistics, in statistical analysis, and Dr. Bryan N. Brown from the University of Pittsburgh, Department of Bioengineering, in examining collagen fiber thickness, is gratefully acknowledged. Additionally, we would like to thank Christopher A. Carruthers from the University of Pittsburgh, Department of Bioengineering, for providing the MatLab code.

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Authors and Affiliations

  1. Department of Bioengineering, Musculoskeletal Research Center, University of Pittsburgh, Pittsburgh, PA, USA

    Katrina M. Knight, Pamela A. Moalli, William R. Barone & Steven D. Abramowitch

  2. Magee-Womens Research Institute, Department of Obstetrics and Gynecology, University of Pittsburgh, Pittsburgh, PA, USA

    Pamela A. Moalli, Alexis Nolfi, Stacy Palcsey & Steven D. Abramowitch

  3. Musculoskeletal Research Center, 405 Center for Bioengineering, 300 Technology Drive, Pittsburgh, PA, 15219, USA

    Steven D. Abramowitch

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  1. Katrina M. Knight
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  2. Pamela A. Moalli
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  4. Stacy Palcsey
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  6. Steven D. Abramowitch
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Correspondence to Steven D. Abramowitch.

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Funding

This study was funded by the National Institutes of Health R01 HD-061811.

Conflicts of interest

K.M. Knight, A. Nolfi, S. Palcsey, and W. Barone have no conflicts of interest to disclose. P.A. Moalli received a research grant from the National Institutes of Health, R01 HD-061811, and has a cooperative research agreement with ACell. S.D. Abramowitch received a research grant from the National Institutes of Health, R01 HD-061811, and has a cooperative research agreement with ACell.

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Knight, K.M., Moalli, P.A., Nolfi, A. et al. Impact of parity on ewe vaginal mechanical properties relative to the nonhuman primate and rodent. Int Urogynecol J 27, 1255–1263 (2016). https://doi.org/10.1007/s00192-016-2963-2

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  • DOI: https://doi.org/10.1007/s00192-016-2963-2

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