Aging of Pelvic Floor in Animal Models: A Sistematic Review of Literature on the Role of the Extracellular Matrix in the Development of Pelvic Floor Prolapse

Pelvic organ prolapse (POP) affects many women and contributes significantly to a decrease in their quality of life causing urinary and/or fecal incontinence, sexual dysfunction and dyspareunia. To better understand POP pathophysiology, prevention and treatment, many researchers resorted to evaluating animal models. Regarding this example and because POP affects principally older women, our aim was to provide an overview of literature on the possible biomechanical changes that occur in the vaginas of animal models and their supportive structures as a consequence of aging. Papers published online from 2000 until May 2021 were considered and particular attention was given to articles reporting the effects of aging on the microscopic structure of the vagina and pelvic ligaments in animal models. Most research has been conducted on rodents because their vagina structure is well characterized and similar to those of humans; furthermore, they are cost effective. The main findings concern protein structures of the connective tissue, known as elastin and collagen. We have noticed a significant discordance regarding the quantitative changes in elastin and collagen related to aging, especially because it is difficult to detect them in animal specimens. However, it seems to be clear that aging affects the qualitative properties of elastin and collagen leading to aberrant forms which may affect the elasticity and the resilience of tissues leading to pelvic floor disease. The analysis of histological changes of pelvic floor tissues related to aging underlines how these topics appear to be not fully understood so far and that more research is necessary.

Mechanics of Uterosacral Ligaments: Current Knowledge, Existing Gaps, and Future Directions

The uterosacral ligaments (USLs) are important anatomical structures that support the uterus and apical vagina within the pelvis. As these structures are over-stretched, become weak, and exhibit laxity, pelvic floor disorders such as pelvic organ prolapse occur. Although several surgical procedures to treat pelvic floor disorders are directed toward the USLs, there is still a lot that is unknown about their function. This manuscript presents a review of the current knowledge on the mechanical properties of the USLs. The anatomy, microstructure, and clinical significance of the USLs are first reviewed. Then, the results of published experimental studies on the in vivo and ex vivo, uniaxial and biaxial tensile tests are compiled. Based on the existing findings, research gaps are identified and future research directions are discussed. The purpose of this exhaustive review is to help new researchers navigate scientific literature on the mechanical properties of the USLs. The use of these structures remains very popular in reconstructive surgeries that restore and augment the support of pelvic organs, especially as synthetic surgical mesh implants continue to be highly controversial.

Low expression of collagen type-1 in sacrouterine ligament as risk factor of stage III-IV uterine prolapse

BACKGROUND

Despite being non-life threatening, uterine prolapse is a reproductive health problem that interferes psychosocial life, economical and sexual function. Uterine prolapse can be caused by direct trauma resulting in damaged and weakened levator ani muscle which in turn causing sacrouterine ligament to stretch in order to maintain uterus normal position. The main component of sacrouterine ligament is collagen. Types of collagen that was involved in the occurrence of uterine prolapse are which plays a role of risk of occurrence uterine prolapse is collagen type-1 and type-3. Collagen type-1 has a good resistance and flexible to strain. If there is a disruption in the expression of collagen in sacrouterine ligament, it will result in cause uterine prolapse.

OBJECTIVE

The aim of this study is to prove low expression of collagen type-1 in sacrouterine ligament is a risk factor for the occurrence of stage III-IV uterine prolapse.

STUDY DESIGN

This study was an observational study using case-control approach. A total of 22 cases of stage III-IV uterine prolapse and 22 cases of non-uterine prolapse as control group were selected by consecutive sampling. This study was carried out in Sanglah General Hospital and Pathobiology Laboratory of Veterinary Faculty of Udayana. Samples were taken from sacrouterine ligament of individual with stage III-IV uterine prolapse compared to non-prolapse uterine who had undergone total hysterectomy.

RESULTS

Chi-square analysis with 95 % confidence interval indicated that low expression of collagen type-1 was 6 times more likely to be the risk factor of stage III-IV uterine prolapse (OR = 5.95; 95 %CI = 1.59-22.33; p = 0.006).

CONCLUSION

Low collagen type-1 in sacrouterine ligament is a risk factor of stage III-IV uterine prolapse.

Effect of hormone replacement and selective estrogen receptor modulators (SERMs) on the biomechanics and biochemistry of pelvic support ligaments in the cynomolgus monkey (Macaca fascicularis)

OBJECTIVE

To evaluate the effect of selective estrogen receptor modulators and ethinyl estradiol on the biomechanical and biochemical properties of the uterosacral and round ligaments in the monkey model of menopause.

STUDY DESIGN

A randomized, double-blind, placebo-controlled study on 11 female macaque monkeys. Ovariectomized monkeys received 12 weeks of placebo, raloxifene, tamoxifen, or ethinyl estradiol. Biomechanical step-strain testing and real-time polymerase chain reaction was performed on the uterosacral and round ligaments.

RESULTS

Tamoxifen and raloxifene uterosacrals expressed differing collagen I/III receptor density ratios, but both selective estrogen receptor modulators showed decreased tensile stiffness compared to ethinyl estradiol and controls.

CONCLUSION

These findings support a possible effect of selective estrogen receptor modulators on biomechanical and biochemical properties of uterosacrals. This may play a role in pelvic organ prolapse.