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1. Contractile Properties of Vaginal Tissue

   https://doi.org/10.1115/1.4046712  

   Huntington, Alyssa; Donaldson, Kandace; De Vita, Raffaella (August 2020, Journal of Biomechanical Engineering)

   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. 

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2. Biaxial Murine Vaginal Remodeling With Reproductive Aging

   https://doi.org/10.1115/1.4054362  

   White, Shelby E.; Kiley, Jasmine X.; Visniauskas, Bruna; Lindsey, Sarah H.; Miller, Kristin S. (June 2022, Journal of Biomechanical Engineering)

   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. 

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3. Prolonging youth or prolonging perimenopause? Beware the Monkey’s Paw

   https://doi.org/10.1097/GME.0000000000002590  

   Santoro, Nanette F; Lawley, Sean D; Sammel, Mary D; Johnson, Joshua (June 2025, Menopause)

   Objective:To discuss the potential for adverse consequences that could arise from the quest to prolong the functional life span of the human ovary. Methods:A series of arguments are presented that: (a) question the dogma that monthly ovulatory menstrual cycles are critical for women’s health; (b) review adverse consequences of decades of menstrual cyclicity; (c) review the evidence for a longevity benefit of ovarian steroid hormone treatment after the age at natural menopause has been achieved; and (d) utilize a mathematical model of ovarian follicle loss over time to raise the possibility that current strategies directed at delaying menopause might well backfire and in fact cause a woman to have a prolonged menopause transition. Results:Regular, monthly menstrual cycles have not been the reality for women for most of history. Rather, when not pregnant, lactational amenorrhea and nutritionally based hypothalamic amenorrhea were the norm for reproductive-aged women. Moreover, monthly menstrual cycles cause substantial morbidity for women during their reproductive years. Providing steroid hormones after menopause has failed to demonstrate an increase in the female life span. Restoring ovarian follicles either surgically or medically has a high probability of causing women to spend more years of life in the menopause transition. Conclusions:Strategies to prevent or delay menopause would benefit from careful consideration of unintended consequences as they are implemented. Directing treatment trials to those with the greatest chance for benefit should be undertaken before adopting this type of treatment for a broader population. 

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4. Modeling the extension of ovarian function after therapeutic targeting of the primordial follicle reserve

   https://doi.org/10.1093/humupd/dmaf009  

   Johnson, Joshua; Emerson, John_W; Smith, Annika; Medina, Kayla; Telfer, Evelyn_E; Anderson, Richard_A; Lawley, Sean_D (May 2025, Human Reproduction Update)

   Abstract BACKGROUNDWomen are increasingly choosing to delay childbirth, and those with low ovarian reserves indicative of primary ovarian insufficiency are at risk for sub- and infertility and also the early onset of menopause. Experimental strategies that promise to extend the duration of ovarian function in women are currently being developed. One strategy is to slow the rate of loss of existing primordial follicles (PFs), and a second is to increase, or ‘boost’, the number of autologous PFs in the human ovary. In both cases, the duration of ovarian function would be expected to be lengthened, and menopause would be delayed. This might be accompanied by an extended production of mature oocytes of sufficient quality to extend the fertile lifespan. OBJECTIVE AND RATIONALEIn this work, we consider how slowing physiological ovarian aging might improve the health and well-being of patients, and summarize the current state-of-the-art of approaches being developed. We then use mathematical modeling to determine how interventions are likely to influence the duration of ovarian function quantitatively. Finally, we consider efficacy benchmarks that should be achieved so that individuals will benefit, and propose criteria that could be used to monitor ongoing efficacy in different patients as these strategies are being validated. SEARCH METHODSCurrent methods to estimate the size of the ovarian reserve and its relationship to the timing of the menopausal transition and menopause were compiled, and publications establishing methods designed to slow loss of the ovarian reserve or to deliver additional ovarian PFs to patients were identified. OUTCOMESWe review our current understanding of the consequences of reproductive aging in women, and compare different approaches that may extend ovarian function in women at risk for POI. We also provide modeling of primordial reserve decay in the presence of therapies that slow PF loss or boost PF numbers. An interactive online tool is provided that estimates how different interventions would impact the duration of ovarian function across the natural population. Modeling output shows that treatments that slow PF loss would need to be applied as early as possible and for many years to achieve significant delay of menopause. In contrast, treatments that add additional PFs should occur as late as possible relative to the onset of menopause. Combined approaches slowing ovarian reserve loss while also boosting numbers of (new) PFs would likely offer some additional benefits in delaying menopause. WIDER IMPLICATIONSExtending ovarian function, and perhaps the fertile lifespan, is on the horizon for at least some patients. Modeling ovarian aging with and without such interventions complements and helps guide the clinical approaches that will achieve this goal. REGISTRATION NUMBERNot applicable. 

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5. Polymers under nanoconfinement: where are we now in understanding local property changes?

   https://doi.org/10.1039/D1CS00054C  

   Roth, Connie B. (July 2021, Chemical Society Reviews)

   Polymers are increasingly being used in applications with nanostructured morphologies where almost all polymer molecules are within a few tens to hundreds of nanometers from some interface. From nearly three decades of study on polymers in simplified nanoconfined systems such as thin films, we have come to understand property changes in these systems as arising from interfacial effects where local dynamical perturbations are propagated deeper into the material. This review provides a summary of local glass transition temperature T g changes near interfaces, comparing across different types of interfaces: free surface, substrate, liquid, and polymer–polymer. Local versus film-average properties in thin films are discussed, making connections to other related property changes, while highlighting several historically important studies. By experimental necessity, most studies are on high enough molecule weight chains to be well entangled, although aspects that connect to lower molecule weight materials are described. Emphasis is made to identify observations and open questions that have yet to be fully understood such as the evidence of long-ranged interfacial effects, finite domain size, interfacial breadth, and chain connectivity. 

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