Anisotropy of the Passive and Active Rat Vagina Under Biaxial Loading
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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.
KeywordsVagina Biaxial tests Anisotropy Contractility Mechanical properties
Funding was provided by NSF Grant No. 1511603.
Conflicts of interest
The authors have no conflict of interest.
- 1.Abrams, P., K. E. Andersson, L. Birder, L. Brubaker, L. Cardozo, C. Chapple, A. Cottenden, W. Davila, D. de Ridder, R. Dmochowski, M. Drake, C. DuBeau, C. Fry, P. Hanno, J. H. Smith, S. Herschorn, G. Hosker, C. Kelleher, H. Koelbl, S. Khoury, R. Madoff, I. Milsom, K. Moore, D. Newman, V. Nitti, C. Norton, I. Nygaard, C. Payne, A. Smith, D. Staskin, S. Tekgul, J. Thuroff, A. Tubaro, D. Vodusek, A. Wein, and J. J. Wyndaele. Fourth international consultation on incontinence recommendations of the international scientific committee: evaluation and treatment of urinary incontinence, pelvic organ prolapse, and fecal incontinence. Neurourol. Urodyn. 29:213–240, 2010.CrossRefGoogle Scholar
- 5.Basha, M., S. Chang, E. M. Smolock, R. S. Moreland, A. J. Wein, and S. Chacko. Regional differences in myosin heavy chain isoform expression and maximal shortening velocity of the rat vaginal wall smooth muscle. Am. J. Physiol. Regul. Integr. Comp. Physiol. 291:R1076–R1084, 2006.CrossRefGoogle Scholar
- 23.Inal, H. A., P. B. Kaplan, U. Usta, E. Taştekin, A. Aybatlı, and B. Tokuc. Neuromuscular morphometry of the vaginal wall in women with anterior vaginal wall prolapse. Neurourol. Urodyn. 29:458–463, 2010.Google Scholar
- 24.Jallah Z. C. The Role of Vaginal Smooth Muscle in the Pathogenesis of Pelvic Organ Prolapse. University of Pittsburgh, 2014.Google Scholar
- 38.Patnaik S. S., B. Brazile, V. Dandolu, M. Damaser, C. van der Vaart, and J. Liao. Sheep as an animal model for pelvic organ prolapse and urogynecological research. In: ASB 2015 Annual Conference, 2015Google Scholar
- 39.Peña, E., B. Calvo, M. A. Martínez, P. Martins, T. Mascarenhas, R. M. N. Jorge, A. Ferreira, and M. Doblaré. Experimental study and constitutive modeling of the viscoelastic mechanical properties of the human prolapsed vaginal tissue. Biomech. Model. Mechanobiol. 9:35–44, 2010.CrossRefGoogle Scholar
- 48.Subak, L. L., L. E. Waetjen, S. Van Den Eeden, D. H. Thom, E. Vittinghoff, and J. S. Brown. Cost of pelvic organ prolapse surgery in the United States. Obstet. Gynecol. 98:646–651, 2001.Google Scholar
- 50.Tokar S., A. Feola, P. A. Moalli, and S. Abramowitch. Characterizing the biaxial mechanical properties of vaginal maternal adaptations during pregnancy. In: ASME 2010 Summer Bioengineering Conference, American Society of Mechanical Engineers, 2010, pp. 689–690.Google Scholar
- 53.Urbankova, I., G. Callewaert, S. Blacher, D. Deprest, L. Hympanova, A. Feola, L. De Landsheere, and J. Deprest. First delivery and ovariectomy affect biomechanical and structural properties of the vagina in the ovine model. Int. Urogynecol. J. 2018. https://doi.org/10.1007/s00192-017-3535-9.Google Scholar