Smooth muscle regional contribution to vaginal wall function

Abstract

Pelvic organ prolapse is characterized as the descent of the pelvic organs into the vaginal canal. In the USA, there is a 12% lifetime risk for requiring surgical intervention. Although vaginal childbirth is a well-established risk factor for prolapse, the underlying mechanisms are not fully understood. Decreased smooth muscle organization, composition and maximum muscle tone are characteristics of prolapsed vaginal tissue. Maximum muscle tone of the vaginal wall was previously investigated in the circumferential or axial direction under uniaxial loading; however, the vaginal wall is subjected to multiaxial loads. Further, the contribution of vaginal smooth muscle basal (resting) tone to mechanical function remains undetermined. The objectives of this study were to determine the contribution of smooth muscle basal and maximum tone to the regional biaxial mechanical behaviour of the murine vagina. Vaginal tissue from C57BL/6 mice was subjected to extension–inflation protocols ( n = 10) with and without basal smooth muscle tone. Maximum tone was induced with KCl under various circumferential ( n = 5) and axial ( n = 5) loading conditions. The microstructure was visualized with multiphoton microscopy ( n = 1), multiaxial histology ( n = 4) and multiaxial immunohistochemistry ( n = 4). Smooth muscle basal tone decreased material stiffness and increased anisotropy. In addition, maximum vaginal tone was decreased with increasing intraluminal pressures. This study demonstrated that vaginal muscle tone contributed to the biaxial mechanical response of murine vaginal tissue. This may be important in further elucidating the underlying mechanisms of prolapse, in order to improve current preventative and treatment strategies.

Mechanical and structural characterisation of the dural venous sinuses

“…Specimens were observed under an optical microscope at 4 x magnification and images were then stitched using Adobe Photoshop Lightroom Classic (Version 8.4.1) to produce an image of the whole sinus cross-section. The images were then processed using a colour deconvolution plugin 49 as has been utilised previously on a host of biological tissues 50 – 52 . The area fraction of collagen and smooth muscle tissue was determined from the deconvolved images by utilising ImageJ to determine the ratio of stained constituent pixels to the total number of pixels representing each sample 53 .…”

Single-cell transcriptome profiling of the vaginal wall in women with severe anterior vaginal prolapse

“…The cellular composition of the vaginal wall is complex, comprising primarily fibroblasts and smooth muscle cells (SMCs), which play important roles in the extracellular integrity and mechanical stretching of the anterior vaginal wall 21 , 22 . However, the complete cell type composition and aspects of cellular heterogeneity leading to vaginal prolapse remain largely unknown.…”

Role of fibulin-5 insufficiency and prolapse progression on murine vaginal biomechanical function

“…Elastic fibers contribute to the integrity of the vaginal wall by imparting compliance and extensibility 12 – 14 . Additionally, intact and mature elastic fibers may be critical to maintain smooth muscle cell (SMC) contractility 15 – 18 . POP is common in women with certain, genetic disorders, such as Marfan syndrome, which results in defects in elastic fiber synthesis or assembly 11 .…”