Developing Repair Materials for Stress Urinary Incontinence to Withstand Dynamic Distension

Where are we in 2024 in the development of materials for surgical treatment of pelvic organ prolapse and stress urinary incontinence?

PURPOSE OF REVIEW

There is a long history of implantation of absorbable and nonabsorbable materials to treat stress urinary incontinence (SUI) and pelvic organ prolapse (POP). The focus of this review is to review the development of new materials for use in the surgical management of both pelvic conditions following an unacceptable level of severe complications in the use of polypropylene mesh (PPM). We discuss current concepts relating to the development of new materials with particular reference to our experience with polyurethane mesh.

RECENT FINDINGS

Our review highlights the strategies that manufacturers and researchers are employing to improve PPM using collagen gels and stem cells, or to find alternatives. We conclude that current preclinical safety testing is inadequate, and the field requires better in vivo testing. Specifically, we highlight novel techniques demonstrating the degradation of polypropylene potentially elucidating the link between PPM degradation and induction of inflammation leading to adverse side effects.

SUMMARY

This field badly needs innovation in developing new materials and in testing these to ensure materials will benefit patients. A collaboration between materials scientists and clinicians is needed to facilitate the translation of basic research and preclinical testing into patient benefit for the treatment of SUI and POP.

Modification of transvaginal polypropylene mesh with co-axis electrospun nanofibrous membrane to alleviate complications following surgical implantation

BACKGROUND

Surgeries for treating pelvic organ prolapse involving the utilization of synthetic mesh have been associated with complications such as mesh erosion, postoperative pain, and dyspareunia. This work aimed to reduce the surgical implantation-associated complications by nanofibrous membranes on the surface of the polypropylene mesh. The nanofiber of the nanofibrous membrane, which was fabricated by co-axial electrospinning, was composed of polyurethane as fiber core and gelatin as the fiber out layer. The biocompatibility of the modified mesh was evaluated in vitro by cell proliferation assay, immunofluorescence stain, hematoxylin-eosin (HE) staining, and mRNA sequencing. Polypropylene mesh and modified mesh were implanted in a rat pelvic organ prolapse model. Mesh-associated complications were documented. HE and Picro-Sirius red staining, immunohistochemistry, and western blotting were conducted to assess the interactions between the modified mesh and vaginal tissues.

RESULTS

The modified mesh significantly enhanced the proliferation of fibroblasts and exerted a positive regulatory effect on the extracellular matrix anabolism in vitro. When evaluated in vivo, no instances of mesh exposure were observed in the modified mesh group. The modified mesh maintained a relatively stable histological position without penetrating the muscle layer or breaching the epidermis. The collagen content in the vaginal wall of rats with modified mesh was significantly higher, and the collagen I/III ratio was lower, indicating better tissue elasticity. The expression of metalloproteinase was decreased while the expression levels of tissue inhibitor of metalloproteinase were increased in the modified mesh group, suggesting an inhibition of collagen catabolism. The expression of TGF-β1 and the phosphorylation levels of Smad3, p38 and ERK1/2 were significantly increased in the modified mesh group. NM significantly improved the biocompatibility of PP mesh, as evidenced by a reduction in macrophage count, decreased expression levels of TNF-α, and an increase in microvascular density.

CONCLUSIONS

The nanofibrous membrane-coated PP mesh effectively reduced the surgical implantation complications by inhibiting the catabolism of collagen in tissues and improving the biocampibility of PP mesh. The incorporation of co-axial fibers composed of polyurethane and gelatin with polypropylene mesh holds promise for the development of enhanced surgical materials for pelvic organ prolapse in clinical applications.

Tissue-engineered repair material for pelvic floor dysfunction

Pelvic floor dysfunction (PFD) is a highly prevalent urogynecology disorder affecting many women worldwide, with symptoms including pelvic organ prolapse (POP), stress urinary incontinence (SUI), fecal incontinence, and overactive bladder syndrome (OAB). At present, the clinical treatments of PFD are still conservative and symptom-based, including non-surgical treatment and surgery. Surgical repair is an effective and durable treatment for PFD, and synthetic and biological materials can be used to enforce or reinforce the diseased tissue. However, synthetic materials such as polypropylene patches caused a series of complications such as mesh erosion, exposure, pain, and inflammation. The poor mechanical properties and high degradation speed of the biomaterial meshes resulted in poor anatomical reduction effect and limitation to clinical application. Therefore, the current treatment options are suboptimal. Recently, tissue-engineered repair material (TERM) has been applied to repair PFD and could markedly improve the prognosis of POP and SUI repair surgery in animal models. We review the directions and progression of TERM in POP and SUI repair. Adipose-derived stem cells (ADSCs) and endometrial mesenchymal stem cells (eMSCs) appear to be suitable cell types for scaffold seeding and clinical implantation. The multidisciplinary therapy approach to tissue engineering is a promising direction for tissue repair. More and longer follow-up studies are needed before determining cell types and materials for PFD repair.

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,...

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.

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.

Biocompatible Polymers and their Potential Biomedical Applications: A Review

Background:

Biocompatible polymers are gaining great interest in the field of biomedical applications. The term biocompatibility refers to the suitability of a polymer to body and body fluids exposure. Biocompatible polymers are both synthetic (man-made) and natural and aid in the close vicinity of a living system or work in intimacy with living cells. These are used to gauge, treat, boost, or substitute any tissue, organ or function of the body. A biocompatible polymer improves body functions without altering its normal functioning and triggering allergies or other side effects. It encompasses advances in tissue culture, tissue scaffolds, implantation, artificial grafts, wound fabrication, controlled drug delivery, bone filler material, etc.

Objectives:

This review provides an insight into the remarkable contribution made by some well-known biopolymers such as polylactic-co-glycolic acid, poly(ε-caprolactone) (PCL), polyLactic Acid, poly(3- hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), Chitosan and Cellulose in the therapeutic measure for many biomedical applications.

Methods: :

Various techniques and methods have made biopolymers more significant in the biomedical fields such as augmentation (replaced petroleum based polymers), film processing, injection modeling, blow molding techniques, controlled / implantable drug delivery devices, biological grafting, nano technology, tissue engineering etc.

Results:

The fore mentioned techniques and other advanced techniques have resulted in improved biocompatibility, nontoxicity, renewability, mild processing conditions, health condition, reduced immunological reactions and minimized side effects that would occur if synthetic polymers are used in a host cell.

Conclusion:

Biopolymers have brought effective and attainable targets in pharmaceutics and therapeutics. There are huge numbers of biopolymers reported in the literature that has been used effectively and extensively.

Landmarks in vaginal mesh development: polypropylene mesh for treatment of SUI and POP

Vaginal meshes used in the treatment of stress urinary incontinence (SUI) and pelvic organ prolapse (POP) have produced highly variable outcomes, causing life-changing complications in some patients while providing others with effective, minimally invasive treatments. The risk:benefit ratio when using vaginal meshes is a complex issue in which a combination of several factors, including the inherent incompatibility of the mesh material with some applications in pelvic reconstructive surgeries and the lack of appropriate regulatory approval processes at the time of the premarket clearance of these products, have contributed to the occurrence of complications caused by vaginal mesh. Surgical mesh used in hernia repair has evolved over many years, from metal implants to knitted polymer meshes that were adopted for use in the pelvic floor for treatment of POP and SUI. The evolution of the material and textile properties of the surgical mesh was guided by clinical feedback from hernia repair procedures, which were also being modified to obtain the best outcomes with use of the mesh. Current evidence shows how surgical mesh fails biomechanically when used in the pelvic floor and materials with improved performance can be developed using modern material processing and tissue engineering techniques.

Multi-Functional Electrospun Nanofibers from Polymer Blends for Scaffold Tissue Engineering

Electrospinning and polymer blending have been the focus of research and the industry for their versatility, scalability, and potential applications across many different fields. In tissue engineering, nanofiber scaffolds composed of natural fibers, synthetic fibers, or a mixture of both have been reported. This review reports recent advances in polymer blended scaffolds for tissue engineering and the fabrication of functional scaffolds by electrospinning. A brief theory of electrospinning and the general setup as well as modifications used are presented. Polymer blends, including blends with natural polymers, synthetic polymers, mixture of natural and synthetic polymers, and nanofiller systems, are discussed in detail and reviewed.

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.

Tissue engineering for the pelvic floor

PURPOSE OF REVIEW

To set in context the challenge of developing tissue-engineered constructs for use in the female pelvic floor compared with at least 30 years of research progress in tissue engineering for other tissues.

RECENT FINDINGS

The relative lack of information on the mechanical requirements of the pelvic floor in women who have suffered damage to these tissues is a major challenge to designing tissue-engineered materials for use in this area. A few groups are now using autologous cells and biomaterials to develop constructs for repair and regeneration of the pelvic floor. Progress with these has reached early stage evaluation in small animal models. Meanwhile the regulatory challenge of introducing laboratory-expanded cell therapy into the clinic is prompting groups to look at alternatives, such as using lipoaspirate retrieved in theatre as a source of adult stem cells for a number of tissues. In our group, we have begun to look at lipoaspirate for repair of the pelvic floor.

SUMMARY

There is a need for research to harvest the advances made over the last 30 years in developing tissue-engineered constructs for several tissues to now tackle the problems of the weakened pelvic floor. At present, there are relatively few groups engaged in this challenge despite the growing clinical need.

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.

Polylactic acid (PLA) controlled delivery carriers for biomedical applications

Polylactic acid (PLA) and its copolymers have a long history of safety in humans and an extensive range of applications. PLA is biocompatible, biodegradable by hydrolysis and enzymatic activity, has a large range of mechanical and physical properties that can be engineered appropriately to suit multiple applications, and has low immunogenicity. Formulations containing PLA have also been Food and Drug Administration (FDA)-approved for multiple applications making PLA suitable for expedited clinical translatability. These biomaterials can be fashioned into sutures, scaffolds, cell carriers, drug delivery systems, and a myriad of fabrications. PLA has been the focus of a multitude of preclinical and clinical testing. Three-dimensional printing has expanded the possibilities of biomedical engineering and has enabled the fabrication of a myriad of platforms for an extensive variety of applications. PLA has been widely used as temporary extracellular matrices in tissue engineering. At the other end of the spectrum, PLA's application as drug-loaded nanoparticle drug carriers, such as liposomes, polymeric nanoparticles, dendrimers, and micelles, can encapsulate otherwise toxic hydrophobic anti-tumor drugs and evade systemic toxicities. The clinical translation of these technologies from preclinical experimental settings is an ever-evolving field with incremental advancements. In this review, some of the biomedical applications of PLA and its copolymers are highlighted and briefly summarized.