Biomechanical properties of prolapsed vaginal tissue in pre- and postmenopausal women

The Effect of Menopause on Vaginal Tissue Mechanics: A Brief Review

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.

Promoting cell proliferation and collagen production with ascorbic acid 2-phosphate-releasing poly(l-lactide-co-ε-caprolactone) membranes for treating pelvic organ prolapse

Pelvic organ prolapse (POP) afflicts millions of women globally. In POP, the weakened support of the pelvic floor results in the descent of pelvic organs into the vagina, causing a feeling of bulging, problems in urination, defaecation and/or sexual function. However, the existing surgical repair methods for relapsed POP remain insufficient, highlighting the urgent need for more effective alternatives. Collagen is an essential component in pelvic floor tissues, providing structural support, and its production is controlled by ascorbic acid. Therefore, we investigated novel ascorbic acid 2-phosphate (A2P)-releasing poly(l-lactide-co-ε-caprolactone) (PLCLA2P) membranes in vitro to promote cell proliferation and extracellular matrix protein production to strengthen the natural support of the pelvic fascia for POP applications. We analysed the mechanical properties and the impact of PLCLA2P on cellular responses through cell culture analysis using human vaginal fibroblasts (hVFs) and human adipose-derived stem/stromal cells (hASCs) compared to PLCL. In addition, the A2P release from PLCLA2P membranes was assessed in vitro. The PLCLA2P demonstrated slightly lower tensile strength (2.2 ± 0.4 MPa) compared to PLCL (3.7 ± 0.6 MPa) for the first 4 weeks in vitro. The A2P was most rapidly released during the first 48 h of in vitro incubation. Our findings demonstrated significantly increased proliferation and collagen production of both hVFs and hASCs on A2P-releasing PLCLA2P compared to PLCL. In addition, extracellular collagen Type I fibres were detected in hVFs, suggesting enhanced collagen maturation on PLCLA2P. Moreover, increased extracellular matrix protein expression was detected on PLCLA2P in both hVFs and hASCs compared to plain PLCL. In conclusion, these findings highlight the potential of PLCLA2P as a promising candidate for promoting tissue regeneration in applications aimed for POP tissue engineering applications.

Roles and mechanisms of biomechanical-biochemical coupling in pelvic organ prolapse

Pelvic organ prolapse (POP) is a significant contributor to hysterectomy among middle-aged and elderly women. However, there are challenges in terms of dedicated pharmaceutical solutions and targeted interventions for POP. The primary characteristics of POP include compromised mechanical properties of uterine ligaments and dysfunction within the vaginal support structure, often resulting from delivery-related injuries. Fibroblasts secrete extracellular matrix, which, along with the cytoskeleton, forms the structural foundation that ensures proper biomechanical function of the fascial system. This system is crucial for maintaining the anatomical position of each pelvic floor organ. By systematically exploring the roles and mechanisms of biomechanical-biochemical transformations in POP, we can understand the impact of forces on the injury and repair of these organs. A comprehensive analysis of the literature revealed that the extracellular matrix produced by fibroblasts, as well as their cytoskeleton, undergoes alterations in patient tissues and cellular models of POP. Additionally, various signaling pathways, including TGF-β1/Smad, Gpx1, PI3K/AKT, p38/MAPK, and Nr4a1, are implicated in the biomechanical-biochemical interplay of fibroblasts. This systematic review of the biomechanical-biochemical interplay in fibroblasts in POP not only enhances our understanding of its underlying causes but also establishes a theoretical foundation for future clinical interventions.

Remodeling of murine vaginal smooth muscle function with reproductive age and elastic fiber disruption

Advanced maternal age during pregnancy is associated with increased risk of vaginal tearing during delivery and maladaptive postpartum healing. Although the underlying mechanisms of age-related vaginal injuries are not fully elucidated, changes in vaginal microstructure may contribute. Smooth muscle cells promote the contractile nature of the vagina and contribute to pelvic floor stability. While menopause is associated with decreased vaginal smooth muscle content, whether contractile changes occur before the onset of menopause remains unknown. Therefore, the first objective of this study was to quantify the active mechanical behavior of the murine vagina with age. Further, aging is associated with decreased vaginal elastin content. As such, the second objective was to determine if elastic fiber disruption alters vaginal contractility. Vaginal samples from mice aged 2-14 months were used in maximum contractility experiments and biaxial extension-inflation protocols. To evaluate the role of elastic fibers with age, half of the vaginal samples were randomly allocated to enzymatic elastic fiber disruption. Contractile potential decreased and vaginal material stiffness increased with age. These age-related changes in smooth muscle function may be due, in part, to changes in microstructural composition or contractile gene expression. Furthermore, elastic fiber disruption had a diminished effect on smooth muscle contractility in older mice. This suggests a decreased functional role of elastic fibers with age. Quantifying the age-dependent mechanical contribution of smooth muscle cells and elastic fibers to vaginal properties provides a first step towards better understanding how age-related changes in vaginal structure may contribute to tissue integrity and healing. STATEMENT OF SIGNIFICANCE: Advanced maternal age at the time of pregnancy is linked to increased risks of vaginal tearing during delivery, postpartum hemorrhaging, and the development of pelvic floor disorders. While the underlying causes of increased vaginal injuries with age and associated pathologies remain unclear, changes in vaginal microstructure, such as elastic fibers and smooth muscle cells, may contribute. Menopause is associated with fragmented elastic fibers and decreased smooth muscle content; however, how reproductive aging affects changes in the vaginal composition and the mechanical properties remains unknown. Quantifying the mechanical contribution of smooth muscle cells and elastic fibers to vaginal properties with age will advance understanding of the potential structural causes of age-related changes to tissue integrity and healing.

Risk factors for 5-year complications after midurethral sling surgery for stress urinary incontinence: a retrospective cohort study from Taiwan

Midurethral sling surgery is the current gold standard worldwide for stress urinary incontinence (SUI) surgery, with over 90% of surgeons worldwide using the midurethral sling for SUI between 2008 and 2018. However, concerns surround mesh-related adverse events associated with the midurethral sling. The decision to use the midurethral sling for surgical treatment has become a challenging one for clinicians, surgeons and patients. We sought to determine the factors for 5-year complications after midurethral sling surgery, to improve the clinical decision-making process. Records were reviewed from a total of 1961 female patients who underwent their first midurethral sling surgery for SUI between 2003 and 2018 at a single teaching hospital in Taiwan. A multivariable Cox proportional hazard model calculated the hazard ratios of risk factors for surgical complications, after adjusting for confounders. Surgical complications (i.e., secondary surgery and urinary retention) occurred in 93 (4.7%) patients within 5 years following the index operations. These patients were more likely to be older, to have a history of menopausal syndrome within 1 year prior to the index operation, a medication history of oral antidiabetic drug use, hormone replacement therapy (HRT), slower average flow rate, and longer voiding time compared with patients without surgical complications. In the multivariate analysis, HRT (adjusted hazard ratio, 1.787; 95% confidence interval, 1.011-3.158, p = 0.04) was significantly associated with surgical complications at 5 years, after adjusting for age, gender, diabetes, menopause syndrome, average flow rate, and sling type. Our findings suggest that a medication history of HRT may be a risk factor associated with surgical complications, especially urinary retention, at 5 years in women undergoing midurethral sling surgery for SUI.

Creation of a decellularized vaginal matrix from healthy human vaginal tissue for potential vagina reconstruction: experimental studies

BACKGROUND

When a disorder causes the absence of a healthy, full-size vagina, various neovaginal creation methods are available. Sometimes dilation or stretching of the vaginal cavity is sufficient, but intestinal or dermal flap tissue is generally required. However, different inherent tissue properties cause complications. Therefore, a lost body part should be replaced with a similar material. The use of organ-specific acellular vaginal tissue carries great potential, as its similar architecture and matrix composition make it suitable for vaginal regeneration.

METHODS

The authors developed an optimized protocol for decellularization of healthy human vaginal tissue. Resected colpectomy tissue from 12 healthy transgender patients was used. Successful decellularization was confirmed by applying acellular criteria from in-vivo remodeling reports. Suitability as a tissue-mimicking scaffold for vaginal reconstruction was determined by visible structural features, biocompatibility during stretching, and the presence of visible collagen, elastin, laminin, and fibronectin.

RESULTS

Histological examination confirmed the preservation of structural features, and minimal cellular residue was seen during fluorescence microscopy, DNA and RNA quantification, and fragment length examination. Biomechanical testing showed decreased peak load (55%, P <0.05), strain at rupture (23%, P <0.01), and ultimate tensile stress (55%, P <0.05) after decellularization, while the elastic modulus (68%) did not decrease significantly. Fluorescence microscopy revealed preserved Fibronectin-I/II/III and Laminin-I/II, while Collagen-I and Ficolin-2B were decreased but mostly retained.

CONCLUSIONS

The absence of cellular residue, moderately altered biomechanical extracellular matrix properties, and mostly preserved structural proteins appear to make our decellularized human vaginal matrix a suitable tissue-mimicking scaffold for vagina transplantation when tissue survival through vascularization and innervation are accomplished in the future.

Vaginal reconstruction with a double-sided biomembrane-a preclinical experimental study on large animals

Tissue engineering techniques bring the promise of vaginal reconstruction with low invasiveness and fewer complications. However, existing biomaterial scaffolds remain limited in efficient vaginal recovery, focusing only on regenerating an epithelial layer, but muscle layers are missing or abnormal. The lack of a multi-tissue hierarchical structure in the reconstructed vagina leads to shrinking, stenosis, and fibrosis. Here, an acellular matrix named a double-sided biomembrane (DBM) is demonstrated for vaginal recovery. The regeneration of epithelial and muscle layers is achieved simultaneously since the smooth side of the DBM is helpful for guiding epithelial cell growth, while its loose and porous side guides muscle cell growth. In addition, the DBM demonstrates excellent mechanical properties similar to vaginal tissue, and hydrophilicity. Therefore, neovaginas were observed in the fourth and twelfth weeks after DBMs were transplanted to repair full-thickness vaginal defects (4 cm) that we established in large animals. The DBMs can effectively promote rapid epithelialization, the formation of large muscle bundles, higher rates of angiogenesis, and the restoration of physiological function in a neovagina. That is, the injured vagina achieves nearly complete recovery in anatomy and function, similar to a normal vagina. These preclinical results indicate that the DBM has prospects for vaginal injury repair.

A novel 3D printed type II silk fibroin/polycaprolactone mesh for the treatment of pelvic organ prolapse

Pelvic organ prolapse (POP) is one of the common diseases in middle-aged and elderly women, caused by weakened pelvic floor muscle ligament tissue support. Pelvic floor reconstruction with mesh implantation has been proven to be an effective treatment for POP. However, traditional non-degradable and inflexible pelvic floor implantation meshes have been associated with pain, vaginal infections, and the need for additional surgeries. In this study, novel meshes with pre-designed structures were fabricated with solution-based electrohydrodynamic printing (EHDP) technology, using a series of polycaprolactone/silk fibroin composites as bioinks. The PCL/SF mesh mechanical performances were particularly enhanced with the addition of silk II, leading it to obtain higher adaptability with soft tissue repair. The mesh containing SF showed more robust degradation performance in the in vitro degradation assay. Furthermore, biocompatibility tests conducted on mouse embryonic fibroblasts (NIH/3T3) revealed enhanced cell affinity. Finally, the biocompatibility and tissue repair properties of PCL/SF mesh were verified through the implantation of meshes in the muscle defect site of mice. The results demonstrated that the 3D printed PCL/SF mesh prepared by EHDP exhibits superior mechanical properties, biocompatibility, biodegradability, as well as ligament and muscle fiber repair ability. The novel implantable meshes are promising for curing POP.

Deformation and Durability of Soft Three-Dimensional-Printed Polycarbonate Urethane Porous Membranes for Potential Use in Pelvic Organ Prolapse

Pelvic organ prolapse (POP) is the herniation of the pelvic organs into the vaginal space, resulting in the feeling of a bulge and organ dysfunction. Treatment of POP often involves repositioning the organs using a polypropylene mesh, which has recently been found to have relatively high rates of complications. Complications have been shown to be related to stiffness mismatches between the vagina and polypropylene, and unstable knit patterns resulting in mesh deformations with mechanical loading. To overcome these limitations, we have three-dimensional (3D)-printed a porous, monofilament membrane composed of relatively soft polycarbonate-urethane (PCU) with a stable geometry. PCU was chosen for its tunable properties as it is comprised of both hard and soft segments. The bulk mechanical properties of PCU were first characterized by testing dogbone samples, demonstrating the dependence of PCU mechanical properties on its measurement environment and the effect of print pathing. The pore dimensions and load-relative elongation response of the 3D-printed PCU membranes under monotonic tensile loading were then characterized. Finally, a fatigue study was performed on the 3D-printed membrane to evaluate durability, showing a similar fatigue resistance with a commercial synthetic mesh and hence its potential as a replacement.

Biomechanically Compliant Gynecologic Training Simulator

INTRODUCTION

Pap smear training is commonly conducted using simulators before practicing with humans. Unfortunately, existing simulators do not well simulate the biomechanical properties of pelvic tissues, and this may negatively impact the training outcome. In this study, we used finite element analysis (FEA) to identify a material that most accurately simulates pelvic tissues in terms of biomechanical properties for fabricating gynecologic training simulators. The selected material was then used to fabricate a vagina and cervix model using a hybrid technique of fused deposition modeling and molding to qualitatively confirm the structural integrity of the simulator.

METHODS

The vagina and cervix were reconstructed in a 3-dimensional feature according to geometrical parameters reported in the literature. The biomechanical compliance of the simulators was investigated by comparing 5 materials-RTV615, Dragon Skin 10, Dragon Skin 30, Dragon Skin FX-Pro, and Ecoflex 00-30-and a pelvic tissue model (control) using 2 FEA modules. The structural mechanics module simulated the insertion and opening of a vaginal speculum, and the (1) horizontal opening of the vagina and peak von Mises stress at the anterior and (2) posterior walls of the vagina were obtained. The explicit dynamics module estimated (1) the fracture stress during punch biopsies and (2) maximum perpendicular deformation of the cervix before break. The most biomechanically compliant material was subsequently used to fabricate the simulator using the hybrid technique.

RESULTS

From the FEA, the horizontal opening of the vagina, peak von Mises stress at the anterior wall of the vagina, peak von Mises stress at the posterior wall of the vagina fracture stress, and maximum perpendicular deformation of the cervix before break were obtained; the results of Dragon Skin 10 and the control were most similar. Therefore, the simulator was fabricated using the material. A qualitative evaluation of the simulator by the naked eye verified its structural integrity.

CONCLUSIONS

Of the materials studied, the FEA results showed that Dragon Skin 10 was the most accurate material for simulating pelvic tissues in terms of the biomechanical properties in a gynecologic training simulator. The simulator was also successfully fabricated using the hybrid technique. Further studies may also involve experimental testing to support the simulation results.

Electrospun nanofiber mesh with connective tissue growth factor and mesenchymal stem cells for pelvic floor repair: Long-term study

Pelvic organ prolapse (POP) affects many women, with an estimated lifetime risk of surgical intervention of 18.7%. There is a need for alternative approaches as the use of synthetic nondegradable mesh was stopped due to severe adverse events, and as current methods for pelvic floor repair have high POP recurrence rates. Thus, we hypothesized that electrospun degradable meshes with stem cells and growth factor were safe and durable for the long term in elderly rats. In an abdominal repair model, electrospun polycaprolactone (PCL) meshes coated with connective tissue growth factor (CTGF)/PEG-fibrinogen (PF) and rat mesenchymal stem cells were implanted in elderly female rats and removed after in average 53 weeks (53-week group). Collagen amount and production were quantified by qPCR and Western blotting. Moreover, histological appearance and biomechanical properties were evaluated. Results were compared with previous results of young rats with identical mesh implanted for 24 weeks (24-week group). The 53-week group differed from the 24-week group in terms of (1) reduced collagen III, (2) strong reduction in foreign body response, and (3) altered histological appearance. We found comparable biomechanical properties, aside from higher, not significant, mean tissue stiffness in the 53-week group. Lastly, we identified mesh components 53 weeks after implantation. This study provides new insights into future POP repair in postmenopausal women by showing how CTGF/PF-coated electrospun PCL meshes with stem cells exhibit sufficient support, biocompatibility, and no mesh-related complications long term in an abdominal repair model in elderly rats.

Tissue Engineering Neovagina for Vaginoplasty in Mayer-Rokitansky-Küster-Hauser Syndrome and Gender Dysphoria Patients: A Systematic Review

Background: Vaginoplasty is a surgical solution to multiple disorders, including Mayer-Rokitansky-Küster-Hauser syndrome and male-to-female gender dysphoria. Using nonvaginal tissues for these reconstructions is associated with many complications, and autologous vaginal tissue may not be sufficient. The potential of tissue engineering for vaginoplasty was studied through a systematic bibliography search. Cell types, biomaterials, and signaling factors were analyzed by investigating advantages, disadvantages, complications, and research quantity. Search Methods: A systematic search was performed in Medline, EMBASE, Web of Science, and Scopus until March 8, 2022. Term combinations for tissue engineering, guided tissue regeneration, regenerative medicine, and tissue scaffold were applied, together with vaginoplasty and neovagina. The snowball method was performed on references and a Google Scholar search on the first 200 hits. Original research articles on human and/or animal subjects that met the inclusion (reconstruction of vaginal tissue and tissue engineering method) and no exclusion criteria (not available as full text; written in foreign language; nonoriginal study article; genital surgery other than neovaginal reconstruction; and vaginal reconstruction with autologous or allogenic tissue without tissue engineering or scaffold) were assessed. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist, the Newcastle-Ottawa Scale, and the Gold Standard Publication Checklist were used to evaluate article quality and bias. Outcomes: A total of 31 out of 1569 articles were included. Data extraction was based on cell origin and type, biomaterial nature and composition, host species, number of hosts and controls, neovaginal size, replacement fraction, and signaling factors. An overview of used tissue engineering methods for neovaginal formation was created, showing high variance of cell types, biomaterials, and signaling factors and the same topics were rarely covered multiple times. Autologous vaginal cells and extracellular matrix-based biomaterials showed preferential properties, and stem cells carry potential. However, quality confirmation of orthotopic cell-seeded acellular vaginal matrix by clinical trials is needed as well as exploration of signaling factors for vaginoplasty. Impact statement General article quality was weak to sufficient due to unreported cofounders and incomplete animal study descriptions. Article quality and heterogenicity made identification of optimal cell types, biomaterials, or signaling factors unreliable. However, trends showed that autologous cells prevent complications and compatibility issues such as healthy cell destruction, whereas stem cells prevent cross talk (interference of signaling pathways by signals from other cell types) and rejection (but need confirmation testing beyond animal trials). Natural (orthotopic) extracellular matrix biomaterials have great preferential properties that encourage future research, and signaling factors for vascularization are important for tissue engineering of full-sized neovagina.

Biaxial Murine Vaginal Remodeling With Reproductive Aging

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.

Establishment of Rat Model of Female Genital Sexual Arousal Disorder

Introduction

Female Genital Sexual Arousal Disorder (FGSAD) seriously affects women's quality of life and Sexual life, but it still lacks ideal FGSAD animal models for further study.

Aim

To establish a specific model of female genital sexual arousal disorder and explore the mechanisms resulting in FGSAD.

Methods

After delivery, female rats were guided by expansions of the vagina and ovariectomy (VD+OVX, n = 10); in VD group female rats were just extended by the vagina (VD, n = 10), in OVX group female rats were treated with ovariectomy (OVX, n = 10);the remaining had 1 longitudinal incision as sham group(n = 10).

Outcomes

Vaginal dilatation combined with ovariectomy in rats may reflect female genital sexual arousal disorder with high reproducibility and stability.

Results

Vaginal tissue of female rats in OVX group and VD+OVX group showed an increase in blood flow, decrease in muscle content compared to the sham group. The proportion of collagen fiber I/III decreased and the elastic fiber showed significant rupture and fragmentation; Structural reticular integrity was also significantly separated and broken from the muscle fibers. However, there was no significant difference in vaginal blood flow, fibers and vascular between VD group and Sham group. The damage of vaginal tissue in VD+OVX group was more significant than that in OVX and VD groups.

Clinical Translation

We have constructed a specific animal model that can provide clinical insights into the mechanism of FGSAD and serves as a good avenue for further research of its treatment.

Strengths and Limitations

Vaginal dilatation combined with ovariectomy in rats is a specific animal model with high reproducibility and stability, but we do acknowledge the shortcomings and limitation present in our study. Since genital arousal disorder has many different etiologies that impact the vagina, the clitoris and surrounding tissues, there is no “gold standard” model that different models attempt to investigate different etiologies.

Conclusion

The female genital sexual arousal disorder model established by vaginal dilatation combined with ovariectomy is a novel rat model with simple induction conditions, which pathogenic mechanism of female genital sexual arousal disorders maybe connected with the change of VEGF and MMP-9 in vaginal fibromuscular system and microvascular.

Li G, Yu P, Hu Y, et al. Establishment of Rat Model of Female Genital Sexual Arousal Disorder. Sex Med 2022;10:100530.

Development and in vitro investigation of a biodegradable mesh for the treatment of stress urinary incontinence

Introduction and hypothesis

The use of polypropylene (PP) mesh for stress urinary incontinence (SUI) surgery has declined because of safety concerns. The aim of this study is to evaluate a biodegradable polycaprolactone (PCL) mesh and a PCL composite mesh tissue engineered with human uterine fibroblasts (HUFs) for SUI surgery by comparing mechanical properties and in vitro biocompatibility to commercially available PP and porcine dermis (PD).

Methods

The mechanical properties of four scaffold materials were evaluated: PCL, PCL-collagen-hyaluronic acid composite, acellular porcine dermal collagen (PD) (Pelvicol™) and polypropylene (Gynecare TVT™ Exact®). HUFs were seeded on separate scaffolds. After 7 and 14 days scaffolds were assessed for metabolic activity and cell proliferation using Alamar Blue, Live/Dead and PicoGreen assays. Soluble collagen production was evaluated using a Sircol assay.

Results

PCL and the composite scaffold reached ultimate tensile strength (UTS) values closest to healthy pelvic floor tissue (PCL = 1.19 MPa; composite = 1.13 MPa; pelvic floor = 0.79 MPa; Lei et al. Int Urogynecol J Pelvic Floor Dysfunct. 18(6):603-7, 2007). Cells on PCL showed significantly greater cell viability than PP at day 7 (p < 0.0001). At D14 the composite scaffold showed significantly greater cell viability than PP (p = 0.0006). PCL was the best performing scaffold for soluble collagen production at day 14 (106.1 μg versus 13.04 μg for PP, p = 0.0173).

Conclusions

We have designed a biodegradable PCL mesh and a composite mesh which demonstrate better biocompatibility than PP and mechanical properties closer to that of healthy pelvic floor tissue. This in vitro study provides promising evidence that these two implants should be evaluated in animal and human trials.

A soft elastomer alternative to polypropylene for pelvic organ prolapse repair: a preliminary study

INTRODUCTION AND HYPOTHESIS

We compared the impact of a mesh manufactured from the soft elastomer polydimethylsiloxane (PDMS) to that of a widely used lightweight polypropylene (PP) mesh. To achieve a similar overall device stiffness between meshes, the PDMS mesh was made with more material and therefore was heavier and less porous. We hypothesized that the soft polymer PDMS mesh, despite having more material, would have a similar impact on the vagina as the PP mesh.

METHODS

PDMS and PP meshes were implanted onto the vaginas of 20 rabbits via colpopexy. Ten rabbits served as sham. At 12 weeks, mesh-vagina complexes were explanted and assessed for contractile function, histomorphology, total collagen, and glycosaminoglycan content. Outcome measures were compared using one-way ANOVA and Kruskal-Wallis testing with appropriate post-hoc testing.

RESULTS

Relative to sham, vaginal contractility was reduced following the implantation of PP (p = 0.035) but not the softer PDMS (p = 0.495). PP had an overall greater negative impact on total collagen and glycosaminoglycan content, decreasing by 53% (p < 0.001) and 54% (p < 0.001) compared to reductions of 35% (p = 0.004 and p < 0.001) with PDMS. However, there were no significant differences in the contractility, collagen fiber thickness, total collagen, and glycosaminoglycan content between the two meshes.

CONCLUSIONS

Despite having a substantially higher weight, PDMS had a similar impact on the vagina compared to a low-weight PP mesh, implicating soft polymers as potential alternatives to PP. The notion that heavyweight meshes are associated with a worse host response is not applicable when comparing across materials.

Melt-extrusion 3D printing of resorbable levofloxacin-loaded meshes: Emerging strategy for urogynaecological applications

Current surgical strategies for the treatment of pelvic floor dysfunctions involve the placement of a polypropylene mesh into the pelvic cavity. However, polypropylene meshes have proven to have inadequate mechanical properties and have been associated to the arising of severe complications, such as infections. Furthermore, currently employed manufacturing strategies are unable to produce compliant and customisable devices. In this work, polycaprolactone has been used to produce resorbable levofloxacin-loaded meshes in two different designs (90° and 45°) via melt-extrusion 3D printing. Drug-loaded meshes were produced using a levofloxacin concentration of 0.5% w/w. Drug loaded meshes were successfully produced with highly reproducible mechanical and physico-chemical properties. Tensile test results showed that drug-loaded 45° meshes possessed a mechanical behaviour close to that of the vaginal tissue (E ≃ 8.32 ± 1.85 MPa), even after 4 weeks of accelerated degradation. Meshes released 80% of the loaded levofloxacin in the first 3 days and were capable of producing an inhibitory effect against S. Aureus and E. coli bacterial strains with an inhibition zone equal to 12.8 ± 0.45 mm and 15.8 ± 0.45 mm respectively. Thus, the strategy adopted in this work holds great promise for the manufacturing of custom-made surgical meshes with antibacterial properties.

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

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.

Mechanical properties of whole-body soft human tissues: a review

The mechanical properties of soft tissues play a key role in studying human injuries and their mitigation strategies. While such properties are indispensable for computational modelling of biological systems, they serve as important references in loading and failure experiments, and also for the development of tissue simulants. To date, experimental studies have measured the mechanical properties of peripheral tissues (e.g. skin)in-vivoand limited internal tissuesex-vivoin cadavers (e.g. brain and the heart). The lack of knowledge on a majority of human tissues inhibit their study for applications ranging from surgical planning, ballistic testing, implantable medical device development, and the assessment of traumatic injuries. The purpose of this work is to overcome such challenges through an extensive review of the literature reporting the mechanical properties of whole-body soft tissues from head to toe. Specifically, the available linear mechanical properties of all human tissues were compiled. Non-linear biomechanical models were also introduced, and the soft human tissues characterized using such models were summarized. The literature gaps identified from this work will help future biomechanical studies on soft human tissue characterization and the development of accurate medical models for the study and mitigation of injuries.

An anthropomorphic deformable phantom of the vaginal wall and cavity

Brachytherapy is a common treatment in cervical, uterine and vaginal cancer management. The technique is characterised by rapid developments in the fields of medical imaging, dosimetry planning and personalised medical device design. To reduce unnecessary burden on patients, assessments and training of these technologies should preferable be done using high-fidelity physical phantoms. In this study, anthropomorphic deformable phantoms of the vaginal wall and cavity were developed for image-guided adaptive brachytherapy, in which vaginal wall biomechanics were mimicked. Phantoms were produced from both silicone and polyvinyl alcohol materials. Material characterisations were performed with uniaxial tensile tests, via which Young's moduli and toughness were quantified. In addition, the contrast between adjacent phantom layers was quantified in magnetic resonance images. The results showed that stress-strain curves of the silicone phantoms were within the range of those found in healthy human vaginal wall tissues. Sample preconditioning had a large effect on Young's moduli, which ranged between 2.13 and 6.94 MPa in silicone. Toughness was a more robust and accurate metric for biomechanical matching, and ranged between 0.23 and 0.28 ·10⁶J·m^-3as a result of preconditioning. The polyvinyl alcohol phantoms were not stiff or tough enough, with a Young's modulus of 0.16 MPa and toughness of 0.02 ·10⁶J·m^-3. All materials used could be clearly delineated in magnetic resonance images, although the MRI sequence did affect layer contrast. In conclusion, we developed anthropomorphic deformable phantoms that mimic vaginal wall tissue and are well visible in magnetic resonance images. These phantoms will be used to evaluate the properties and to optimise the development and use of personalised brachytherapy applicators.

Biodegradable materials for surgical management of stress urinary incontinence: A narrative review

Stress urinary incontinence (SUI) was managed with techniques such as colposuspension, autologous fascia sling and urethral bulking agents. The introduction of the mid-urethral polypropylene (PP) sling in the 1990s led to a significant and rapid global change in SUI surgery. The synthetic non-degradable PP sling had superior results to traditional SUI procedures but its use has now declined due to significant complications such as pain and mesh erosion. These complications are attributed to its poor biocompatibility and integration into vaginal tissues. The efficacy of PP was extrapolated from studies on abdominal wall repair and it is now clear that integration of implanted materials in the pelvic floor differs from the abdominal wall. With PP prohibited in some jurisdictions, female patients with SUI have few management options. In the present review we summarise recent advances in SUI surgery and evaluate potential alternatives to PP slings with a particular focus on degradable materials. Allograft and xenograft materials demonstrate good biocompatibility but have yielded suboptimal cure rates. Tissue engineered synthetic degradable materials outperform unmodified synthetic degradable materials in terms of biomechanics and cell support. Synthetic tissue engineered degradable materials show promising results from in vitro studies and future research should focus on animal and human trials in this field.

Pelvic Organ Prolapse: A Review of In Vitro Testing of Pelvic Support Mechanisms

Background: Pelvic organ prolapse (POP) affects a significant portion of the female population, impacting quality of life and often requiring intervention. The exact cause of prolapse is unknown.

Methods: We review some of the current research that focuses on defining the elements involved in POP, with a focus on in vitro testing.

Results: Treatment for POP, ranging from physical therapy or pessary use to more invasive surgery, has varying success rates. This variation is, in part, because the pathophysiology of pelvic floor support—and thus dysfunction—is incompletely understood, particularly regarding the structural components and biomechanical properties of tissue. However, researchers are working to identify and quantify the structural and functional dysfunction that may lead to the development of this condition.

Conclusion: Given the limited understanding of prolapse development, more research is needed to quantify the microstructure of the pelvic organs and pelvic support structures, with and without prolapse. Identifying biomechanical properties in multiaxial configurations will improve our understanding of pelvic tissue support, as well as our ability to establish predictive models and improve clinical treatment strategies.

Tissue engineering in female pelvic floor reconstruction

Pelvic organ prolapse is a common and frequently occurring disease in middle-aged and elderly women. Mesh implantation is an ideal surgical treatment. The polypropylene mesh commonly used in clinical practice has good mechanical properties, but there are long-term complications. The application of tissue engineering technology in the treatment of pelvic organ prolapse disease can not only meet the mechanical requirements of pelvic floor support, but also be more biocompatible than traditional polypropylene mesh, and can promote tissue repair to a certain extent. In this paper, the progress of tissue engineering was summarized to understand the application of tissue engineering in the treatment of pelvic organ prolapse disease and will help in research.

The histological microstructure and in vitro mechanical properties of pregnant and postmenopausal ewe perineal body

OBJECTIVE

The mechanical properties and microstructure of the perineal body are important for the improvement of numerical models of pelvic organs. We determined the mechanical parameters and volume fractions of the ewe perineal body as an animal model.

METHODS

The 39 specimens of 13 pregnant swifter ewes delivering by cesarean section (aged 2 years, weight 61.2 ± 6.2 kg (mean ± standard deviation) and 24 specimens of 8 postmenopausal swifter ewes 150 days after surgical ovariectomy (aged 7 years, 58.6 ± 4.6 kg)) were loaded uniaxially to determine Young's moduli of elasticity in the small (E0) and large (E1) deformation regions, and ultimate stresses and strains. The 63 adjacent tissue samples were processed histologically to assess volume fractions of smooth and skeletal muscle, adipose cells, elastin, and type I collagen using a stereological point testing grid. We compared the structural and mechanical differences along the ewe perineal body, and between pregnant and postmenopausal groups.

RESULTS

The pregnant/postmenopausal perineal body was composed of smooth muscle (12/14%; median), skeletal muscle (12/16%), collagen (10/23%), elastin (8/7%), and adipose cells (6/6%). The E0 was 37/11 kPa (median), E1 was 0.97/1.04 MPa, ultimate stress was 0.55/0.59 MPa, and ultimate strain was 0.90/0.87 for pregnant/postmenopausal perineal body. The perineal body showed a structural and mechanical stability across the sites. The pregnant ewes had a higher amount of skeletal muscle, higher E0, and a less amount of collagen when compared with postmenopausal ewes.

CONCLUSIONS

The data can be used as input for models simulating vaginal delivery, pelvic floor prolapsed, or dysfunction.

Role of sex steroid hormones in pelvic organ prolapse

OBJECTIVE

Pelvic organ prolapse (POP) affects a significant percentage of women and contributes to major healthcare costs both in the United States and worldwide. This review examines the current understanding of the role of sex steroid hormones (estrogens, androgens, and progesterone) in POP in premenopausal, perimenopausal, and postmenopausal women.

METHODS

We reviewed the relevant studies on POP related to estrogens, androgens, and progesterone in both animal models and humans.

RESULTS

Estrogen has a profound influence on the synthesis and metabolism of pelvic connective tissues, and may have the ability to both prevent POP and improve prognosis if used therapeutically. There is limited research regarding the role of androgens and progesterone and their receptors in POP and results so far have been contradictory, warranting further study to determine whether changes in androgen and progesterone receptor expression are a cause or effect of POP.

CONCLUSIONS

Because of the role that estrogen plays in maintaining the integrity of pelvic floor connective tissues, we propose that rigorous and well-controlled studies are needed on the role of exogenous estrogen administration as a form of POP prevention. : Video Summary:http://links.lww.com/MENO/A583.

The histological microstructure and in vitro mechanical properties of the human female postmenopausal perineal body

OBJECTIVE

The perineal body connects muscles from the pelvic floor and is critical for support of the lower part of the vagina and proper function of the anal canal. We determined mechanical parameters and volume fractions of main components of the human female postmenopausal perineal body.

METHODS

The specimens were taken from 15 fresh female cadavers (age 74 ± 10, mean ± standard deviation). Seventy-five specimens from five regions of the perineal body were processed histologically to assess volume fractions of tissue components using stereological point testing grid. Fifteen specimens taken from the midline region were loaded uniaxially with 6 mm/min velocity until tissue rupture to determine Young's modulus of elasticity, ultimate stresses, and strains.

RESULTS

The perineal body was composed of collagen (29%), adipose cells (27%), elastin (7%), smooth muscle (11%), and skeletal muscle (3%). The residual tissue (19%) constituted mostly peripheral nerves, lumina of blood vessels, fibroblasts, and fibrocytes. Young's modulus of elasticity at midline region was 18 kPa (median) at small and 232 kPa at large deformations, respectively. The ultimate stress was 172 kPa and the ultimate strain was 1.4.

CONCLUSIONS

We determined the structural and mechanical parameters of the perineal body. The resultant data could be used as input for models simulating pelvic floor prolapse or dysfunction.

YAP/TAZ are Activated by Mechanical and Hormonal Stimuli in Myometrium and Exhibit Increased Baseline Activation in Uterine Fibroids

Uterine fibroids (UFs) are benign myometrial neoplasms. The mechanical environment activates signaling through the Hippo pathway effectors Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding domain (TAZ) in other fibrotic disorders. Here, we assess the differences in YAP/TAZ responsiveness to signals in UF compared with myometrium (Myo). Matched samples of UF and Myo were collected. Atomic force microscopy (AFM) was used to determine in situ stiffness. Cells were plated sparsely on hydrogels or at confluence. Ten nanomolars of estradiol (E2) and 100 nM progesterone (P4) were used. Immunostaining for YAP/TAZ and extracellular matrix (ECM) proteins was performed. Cells were incubated with control or YAP1 (YAP)/WWTR1 (TAZ) small interfering RNA (siRNA). Real time qPCR was completed for connective tissue growth factor (CTGF). Cells were treated with verteporfin (a YAP inhibitor) or Y27632 (a ROCK inhibitor), and ECM gene expression was analyzed. Paired t test and Wilcoxon sign-rank test were used. AFM-measured tissue stiffness and YAP/TAZ nuclear localization in situ and in confluent cells were higher in UF compared with Myo (p < 0.05). Decreasing substrate stiffness reduced YAP/TAZ nuclear localization for both Myo and UF (p = 0.05). Stimulating cells with E2 or P4 increased YAP/TAZ nuclear localization, but only in Myo (p = 0.01). UFs had increased FN, COLI, and COLIII deposition. Following siRNA targeting, CTGF was found to be statistically decreased. Verteporfin treatment reduced cell survival and reduced FN deposition. Treatment with Y27632 demonstrated better cell tolerance and a reduction in ECM deposition. The mechanosensitive pathway may be linked to YAP/TAZ function and involved in transducing fibroid growth.

Managing female pelvic floor disorders: a medical device review and appraisal

Pelvic floor disorders (PFDs) will affect most women during their lifetime. Sequelae such as pelvic organ prolapse, stress urinary incontinence, chronic pain and dyspareunia significantly impact overall quality of life. Interventions to manage or eliminate symptoms from PFDs aim to restore support of the pelvic floor. Pessaries have been used to mechanically counteract PFDs for thousands of years, but do not offer a cure. By contrast, surgically implanted grafts or mesh offer patients a more permanent resolution but have been in wide use within the pelvis for less than 30 years. In this perspective review, we provide an overview of the main theories underpinning PFD pathogenesis and the animal models used to investigate it. We highlight the clinical outcomes of mesh and grafts before exploring studies performed to elucidate tissue level effects and bioengineering considerations. Considering recent turmoil surrounding transvaginal mesh, the role of pessaries, an impermanent method, is examined as a means to address patients with PFDs.

Tissue Composition and Biomechanical Property Changes in the Vaginal Wall of Ovariectomized Young Rats

Ideal animal models are needed to reflect the changes in the biochemical and biomechanical properties of the vagina that occur in pelvic organ prolapse (POP). In this study, we aimed to demonstrate the short and long-term effect of menopause on the biochemical and biomechanical properties of rat anterior vaginas. Here, Sprague-Dawley rats were bilaterally ovariectomized to induce menopause. Rats without ovariectomy served as the normal control group (n=12). The histology changes and the expression of collagen I, III, and a-SMA were assessed to indicate the biochemical changes in the vagina 2 weeks, 4 weeks, and 16 weeks after ovariectomy (n=6 for 2 and 4 weeks, n=12 for 16 weeks). Uniaxial biomechanical testing was conducted in the control group and ovariectomized rats 16 weeks after ovariectomy. Compared with the control group, the ovariectomy group showed a significant increase in the expression of collagen I 2 weeks after ovariectomy, while collagen III showed a declining trend. Two weeks after ovariectomy, the smooth muscle bundles began to become disorganized, and the fraction of smooth muscle in the nonvascular muscularis of the proximal vagina was significantly decreased (P<0.001). However, there was no difference in the expression of a-SMA in the distal vagina. Compared with the control group, the ovariectomy group had stiffer vaginas with a declining trend in the ultimate load 16 weeks after ovariectomy. In conclusion, surgically induced menopause had a significant short- and long-term impact on tissue composition and biomechanical properties of the rat vagina, which may lead to increased susceptibility to POP development.

Recent advances in pelvic floor repair

Stress urinary incontinence (SUI) and pelvic organ prolapse (POP) are conditions which result in significant physical, mental and social consequences for women worldwide. The high rates of recurrence reported with primary repair for POP led to the use of synthetic mesh to augment repairs in both primary and secondary cases following failed previous POP repair. The widely reported, unacceptably high rates of complications associated with the use of synthetic, transvaginal mesh in pelvic floor repair have severely limited the treatment options that surgeons can offer. This article summarises the recent advances in pelvic floor repair, such as improved quantification and modelling of the biomechanics of the pelvic floor and the developing technology within the field of tissue engineering for treatment of SUI/POP, including biomaterials and cell-based therapies. Finally, we will discuss the issues surrounding the commercial introduction of synthetic mesh for use within the pelvic floor and what lessons can be learned for the future as well as the current guidance surrounding treatment for SUI/POP.

Fabricated tropoelastin-silk yarns and woven textiles for diverse tissue engineering applications

Electrospun yarns offer substantial opportunities for the fabrication of elastic scaffolds for flexible tissue engineering applications. Currently available yarns are predominantly made of synthetic elastic materials. Thus scaffolds made from these yarns typically lack cell signaling cues. This can result in poor integration or even rejection on implantation, which drive demands for a new generation of yarns made from natural biologically compatible materials. Here, we present a new type of cell-attractive, highly twisted protein-based yarns made from blended tropoelastin and silk fibroin. These yarns combine physical and biological benefits by being rendered elastic and bioactive through the incorporation of tropoelastin and strengthened through the presence of silk fibroin. Remarkably, the process delivered multi-meter long yarns of tropoelastin-silk mixture that were conducive to fabrication of meshes on hand-made frames. The resulting hydrated meshes are elastic and cell interactive. Furthermore, subcutaneous implantation of the meshes in mice demonstrates their tolerance and persistence over 8 weeks. This combination of mechanical properties, biocompatibility and processability into diverse shapes and patterns underscores the value of these materials and platform technology for tissue engineering applications. STATEMENT OF SIGNIFICANCE: Synthetic yarns are used to fabricate textile materials for various applications such as surgical meshes for hernia repair and pelvic organ prolapse. However, synthetic materials lack the attractive biological and physical cues characteristic of extracellular matrix and there is a demand for materials that can minimize postoperative complications. To address this need, we made yarns from a combination of recombinant human tropoelastin and silk fibroin using a modified electrospinning approach that blended these proteins into functional yarns. Prior to this study, no protein-based yarns using tropoelastin were available for the fabrication of functional textile materials. Multimeter-long, uniform and highly twisted yarns based on these proteins were elastic and cell interactive and demonstrated processing to yield textile fabrics. By using these yarns to weave fabrics, we demonstrate that an elastic human matrix protein blend can deliver a versatile platform technology to make textiles that can be explored for efficacy in tissue repair.

Biomechanical properties of female dolphin reproductive tissue

Whales, dolphins, and porpoises have unusual vaginal folds of unknown function(s) that are hypothesized to play an important role in sexual selection. The potential function of vaginal folds was assessed by testing the mechanical properties of common bottlenose dolphin (Tursiops truncatus) reproductive tract tissues in 6 different regions and across age classes in post-mortem specimens. We assessed the regional (local) and overall effective elastic modulus of tissues using indentation and tensile tests, respectively. We explore the non-linear mechanical response of biological tissues, which are not often quantified. Indentation tests demonstrated that sexual maturity state, tissue region, force history, and force magnitude values significantly affected the measured effective elastic modulus. Tissue was stiffest in the vaginal fold region and overall stiffer in sexually immature compared to mature animals, likely reflecting biomechanical adaptations associated with copulation and parturition. Tensile tests showed that only tissue region significantly affected the effective modulus. Our data support the hypothesis that vaginal folds function as mechanical barriers to the penis and may provide females with mechanisms to reduce copulatory forces on other reproductive tissue. STATEMENT OF SIGNIFICANCE: Cetaceans have unusual folds of vaginal wall tissue that appear to evolve under sexual selection mechanisms and present physical barriers to the penis during copulation. We explore the biomaterial properties of vaginal fold tissue, how it varies from other reproductive tract tissues, and ontogenetic patterns. We demonstrate that vaginal folds can withstand higher mechanical forces and respond in a manner conducive to dissipating copulatory forces to other reproductive tissues. This study yields exciting insights on how female genital tissue may function during copulation, and is the first to do so in any vertebrate species. Additionally, we provide an example for testing biological tissues, non-linear properties, and materials with uneven surface structure and uneven thickness.

Characterizing the Biomechanical Properties of the Pubovisceralis Muscle Using a Genetic Algorithm and the Finite Element Method

To better understand the disorders in the pelvic cavity associated with the pelvic floor muscles (PFM) using computational models, it is fundamental to identify the biomechanical properties of these muscles. For this purpose, we implemented an optimization scheme, involving a genetic algorithm (GA) and an inverse finite element analysis (FEA), in order to estimate the material properties of the pubovisceralis muscle (PVM). The datasets of five women were included in this noninvasive analysis. The numerical models of the PVM were built from static axial magnetic resonance (MR) images, and the hyperplastic Mooney-Rivlin constitutive model was used. The material parameters obtained were compared with the ones established through a similar optimization scheme, using Powell's algorithm. To validate the values of the material parameters that characterize the passive behavior of the PVM, the displacements obtained via the numerical models with both methods were compared with dynamic MR images acquired during Valsalva maneuver. The material parameters (c1 and c2) were higher for the GA than for Powell's algorithm, but when comparing the magnitude of the displacements in millimeter of the PVM, there was only a 5% difference, and 4% for the principal logarithmic strain. The GA allowed estimating the in vivo biomechanical properties of the PVM of different subjects, requiring a lower number of simulations when compared to Powell's algorithm.

Anisotropy of the Passive and Active Rat Vagina Under Biaxial Loading

Pelvic organ prolapse, the descent of the pelvic organs from their normal anatomical position, is a common condition among women that is associated with mechanical alterations of the vaginal wall. In order to characterize the complex mechanical behavior of the vagina, we performed planar biaxial tests of vaginal specimens in both the passive (relaxed) and active (contracted) states. Specimens were isolated from virgin, female Long-Evans rats (n = 16) and simultaneously stretched along the longitudinal direction (LD) and circumferential direction (CD) of the vagina. Tissue contraction was induced by electric field stimulation (EFS) at incrementally increasing values of stretch and, subsequently, by KCl. On average, the vagina was stiffer in the CD than in the LD (p < 0.001). The mean maximum EFS-induced active stress was significantly higher in the CD than in the LD (p < 0.01). On the contrary, the mean KCl-induced active stress was lower in the CD than in the LD (p < 0.01). When comparing the mean maximum EFS-induced active stress to the mean KCl-induced active stress, no differences were found in the CD (p = 0.366) but, in the LD, the mean active stress was much higher in response to the KCl stimulation (p < 0.001). Collectively, these results suggest that the anisotropic behavior of the vaginal tissue is determined not only by collagen and smooth muscle fiber organization but also by the innervation.

Porous poly-l-lactide-co-ɛ-caprolactone scaffold: a novel biomaterial for vaginal tissue engineering

The surgical reconstruction of functional neovagina is challenging and susceptible to complications. Therefore, developing tissue engineering-based treatment methods for vaginal defects is important. Our aim was to develop and test a novel supercritical carbon dioxide foamed poly-l-lactide-co-ɛ-caprolactone (scPLCL) scaffold for vaginal reconstruction. The scaffolds were manufactured and characterized for porosity (65 ± 4%), pore size (350 ± 150 µm) and elastic modulus (2.8 ± 0.4 MPa). Vaginal epithelial (EC) and stromal cells (SC) were isolated, expanded and characterized with flow cytometry. Finally, cells were cultured with scPLCL scaffolds in separate and/or co-cultures. Their attachment, viability, proliferation and phenotype were analysed. Both cell types strongly expressed cell surface markers CD44, CD73 and CD166. Strong expression of CD326 was detected with ECs and CD90 and CD105 with SCs. Both ECs and SCs attached and maintained viability on scPLCL. Further, scPLCL supported the proliferation of especially ECs, which also maintained epithelial phenotype (cytokeratin expression) during 14-day assessment period. Interestingly, ECs expressed uroplakin (UP) Ia, UPIb and UPIII markers; further, UPIa and UPIII expression was significantly higher on ECs cultured on scPLCL than on cell culture plastic. In conclusion, the scPLCL is potential scaffold for vaginal tissue engineering and the results of this study further illustrate the excellent biocompatibility of PLCL.

Porous poly-l-lactide-co-ɛ-caprolactone scaffold: a novel biomaterial for vaginal tissue engineering

The surgical reconstruction of functional neovagina is challenging and susceptible to complications. Therefore, developing tissue engineering-based treatment methods for vaginal defects is important. Our aim was to develop and test a novel supercritical carbon dioxide foamed poly-l-lactide-co-ɛ-caprolactone (scPLCL) scaffold for vaginal reconstruction. The scaffolds were manufactured and characterized for porosity (65 ± 4%), pore size (350 ± 150 µm) and elastic modulus (2.8 ± 0.4 MPa). Vaginal epithelial (EC) and stromal cells (SC) were isolated, expanded and characterized with flow cytometry. Finally, cells were cultured with scPLCL scaffolds in separate and/or co-cultures. Their attachment, viability, proliferation and phenotype were analysed. Both cell types strongly expressed cell surface markers CD44, CD73 and CD166. Strong expression of CD326 was detected with ECs and CD90 and CD105 with SCs. Both ECs and SCs attached and maintained viability on scPLCL. Further, scPLCL supported the proliferation of especially ECs, which also maintained epithelial phenotype (cytokeratin expression) during 14-day assessment period. Interestingly, ECs expressed uroplakin (UP) Ia, UPIb and UPIII markers; further, UPIa and UPIII expression was significantly higher on ECs cultured on scPLCL than on cell culture plastic. In conclusion, the scPLCL is potential scaffold for vaginal tissue engineering and the results of this study further illustrate the excellent biocompatibility of PLCL.

BIOMECHANICAL CHARACTERIZATION OF NORMAL AND PROLAPSED VAGINAL TISSUE SURROGATES

In the recent years, poorly evaluated gynecological surgeries and urogynecological mesh implantations have been affecting millions of women in the US and across the globe. These failed surgeries could be mainly attributed to the nonavailability of vaginal tissues (due to ethical and biosafety issues), which does not allow any experimental testing of operation and mesh implantation techniques before an actual surgery. A surrogate which behaves biomechanically like the human vaginal tissue would be indispensable for simulating surgical suture of vaginal tissues in prolapse surgery, hysterectomy or surgery during traumatic child births (such as Cesarean). Also, vaginal tissue surrogates simulating the various prolapse conditions (such as vaginal tissue stiffening) would be very useful to evaluate tissue modifications due to prolapse, and also mesh and vaginal tissue interactions. In the current work, a low cost four-part silicone-based material was developed, which precisely simulates the linear and nonlinear mechanical behavior of the normal human vaginal tissue. Additionally, a range of four-part silicone-based novel materials were developed which precisely mimics the mechanical behavior of stiffened vaginal tissues at different degrees of prolapse. The linear and nonlinear mechanical behavior of all such novel materials were characterized using elastic and hyperelastic formulations. Such precisely characterized normal and prolapsed vaginal tissue surrogates have not been developed anywhere to date as per the best of our knowledge and would be clinically helpful for gynecological surgical planning in the future.

Biaxial Mechanical Assessment of the Murine Vaginal Wall Using Extension-Inflation Testing

Progress toward understanding the underlying mechanisms of pelvic organ prolapse (POP) is limited, in part, due to a lack of information on the biomechanical properties and microstructural composition of the vaginal wall. Compromised vaginal wall integrity is thought to contribute to pelvic floor disorders; however, normal structure-function relationships within the vaginal wall are not fully understood. In addition to the information produced from uniaxial testing, biaxial extension-inflation tests performed over a range of physiological values could provide additional insights into vaginal wall mechanical behavior (i.e., axial coupling and anisotropy), while preserving in vivo tissue geometry. Thus, we present experimental methods of assessing murine vaginal wall biaxial mechanical properties using extension-inflation protocols. Geometrically intact vaginal samples taken from 16 female C57BL/6 mice underwent pressure-diameter and force-length preconditioning and testing within a pressure-myograph device. A bilinear curve fit was applied to the local stress-stretch data to quantify the transition stress and stretch as well as the toe- and linear-region moduli. The murine vaginal wall demonstrated a nonlinear response resembling that of other soft tissues, and evaluation of bilinear curve fits suggests that the vagina exhibits pseudoelasticity, axial coupling, and anisotropy. The protocols developed herein permit quantification of biaxial tissue properties. These methods can be utilized in future studies in order to assess evolving structure-function relationships with respect to aging, the onset of prolapse, and response to potential clinical interventions.

Scaffolds for Pelvic Floor Prolapse: Logical Pathways

Pelvic organ prolapse (POP) has borrowed principles of treatment from hernia repair and in the last two decades we saw reinforcement materials to treat POP with good outcomes in terms of anatomy but with alarming complication rates. Polypropylene meshes to specifically treat POP have been withdrawn from market by manufactures and a blank space was left to be filled with new materials. Macroporous monofilament meshes are ideal candidates and electrospinning emerged as a reliable method capable of delivering production reproducibility and customization. In this review, we point out some pathways that seem logical to be followed but have been only researched in last couple of years.

Measuring tissue displacement of the anterior vaginal wall using the novel aspiration technique in vivo

Little is known about the mechanical properties of pelvic floor structures and their role in the course and treatment of pelvic organ prolapse (POP). We hypothesize that in vivo mechanical properties of the vaginal wall are related to the appearance of POP and pre-and post-operative states. We used a suction device for intravaginal application, the aspiration device, to evaluate two in vivo mechanical parameters of the anterior vaginal wall, the load dependent tissue displacement and the initial displacement, by image analysis in pre- and post-menopausal women with (POP) and without (control) cystocele (POP: pre-menopausal: N = 6, post-menopausal: N = 19, control: pre-menopausal: N = 17, post-menopausal: N = 6). Mechanical parameters in women with and without cystocele and pre- and post-operative parameters were compared. Statistically significant differences were observed between the two mechanical parameters in pre- and post-operative states (P = 0.04, P = 0.03), but not between the parameters for women with and without cystocele (P = 0.92, P = 0.75). The mechanical behavior of pelvic floor structures is influenced by factors such as POP, age or estrogenization that are apparent at different length scales, which cannot be separated by the aspiration based biomechanical measurements. When comparing pre- and post-operative states of the same patient, a firmer tissue response was observed after intervention.

THE INFLUENCE OF PELVIC ORGAN PROLAPSE ON THE PASSIVE BIOMECHANICAL PROPERTIES OF PELVIC FLOOR MUSCLES

The biomechanical properties of the female pelvic floor tissues, such as muscles, fascia or ligaments are relevant when explaining pelvic disorders, since these may result from changes in the properties of those tissues. The aim of this study is to understand the influence of pelvic organ prolapse (POP) on the passive biomechanical properties of the pelvic floor muscles. For this purpose, magnetic resonance images at Valsalva maneuver were used, and an inverse finite element analysis technique was applied. The numerical models of the pubovisceralis muscle and pelvic bones were built from axial magnetic resonance images acquired at rest. The numerical simulation was based on the finite element method (FEM), by which the material constants were determined for three different constitutive models (Neo-Hookean, Mooney–Rivlin and Yeoh). The ratio between the values of the material constants for women with and without prolapse was approximately 43% for the parameter [Formula: see text] in the Neo-Hookean constitutive model, 57% and 24% for [Formula: see text] and [Formula: see text] in the Mooney–Rivlin constitutive model, and 35%, 21% and 14% for [Formula: see text], [Formula: see text] and [Formula: see text] in the Yeoh constitutive model. For the three constitutive models, the mean values of the material properties related with stiffness were higher for the muscles of women with POP. These increases in stiffness are in line with other experimental works involving vaginal tissue, which showing that the elasticity module is significantly higher in the prolapsed tissue when compared with normal tissue.

The present work presents a noninvasive methodology based on the application of the FEM, which allows the establishment of a relationship between the stiffness of the pelvic floor muscles of women with POP and without this pathology.

Oestradiol-releasing Biodegradable Mesh Stimulates Collagen Production and Angiogenesis: An Approach to Improving Biomaterial Integration in Pelvic Floor Repair

BACKGROUND

Polypropylene meshes cause severe complications in some patients. Materials that are biomechanically compatible and can better integrate into host tissues are urgently needed.

OBJECTIVE

To design an oestradiol-releasing electrospun poly-l-lactic acid (PLA) mesh and evaluate its ability to stimulate new extracellular matrix and new blood vessel formation.

DESIGN, SETTING, AND PARTICIPANTS

Human adipose derived mesenchymal cells (ADMSC) were isolated from fat. PLA meshes with micro- to nano-sized fibres containing 1%, 5%, and 10% oestradiol were constructed and used for in vitro and in vivo experiments.

INTERVENTION

The angiogenic potential of the fibrous meshes was evaluated using an in vivo chorioallantoic membrane and an in vitro chick aortic arch assays.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Oestradiol release was measured fluorometrically. The effect of fibrous meshes on proliferation and extracellular matrix (ECM) production of ADMSC was assessed using immunohistology. Mechanical properties were tested using a tensiometer.

RESULTS AND LIMITATIONS

The ultrastructure of the mesh was not affected by the inclusion of oestradiol and mechanical properties were only slightly modified. Oestradiol was released from PLA meshes over a 5-mo period. ADMSCs cultured on oestradiol-releasing PLA meshes produced more ECM involving collagen I, collagen III, and elastin. Oestradiol-releasing meshes doubled new blood vessel formation in the chorioallantoic membrane assay (p=0.001) and outgrowth of pro-angiogenic cells in the aortic arch assay (p=0.001). Further studies in longer-term animal models are required to confirm these results.

CONCLUSIONS

Oestradiol-releasing PLA meshes increase ECM production and stimulate angiogenesis. As such, they are promising candidate materials to be used in pelvic floor repair and to improve the initial healing phase of a repair material following implantation.

PATIENT SUMMARY

In this study, we designed a tissue engineered material to be used to support weakened pelvic floor tissues in women to avoid the complications associated with current surgical mesh. Our results showed that this material can stimulate new blood vessel formation in simple chick assays and tissue production in vitro. Both properties should help with the integration of this material into patients' tissues and merit further study in physiologically relevant animal models.

Platelet rich plasma as a minimally invasive approach to uterine prolapse

Pelvic organ prolapse (POP) is a major health problem that affects many women with potentially severe physical and psychological impact as well as impact on their daily activities, and quality of life. Several surgical techniques have been proposed for the treatment of POP. The FDA has published documents that refer to concerns about the use of synthetic meshes for the treatment of prolapse, in view of the severe complications that may occur. These led to hesitancy in use of these meshes and partial increase in use of other biological grafts such as allografts and xenografts. Although there seems to be an increasing tendency to use grafts in pelvic floor reconstructive procedures due to lower risks of erosion than synthetic meshes, there are inconclusive data to support the routine use of biological grafts in pelvic organ prolapse treatment. In light of these observations new strategies are needed for the treatment of prolapse. Platelet rich plasma (PRP) is extremely rich in growth factors and cytokines, which regulate tissue reconstruction and has been previously used in orthopaedics and plastic surgery. To date, however, it has never been used in urogynaecology and there is no evidence to support or oppose its use in women who suffer from POP, due to uterine ligament defects. PRP is a relatively inexpensive biological material and easily produced directly from patients' blood and is, thus, superior to synthetic materials in terms of potential adverse effects such as foreign body reaction. In the present article we summarize the existing evidence, which supports the conduct of animal experimental and clinical studies to elucidate the potential role of PRP in treating POP by restoring the anatomy and function of ligament support.