Influence of sling material on inflammation and collagen deposit in an animal model

Dysregulated wound healing in the pathogenesis of urogynecologic mesh complications

To test the hypothesis that dysregulated wound healing is associated with Urogynecologic mesh complications, we collected vaginal cell secretions using vaginal swabs after polypropylene mesh implantation in patients with (N = 39) and without (N = 40) complication. A customized multiplex immunoassay measured markers of inflammation (MCP-1, IGFBP-1, IL-2, IL-10, IL-17, PDGF-BB, bFGF, IL-1b, IL-6, IL-12p70, TNF-α), neuroinflammation (IL-1RA, TGF-β, IL-15, IL-18, IL-3, M-CSF), angiogenesis (VEGF), and matrix proteins (fibronectin, tenasin c, thrombospondin-2, lumican) between groups. Patients with complications were younger, heavier, implanted with mesh longer, and more likely to be ever smokers. A 5 kg/m2 BMI increase and ever-smoking were associated with a 2.4-fold and sixfold increased risk of complication, respectively. Patients with the highest tertile of bFGF, fibronectin, thrombospondin-2, TNF-β, or VEGF had an odds ratio (OR) of 11.8 for having a mesh complication while ≥ 3 elevated had an OR of 237 while controlling for age, BMI, and smoking. The highest tertile of bFGF, thrombospondin-2, and fibronectin together perfectly indicated a complication (P < 0.0001). A receiver-operator curve for high bFGF, thrombospondin-2, and fibronectin showed excellent discrimination between complications and controls (AUC 0.87). These data provide evidence of dysregulated wound healing in mesh complications. Modifiable factors provide potential targets for patient counseling and interventions.

Host-biomaterial interactions in mesh complications after pelvic floor reconstructive surgery

Polypropylene (PPL) mesh is widely used in pelvic floor reconstructive surgery for prolapse and stress urinary incontinence. However, some women, particularly those treated using transvaginal PPL mesh placement for prolapse, experience intractable pain and mesh exposure or extrusion. Explanted tissue from patients with complications following transvaginal implantation of mesh is typified by a dense fibrous capsule with an immune cell-rich infiltrate, suggesting that the host immune response has a role in transvaginal PPL mesh complications through the separate contributions of the host (patient), the biological niche within which the material is implanted and biomaterial properties of the mesh. This immune response might be strongly influenced by both the baseline inflammatory status of the patient, surgical technique and experience, and the unique hormonal, immune and microbial tissue niche of the vagina. Mesh porosity, surface area and stiffness also might have an effect on the immune and tissue response to transvaginal mesh placement. Thus, a regulatory pathway is needed for mesh development that recognizes the roles of host and biological factors in driving the immune response to mesh, as well as mandatory mesh registries and the longitudinal surveillance of patients.

Urethral Diverticulum following Polypropylene Mesh Midurethral Slings: A Literature Review

Aims

It is currently unknown whether an association exists between polypropylene mesh and urethral diverticulum formation following placement of polypropylene midurethral slings (MUS) for the treatment of stress urinary incontinence (SUI). We aimed to examine the literature associating MUS with the occurrence of urethral diverticula.

Methods

Multiple online research databases, including PubMed, Google Scholar, EBSCOhost, and the Cochrane Library, were searched, from January 2019 to February 2019, for evidence related to the occurrence of urethral diverticula following polypropylene MUS procedures.

Results

Four case reports were published demonstrating the occurrence of urethral diverticula following the use of polypropylene mesh for surgical treatment of SUI. Subjects of these cases were menopausal and had an elevated body mass index (BMI), recurrent urinary tract infections (UTIs), autoimmune conditions, or prior pelvic floor surgeries. A thorough urologic workup, including imaging prior to sling placement, was not always performed.

Conclusion

No clear association exists between polypropylene MUS placement and subsequent urethral diverticulum formation. Factors that diminish polypropylene mesh biocompatibility include elevated BMI, menopause, recurrent UTIs, prior pelvic surgeries, and preexisting medical conditions. Symptoms associated with urethral diverticula should prompt a complete urologic workup prior to MUS placement.

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.

Effect of platelet-rich plasma on polypropylene meshes implanted in the rabbit vagina: histological analysis

PURPOSE

The polypropylene mesh (PPM) is used in many surgical interventions because of its good incorporation and accessibility. However, potential mesh-related complications are common. Platelet-rich plasma (PRP) improves the healing of wounds and is inexpensive. Thus, the purpose of this study was to analyze the effect of the PRP-gel coating of a PPM on inflammation, production of collagen, and smooth muscle in the rabbit vagina.

MATERIALS AND METHODS

The intervention consisted of a 1.5cm incision and divulsion of the vaginal mucosa for the implantation of a PRP-coated PPM. The PRP-coated mesh was implanted in 15 rabbits, and in the second group, the same implant was used without the PRP coating. In the sham group, the intervention consisted of the incision, divulsion, and suture. The rabbits were euthanized at 7, 30 and 90 days, and full-thickness sagittal sections of the posterior vaginal wall and rectum were scored. The inflammatory infiltrate was evaluated using hematoxylin and eosin staining. The Sirius Red stain was used to examine deposition of collagen I and III, and Masson's trichrome staining was used to visualize the smooth muscle.

RESULTS

The group with PRP-coated meshes had a lower inflammatory infiltrate count at 30 days. Deposition of collagen III increased with the use of PRP-coating at 90 days.

CONCLUSIONS

The area of inflammatory infiltrate was significantly increased in the group without the PRP-coated mesh at 30 days but not in the group with the PRPcoated mesh, indicating a less intense inflammatory response. In addition, a significant increase in collagen III occurred at 90 days.

Structural differences and architectural features of two different polypropylene slings (TVT-O and I-STOP) have no impact on biocompatibility and tissue reactions

Introduction

To evaluate the impact of design features of the synthetic mid-urethral slings on tissue integrity and inflammatory responses.

Material and methods

In total 30 female Sprague-Dawley rats were implanted with type I monofilamentous, macroporous polypropylene meshes: Gynecare TVT-Obturator tape^® (Ethicon Inc., Johnson & Johnson, Somerville, NJ, USA) and I-STOP^® (CL Medical Inc., Lyon, France). All animal groups were sacrificed at set time intervals – 6 weeks, 3 months, 6 months, 9 months and 12 months – and the abdominal wall was harvested with mesh strips for histological evaluation.

Results

All mesh strips appeared to be well incorporated into the abdominal wall, and no signs of shrinkage was noticed. All specimens showed a thin/delicate, loose, fibrous interface between the synthetic graft plate and abdominal wall, along with mild inflammatory reactions from 6 weeks to 12 months.

Conclusions

Both mesh brands induced comparable, minimal foreign body reactions and integrated well into the host tissues despite differences in architectural features. TVT-O^® and I-STOP^® evoked similar low-grade inflammatory responses up to 12 months in this animal model.

Structural differences and architectural features of polypropylene slings used in this study have had no impact on tissue integrity and inflammatory responses.

Histological response to platelet-rich plasma added to polypropylene mesh implemented in rabbits

Introduction:

The platelet-rich plasma (PRP) is part of a set of biotechnologies, providing some growth factors that promote repair of different tissues. The polypropylene meshes (PPM) are applied in the correction of abdominal defects, pelvic floor and urinary incontinence, however, they induce many significant complications, as a result of an inappropriate inflammatory response.

Purpose:

To investigate the changes caused by PRP associated with the implantation of PPM in the abdomen of female rabbits, in the production of collagen I and III and the inflammatory infiltrate (ININ).

Materials and Methods:

We performed implant meshes with and without PRP in adult rabbits (n=30) and euthanasia at 7, 30 and 90 days. Two plates were prepared from each animal and analyzed in five different fields. The ININ was evaluated by quantification of inflammatory cells using hematoxylin-eosin and the collagen by Sirius red method. The results were analyzed applying the Wilcoxon, Kruskal-Wallis, Junckheere and Friedmann tests.

Results:

There was a significant difference in the number of inflammatory cells between the groups with and without PRP (p=0.01) at 90 days. There was increased production of collagen I, III and total with the use of PRP, at seven days.

Conclusion:

The PPM coating with PRP was associated with increased ININ at the implant area, and an increasing trend during the process of tissue repair. The PPM coated with PRP was related to increased concentration of collagen I, collagen III and the concentration of total collagen increased after seven days of implantation.

BIOMECHANICAL PROPERTIES OF MESHES FOLLOWING IMPLANTATION IN THE RAT ABDOMINAL WALL MODEL

The objective of our study was to (1) evaluate mesh strength and collagen incorporation after 4 and 12 weeks of implantation in a rat abdominal wall model and (2) determine the relationship between collagen deposition and mechanical strength of a chitosan-coated polypropylene mesh. We implanted 0.5% chitosan-coated polypropylene mesh (PPM), collagen-coated PPM (PelvitexTM; C.R. Bard), and PPM (Avaulta Solo[Formula: see text]; C.R. Bard) using a rat abdominal defect model. Mechanical properties were determined from uniaxial tensile testing and collagen deposition of each mesh was evaluated 4 and 12 weeks post-implantation. We found that after implantation, the neo tissue of Ch-PPM is stiffer than the commercially available meshes. We also observed no significant difference in the ratio of collagen types I/III between mesh samples at 4 weeks or 12 weeks. We found no relationship between the ratio of collagen types I/III and the mechanical strength of mesh samples after implantation. The increased stiffness with chitosan coating could be due to increased muscle tissue ingrowth.

Biomaterials for pelvic floor reconstructive surgery: how can we do better?

Stress urinary incontinence (SUI) and pelvic organ prolapse (POP) are major health issues that detrimentally impact the quality of life of millions of women worldwide. Surgical repair is an effective and durable treatment for both conditions. Over the past two decades there has been a trend to enforce or reinforce repairs with synthetic and biological materials. The determinants of surgical outcome are many, encompassing the physical and mechanical properties of the material used, and individual immune responses, as well surgical and constitutional factors. Of the current biomaterials in use none represents an ideal. Biomaterials that induce limited inflammatory response followed by constructive remodelling appear to have more long term success than biomaterials that induce chronic inflammation, fibrosis and encapsulation. In this review we draw upon published animal and human studies to characterize the changes biomaterials undergo after implantation and the typical host responses, placing these in the context of clinical outcomes.

Histopathology of excised midurethral sling mesh

INTRODUCTION AND HYPOTHESIS

The objective of this study was to compare the histological characteristics of pathological specimens of excised midurethral sling mesh and surrounding vaginal tissue in patients who presented preoperatively with pain and/or exposure of mesh to patients who underwent mesh excision for voiding dysfunction without pain and/or erosion.

METHODS

This is a retrospective case-control study of women who underwent excision of midurethral sling mesh between 2008 and 2013. Three groups were identified: (1) voiding dysfunction without pain or exposure (control group), (2) pain and/or mesh exposure, and (3) voiding dysfunction with pain and/or mesh exposure. All original pathological specimens were rereviewed by one pathologist blinded to indication for excision and the previous pathology report. Degree of inflammation and fibrosis were recorded based on a 4-point scale along with the presence of giant cell reaction.

RESULTS

A total of 130 subjects met inclusion criteria: 60 (46.2 %) with voiding dysfunction only, 21 (16.2 %) with pain/erosion, and 49 (37.7 %) with both pain/exposure and voiding dysfunction. The voiding dysfunction only group was found to have significantly higher levels of inflammation, median grade 2 (1-3), compared to the other two groups with a p value of 0.007. There were no statistical differences in fibrosis and giant cell reaction between the three groups.

CONCLUSIONS

Midurethral sling mesh excised for voiding dysfunction demonstrates elevated levels of inflammation compared to mesh that is excised for pain and/or exposure. The vaginal tissue fibrosis and giant cell reaction are similar in patients who undergo mesh excision for voiding dysfunction and pain, and/or mesh exposure.

Polypropylene mesh and the host response

The use of polypropylene (PP) mesh for pelvic floor repair has been increasing dramatically over the past decade; however, tissue response in humans has not been extensively studied. This review discusses PP mesh and postimplantation host tissue response. Emphasis is placed on studies investigating the relationship between individual mesh properties and specific responses. There is an immediate inflammatory response after PP mesh implantation that lays the framework for tissue ingrowth and subsequent mesh integration. This response varies based on physical properties of individual mesh, such as pore size, weight, coatings, bacterial colonization, and biofilm production.

Mechanical properties and tissue reinforcement of polypropylene grafts used for pelvic floor repair--an experimental study

PURPOSE

Although grafts can be made from the same materials, the final weave of the product may play a role in the ultimate outcomes or complications. The aim of this experimental study is to evaluate and compare the mechanical properties of the meshes and their influence on biological characteristics as well.

METHODS

Full-thickness abdominal wall defect with respect to the peritoneum was primary repaired in 144 male Wister rats using the overlay technique. Monofilament, multifilament and coated polypropylene grafts were used for the repairs. Graft shrinkage, thickness and tensile strength of the explants were analysed after 3 and 6 weeks.

RESULTS

Monofilament grafts showed the highest shrinkage level of 11.97-18% during the investigated period. The thickness of monofilament explants increased gradually, with a maximum of 25.35% after 6 weeks. Multifilament and collagen explants did swell more rapidly in the third week, decreasing thereafter to 19.63-23.04% above the pre-implantation values after 6 weeks. The tensile strength showed a gradual increase over the course of the experiment in all groups.

CONCLUSION

After graft stabilisation, all samples had similar strength, regardless of the significant differences in the pre-implantation values of graft strength.