Assessment of Electrospun and Ultra-lightweight Polypropylene Meshes in the Sheep Model for Vaginal Surgery

The use of animal models in preclinical investigations for the development of a surgical mesh for pelvic organ prolapse

INTRODUCTION AND HYPOTHESIS

Polypropylene (PP) mesh for the treatment of pelvic organ prolapse (POP) has raised substantial concerns over long-term complications, leading to its ban in multiple countries. In response, emerging materials are being explored as alternatives for prolapse surgery. Preclinical animal models have historically played a pivotal role in validating medical devices, prior to clinical trials. Successful translation of these materials necessitates the identification of suitable animal models that replicate the female human pelvis and its biomechanical properties. Preclinical in vivo testing assesses the safety of surgical mesh and treatment efficacy in preventing POP recurrence.

METHODS

The research critically reviews animal models used for preclinical pelvic mesh testing over the last decade and proposes a promising model for future preclinical studies.

RESULTS

Rats were the most common mammal used for toxicity and biocompatibility investigations through abdominal implantation. Although non-human primates serve as a gold standard for efficacy testing, ethical considerations limit their use owing to their close biological and cognitive resemblance to humans. Consequently, sheep were the most preferred large animal model owing to their reproductive system similarities and propensity for spontaneous POP following parity.

CONCLUSION

The study contributes valuable insights into the selection of appropriate animal models for preclinical pelvic mesh testing, offering guidance that is crucial for enhancing the safety and efficacy of novel surgical interventions in the treatment of POP.

Two-Year Preclinical Evaluation of Long-Term Absorbable Poly-4-hydroxybutyrate Scaffold for Surgical Correction of Pelvic Organ Prolapse

INTRODUCTION AND HYPOTHESIS

Fully absorbable implants may be an alternative to permanent meshes in the correction pf pelvic organ prolapse (POP) as they may reduce adverse events by promoting tissue regeneration and collagen metabolism. This study was aimed at evaluating the long-term host and biomechanical response to a fully absorbable poly-4-hydroxybutyrate (P4HB) scaffold in comparison with polypropylene (PP) mesh.

METHODS

Poly-4-hydroxybutyrate scaffold (n = 16) and PP mesh (n = 16) were surgically implanted in the posterior vaginal wall of parous female Dohne Merino sheep. Vaginal explants were evaluated in terms of gross necropsy, host response (immune response, collagen deposition, tissue regeneration), biomechanics, and degradation of P4HB at 12 and 24 months post-implantation.

RESULTS

Gross necropsy revealed no infection or fluid collection using P4HB or PP. At 12 months, exposures were observed with both P4HB (3 out of 8) and PP (4 out of 8), whereas at 24 months, exposures were observed only with PP (4 out of 8). The tensile stiffness of the P4HB explants was maintained over time despite complete absorption of P4HB. The collagen amount of the vaginal tissue after P4HB implantation increased over time and was significantly higher than PP at 24 months. P4HB scaffolds exhibited significantly lower myofibroblast differentiation than PP meshes at 24 months.

CONCLUSIONS

The P4HB scaffold allowed for gradual load transfer to the vaginal wall and resulted in mechanically self-sufficient tissue. P4HB scaffold had a more favorable host response than PP mesh, with higher collagen content, lower myofibroblastic differentiation, and no exposures at 24 months. P4HB scaffolds have potential as an alternative to permanent implants in treating POP.

Injectable polyisocyanide hydrogel as healing supplement for connective tissue regeneration in an abdominal wound model

In pelvic organ prolapse (POP) patients, the uterus, bladder and/or rectum descends into vagina due to weakened support tissues. High recurrence rates after POP surgery suggest an urgent need for improved surgical outcomes. Our aim is to promote connective tissue healing that results in stimulated tissue support functions by surgically applying a hydrogel functionalized with biological cues. We used known vaginal wound healing promoting factors (basic fibroblast growth factor, β-estradiol, adipose-derived stem cells) in the biomimetic and injectable polyisocyanide (PIC) hydrogel, which in itself induces regenerative vaginal fibroblast behavior. The regenerative capacity of injected PIC hydrogel, and the additional pro-regenerative effects of these bioactive factors was evaluated in abdominal wounds in rabbits. Assessment of connective tissue healing (tensile testing, histology, immunohistochemistry) revealed that injection with all PIC formulations resulted in a statistically significant stiffness and collagen increase over time, in contrast to sham. Histological evaluation indicated new tissue growth with moderate to mild immune activity at the hydrogel - tissue interface. The results suggest that PIC injection in an abdominal wound improves healing towards regaining load-bearing capacity, which encourages us to investigate application of the hydrogel in a more translational vaginal model for POP surgery in sheep.

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.

Extracellular Matrix-Based and Electrospun Scaffolding Systems for Vaginal Reconstruction

Congenital vaginal anomalies and pelvic organ prolapse affect different age groups of women and both have significant negative impacts on patients' psychological well-being and quality of life. While surgical and non-surgical treatments are available for vaginal defects, their efficacy is limited, and they often result in long-term complications. Therefore, alternative treatment options are urgently needed. Fortunately, tissue-engineered scaffolds are promising new treatment modalities that provide an extracellular matrix (ECM)-like environment for vaginal cells to adhere, secrete ECM, and be remodeled by host cells. To this end, ECM-based scaffolds or the constructs that resemble ECM, generated by self-assembly, decellularization, or electrospinning techniques, have gained attention from both clinicians and researchers. These biomimetic scaffolds are highly similar to the native vaginal ECM and have great potential for clinical translation. This review article aims to discuss recent applications, challenges, and future perspectives of these scaffolds in vaginal reconstruction or repair strategies.

Polypropylene Pelvic Mesh: What Went Wrong and What Will Be of the Future?

Background: Polypropylene (PP) pelvic mesh is a synthetic mesh made of PP polymer used to treat pelvic organ prolapse (POP). Its use has become highly controversial due to reports of serious complications. This research critically reviews the current management options for POP and PP mesh as a viable clinical application for the treatment of POP. The safety and suitability of PP material were rigorously studied and critically evaluated, with consideration to the mechanical and chemical properties of PP. We proposed the ideal properties of the ‘perfect’ synthetic pelvic mesh with emerging advanced materials. Methods: We performed a literature review using PubMed/Medline, Embase, Cochrane Library (Wiley) databases, and ClinicalTrials.gov databases, including the relevant keywords: pelvic organ prolapse (POP), polypropylene mesh, synthetic mesh, and mesh complications. Results: The results of this review found that although PP is nontoxic, its physical properties demonstrate a significant mismatch between its viscoelastic properties compared to the surrounding tissue, which is a likely cause of complications. In addition, a lack of integration of PP mesh into surrounding tissue over longer periods of follow up is another risk factor for irreversible complications. Conclusions: PP mesh has caused a rise in reports of complications involving chronic pain and mesh exposure. This is due to the mechanical and physicochemical properties of PP mesh. As a result, PP mesh for the treatment of POP has been banned in multiple countries, currently with no alternative available. We propose the development of a pelvic mesh using advanced materials including emerging graphene-based nanocomposite materials.

Transvaginal Mesh-related Complications and the Potential Role of Bacterial Colonization: An Exploratory Observational Study

STUDY OBJECTIVE

This study aimed to investigate the potential role of transvaginal mesh bacterial colonization in the development of mesh-related complications (MRCs).

DESIGN

An observational and exploratory study.

SETTING

Tertiary referral center (Amsterdam UMC, location AMC, Amsterdam, The Netherlands). PATIëNTS: 49 patients indicated for mesh removal and 20 women of whom vaginal tissue was retrieved during prolapse surgery as a reference cohort.

INTERVENTIONS

collection of mesh-tissue complex (patient cohort) or vaginal tissue (reference cohort) MEASUREMENTS AND MAIN RESULTS: Homogenized samples were used for quantitative microbiological culture. Inflammation and fibrosis were semiquantitatively histologically scored; Gram staining and fluorescence in situ hybridization were used to detect bacteria and bacterial biofilms. Of the 49 patients, 44 samples (90%) were culture positive, with a higher diversity of species and more Gram-negative bacteria and polymicrobial cultures in the MRC cohort than the reference cohort, with mostly staphylococci, streptococci, Actinomyces spp., Cutibacterium acnes, and Escherichia coli. Patients with clinical signs of infection or exposure had the highest bacterial counts. Histology demonstrated moderate to severe inflammation in most samples. Gram staining showed bacteria in 57% of culture-positive samples, and in selected samples, fluorescence in situ hybridization illustrated a polymicrobial biofilm.

CONCLUSION

In this study, we observed distinct differences in bacterial numbers and species between patients with MRCs and a reference cohort. Bacteria were observed at the mesh-tissue interface in a biofilm. These results strongly support the potential role of bacterial mesh colonization in the development of MRCs.

Long-term Data on Graft-Related Complications After Sacrocolpopexy With Lightweight Compared With Heavier-Weight Mesh

OBJECTIVE

To estimate the long-term incidence and characteristics of graft-related complications, rate of reintervention for graft-related complications and prolapse, and subjective and anatomical outcomes after laparoscopic sacrocolpopexy with heavier-weight (more than 44 g/m2) compared with lightweight (28 g/m2) polypropylene mesh, the latter with resorbable poliglecaprone component.

METHODS

We conducted a single-center study that compared two consecutive prospective cohorts of patients who were undergoing laparoscopic sacrocolpopexy for symptomatic stage 2 or greater cervical or vault prolapse, by using either heavier-weight polypropylene mesh or lightweight polypropylene mesh at a similar duration of follow-up. The primary outcome was the occurrence of graft-related complications and their nature. Secondary outcomes included reinterventions for graft-related complications, recurrent apical prolapse, a subjective outcome (PGIC [Patient Global Impression of Change] score 4 or higher), and an anatomical outcome (point C -1 cm or greater).

RESULTS

We identified consecutive patients: 101 were implanted with heavier-weight polypropylene, and 238 were implanted with lightweight polypropylene; all were audited at comparable follow-up times (heavier-weight mesh: 97 months [interquartile range 16 months]; lightweight mesh: 92.5 months [interquartile range 58 months]). Graft-related complications were more frequent in patients with heavier-weight than lightweight mesh (22.8% [23/101] vs 7.3% [13/178]; hazard ratio [HR] 3.3, 95% CI 1.6-7.1), more frequently symptomatic (heavier-weight mesh: 16.8% [17/101] vs lightweight mesh: 2.8% [5/178]; HR 6.0, 95% CI 2.5-14.3), and more frequently lead to reintervention for graft-related complications (heavier-weight mesh: 18.8% [19/101] vs lightweight mesh: 2.1% [5/238]; HR 4.6, 95% CI 1.9-11.2). The vast majority of patients improved (PGIC score 4 or higher), without difference between groups (heavier-weight mesh: 71/84 [84.9%]; lightweight mesh: 154/178 [86.5%]; HR 0.8, 95% CI 0.6-1.1); neither was there a difference in anatomical failure rate (heavier-weight mesh: 1/60 [1.7%] vs lightweight mesh: 8/131 [6.1%]; HR 0.3, 95% CI 0.1-1.4). Reoperations for recurrent vault prolapse were scarce (0.0% in heavier-weight mesh, vs 0.4% in lightweight mesh).

CONCLUSION

In two consecutive cohorts, the number of graft-related complications, symptomatic graft-related complications, and reinterventions for graft-related complications were higher in patients implanted with heavier-weight polypropylene than when lightweight polypropylene was used. There were no differences in subjective, objective outcomes, and reoperation rates for prolapse.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT04378400.

FUNDING

To assist in this audit, the University Hospitals Leuven received support from Ethicon Endosurgery.

Absorbable Electrospun Poly-4-hydroxybutyrate Scaffolds as a Potential Solution for Pelvic Organ Prolapse Surgery

Women with pelvic organ prolapse (POP) have bothersome complaints that significantly affect their quality of life. While native tissue repair is associated with high recurrence rates, polypropylene knitted implants have caused specific implant-related adverse events that have detrimental, often irreversible, effects. We hypothesize that surgical outcome can be improved with a tissue-engineered solution using an absorbable implant that mimics the natural extracellular matrix (ECM) structure, releases estrogen, and activates collagen metabolism by fibroblasts as the main regulators of wound healing. To this aim, we produced electrospun poly-4-hydroxybutyrate (P4HB) scaffolds and biofunctionalized them with estradiol (E2). The cell-implant interactions relevant for POP repair were assessed by seeding primary POP vaginal fibroblasts isolated from patients on electrospun P4HB scaffolds with 1%, 2%, or 5% E2 and without E2. To test our hypothesis on whether ECM mimicking structures should improve regeneration, electrospun P4HB was compared to knitted P4HB implants. We evaluated vaginal fibroblast proliferation, ECM deposition, and metabolism by quantification of collagen, elastin, and matrix metalloproteinases and by gene expression analysis for 28 days. We established effective E2 drug loading with a steady release over time. Significantly higher cell proliferation, collagen-, and elastin deposition were observed on electrospun P4HB scaffolds as compared to knitted P4HB. For this study, physical properties of the scaffolds were more determinant on the cell response than the release of E2. These results indicate that making these electrospun P4HB scaffolds E2-releasing appears to be technically feasible. In addition, electrospun P4HB scaffolds promote the cellular response of vaginal fibroblasts and further studies are merited to assess if their use results in improved surgical outcomes in case of POP repair.

Validation of an ovine vesicovaginal fistula model

INTRODUCTION AND HYPOTHESIS

A representative, large animal model of vesicovaginal fistulas is needed for the training of surgeons and for the development of new surgical techniques and materials for obstetric fistula repair.

METHODS

The safety, feasibility, and reproducibility of vesicovaginal fistula creation were studied in 4 adult female sheep. A 1-cm fistula was created between the vagina and the bladder through a transvaginal approach. The defect was allowed to heal for 8 weeks and the animals were then euthanized. The primary outcome was the fistula patency. Secondary outcomes were fistula size, urogenital dimensions, urodynamic evaluation, histology (inflammation, vascularization, collagen deposition) and biomechanical characteristics of the fistula edge (stress at break, maximum elongation, and stiffness).

RESULTS

The transvaginal creation of a vesicovaginal fistula was safe. All animals survived the surgical procedure and follow-up period, without complications. Three of the four animals demonstrated a patent vesicovaginal fistula after 8 weeks. Baseline data are provided of the urogenital dimensions and the urodynamic, histological, and biomechanical characteristics of the model.

CONCLUSIONS

The ewe is a safe, feasible, and reproducible model for vesicovaginal fistulas. The model can help to study new techniques and materials to boost surgical innovation for vesicovaginal fistula repair.

Cog Threads for Transvaginal Prolapse Repair: Ex-Vivo Studies of a Novel Concept

The diagnosis and treatment of pelvic organ prolapse (POP) remain a relevant and scientifically challenging topic. The number of cases of genital prolapse increases each year, one in ten women need at least one surgical procedure and one in four women in midlife have asymptomatic prolapse. Using mesh implants to correct POP presents unsatisfactory clinical outcomes, requiring hospital readmission and further surgery. We hypothesize using an alternative surgical intervention technique, applying injectable biodegradable cog threads, currently used for face lifting procedures, to reinforce and correct vaginal wall defects. The threads used in this investigation are commercially available 360° 4D barb threads (PCL-19G-100), made of polycaprolactone (PCL), supplied in sterile packs (Yastrid, Shanghai, China). Eleven sows’ vaginal walls were used to analyze the immediate reinforcement effect of the threads. Uniaxial tensile testing and scanning electron microscopy (SEM) was performed for the initial characterization of the threads. Threads were inserted into the vaginal wall (control n = 5, cog n = 5) and were characterized by ball burst testing; a pull-out test was performed (n = 6). With SEM images, dimensions, such as thread diameter (≈630 µm), cut angle (≈135°), cut depth (≈200 µm) and cog distance (≈1600 µm) were measured. The mechanical behavior during uniaxial tensile testing was nonlinear. Threads could sustain 17–18 N at 18–22% of deformation. During the ball burst test, vaginal tissue reinforced with threads could support 68 N more load than normal tissue (p < 0.05), indicating its strengthening effect. Comfort and stress zones were significantly stiffer in the tissues reinforced with threads (p < 0.05; p < 0.05). Both groups showed identical deformation (elongation); no significant differences in the comfort zone length were observed, showing that threads do not affect tissue compliance. The pull-out test showed that the threads could sustain 3.827 ± 0.1891 N force when the first cog slip occurs, at 11.93 ± 0.8291 mm. This preliminary research on using PCL cog threads for POP treatment showed promising results in increased vaginal wall resistance to pressure load and, at the same time, not affecting its compliance. Nevertheless, to obtain long term host response in vivo, further investigation will be carried out.

The impact of bacterial contamination on the host response towards fully absorbable poly-4-hydroxybutyrate and nonabsorbable polypropylene pelvic floor implants

Polypropylene (PP) implants for the vaginal surgical correction of pelvic organ prolapse (POP) are known for adverse events, like vaginal or visceral exposures. It is hypothesized that this is a result of a prolonged inflammatory response. One of the triggering factors of prolonged inflammation might be bacterial contamination. A possible solution might lie in an absorbable biomaterial, which provides initial mechanical support while being gradually replaced by the host tissue.

With this study we aimed to compare the host response, in a subcutaneous mouse implant infection model, to delayed absorbable poly-4-hydroxybutyrate (P4HB) and a latest generation PP implant. By comparing non-infected to Staphylococcus aureus infected mice, we assessed how bacterial contamination affects the host response and its role in the development of complications. Further, we included sham surgery as a control, mimicking the wound response in native tissue repair.

Despite the higher surface area of the P4HB implants, the clearance of infection was similarly delayed in the presence of a P4HB or PP implant, as compared to sham. Further, the host response towards P4HB and PP was quite comparable, yet collagen deposition was significantly increased around infected P4HB implants at early time points. Adverse event rates were similar, though implant exposures were only seen in infected mice and more often with PP (11.1%) than P4HB implants (5.6%). Infected mice overall had significantly higher levels of infiltration of inflammatory cells and lower levels of vascularization and collagen deposition compared to non-infected mice. Thus, for both P4HB and PP, bacterial contamination negatively affected mesh integration by increased inflammation and an increased adverse event rate. Altogether, our results from this subcutaneous mouse implant infection study suggest that P4HB could be a promising degradable alternative to PP, warranting further research to study its potential as a new surgical solution for women with POP.

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Absorbable poly-4-hydroxybutyrate (P4HB) is studied as a novel pelvic floor implant.

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Comparable host response to P4HB and polypropylene in a subcutaneous mouse implant infection model.

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Implant exposures exclusively occurred upon Staphylococcus aureus infection.

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Exposures occurred less with P4HB (5.6%) compared to polypropylene (11.1%).

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S. aureus infection increased inflammation and deranged the host response.

Role of Fibroblasts and Myofibroblasts on the Pathogenesis and Treatment of Pelvic Organ Prolapse

Pelvic organ prolapse (POP) is a multifactorial connective tissue disorder caused by damage to the supportive structures of the pelvic floor, leading to the descent of pelvic organs in the vagina. In women with POP, fibroblast function is disturbed or altered, which causes impaired collagen metabolism that affects the mechanical properties of the tissue. Ideal surgical repair, either native tissue repair or POP surgery using an implant, aims to create a functional pelvic floor that is load-bearing, activating fibroblasts to regulate collagen metabolism without creating fibrotic tissue. Fibroblast function plays a crucial role in the pathophysiology of POP by directly affecting the connective tissue quality. On the other hand, fibroblasts determine the success of the POP treatment, as the fibroblast-to-(myo)fibroblast transition is the key event during wound healing and tissue repair. In this review, we aim to resolve the question of “cause and result” for the fibroblasts in the development and treatment of POP. This review may contribute to preventing the development and progress of anatomical abnormalities involved in POP and to optimizing surgical outcomes.

Design, mechanical and degradation requirements of biodegradable metal mesh for pelvic floor reconstruction

Pelvic organ prolapse (POP) is the herniation of surrounding tissue and organs into the vagina and or rectum, and is a result of weakening of pelvic floor muscles, connective tissue,...

Evaluation of the short-term host response and biomechanics of an absorbable poly-4-hydroxybutyrate scaffold in a sheep model following vaginal implantation

Objective

To evaluate the host‐ and biomechanical response to a fully absorbable poly‐4‐hydroxybutyrate (P4HB) scaffold in comparison with the response to polypropylene (PP) mesh.

Design

In vivo animal experiment.

Setting

KU Leuven Center for Surgical Technologies.

Population

Fourteen parous female Mule sheep.

Methods

P4HB scaffolds were surgically implanted in the posterior vaginal wall of sheep. The comparative PP mesh data were obtained from an identical study protocol performed previously.

Main outcome measures

Gross necropsy, host response and biomechanical evaluation of explants, and the in vivo P4HB scaffold degradation were evaluated at 60‐ and 180‐days post‐implantation. Data are reported as mean ± standard deviation (SD) or standard error of the mean (SEM).

Results

Gross necropsy revealed no implant‐related adverse events using P4HB scaffolds. The tensile stiffness of the P4HB explants increased at 180‐days (12.498 ± 2.66 N/mm SEM [p =0.019]) as compared to 60‐days (4.585 ± 1.57 N/mm) post‐implantation, while P4HB degraded gradually. P4HB scaffolds exhibited excellent tissue integration with dense connective tissue and a moderate initial host response. P4HB scaffolds induced a significantly higher M2/M1 ratio (1.70 ± 0.67 SD, score 0–4), as compared to PP mesh(0.99 ± 0.78 SD, score 0–4) at 180‐days.

Conclusions

P4HB scaffold facilitated a gradual load transfer to vaginal tissue over time. The fully absorbable P4HB scaffold, in comparison to PP mesh, has a favorable host response with comparable load‐bearing capacity. If these results are also observed at longer follow‐up in‐vivo, a clinical study using P4HB for vaginal POP surgery may be warranted to demonstrate efficacy.

Tweetable Abstract

Degradable vaginal P4HB implant might be a solution for treatment of POP.

Degradable vaginal P4HB implant might be a solution for treatment of POP.

Recent advances in electrospun nanofiber vaginal formulations for women's sexual and reproductive health

Electrospinning is an innovative technique that allows production of nanofibers and microfibers by applying a high voltage to polymer solutions of melts. The properties of these fibers - which include high surface area, high drug loading capacity, and ability to be manufactured from mucoadhesive polymers - may be particularly useful in a myriad of drug delivery and tissue engineering applications. The last decade has witnessed a surge of interest in the application of electrospinning technology for the fabrication of vaginal drug delivery systems for the treatment and prevention of diseases associated with women's sexual and reproductive health, including sexually transmitted infections (e.g. infection with human immunodeficiency virus and herpes simplex virus) vaginitis, preterm birth, contraception, multipurpose prevention technology strategies, cervicovaginal cancer, and general maintenance of vaginal health. Due to their excellent mechanical properties, electrospun scaffolds are also being investigated as next-generation materials in the surgical treatment of pelvic organ prolapse. In this article, we review the latest advances in the field.

Update in Transvaginal Grafts: The Role of Lightweight Meshes, Biologics, and Hybrid Grafts in Pelvic Organ Prolapse Surgery

Transvaginal mesh/grafts have been popularized over the past 20 years in an attempt to improve the longevity of traditional vaginal pelvic organ prolapse (POP) surgery. Several national bodies have concluded that the proposed benefits of mesh/graft implantation are outweighed by the significant increase in surgery complications related to these products. As a consequence mesh products for vaginal POP surgery have been withdrawn from use in many countries. This article is a narrative review of newer mesh and graft products including lightweight polypropylene mesh products, biological grafts, hybrid grafts, and tissue engineered grafts.

Tissue engineering to treat pelvic organ prolapse

Pelvic organ prolapse (POP) is a frequent chronic illness, which seriously affects women's living quality. In recent years, tissue engineering has made superior progress in POP treatment, and biological scaffolds have received considerable attention. Nevertheless, pelvic floor reconstruction still faces severe challenges, including the construction of ideal scaffolds, the selection of optimal seed cells, and growth factors. This paper summarizes the recent progress of pelvic floor reconstruction in tissue engineering, and discusses the problems that need to be further considered and solved to provide references for the further development of this field.

In Vitro Bacterial Adhesion and Biofilm Formation on Fully Absorbable Poly-4-hydroxybutyrate and Nonabsorbable Polypropylene Pelvic Floor Implants

Knitted polypropylene (PP) implants for the correction of pelvic organ prolapse have been associated with complications such as vaginal exposure, infection, and pain. Since certain complications may be linked to bacterial contamination and persistent inflammation, there is a rationale to develop a biocompatible implant that is less prone to bacterial adhesion and biofilm formation. Delayed absorbable materials could meet these requirements and poly-4-hydroxybutyrate (P4HB) might be such a new material for future pelvic floor implants. We studied in vitro bacterial adhesion and biofilm formation on P4HB in comparison to PP. We investigated the influence of both polymers using flat films and compared P4HB and PP implants with different knitting designs. P4HB flat films were demonstrated to be hydrophilic with significantly less Staphylococcus aureus and Escherichia coli cultured from P4HB films than from hydrophobic PP films after 24 h of incubation. On the implants, a higher number of E. coli were cultured after 1 h of incubation from the knitted P4HB implant with the highest density and smallest pore size, compared to other P4HB and PP implants. No differences were observed between the implants for E. coli at later time points or for S. aureus incubation. These results show that in flat films, the polymer influences biofilm formation, demonstrated by a reduced biofilm formation on P4HB compared with PP flat films. In addition, the knitting design may affect bacterial adhesion. Despite certain design and material characteristics that give the knitted P4HB implants a higher surface area, this did not result in more bacterial adhesion and biofilm formation overall. Collectively, these results warrant further (pre)clinical investigations of P4HB pelvic floor implants.

A novel tropoelastin-based resorbable surgical mesh for pelvic organ prolapse repair

Pelvic organ prolapse is a common condition that affects 1 in 4 women across all age groups. It is mainly caused by vaginal birth injury and can be exacerbated by obesity and increased age. Until recently, treatment strategies often used non-degradable synthetic meshes for reconstructive surgery. However, owing to their frequent, unacceptable rate of adverse events such as mesh erosion, transvaginal meshes have been banned in many countries. Recent reports have highlighted the urgent need for biocompatible design of meshes for a safe and effective treatment in the long term. This study reports the design and evaluation of a novel, elastin based degradable mesh using an ovine model of POP as a potential surgical treatment. Elastin is a protein component of the ECM and provides elasticity to tissues throughout the body. Tropoelastin, the monomer subunit of elastin, has been used with success in electrospun constructs as it is a naturally cell interactive polymer. Biomaterials that incorporate tropoelastin support cell attachment and proliferation, and have been proven to encourage elastogenesis and angiogenesis in vitro and in vivo. The biological properties of tropoelastin were combined with the physical properties of PCL, a degradable synthetic polymer, with the aim of producing, characterizing and assessing the performance of continuous tropoelastin:PCL electrospun yarns. Using a modified spinneret electrospinning system and adjusting settings based on relative humidity, four blends of tropoelastin:PCL yarns were fabricated with concentration ratios of 75:25, 50:50, 25:75 and 0:100. Yarns were assessed for ease of manufacture, fibrous architecture, protein/polymer content, yarn stability - including initial tropoelastin release, mechanical strength, and ability to support cell growth. Based on overall favorable properties, a mesh woven from the 50:50 tropoelastin:PCL yarn was implanted into the vagina of a parous ewe with vaginal wall weakness as a model of pelvic organ prolapse. This mesh showed excellent integration with new collagen deposition by SEM and a predominant M2 macrophage response with few pro-inflammatory M1 macrophages after 30 days. The woven tropoelastin:PCL electrospun mesh shows potential as an alternative to non-degradable, synthetic pelvic organ prolapse mesh products.

Urogynecological surgical mesh implants: New trends in materials, manufacturing and therapeutic approaches

Pelvic Organ Prolapse (POP) and Stress Urinary Incontinence (SUI) are two prevalent disorders affecting 30-40% of women worldwide. Current strategies to repair or improve these medical conditions are non-surgical options such as physiotherapy, or surgical options such as the use of vaginal meshes. The synthetic material polypropylene (PP), which has long been used for manufacturing these vaginal meshes, is associated with severe complications such as chronic pain, infection or mesh erosion. As a result of a widespread reporting and unacceptably high rates of complications, these issues have become a public health concern. Regulatory bodies have recently deemed the transvaginal placement of PP mesh in the pelvic floor (PF) no longer a suitable treatment method for PF repair, leading to the need for a novel approach to the manufacture and selection of materials for urogynecological meshes. Medical devices, such as vaginal meshes can be manufactured using a variety of techniques including injection moulding, electrospinning, hot-melt extrusion (HME) or more recently 3D printing. Over the past decade, the use of 3D printing within the medical device industry has expanded and offers a promising approach to manufacture patient-specific surgical mesh when combined with imaging tools. This review will summarise the current strategies to treat POP and SUI, the issues and use of current meshes for the treatment of these pelvic floor disorders (PFDs), and the future directions for the manufacture of more suitable urogynecological meshes, as well as their potential materials.

Emerging Nano/Micro-Structured Degradable Polymeric Meshes for Pelvic Floor Reconstruction

Pelvic organ prolapse (POP) is a hidden women's health disorder that impacts 1 in 4 women across all age groups. Surgical intervention has been the only treatment option, often involving non-degradable meshes, with variable results. However, recent reports have highlighted the adverse effects of meshes in the long term, which involve unacceptable rates of erosion, chronic infection and severe pain related to mesh shrinkage. Therefore, there is an urgent unmet need to fabricate of new class of biocompatible meshes for the treatment of POP. This review focuses on the causes for the downfall of commercial meshes, and discusses the use of emerging technologies such as electrospinning and 3D printing to design new meshes. Furthermore, we discuss the impact and advantage of nano-/microstructured alternative meshes over commercial meshes with respect to their tissue integration performance. Considering the key challenges of current meshes, we discuss the potential of cell-based tissue engineering strategies to augment the new class of meshes to improve biocompatibility and immunomodulation. Finally, this review highlights the future direction in designing the new class of mesh to overcome the hurdles of foreign body rejection faced by the traditional meshes, in order to have safe and effective treatment for women in the long term.

The Patenting and Technological Trends in Hernia Mesh Implants

Described as a projection (prolapse) of tissue through a fascial defect in the abdominal wall, hernias are associated with significant rates of complications, recurrence, and reoperations. This literature review is aimed at providing an overview of the prosthetic surgical meshes used for the repairing of hernia defects. The review was carried out using two specialized online databases: Espacenet, from the European Patent Office (EPO), and WIPO from the World Intellectual Property Organization. Of the 56 patents selected from 2008 to 2018, China was the largest contributor with 55% (31 patents) of the total patent applicant filings, followed by the United States of America (US), with 29% (16 patents). Although the majority of patent applications (39 documents) had at least one company (industry) assigned to the patent application, 4 patents were solely from academic research. Our data showed that only 13 industry applicants have had their products included in the market, and the majority of meshes available on the market are still made from polypropylene. Chemical, physical, and mesh surface modifications have been implemented, and a few reviews describing mesh design, composition, and mechanical properties are available. However, to date, the ideal mesh implant from a clinical point of view has not been developed.

Electrospun Nanofiber Meshes With Endometrial MSCs Modulate Foreign Body Response by Increased Angiogenesis, Matrix Synthesis, and Anti-Inflammatory Gene Expression in Mice: Implication in Pelvic Floor

Purpose

Transvaginal meshes for the treatment of Pelvic Organ Prolapse (POP) have been associated with severe adverse events and have been banned for clinical use in many countries. We recently reported the design of degradable poly L-lactic acid-co-poly ε-caprolactone nanofibrous mesh (P nanomesh) bioengineered with endometrial mesenchymal stem/stromal cells (eMSC) for POP repair. We showed that such bioengineered meshes had high tissue integration as well as immunomodulatory effects in vivo. This study aimed to determine the key molecular players enabling eMSC-based foreign body response modulation.

Methods

SUSD2⁺ eMSC were purified from single cell suspensions obtained from endometrial biopsies from cycling women by magnetic bead sorting. Electrospun P nanomeshes with and without eMSC were implanted in a NSG mouse skin wound repair model for 1 and 6 weeks. Quantitative PCR was used to assess the expression of extracellular matrix (ECM), cell adhesion, angiogenesis and inflammation genes as log₂ fold changes compared to sham controls. Histology and immunostaining were used to visualize the ECM, blood vessels, and multinucleated foreign body giant cells around implants.

Results

Bioengineered P nanomesh/eMSC constructs explanted after 6 weeks showed significant increase in 35 genes associated with ECM, ECM regulation, cell adhesion angiogenesis, and immune response in comparison to P nanomesh alone. In the absence of eMSC, acute inflammatory genes were significantly elevated at 1 week. However, in the presence of eMSC, there was an increased expression of anti-inflammatory genes including Mrc1 and Arg1 by 6 weeks. There was formation of multinucleated foreign body giant cells around both implants at 6 weeks that expressed CD206, a M2 macrophage marker.

Conclusion

This study reveals that eMSC modulate the foreign body response to degradable P nanomeshes in vivo by altering the expression profile of mouse genes. eMSC reduce acute inflammatory and increase ECM synthesis, angiogenesis and anti-inflammatory gene expression at 6 weeks while forming newly synthesized collagen within the nanomeshes and neo-vasculature in close proximity. From a tissue engineering perspective, this is a hallmark of a highly successful implant, suggesting significant potential as alternative surgical constructs for the treatment of POP.

3D Printing of Drug-Loaded Thermoplastic Polyurethane Meshes: A Potential Material for Soft Tissue Reinforcement in Vaginal Surgery

Current strategies to treat pelvic organ prolapse (POP) or stress urinary incontinence (SUI), include the surgical implantation of vaginal meshes. Recently, there have been multiple reports of issues generated by these meshes conventionally made of poly(propylene). This material is not the ideal candidate, due to its mechanical properties leading to complications such as chronic pain and infection. In the present manuscript, we propose the use of an alternative material, thermoplastic polyurethane (TPU), loaded with an antibiotic in combination with fused deposition modelling (FDM) to prepare safer vaginal meshes. For this purpose, TPU filaments containing levofloxacin (LFX) in various concentrations (e.g., 0.25%, 0.5%, and 1%) were produced by extrusion. These filaments were used to 3D print vaginal meshes. The printed meshes were fully characterized through different tests/analyses such as fracture force studies, attenuated total reflection-Fourier transform infrared, thermal analysis, scanning electron microscopy, X-ray microcomputed tomography (μCT), release studies and microbiology testing. The results showed that LFX was uniformly distributed within the TPU matrix, regardless the concentration loaded. The mechanical properties showed that poly(propylene) (PP) is a tougher material with a lower elasticity than TPU, which seemed to be a more suitable material due to its elasticity. In addition, the printed meshes showed a significant bacteriostatic activity on both Staphylococcus aureus and Escherichia coli cultures, minimising the risk of infection after implanting them. Therefore, the incorporation of LFX to the TPU matrix can be used to prepare anti-infective vaginal meshes with enhanced mechanical properties compared with current PP vaginal meshes.

Medium-term outcome of laparoscopic sacrocolpopexy using polivinylidene fluoride as compared to a hybrid polyglecaprone and polypropylene mesh: A matched control study

AIM

To compare 2-year outcomes of laparoscopic sacrocolpopexy (LSCP) either with polyvinylidene fluoride (PVDF) or hybrid polypropylene containing a resorbable polyglecaprone (PP+ PG) mesh.

MATERIALS AND METHODS

Retrospective audit on 105 consecutive patients undergoing LSCP a with PVDF-mesh (DynaMesh, FEG Textiltechniken), matched by prolapse stage and cervicopexy or vault suspension to 105 controls undergoing LSCP with a hybrid PP + PG-mesh (Ultrapro, Ethicon). Patients are part of an ongoing prospective study. The primary outcome measure was the Patient Global Impression of Change score (PGIC), the coprimary variable was failure rate at the vault (≤1 cm). Other outcomes were intraoperative and postoperative complications within 3 months categorized by the Clavien-Dindo classification, reinterventions, graft-related complications (GRCs) and functional outcomes. All assessments were performed by an independent assessor. Data are reported as median (interquartile range) number and percent as appropriate, the Mann-Whitney U, χ² , or Fisher exact were used for comparison.

RESULTS

Patient satisfaction in the PVDF group, as measured with the PGIC, was high (90.9% PGIC, ≥4) as well as was the anatomical success (97.3%) at a follow-up of 26 months. These outcomes were comparable to those of PP + PG-patients (84.8% PGIC, ≥4; 94.9% anatomical success). There were five patients (2.4%) with Dindo-III or higher complications and three patients had GRCs (1.5%), without differences between mesh type. Level-II posterior defects (Bp ≥ -1) were less likely in PVDF patients (34.1% vs 50% for PP + PG-patients; P = .003). Women in the PVDF group also were less bothered by prolapse (7.5% vs 26.4%; P = .001), yet they complained more of constipation (15.0% vs 9.0%; P = .01).

CONCLUSION

There were no differences in patient satisfaction and anatomical outcomes after LSCP either with PVDF or PP + PG mesh.

Macrophage-Driven Biomaterial Degradation Depends on Scaffold Microarchitecture

In situ tissue engineering is a technology in which non-cellular biomaterial scaffolds are implanted in order to induce local regeneration of replaced or damaged tissues. Degradable synthetic electrospun scaffolds are a versatile and promising class of biomaterials for various in situ tissue engineering applications, such as cardiovascular replacements. Functional in situ tissue regeneration depends on the balance between endogenous neo-tissue formation and scaffold degradation. Both these processes are driven by macrophages. Upon invasion into a scaffold, macrophages secrete reactive oxygen species (ROS) and hydrolytic enzymes, contributing to oxidative and enzymatic biomaterial degradation, respectively. This study aims to elucidate the effect of scaffold microarchitecture, i.e., μm-range fiber diameter and fiber alignment, on early macrophage-driven scaffold degradation. Electrospun poly-ε-caprolactone-bisurea (PCL-BU) scaffolds with either 2 or 6 μm (Ø) isotropic or anisotropic fibers were seeded with THP-1 derived human macrophages and cultured in vitro for 4 or 8 days. Our results revealed that macroph age-induced oxidative degradation in particular was dependent on scaffold microarchitecture, with the highest level of ROS-induced lipid peroxidation, NADPH oxidase gene expression and degradation in the 6 μm Ø anisotropic group. Whereas, biochemically polarized macrophages demonstrated a phenotype-specific degradative potential, the observed differences in macrophage degradative potential instigated by the scaffold microarchitecture could not be attributed to either distinct M1 or M2 polarization. This suggests that the scaffold microarchitecture uniquely affects macrophage-driven degradation. These findings emphasize the importance of considering the scaffold microarchitecture in the design of scaffolds for in situ tissue engineering applications and the tailoring of degradation kinetics thereof.