- Award ID(s):
- 1929731
- NSF-PAR ID:
- 10247250
- Date Published:
- Journal Name:
- Journal of Biomechanical Engineering
- Volume:
- 142
- Issue:
- 3
- ISSN:
- 0148-0731
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract The vagina plays a critical role in supporting the pelvic organs and loss of support leads to pelvic organ prolapse. It is unknown what microstructural changes influence prolapse progression nor how decreased elastic fibers contributes to vaginal remodeling and smooth muscle contractility. The objective for this study was to evaluate the effect of fibulin-5 haploinsufficiency, and deficiency with progressive prolapse on the biaxial contractile and biomechanical function of the murine vagina. Vaginas from wildtype (n = 13), haploinsufficient (n = 13), and deficient mice with grade 1 (n = 9) and grade 2 or 3 (n = 9) prolapse were explanted for biaxial contractile and biomechanical testing. Multiaxial histology (n = 3/group) evaluated elastic and collagen fiber microstructure. Western blotting quantified protein expression (n = 6/group). A one-way ANOVA or Kruskal–Wallis test evaluated statistical significance. Pearson’s or Spearman’s test determined correlations with prolapse grade. Axial contractility decreased with fibulin-5 deficiency and POP (p < 0.001), negatively correlated with prolapse grade (ρ = − 0.80; p < 0.001), and positively correlated with muscularis elastin area fraction (ρ = − 0.78; p = 0.004). Circumferential (ρ = 0.71; p < 0.001) and axial (ρ = 0.69; p < 0.001) vaginal wall stresses positively correlated with prolapse grade. These findings demonstrated that fibulin-5 deficiency and prolapse progression decreased vaginal contractility and increased vaginal wall stress. Future work is needed to better understand the processes that contribute to prolapse progression in order to guide diagnostic, preventative, and treatment strategies.more » « less
-
null (Ed.)Abstract The vagina is an important organ of the female reproductive system that has been largely understudied in the field of biomechanics. In recent years, some research has been conducted to evaluate the mechanical properties of the vagina, but much has focused on characterizing the passive mechanical properties. Because vaginal contractions play a central role in sexual function, childbirth, and development and treatment of pelvic floor disorders, the active mechanical properties of the vagina must be also quantified. This review surveys and summarizes published experimental studies on the active properties of the vagina including the differences in such properties determined by anatomic regions and orientations, neural pathways, life events such as pregnancy and menopause, pelvic floor disorders such as prolapse, and surgical mesh treatment. Conflicting experimental findings are presented, illustrating the need for further research on the active properties of the vagina. However, consensus currently exists regarding the negative impact of surgical mesh on vaginal contractility. This review also identifies knowledge gaps and future research opportunities, thus proving a firm foundation for novice and experienced researchers in this emerging area of biomechanics and encouraging more activity on women's sexual and reproductive health research.more » « less
-
Abstract The vagina is a highly inhomogeneous, anisotropic, and viscoelastic organ that undergoes significant deformations in vivo. The mechanical attributes of this organ facilitate important physiological functions during menstruation, intercourse, and birthing. Despite the crucial mechanical role that the vagina plays within the female reproductive system, the deformations that the organ can sustain over time under constant pressure, in both the longitudinal direction (LD) and circumferential direction (CD), have not been fully characterized. This experimental study focuses on quantifying the creep properties of the vagina via ex vivo inflation testing using the rat as an animal model. Toward this end, rat vaginas were subjected to three consecutively increasing constant luminal pressures (28, 55, and 83 kPa) using a custom-built experimental setup and the resulting inhomogeneous deformations were measured using the digital image correlation (DIC) method. The vagina was found to deform significantly more in the CD than the LD at any constant pressure, suggesting that the organ primarily adapts to constant pressures by significantly changing the diameter rather that the length. The change in deformation over time was significantly higher during the first inflation test at a constant pressure of 28 kPa than during the second and third inflation tests at constant pressures of 55 and 83 kPa, respectively. The findings of this study on the mechanical behavior of the vagina could serve to advance our limited knowledge about the physiology and pathophysiology of this important reproductive organ.
-
Abstract Higher reproductive age is associated with an increased risk of gestational diabetes, pre-eclampsia, and severe vaginal tearing during delivery. Further, menopause is associated with vaginal stiffening. However, the mechanical properties of the vagina during reproductive aging before the onset of menopause are unknown. Therefore, the first objective of this study was to quantify the biaxial mechanical properties of the nulliparous murine vagina with reproductive aging. Menopause is further associated with a decrease in elastic fiber content, which may contribute to vaginal stiffening. Hence, our second objective was to determine the effect of elastic fiber disruption on the biaxial vaginal mechanical properties. To accomplish this, vaginal samples from CD-1 mice aged 2–14 months underwent extension-inflation testing protocols (n = 64 total; n = 16/age group). Then, half of the samples were randomly allocated to undergo elastic fiber fragmentation via elastase digestion (n = 32 total; 8/age group) to evaluate the role of elastic fibers. The material stiffness increased with reproductive age in both the circumferential and axial directions within the control and elastase-treated vaginas. The vagina demonstrated anisotropic mechanical behavior, and anisotropy increased with age. In summary, vaginal remodeling with reproductive age included increased direction-dependent material stiffness, which further increased following elastic fiber disruption. Further work is needed to quantify vaginal remodeling during pregnancy and postpartum with reproductive aging to better understand how age-related vaginal remodeling may contribute to an increased risk of vaginal tearing.more » « less
-
null (Ed.)Abstract Background The pia arachnoid complex (PAC) is a cerebrospinal fluid-filled tissue conglomerate that surrounds the brain and spinal cord. Pia mater adheres directly to the surface of the brain while the arachnoid mater adheres to the deep surface of the dura mater. Collagen fibers, known as subarachnoid trabeculae (SAT) fibers, and microvascular structure lie intermediately to the pia and arachnoid meninges. Due to its structural role, alterations to the biomechanical properties of the PAC may change surface stress loading in traumatic brain injury (TBI) caused by sub-concussive hits. The aim of this study was to quantify the mechanical and morphological properties of ovine PAC. Methods Ovine brain samples (n = 10) were removed from the skull and tissue was harvested within 30 min post-mortem. To access the PAC, ovine skulls were split medially from the occipital region down the nasal bone on the superior and inferior aspects of the skull. A template was used to remove arachnoid samples from the left and right sides of the frontal and occipital regions of the brain. 10 ex-vivo samples were tested with uniaxial tension at 2 mm s −1 , average strain rate of 0.59 s −1 , until failure at < 5 h post extraction. The force and displacement data were acquired at 100 Hz. PAC tissue collagen fiber microstructure was characterized using second-harmonic generation (SHG) imaging on a subset of n = 4 stained tissue samples. To differentiate transverse blood vessels from SAT by visualization of cell nuclei and endothelial cells, samples were stained with DAPI and anti-von Willebrand Factor, respectively. The Mooney-Rivlin model for average stress–strain curve fit was used to model PAC material properties. Results The elastic modulus, ultimate stress, and ultimate strain were found to be 7.7 ± 3.0, 2.7 ± 0.76 MPa, and 0.60 ± 0.13, respectively. No statistical significance was found across brain dissection locations in terms of biomechanical properties. SHG images were post-processed to obtain average SAT fiber intersection density, concentration, porosity, tortuosity, segment length, orientation, radial counts, and diameter as 0.23, 26.14, 73.86%, 1.07 ± 0.28, 17.33 ± 15.25 µm, 84.66 ± 49.18°, 8.15%, 3.46 ± 1.62 µm, respectively. Conclusion For the sizes, strain, and strain rates tested, our results suggest that ovine PAC mechanical behavior is isotropic, and that the Mooney-Rivlin model is an appropriate curve-fitting constitutive equation for obtaining material parameters of PAC tissues.more » « less