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Gimenez C, Alperin M, De Vita R. The Effect of Menopause on Vaginal Tissue Mechanics: A Brief Review. J Biomech Eng 2024; 146:060903. [PMID: 37542707 DOI: 10.1115/1.4063101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 08/01/2023] [Indexed: 08/07/2023]
Abstract
Often called "the change of life," menopause affects every part of a woman's body. As the sex hormones decrease, the reproductive organs experience the most remarkable changes, with the vagina becoming thinner, drier, and less elastic. Despite the important implications of these changes in genitourinary conditions, there are only a few experimental studies that focus on quantifying the effect of menopause on the mechanical properties of the vagina. These studies are mostly conducted using uniaxial tests on strips of vaginal tissues isolated from rats, rabbits, and sheep and, in only a few cases, from humans. The purpose of this article is to present a systematic review of experimental protocols, methods, and results that are currently published on how menopause alters the mechanical behavior of the vagina. This review will enable new investigators in the biomechanics field to identify important gaps and frame research questions that inform the design of new treatment options for menopausal symptoms.
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Affiliation(s)
- Clara Gimenez
- STRETCH Lab, Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA 24061
- Virginia Tech
| | - Marianna Alperin
- Division of Urogynecology and Pelvic Reconstructive Surgery, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California San Diego, Sanford Consortium for Regenerative Medicine, La Jolla, CA 92097
| | - Raffaella De Vita
- STRETCH Lab, Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA 24061
- Virginia Tech Services
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Mahapatra C, Kumar R. Biophysical Mechanisms of Vaginal Smooth Muscle Contraction: The Role of the Membrane Potential and Ion Channels. PATHOPHYSIOLOGY 2024; 31:225-243. [PMID: 38804298 PMCID: PMC11130850 DOI: 10.3390/pathophysiology31020018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 05/10/2024] [Accepted: 05/14/2024] [Indexed: 05/29/2024] Open
Abstract
The vagina is an essential component of the female reproductive system and is responsible for providing female sexual satisfaction. Vaginal smooth muscle contraction plays a crucial role in various physiological processes, including sexual arousal, childbirth, and urinary continence. In pathophysiological conditions, such as pelvic floor disorders, aberrations in vaginal smooth muscle function can lead to urinary incontinence and pelvic organ prolapse. A set of cellular and sub-cellular physiological mechanisms regulates the contractile properties of the vaginal smooth muscle cells. Calcium influx is a crucial determinant of smooth muscle contraction, facilitated through voltage-dependent calcium channels and calcium release from intracellular stores. Comprehensive reviews on smooth muscle biophysics are relatively scarce within the scientific literature, likely due to the complexity and specialized nature of the topic. The objective of this review is to provide a comprehensive description of alterations in the cellular physiology of vaginal smooth muscle contraction. The benefit associated with this particular approach is that conducting a comprehensive examination of the cellular mechanisms underlying contractile activation will enable the creation of more targeted therapeutic agents to control vaginal contraction disorders.
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Affiliation(s)
- Chitaranjan Mahapatra
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94158, USA
- Paris Saclay Institute of Neuroscience, 91440 Saclay, France
| | - Ravinder Kumar
- Department of Pathology, College of Medicine, University of Tennessee Health Science Center, Memphis, TN 38163, USA
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Suarez AC, Gimenez CJ, Russell SR, Wang M, Munson JM, Myers KM, Miller KS, Abramowitch SD, De Vita R. Pregnancy-induced remodeling of the murine reproductive tract: a longitudinal in vivo magnetic resonance imaging study. Sci Rep 2024; 14:586. [PMID: 38182631 PMCID: PMC10770079 DOI: 10.1038/s41598-023-50437-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 12/20/2023] [Indexed: 01/07/2024] Open
Abstract
Mammalian pregnancy requires gradual yet extreme remodeling of the reproductive organs to support the growth of the embryos and their birth. After delivery, the reproductive organs return to their non-pregnant state. As pregnancy has traditionally been understudied, there are many unknowns pertaining to the mechanisms behind this remarkable remodeling and repair process which, when not successful, can lead to pregnancy-related complications such as maternal trauma, pre-term birth, and pelvic floor disorders. This study presents the first longitudinal imaging data that focuses on revealing anatomical alterations of the vagina, cervix, and uterine horns during pregnancy and postpartum using the mouse model. By utilizing advanced magnetic resonance imaging (MRI) technology, T1-weighted and T2-weighted images of the reproductive organs of three mice in their in vivo environment were collected at five time points: non-pregnant, mid-pregnant (gestation day: 9-10), late pregnant (gestation day: 16-17), postpartum (24-72 h after delivery) and three weeks postpartum. Measurements of the vagina, cervix, and uterine horns were taken by analyzing MRI segmentations of these organs. The cross-sectional diameter, length, and volume of the vagina increased in late pregnancy and then returned to non-pregnant values three weeks after delivery. The cross-sectional diameter of the cervix decreased at mid-pregnancy before increasing in late pregnancy. The volume of the cervix peaked at late pregnancy before shortening by 24-72 h postpartum. As expected, the uterus increased in cross-sectional diameter, length, and volume during pregnancy. The uterine horns decreased in size postpartum, ultimately returning to their average non-pregnant size three weeks postpartum. The newly developed methods for acquiring longitudinal in vivo MRI scans of the murine reproductive system can be extended to future studies that evaluate functional and morphological alterations of this system due to pathologies, interventions, and treatments.
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Affiliation(s)
- Aileen C Suarez
- STRETCH Lab, Department of Biomedical Engineering and Mechanics, Virginia Tech, 325 Stanger Street, Blacksburg, VA, 24061, USA
| | - Clara J Gimenez
- STRETCH Lab, Department of Biomedical Engineering and Mechanics, Virginia Tech, 325 Stanger Street, Blacksburg, VA, 24061, USA
| | - Serena R Russell
- Department of Mechanical Engineering, Columbia University, 234 S W. Mudd, New York, NY, 10027, USA
| | - Maosen Wang
- Fralin Biomedical Research Institute, Virginia Tech, 4 Riverside Circle,, Roanoke, VA, 24016, USA
| | - Jennifer M Munson
- Fralin Biomedical Research Institute, Virginia Tech, 4 Riverside Circle,, Roanoke, VA, 24016, USA
| | - Kristin M Myers
- Department of Mechanical Engineering, Columbia University, 234 S W. Mudd, New York, NY, 10027, USA
| | - Kristin S Miller
- Department of Mechanical Engineering, The University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080, USA
| | - Steven D Abramowitch
- Department of Bioengineering, University of Pittsburgh, 3700 O'Hara Street, Pittsburgh, PA, 15261, USA
| | - Raffaella De Vita
- STRETCH Lab, Department of Biomedical Engineering and Mechanics, Virginia Tech, 325 Stanger Street, Blacksburg, VA, 24061, USA.
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Clark-Patterson GL, Buchanan LM, Ogola BO, Florian-Rodriguez M, Lindsey SH, De Vita R, Miller KS. Smooth muscle contribution to vaginal viscoelastic response. J Mech Behav Biomed Mater 2023; 140:105702. [PMID: 36764168 DOI: 10.1016/j.jmbbm.2023.105702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 01/22/2023] [Accepted: 02/01/2023] [Indexed: 02/05/2023]
Abstract
Smooth muscle cells contribute to the mechanical function of various soft tissues, however, their contribution to the viscoelastic response when subjected to multiaxial loading remains unknown. The vagina is a fibromuscular viscoelastic organ that is exposed to prolonged and increased pressures with daily activities and physiologic processes such as vaginal birth. The vagina changes in geometry over time under prolonged pressure, known as creep. Vaginal smooth muscle cells may contribute to creep. This may be critical for the function of vaginal and other soft tissues that experience fluctuations in their biomechanical environment. Therefore, the objective of this study was to develop methods to evaluate the contribution of smooth muscle to vaginal creep under multiaxial loading using extension - inflation tests. The vaginas from wildtype mice (C57BL/6 × 129SvEv; 3-6 months; n = 10) were stimulated with various concentrations of potassium chloride then subjected to the measured in vivo pressure (7 mmHg) for 100 s. In a different cohort of mice (n = 5), the vagina was stimulated with a single concentration of potassium chloride then subjected to 5 and 15 mmHg. A laser micrometer measured vaginal outer diameter in real-time. Immunofluorescence evaluated the expression of alpha-smooth muscle actin and myosin heavy chain in the vaginal muscularis (n = 6). When smooth muscle contraction was activated, vaginal creep behavior increased compared to the relaxed state. However, increased pressure decreased the active creep response. This study demonstrated that extension - inflation protocols can be used to evaluate smooth muscle contribution to the viscoelastic response of tubular soft tissues.
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Affiliation(s)
| | - Lily M Buchanan
- University of Texas at Dallas, Department of Bioengineering, 800 W. Campbell Road, Richardson, TX, 75080, USA.
| | - Benard O Ogola
- Augusta University, Vascular Biology Center, Medical College of Georgia at Augusta University, 1460 Laney Walker Blvd, Augusta, GA, 30912, USA.
| | - Maria Florian-Rodriguez
- University of Texas Southwestern Medical Center, Department of Obstetrics and Gynecology, Division of Female Pelvic Medicine and Reconstructive Surgery and Cecil H and Ida Green Center for Reproductive Biological Sciences, 5323 Harry Hines Boulevard, Dallas, TX, 75390-9032, USA.
| | - Sarah H Lindsey
- Tulane University School of Medicine, Department of Pharmacology, 1430 Tulane Ave, New Orleans, LA, 70112, USA.
| | - Raffaella De Vita
- Virginia Tech,Department of Biomedical Engineering and Mechanics, 330 A Kelly Hall, 325 Stanger St, Blacksburg, VA, 24061, USA.
| | - Kristin S Miller
- Tulane University, Department of Biomedical Engineering, 6823 St Charles Ave, New Orleans, LA, 70118, USA; University of Texas at Dallas, Department of Bioengineering, 800 W. Campbell Road, Richardson, TX, 75080, USA.
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Abstract
Despite their evolutionary and biomedical importance, studies of the morphology and function of female genitalia have continued to lag behind those of male genitalia. While studying female genitalia can be difficult because of their soft, deformable and internal nature, recent advances in imaging, geometric analyses of shape and mechanical testing have been made, allowing for a much greater understanding of the incredible diversity of form and function of female genitalia. Here we summarize some of these methods, as well as discuss some big questions in the field that are beginning to be examined now, and will continue to benefit from further work, especially a comparative approach. Topics of further research include examination of the morphology of female genitalia in situ, in-depth anatomical work in many more species, studies of the interplay between natural and sexual selection in influencing features of vaginal morphology, how these diverse functions influence the mechanical properties of tissues, and studies of clitoris morphology and function across amniotes. Many other research topics related to female genitalia remain largely unexplored, and we hope that the papers in this issue will continue to inspire further research on female genitalia.
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Affiliation(s)
- Patricia L R Brennan
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA 01075, USA
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