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Anisotropy of the Passive and Active Rat Vagina Under Biaxial Loading

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Abstract

Pelvic organ prolapse, the descent of the pelvic organs from their normal anatomical position, is a common condition among women that is associated with mechanical alterations of the vaginal wall. In order to characterize the complex mechanical behavior of the vagina, we performed planar biaxial tests of vaginal specimens in both the passive (relaxed) and active (contracted) states. Specimens were isolated from virgin, female Long-Evans rats (n = 16) and simultaneously stretched along the longitudinal direction (LD) and circumferential direction (CD) of the vagina. Tissue contraction was induced by electric field stimulation (EFS) at incrementally increasing values of stretch and, subsequently, by KCl. On average, the vagina was stiffer in the CD than in the LD (p < 0.001). The mean maximum EFS-induced active stress was significantly higher in the CD than in the LD (p < 0.01). On the contrary, the mean KCl-induced active stress was lower in the CD than in the LD (p < 0.01). When comparing the mean maximum EFS-induced active stress to the mean KCl-induced active stress, no differences were found in the CD (p = 0.366) but, in the LD, the mean active stress was much higher in response to the KCl stimulation (p < 0.001). Collectively, these results suggest that the anisotropic behavior of the vaginal tissue is determined not only by collagen and smooth muscle fiber organization but also by the innervation.

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Acknowledgments

Funding was provided by NSF Grant No. 1511603.

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The authors have no conflict of interest.

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  1. Alyssa Huntington and Emanuele Rizzuto have contributed equally to this work.

Authors and Affiliations

  1. STRETCH Laboratory, 330A Kelly Hall, 325 Stanger Street, Virginia Tech, Blacksburg, VA, 24061, USA

    Alyssa Huntington, Emanuele Rizzuto & Raffaella De Vita

  2. Department of Mechanical and Aerospace Engineering, La Sapienza University, 00184, Rome, Italy

    Emanuele Rizzuto & Zaccaria Del Prete

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

    Steven Abramowitch

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  1. Alyssa Huntington
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Associate Editor Elena S. Di Martino oversaw the review of this article.

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Huntington, A., Rizzuto, E., Abramowitch, S. et al. Anisotropy of the Passive and Active Rat Vagina Under Biaxial Loading. Ann Biomed Eng 47, 272–281 (2019). https://doi.org/10.1007/s10439-018-02117-9

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