Mesh biocompatibility: effects of cellular inflammation and tissue remodelling

Recent Advances in Functional Hydrogel for Repair of Abdominal Wall Defects: A Review

The abdominal wall plays a crucial role in safeguarding the internal organs of the body, serving as an essential protective barrier. Defects in the abdominal wall are common due to surgery, infection, or trauma. Complex defects have limited self-healing capacity and require external intervention. Traditional treatments have drawbacks, and biomaterials have not fully achieved the desired outcomes. Hydrogel has emerged as a promising strategy that is extensively studied and applied in promoting tissue regeneration by filling or repairing damaged tissue due to its unique properties. This review summarizes the five prominent properties and advances in using hydrogels to enhance the healing and repair of abdominal wall defects: (a) good biocompatibility with host tissues that reduces adverse reactions and immune responses while supporting cell adhesion migration proliferation; (b) tunable mechanical properties matching those of the abdominal wall that adapt to normal movement deformations while reducing tissue stress, thereby influencing regulating cell behavior tissue regeneration; (c) drug carriers continuously delivering drugs and bioactive molecules to sites optimizing healing processes enhancing tissue regeneration; (d) promotion of cell interactions by simulating hydrated extracellular matrix environments, providing physical support, space, and cues for cell migration, adhesion, and proliferation; (e) easy manipulation and application in surgical procedures, allowing precise placement and close adhesion to the defective abdominal wall, providing mechanical support. Additionally, the advances of hydrogels for repairing defects in the abdominal wall are also mentioned. Finally, an overview is provided on the current obstacles and constraints faced by hydrogels, along with potential prospects in the repair of abdominal wall defects.

Titanium Implants Coated with Hydroxyapatite Used in Orbital Wall Reconstruction-A Literature Review

With the increasing incidences of orbital wall injuries, effective reconstruction materials and techniques are imperative for optimal clinical outcomes. In this literature review, we delve into the efficacy and potential advantages of using titanium implants coated with nanostructured hydroxyapatite for the reconstruction of the orbital wall. Titanium implants, recognized for their durability and mechanical strength, when combined with the osteoconductive properties of hydroxyapatite, present a potentially synergistic solution. The purpose of this review was to critically analyze the recent literature and present the state of the art in orbital wall reconstruction using titanium implants coated with nanostructured hydroxyapatite. This review offers clinicians detailed insight into the benefits and potential drawbacks of using titanium implants coated with nanostructured hydroxyapatite for orbital wall reconstruction. The highlighted results advocate for its benefits in terms of osseointegration and provide a novel strategy for orbital reconstruction, though further studies are essential to establish long-term efficacy and address concerns.

Micro(nano)plastics in the Human Body: Sources, Occurrences, Fates, and Health Risks

The increasing global attention on micro(nano)plastics (MNPs) is a result of their ubiquity in the water, air, soil, and biosphere, exposing humans to MNPs on a daily basis and threatening human health. However, crucial data on MNPs in the human body, including the sources, occurrences, behaviors, and health risks, are limited, which greatly impedes any systematic assessment of their impact on the human body. To further understand the effects of MNPs on the human body, we must identify existing knowledge gaps that need to be immediately addressed and provide potential solutions to these issues. Herein, we examined the current literature on the sources, occurrences, and behaviors of MNPs in the human body as well as their potential health risks. Furthermore, we identified key knowledge gaps that must be resolved to comprehensively assess the effects of MNPs on human health. Additionally, we addressed that the complexity of MNPs and the lack of efficient analytical methods are the main barriers impeding current investigations on MNPs in the human body, necessitating the development of a standard and unified analytical method. Finally, we highlighted the need for interdisciplinary studies from environmental, biological, medical, chemical, computer, and material scientists to fill these knowledge gaps and drive further research. Considering the inevitability and daily occurrence of human exposure to MNPs, more studies are urgently required to enhance our understanding of their potential negative effects on human health.

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.

Attenuating Chronic Fibrosis: Decreasing Foreign Body Response with Acellular Dermal Matrix

Surgical implants are increasingly used across multiple medical disciplines, with applications ranging from tissue reconstruction to improving compromised organ and limb function. Despite their significant potential for improving health and quality of life, biomaterial implant function is severely limited by the body's immune response to its presence: this is known as the foreign body response (FBR) and is characterized by chronic inflammation and fibrotic capsule formation. This response can result in life-threatening sequelae such as implant malfunction, superimposed infection, and associated vessel thrombosis, in addition to soft tissue disfigurement. Patients may require frequent medical visits, as well as repeated invasive procedures, increasing the burden on an already strained health care system. Currently, the FBR and the cells and molecular mechanisms that mediate it are poorly understood. With applications across a wide array of surgical specialties, acellular dermal matrix (ADM) has emerged as a potential solution to the fibrotic reaction seen with FBR. Although the mechanisms by which ADM decreases chronic fibrosis remain to be clearly characterized, animal studies across diverse surgical models point to its biomimetic properties that facilitate decreased periprosthetic inflammation and improved host cell incorporation. Impact Statement Foreign body response (FBR) is a significant limitation to the use of implantable biomaterials. Acellular dermal matrix (ADM) has been observed to decrease the fibrotic reaction seen with FBR, although its mechanistic details are poorly understood. This review is dedicated to summarizing the primary literature on the biology of FBR in the context of ADM use, using surgical models in breast reconstruction, abdominal and chest wall repair, and pelvic reconstruction. This article will provide readers with an overarching review of shared mechanisms for ADM across multiple surgical models and diverse anatomical applications.

Implantable Hydrogel-Protective DNA Aptamer-Based Sensor Supports Accurate, Continuous Electrochemical Analysis of Drugs at Multiple Sites in Living Rats

The ability to track the levels of specific molecules, such as drugs, metabolites, and biomarkers, in the living body, in real time and for long durations, would improve our understanding of health and our ability to diagnose, treat, and monitor disease. To this end, we are developing electrochemical aptamer-based (EAB) biosensors, a general platform supporting high-frequency, real-time molecular measurements in the living body. Here we report that the use of an agarose hydrogel protective layer for EAB sensors significantly improves their signaling stability when deployed in the complex, highly time-varying environments found in vivo. The improved stability is sufficient that these hydrogel-protected sensors achieved good baseline stability and precision when deployed in situ in the veins, muscles, bladder, or tumors of living rats without the use of the drift correction approaches traditionally required in such placements. Finally, our implantable gel-protective EAB sensors achieved good biocompatibility when deployed in vivo in the living rats without causing any severe inflammation.

Poly-L-Lactic Acid Fillers Improved Dermal Collagen Synthesis by Modulating M2 Macrophage Polarization in Aged Animal Skin

Poly-L-lactic acid (PLLA) fillers correct cutaneous volume loss by stimulating fibroblasts to synthesize collagen and by augmenting the volume. PLLA triggers the macrophage-induced activation of fibroblasts that secrete transforming growth factor-β (TGF-β). However, whether M2 macrophage polarization is involved in PLLA-induced collagen synthesis via fibroblast activation in aged skin is not known. Therefore, we evaluated the effect of PLLA on dermal collagen synthesis via M2 polarization in an H₂O₂-induced cellular senescence model and aged animal skin. H₂O₂-treated macrophages had increased expression levels of the M1 marker CD80 and decreased expression levels of the M2 marker CD163, which were reversed by PLLA. The expression levels of interleukin (IL)-4 and IL-13, which mediate M2 polarization, were decreased in H₂O₂-treated macrophages and increased upon the PLLA treatment. CD163, IL-4, and IL-13 expression levels were decreased in aged skin, but increased after the PLLA treatment. The expression levels of TGF-β, pSMAD2/SMAD2, connective tissue growth factor (CTGF), alpha-smooth muscle actin (α-SMA), collagen type 1A1 (COL1A1), and COL3A1 were also decreased in aged skin, but increased after the PLLA treatment. Moreover, PLLA upregulated phosphatidylinositol 3-kinase p85α (PI3-kinase p85α)/protein kinase B (AKT) signaling, leading to fibroblast proliferation. PLLA decreased the expression of matrix metalloproteinase (MMP) 2 and MMP3, which destroy collagen and elastin fibers in aged skin. The amount of collagen and elastin fibers in aged skin increased following the PLLA treatment. In conclusion, PLLA causes M2 polarization by increasing IL-4 and IL-13 levels and upregulating TGF-β expression and collagen synthesis in aged skin.

A Novel Bio-Adhesive Mesh System for Medical Implant Applications: In Vivo Assessment in a Rabbit Model

Injectable surgical sealants and adhesives, such as biologically derived fibrin gels and synthetic hydrogels, are widely used in medical products. While such products adequately adhere to blood proteins and tissue amines, they have poor adhesion with polymer biomaterials used in medical implants. To address these shortcomings, we developed a novel bio-adhesive mesh system utilizing the combined application of two patented technologies: a bifunctional poloxamine hydrogel adhesive and a surface modification technique that provides a poly-glycidyl methacrylate (PGMA) layer grafted with human serum albumin (HSA) to form a highly adhesive protein surface on polymer biomaterials. Our initial in vitro tests confirmed significantly improved adhesive strength for PGMA/HSA grafted polypropylene mesh fixed with the hydrogel adhesive compared to unmodified mesh. Toward the development of our bio-adhesive mesh system for abdominal hernia repair, we evaluated its surgical utility and in vivo performance in a rabbit model with retromuscular repair mimicking the totally extra-peritoneal surgical technique used in humans. We assessed mesh slippage/contraction using gross assessment and imaging, mesh fixation using tensile mechanical testing, and biocompatibility using histology. Compared to polypropylene mesh fixed with fibrin sealant, our bio-adhesive mesh system exhibited superior fixation without the gross bunching or distortion that was observed in the majority (80%) of the fibrin-fixed polypropylene mesh. This was evidenced by tissue integration within the bio-adhesive mesh pores after 42 days of implantation and adhesive strength sufficient to withstand the physiological forces expected in hernia repair applications. These results support the combined use of PGMA/HSA grafted polypropylene and bifunctional poloxamine hydrogel adhesive for medical implant applications.

Modulation of Macrophage Function by Bioactive Wound Dressings with an Emphasis on Extracellular Matrix-Based Scaffolds and Nanofibrous Composites

Bioactive wound dressings that are capable of regulating the local wound microenvironment have attracted a very large interest in the field of regenerative medicine. Macrophages have many critical roles in normal wound healing, and the dysfunction of macrophages significantly contributes to impaired or non-healing skin wounds. Regulation of macrophage polarization towards an M2 phenotype provides a feasible strategy to enhance chronic wound healing, mainly by promoting the transition of chronic inflammation to the proliferation phase of wound healing, upregulating the level of anti-inflammatory cytokines around the wound area, and stimulating wound angiogenesis and re-epithelialization. Based on this, modulation of macrophage functions by the rational design of bioactive scaffolds has emerged as a promising way to accelerate delayed wound healing. This review outlines current strategies to regulate the response of macrophages using bioactive materials, with an emphasis on extracellular matrix-based scaffolds and nanofibrous composites.

Autoimmunity and hernia mesh: fact or fiction?

BACKGROUND

There is an increasing number of patients following hernia surgery with implanted mesh reporting symptoms that could indicate autoimmune or allergic reactions to mesh. 'Allergy' to metals, various drugs, and chemicals is well recognised. However, hypersensitivity, allergy or autoimmunity caused by surgical mesh has not been proven by a scientific method to date. The aim of this study was twofold: to describe the pathophysiology of autoimmunity and foreign body reaction and to undertake a systematic review of surgical mesh implanted at the time of hernia repair and the subsequent development of autoimmune disease.

METHODS

A systematic review using the PRISMA guidelines was undertaken. Pubmed (Medline), Google Scholar and Cochrane databases were searched for all English-written peer-reviewed articles published between 2000 and 2021. The search was performed using the keywords "hernia", "mesh", "autoimmunity", "ASIA", "immune response", "autoimmune response".

RESULTS

Seven papers were included in the final analysis-three systematic reviews, three cohort studies and one case report. Much of the current data regarding the association of hernia mesh and autoimmunity relies on retrospective cohort studies and/or case reports with limited availability of cofounding factor data linked to autoimmune disease such as smoking status or indeed a detailed medical history of patients. Three systematic reviews have discussed this topic, each with a slightly different approach and none of them has identified causality between the use of mesh and the subsequent development of autoimmune disease.

CONCLUSION

There is little evidence that the use of polypropylene mesh can lead to autoimmunity. A large number of potential triggers of autoimmunity along with the genetic predisposition to autoimmune disease and the commonality of hernia, make a cause and effect difficult to unravel at present. Biomaterials cause foreign body reactions, but a chronic foreign body reaction does not indicate autoimmunity, a common misunderstanding in the literature.

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.

Effects of Calcium Carbonate Microcapsules and Nanohydroxyapatite on Properties of Thermosensitive Chitosan/Collagen Hydrogels

Thermosensitive chitosan/collagen hydrogels are osteoconductive and injectable materials. In this study, we aimed to improve these properties by adjusting the ratio of nanohydroxyapatite particles to calcium carbonate microcapsules in a β-glycerophosphate-crosslinked chitosan/collagen hydrogel. Two hydrogel systems with 2% and 5% nanohydroxyapatite particles were studied, each of which had varying microcapsule content (i.e., 0%, 1%, 2%, and 5%). Quercetin-incorporated calcium carbonate microcapsules were prepared. Calcium carbonate microcapsules and nanohydroxyapatite particles were then added to the hydrogel according to the composition of the studied system. The properties of the hydrogels, including cytotoxicity and biocompatibility, were investigated in mice. The calcium carbonate microcapsules were 2-6 µm in size, spherical, with rough and nanoporous surfaces, and thus exhibited a burst release of impregnated quercetin. The 5% nanohydroxyapatite system is a solid particulate gel that supports homogeneous distribution of microcapsules in the three-dimensional matrix of the hydrogels. Calcium carbonate microcapsules increased the mechanical and physical strength, viscoelasticity, and physical stability of the nanohydroxyapatite hydrogels while decreasing their porosity, swelling, and degradation rates. The calcium carbonate microcapsules-nanohydroxyapatite hydrogels were noncytotoxic and biocompatible. The properties of the hydrogel can be tailored by adjusting the ratio of calcium carbonate microcapsules to the nanohydroxyapatite particles. The 1% calcium carbonate microcapsules containing 5% nanohydroxyapatite particle-chitosan/collagen hydrogel exhibited mechanical and physical strength, permeability, and prolonged release profiles of quercetin, which were superior to those of the other studied systems and were optimal for promoting bone regeneration and delivering natural flavonoids.

Mesh erosion into skin following laparoscopic totally extraperitoneal (TEP) inguinal hernia repair

With increasing utilisation of meshes in inguinal hernia repair, reports of mesh-related complications are emerging, particularly late visceral complications, with mesh migration and erosion into the small bowel, bladder and colon reported after laparoscopic totally extraperitoneal (TEP) inguinal hernia repair. We present a case of spontaneous mesh migration through the superficial inguinal ring with skin erosion following TEP inguinal hernia repair, the first published report in the literature to our knowledge. This case highlights the difficulty in diagnosis due to the long latent period of hernia repair and the onset of erosion. A high index of suspicion is required when diagnosing any patient who presents with an unexplained groin abscess following ipsilateral TEP repair. CT scan should be performed early for diagnosis and assessment. Removal of the migrated portion of the mesh, antibiotic therapy and secondary wound closure are strategies for the successful treatment of this complication.

Anti-adhesive bioresorbable elastomer-coated composite hernia mesh that reduce intraperitoneal adhesions

Intraperitoneal adhesions (IAs) are a major complication arising from abdominal repair surgeries, including hernia repair procedures. Herein, we fabricated a composite mesh device using a macroporous monofilament polypropylene mesh and a degradable elastomer coating designed to meet the requirements of this clinical application. The degradable elastomer was synthesized using an organo-base catalyzed thiol-yne addition polymerization that affords independent control of degradation rate and mechanical properties. The elastomeric coating was further enhanced by the covalent tethering of antifouling zwitterion molecules. Mechanical testing demonstrated the elastomer forms a robust coating on the polypropylene mesh does not exhibit micro-fractures, cracks or mechanical delamination under cyclic fatigue testing that exceeds peak abdominal loads (50 N/cm). Quartz crystal microbalance measurements showed the zwitterionic functionalized elastomer further reduced fibrinogen adsorption by 73% in vitro when compared to unfunctionalized elastomer controls. The elastomer exhibited degradation with limited tissue response in a 10-week murine subcutaneous implantation model. We also evaluated the composite mesh in an 84-day study in a rabbit cecal abrasion hernia adhesion model. The zwitterionic composite mesh significantly reduced the extent and tenacity of IAs by 94% and 90% respectively with respect to uncoated polypropylene mesh. The resulting composite mesh device is an excellent candidate to reduce complications related to abdominal repair through suppressed fouling and adhesion formation, reduced tissue inflammation, and appropriate degradation rate.

Allograft Extensor Mechanism Reconstruction in Salvage Revision Knee Arthroplasty: Surgical Technique

Although extensor mechanism failure remains a catastrophic complication of knee arthroplasty, there are a number of contemporary techniques with reasonable outcomes that restore function. Chronic failures require advanced reconstruction techniques. Similar complication rates have been reported for the use of autografts, allografts, or mesh reconstructions. Here, we describe our surgical technique in allograft extensor mechanism reconstruction for chronic failures in salvage revision knee arthroplasty using a complete extensor mechanism allograft with a modified proximal fixation and case demonstrations.

Therapy of chronic extensor mechanism deficiency after total knee arthroplasty using a monofilament polypropylene mesh

Introduction

Lesions of the quadriceps or patellar tendon after total knee arthroplasty (TKA) are a rare but serious complication which, if left untreated, can lead to loss of function of the knee joint. While acute and subacute extensor mechanism disruptions may have several causes, chronic deficiencies are often related to multiple prior revision surgeries for joint infection or aseptic TKA failure. Up to date, biological allograft reconstruction showed unsatisfying results. The use of a monofilament polypropylene mesh is a promising approach for this pathological condition. The aim of the present study was to evaluate clinical, functional and patient reported outcomes of this procedure in patients with chronic extensor mechanism deficiency.

Materials and Methods

Twenty-eight patients with chronic extensor mechanism deficiency (quadriceps tendon rupture n = 9, patellar tendon rupture n = 19) after TKA were included in this retrospective study. None of the patients were lost to follow-up. Surgical reconstruction was performed at one institution between 2014 and 2020 with a monofilament polypropylene mesh (Marlex Mesh, Bard, Murray Hill, USA). The mean age at the time of surgery was 69 years. Patients presented with a mean BMI of 33 kg/m². The mean follow-up period was 23 months.

Results

The 2-year survivorship free of mesh revision was 89% [95% confidence interval (CI): 75% to 100%]. Three patients (11%) had to undergo revision because of mechanical mesh failure and received another polypropylene mesh. No further revisions were performed thereafter. Flexion was 87° (range, 30–120°) on average. The majority of patients (75%, 21/28) had a full active extension. The mean active extension lag after surgery was 4 degrees (range, 0–30°).

Discussion

We observed a substantial improvement of extensor mechanism function. The majority of patients had full extension and showed good clinical results. A failure rate of over 50% has been published for alternative procedures. Thus, the use of the described augmentation technique represents a reasonable treatment option for chronic extensor mechanism disruptions of the patellar tendon as well as the quadriceps tendon after total knee arthroplasty. However, there might be a potentially higher risk for infection persistence in periprosthetic joint infection cases due to the presence of a foreign material.

Immunomodulation Effect of Biomaterials on Bone Formation

Traditional bone replacement materials have been developed with the goal of directing the osteogenesis of osteoblastic cell lines toward differentiation and therefore achieving biomaterial-mediated osteogenesis, but the osteogenic effect has been disappointing. With advances in bone biology, it has been revealed that the local immune microenvironment has an important role in regulating the bone formation process. According to the bone immunology hypothesis, the immune system and the skeletal system are inextricably linked, with many cytokines and regulatory factors in common, and immune cells play an essential role in bone-related physiopathological processes. This review combines advances in bone immunology with biomaterial immunomodulatory properties to provide an overview of biomaterials-mediated immune responses to regulate bone regeneration, as well as methods to assess the bone immunomodulatory properties of bone biomaterials and how these strategies can be used for future bone tissue engineering applications.

In vitro two-step granuloma formation model for testing innate immune response to implants and coatings

The extensive innate immune response to implanted biomaterials contributes significantly to their sub-par performance and failure. Granuloma formation is one of such reactions which results in multi-cell type clusters in line with the immune reaction to implanted materials. However, currently no in vitro model of granuloma formation exists that takes into account the arrival of multiple cell types (immune cells and connective tissue cells) to the implant insertion site. In this study, we developed a two-step model based on stimulated macrophage seeding followed by fibroblast introduction after a physiologically relevant time period for mimicking initial steps of immune reaction to biomaterials and inducing granuloma like behavior. Both LPS and TNF-α induction resulted in granuloma like formations which persisted longer than the control conditions. Introduction of human fibroblasts resulted in the colonization of the surfaces where the cell numbers and the collagen secretion were dependent on the microenvironment. In order to demonstrate the capacity of our model system to monitor the reaction to a given coating, a validated antimicrobial coating (Polyarginine (PAR)/Hyaluronic acid (HA)) was used as a testing bed. The coating prevented the adhesion of macrophages while allowing the adhesion of the fibroblast at the time of their arrival. Similar to its antimicrobial activity, macrophage metabolic activity and M2 differentiation in the presence of PAR was dependent to its chain length. The incorporation of fibroblasts resulted in decreased TNF-α and increased IL-1RA secretion especially in stimulation conditions. The pro- and anti-inflammatory cytokine secretions were low for PAR/HA coatings in line with the decreased number of macrophage presence. In the presence of complex PBMC population, the coating resulted in slightly less cellular attachment, without any significant cytokine secretion; the absence of inflammatory reaction was also demonstrated in vivo in a mouse model. The described in vitro granuloma testing system can control the macrophage reaction as a function of stimulation. It can also be used for testing new biomaterials for the potential innate immune responses and also for validation of implant coatings beyond their primary function from the immune response point of view.

Latest Trends on the Attenuation of Systemic Foreign Body Response and Infectious Complications of Synthetic Hernia Meshes

Throughout the past few years, hernia incidence has remained at a high level worldwide, with more than 20 million people requiring hernia surgery each year. Synthetic hernia meshes play an important role, providing a microenvironment that attracts and harbors host cells and acting as a permanent roadmap for intact abdominal wall reconstruction. Nevertheless, it is still inevitable to cause not-so-trivial complications, especially chronic pain and adhesion. In long-term studies, it was found that the complications are mainly caused by excessive fibrosis from the foreign body reaction (FBR) and infection resulting from bacterial colonization. For a thorough understanding of their complex mechanism and providing a richer background for mesh development, herein, we discuss different clinical mesh products and explore the interactions between their structure and complications. We further explored progress in reducing mesh complications to provide varied strategies that are informative and instructive for mesh modification in different research directions. We hope that this work will spur hernia mesh designers to step up their efforts to develop more practical and accessible meshes by improving the physical structure and chemical properties of meshes to combat the increasing risk of adhesions, infections, and inflammatory reactions. We conclude that further work is needed to solve this pressing problem, especially in the analysis and functionalization of mesh materials, provided of course that the initial performance of the mesh is guaranteed.

Breast implant illness: scientific evidence of its existence

INTRODUCTION

More than one million breast augmentation procedures using silicone breast implants (SBI) have been performed worldwide. Adverse events of SBI include local complications such as pain, swelling, redness, infections, capsular contracture, implant rupture and gel-bleed. Furthermore, patients experience systemic symptoms such as chronic fatigue, arthralgias, myalgias, pyrexia, sicca, and cognitive dysfunction. These symptoms received different names such as autoimmune/inflammatory syndrome induced by adjuvants (ASIA) due to silicone incompatibility syndrome and breast implant illness (BII). Because of chronic immune activation, BII/ASIA, allergies, autoimmune diseases, immune deficiencies and finally lymphomas may develop in SBI patients.

AREAS COVERED

Causality for SBI-related BII/ASIA is reviewed. To address the role of silicone implants in promoting causality, we utilized the Bradford-Hill criteria, with results highlighted in this article.

EXPERT OPINION

We conclude that there is a causal association between SBIs and BII/ASIA. Using data derived from patients with BII/ASIA and from other medically implanted devices, there appears to be clear pathogenic relationship between SBI and BII/ASIA. Breast implants cause characteristic systemic reactions in certain women, leading to symptoms of sufficient severity to warrant device removal. The morbidity suffered is variable. SBI removal resolves the symptoms in most women and removal is the most effective treatment.

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.

Tissue engineered bovine saphenous vein extracellular matrix scaffolds produced via antigen removal achieve high in vivo patency rates

Diseases of small diameter blood vessels encompass the largest portion of cardiovascular diseases, with over 4.2 million people undergoing autologous vascular grafting every year. However, approximately one third of patients are ineligible for autologous vascular grafting due to lack of suitable donor vasculature. Acellular extracellular matrix (ECM) scaffolds derived from xenogeneic vascular tissue have potential to serve as ideal biomaterials for production of off-the-shelf vascular grafts capable of eliminating the need for autologous vessel harvest. A modified antigen removal (AR) tissue process, employing aminosulfabetaine-16 (ASB-16) was used to create off-the-shelf small diameter (< 3 mm) vascular graft from bovine saphenous vein ECM scaffolds with significantly reduced antigenic content, while retaining native vascular ECM protein structure and function. Elimination of native tissue antigen content conferred graft-specific adaptive immune avoidance, while retention of native ECM protein macromolecular structure resulted in pro-regenerative cellular infiltration, ECM turnover and innate immune self-recognition in a rabbit subpannicular model. Finally, retention of the delicate vascular basement membrane protein integrity conferred endothelial cell repopulation and 100% patency rate in a rabbit jugular interposition model, comparable only to Autograft implants. Alternatively, the lack of these important basement membrane proteins in otherwise identical scaffolds yielded a patency rate of only 20%. We conclude that acellular antigen removed bovine saphenous vein ECM scaffolds have potential to serve as ideal off-the-shelf small diameter vascular scaffolds with high in vivo patency rates due to their low antigen content, retained native tissue basement membrane integrity and preserved native ECM structure, composition and functional properties. STATEMENT OF SIGNIFICANCE: The use of autologous vessels for the treatment of small diameter vascular diseases is common practice. However, the use of autologous tissue poses significant complications due to tissue harvest and limited availability. Developing an alternative vessel for use for the treatment of small diameter vessel diseases can potentially increase the success rate of autologous vascular grafting by eliminating complications related to the use of autologous vessel and increased availability. This manuscript demonstrates the potential of non-antigenic extracellular matrix (ECM) scaffolds derived from xenogeneic vascular tissue as off-the-shelf vascular grafts for the treatment of small diameter vascular diseases.

Ureteral stents cannot decrease the incidence of ureteroileal anastomotic stricture and leakage: A systematic review and meta-analysis

BACKGROUND

The ileal conduit and ileal orthotopic neobladder were the most popular methods for urinary diversion following radical cystectomy. Stenting the anastomosis of ileo-ureter or ureter-neobladder was a common practice. However, it is still controversial if ureteral stents could prevent complications such as ureteroileal anastomosis stricture (UIAS) and ureteroileal anastomosis leakage (UIAL) after ureteral anastomosis.

OBJECTIVES

This study aims to investigate the role of the ureteral stent in preventing UIAS and UIAL.

DATA SOURCES

We systematically searched the related studies in PubMed, Embase, and Cochrane Library up to June 2020.

STUDY ELIGIBILITY CRITERIA

Cohort studies that identified the use of stent and the incidence of UIAS or UIAL were recorded.

DATA SYNTHESIS

Comparative meta-analysis was conducted on four cohort studies for comparison of UIAS and UIAL between the stented and nonstented groups. Besides, eleven studies which reported the events of UIAS and UIAL were used for meta-analysis of single proportion.

RESULTS

A total of 11 studies were qualified for analysis. Comparative meta-analysis identified that the incidence of UIAS was higher in the stented group than that in the nonstented group, but this did not reach a significant difference (odds ratio [OR]: 1.64; 95% confidence interval [CI]: 0.88-3.05; P = 0.12). Besides, there was no difference in the incidences of UIAL between the stented and the nonstented groups. On meta-analysis of single proportion, the incidence of UIAS was 7% (95% CI: 3%-10%) in the stented group and 3% (95% CI: 1%-6%) in the nonstented group. The UIAL rate was 1% (95% CI, 0%-4%) in stented patients and 2% (95% CI, 1%-4%) in nonstented patients.

CONCLUSION

Stenting the ureteroileal anastomosis resulted in a higher incidence of UIAS. There is no evidence to support ureteral stents could prevent the occurrence of UIAL after urinary diversion.

Short-term outcomes and healthcare resource utilization following incisional hernia repair with synthetic mesh in patients with Crohn's disease

PURPOSE

While the use of synthetic mesh for incisional hernia repair reduces recurrence rates, little evidence exists regarding the impact of this practice on the disease burden of a Crohn's patient. We aimed to describe the post-operative outcomes and healthcare resource utilization following incisional hernia repair with synthetic mesh in patients with Crohn's disease.

METHODS

A retrospective review of adult patients with Crohn's disease who underwent elective open incisional hernia repair with extra-peritoneal synthetic mesh from 2014 to 2018 at a single large academic hospital with surgeons specializing in hernia repair was conducted. Primary outcomes included 30-day post-operative complications and long-term rates of fistula formation and hernia recurrence. The secondary outcome compared healthcare resource utilization during a standardized fourteen-month period before and after hernia repair.

RESULTS

Among the 40 patients included, six (15%) required readmission, 4 (10%) developed a surgical site occurrence, 3 (7.5%) developed a surgical site infection, and one (2.5%) required reoperation within the first 30 days. The overall median follow-up time was 42 months (IQR = 33-56), during which time one (2.5%) patient developed an enterocutaneous fistula and eight (20%) experienced hernia recurrence. Healthcare resource utilization remained unchanged or decreased across every category following repair.

CONCLUSION

The use of extra-peritoneal synthetic mesh during incisional hernia repair in patients with Crohn's disease was not associated with a prohibitively high rate of post-operative complications or an increase in healthcare resource utilization to suggest worsening disease during the first 4 years after repair. Future studies exploring the long-term outcomes of this technique are needed.

Collagen and the effect of poly-l-lactic acid based materials on its synthesis

Collagen is an important protein in various biological functions such as providing elasticity and waterproofing to the skin, structural stability to the cells in connective tissues (e.g. tendons, and bone) and stabilisation of atherosclerotic plaques. Collagen as a peptide with a peculiar triple helical structure is majorly composed of glycine and proline amino acids and is synthesised by fibroblasts via intracellular and extracellular mechanisms. Collagen plays an important role in wound healing, bone repair and plaque build-up during atherosclerosis. Various factors such as interleukins, insulin-like growth factor-I, nicotine, and glucose have been shown to influence collagen synthesis. This paper provides an overview of collagen structure, synthesis mechanisms, and the parameters that stimulate those mechanisms. Poly-l-lactic acid as a well-known biocompatible and biodegradable polymer has proved to stimulate collagen synthesis in various physical forms. As such, in this review special emphasis is laid on the effects of poly-l-lactic acid as well as its mechanism of action on collagen synthesis.

Host Response to Biomaterials for Cartilage Tissue Engineering: Key to Remodeling

Biomaterials play a core role in cartilage repair and regeneration. The success or failure of an implanted biomaterial is largely dependent on host response following implantation. Host response has been considered to be influenced by numerous factors, such as immune components of materials, cytokines and inflammatory agents induced by implants. Both synthetic and native materials involve immune components, which are also termed as immunogenicity. Generally, the innate and adaptive immune system will be activated and various cytokines and inflammatory agents will be consequently released after biomaterials implantation, and further triggers host response to biomaterials. This will guide the constructive remolding process of damaged tissue. Therefore, biomaterial immunogenicity should be given more attention. Further understanding the specific biological mechanisms of host response to biomaterials and the effects of the host-biomaterial interaction may be beneficial to promote cartilage repair and regeneration. In this review, we summarized the characteristics of the host response to implants and the immunomodulatory properties of varied biomaterial. We hope this review will provide scientists with inspiration in cartilage regeneration by controlling immune components of biomaterials and modulating the immune system.

Evaluation of a Novel Absorbable Mesh in a Porcine Model of Abdominal Wall Repair

Bioabsorbable meshes have seen increasing clinical use to reinforce soft tissue, and exist on a spectrum of strength loss versus absorption: several retain their strength for months, but remain in situ for years. Others lose strength fully by 6 weeks. An intermediate profile, with some strength for 3 -4 months, but consistent absorption in less than a year, may be an optimal balance of near-term support and long-term safety. In this large animal study, we evaluate such a mesh (DuraSorb, SIA), assessing its utility in a porcine model of abdominal wall repair.

METHODS

Two full-thickness defects were created in the abdominal walls of nine Yucatan swine via midline approach and repaired preperitoneally with either DuraSorb or long-lasting control mesh (TIGR, Novus Scientific). At 30 days, 3 months, and 1 year, the implantations were assessed by clinical pathology, post-necropsy histopathology, and burst strength testing.

RESULTS

No device-associated complications were found in vivo, at necropsy, or histologically. DuraSorb was well-integrated and vascularized by 30 days. DuraSorb demonstrated minimal/mild inflammation and fibroplasia, and lower inflammatory scores when compared with TIGR at all time points (P < 0.05). Burst strength of the repair sites was higher than adjacent abdominal wall at all time points (P < 0.05).

CONCLUSIONS

DuraSorb provided durable long-term support, minimal inflammation, and consistent absorption in this porcine model of abdominal wall repair, as compared to a long-term control. Clinical data is needed, but these results suggest that this mesh provides adequate structural support while potentially reducing long-term device reactions.

The State of the Art and Prospects for Osteoimmunomodulatory Biomaterials

The critical role of the immune system in host defense against foreign bodies and pathogens has been long recognized. With the introduction of a new field of research called osteoimmunology, the crosstalk between the immune and bone-forming cells has been studied more thoroughly, leading to the conclusion that the two systems are intimately connected through various cytokines, signaling molecules, transcription factors and receptors. The host immune reaction triggered by biomaterial implantation determines the in vivo fate of the implant, either in new bone formation or in fibrous tissue encapsulation. The traditional biomaterial design consisted in fabricating inert biomaterials capable of stimulating osteogenesis; however, inconsistencies between the in vitro and in vivo results were reported. This led to a shift in the development of biomaterials towards implants with osteoimmunomodulatory properties. By endowing the orthopedic biomaterials with favorable osteoimmunomodulatory properties, a desired immune response can be triggered in order to obtain a proper bone regeneration process. In this context, various approaches, such as the modification of chemical/structural characteristics or the incorporation of bioactive molecules, have been employed in order to modulate the crosstalk with the immune cells. The current review provides an overview of recent developments in such applied strategies.

In-vitro Characterization of a Hernia Mesh Featuring a Nanostructured Coating

Abdominal hernia repair is a frequently performed surgical procedure worldwide. Currently, the use of polypropylene (PP) surgical meshes for the repair of abdominal hernias constitutes the primary surgical approach, being widely accepted as superior to primary suture repair. Surgical meshes act as a reinforcement for the weakened or damaged tissues and support tissue restoration. However, implanted meshes could suffer from poor integration with the surrounding tissues. In this context, the present study describes the preliminary evaluation of a PCL-Gel-based nanofibrous coating as an element to develop a multicomponent hernia mesh device (meshPCL-Gel) that could overcome this limitation thanks to the presence of a nanostructured biomimetic substrate for enhanced cell attachment and new tissue formation. Through the electrospinning technique, a commercial PP hernia mesh was coated with a nanofibrous membrane from a polycaprolactone (PCL) and gelatin (Gel) blend (PCL-Gel). Resulting PCL-Gel nanofibers were homogeneous and defect-free, with an average diameter of 0.15 ± 0.04 μm. The presence of Gel decreased PCL hydrophobicity, so that membranes average water contact angle dropped from 138.9 ± 1.1° (PCL) to 99.9 ± 21.6°, while it slightly influenced mechanical properties, which remained comparable to those of PCL (E = 15.7 ± 2.7 MPa, σ R = 7.7 ± 0.6 ε R = 118.8 ± 13.2%). Hydrolytic and enzymatic degradation was conducted on PCL-Gel up to 28 days, with maximum weight losses around 20 and 40%, respectively. The meshPCL-Gel device was obtained with few simple steps, with no influences on the original mechanical properties of the bare mesh, and good stability under physiological conditions. The biocompatibility of meshPCL-Gel was assessed by culturing BJ human fibroblasts on the device, up to 7 days. After 24 h, cells adhered to the nanofibrous substrate, and after 72 h their metabolic activity was about 70% with respect to control cells. The absence of detectable lactate dehydrogenase in the culture medium indicated that no necrosis induction occurred. Hence, the developed nanostructured coating provided the meshPCL-Gel device with chemical and topographical cues similar to the native extracellular matrix ones, that could be exploited for enhancing the biological response and, consequently, mesh integration, in abdominal wall hernia repair.

Results of a previously unreported extravesical ureteroneocystostomy technique without ureteral stenting in 500 consecutive kidney transplant recipients

Urologic complications can still occur following kidney transplantation, sometimes requiring multiple radiological and/or surgical procedures to fully correct the problem. Previously proposed extravesical ureteral reimplantation techniques still carry non-negligible risks of the patient developing urologic complications. About 10 years ago, a new set of modifications to the Lich-Gregoir technique was developed at our center, with the goal of further minimizing the occurrence of urologic complications, and without the need for initial ureteral stent placement. It was believed that an improvement in the surgical technique to minimize the risk of developing urologic complications was possible without the need for stent placement at the time of transplant. In this report, we describe the advantages of this technique (i.e., mobilized bladder, longer spatulation of the ureter, inclusion of bladder mucosa with detrusor muscle layer in the ureteral anastomosis, and use of a right angle clamp in the ureteral orifice to ensure that it does not become stenosed). We also retrospectively report our experience in using this technique among 500 consecutive (prospectively followed) kidney transplant recipients transplanted at our center since 2014. During the first 12mo post-transplant, only 1.4%(7/500) of patients developed a urologic complication; additionally, only 1.0%(5/500) required surgical repair of their original ureteroneocystostomy. Five patients(1.0%) developed a urinary leak, with 3/5 having distal ureteral necrosis, and 1/5 subsequently developing a ureteral stricture. Two other patients developed ureteral stenosis, one due to stricture and one due to ureteral stones. These overall results are excellent when compared with other reports in the literature, especially those in which routine stenting was performed. In summary, we believe that the advantages in using this modified extravesical ureteroneocystostomy technique clearly help in lowering the early post-transplant risk of developing urologic complications. Importantly, these results were achieved without the need for ureteral stent placement at the time of transplant.

Human Primary Dermal Fibroblasts Interacting with 3-Dimensional Matrices for Surgical Application Show Specific Growth and Gene Expression Programs

Several types of 3-dimensional (3D) biological matrices are employed for clinical and surgical applications, but few indications are available to guide surgeons in the choice among these materials. Here we compare the in vitro growth of human primary fibroblasts on different biological matrices commonly used for clinical and surgical applications and the activation of specific molecular pathways over 30 days of growth. Morphological analyses by Scanning Electron Microscopy and proliferation curves showed that fibroblasts have different ability to attach and proliferate on the different biological matrices. They activated similar gene expression programs, reducing the expression of collagen genes and myofibroblast differentiation markers compared to fibroblasts grown in 2D. However, differences among 3D matrices were observed in the expression of specific metalloproteinases and interleukin-6. Indeed, cell proliferation and expression of matrix degrading enzymes occur in the initial steps of interaction between fibroblast and the investigated meshes, whereas collagen and interleukin-6 expression appear to start later. The data reported here highlight features of fibroblasts grown on different 3D biological matrices and warrant further studies to understand how these findings may be used to help the clinicians choose the correct material for specific applications.

Extensor Mechanism Reconstruction Using Marlex Mesh: Is Postoperative Casting Mandatory?

BACKGROUND

Extensor mechanism (EM) disruption after total knee arthroplasty is a catastrophic complication. Reconstruction using monofilament polypropylene mesh (Marlex Mesh; CR Bard, Franklin Lakes, NJ) has emerged as the preferred treatment, but reports are limited to the designing institution. This study describes a nondesigner experience and compares 2 postoperative immobilization strategies: long leg cast vs knee immobilizer.

METHODS

A retrospective review of consecutive EM reconstructions between 2012 and 2019 was performed. Primary repairs and allograft reconstructions were excluded, leaving 33 knees (30 patients) who underwent Marlex reconstruction. Mean time from disruption to reconstruction was 14 months, and 14 of 33 (42%) had previous repair or reconstruction attempts. The mean age was 69 years, and mean body mass index was 35 kg/m². Postoperatively, extension was maintained using a knee immobilizer in 19 of 33 (58%) patients, whereas 14 of 33 (42%) patients were long leg casted. Kaplan-Meier analysis determined all-cause survivorship free of mesh failure.

RESULTS

At mean 25-month follow-up, 19 of 33 (58%) EM reconstructions were functioning. Excluding explanted infections (5 recurrent and 2 new), 19 of 26 (73%) EM reconstructions were in situ. Six-year survivorship was 69% and not influenced by immobilization type (cast: 67%, immobilizer: 71%; P = .74). Extensor lag was not associated with immobilization type, improving from a mean preoperative lag of 43° to a mean postoperative lag of 9°. Among successes, University of California at Los Angeles activity and Knee Injury and Osteoarthritis Outcome Score - Joint Replacement score improvements exceeded minimal clinically important difference (2.2-3.3 and 52.5-64.0, respectively).

CONCLUSION

Marlex mesh EM reconstruction is a durable and reliable treatment with acceptable clinical results achievable outside the designer institution. Provided sufficient duration and compliance with postoperative immobilization, similar outcomes can be obtained with either a cast immobilizer or a knee immobilizer.

Decellularization of porcine carotid arteries using low-concentration sodium dodecyl sulfate

BACKGROUND

The decellularized scaffold is a promising material for producing tissue-engineered vascular grafts (TEVGs) because of its complex, native-like three-dimensional structure and mechanical properties. Sodium dodecyl sulfate (SDS), one of the most commonly used decellularization reagents, appears to be more effective than other detergents for removing cells from dense tissues. The concentrations of SDS used in previous studies and their effects on decellularization are not consistent.

METHODS

In this study, porcine carotid arteries were decellularized using detergent-based protocols using Triton X-100 followed by SDS at different concentrations and exposing time. Cell removal efficiency and composition were evaluated by histological analysis, and DNA and collagen quantification. Ultrastructure, mechanical properties, pore size distribution, and in vivo biocompatibility of decellularized arteries were also evaluated.

RESULTS

The DNA content of decellularized scaffolds treated with 0.3% SDS for 72 h or 0.5% SDS for 48 h was significantly less than that treated with 1% SDS for 30 h. There was a significant loss of soluble collagen after treatment with 1% SDS relative to native arteries. The extensive loss of elastin and glycosaminoglycans was observed in decellularized arteries treated with 0.5% SDS or 1% SDS. The basement membrane and biomechanics were also damaged by these two protocols. Moreover, decellularized scaffolds became more porous with many large pores after treatment with 0.3% SDS.

CONCLUSION

Low-concentration SDS could be a suitable choice for artery decellularization. Decellularized porcine carotid arteries, prepared using Triton X-100 followed by 0.3% SDS, may be a promising biological scaffold for TEVGs.

Enhanced Biomechanical Performance of a Modern Polyester Surgical Mesh for Extensor Mechanism Reconstruction in Total Knee Arthroplasty

BACKGROUND

Extensor mechanism (EM) disruption following total knee arthroplasty is a devastating postoperative complication. Reconstruction with a synthetic mesh is one treatment option, although the optimal mesh material remains unknown. This study sought to compare the mechanical properties of 2 mesh material types that can be used for EM reconstruction.

METHODS

Mechanical properties of a polypropylene mesh (Marlex mesh) and Ligament Advanced Reinforcement System (LARS) mesh were compared using force-displacement data from a material testing machine simulating knee movement during normal human gait. Tension to failure/ultimate tensile load, stiffness coefficients, axial strain, and cyclic hysteresis testing were measured and calculated.

RESULTS

Compared to polypropylene mesh, LARS mesh demonstrated a significantly higher mean ultimate tensile load (2223 N vs 1245 N, P = .002) and stiffness coefficient (255 N/mm vs 14 N/mm, P = .035) in tension to failure testing, and significantly more energy dissipation (hysteresis) in hysteresis testing (771 kJ vs 23 kJ; P ≤ .040). LARS mesh also demonstrated significantly less maximum displacement compared to the polypropylene mesh (9.2 mm vs 90.4 mm; P ≤ .001).

CONCLUSION

Compared to polypropylene mesh, LARS mesh showed superior performance related to force-displacement testing. The enhanced mechanical performance of LARS mesh may correlate clinically to fewer failures, increased longevity, and higher resistance to plastic deformation (extensor lag). Future research should evaluate survivorship and clinical outcomes of these meshes when used for EM reconstruction.

Facile fabrication of elastic, macro-porous, and fast vascularized silicone orbital implant

Orbital implants with interconnected porous architecture had gained prominence, as they were capable of being colonized by fibrovascular tissue and minimizing complications. However, mechanical properties of orbital implant had received little attention among existing design philosophy. Herein, a compliant porous silicone scaffold was developed by gelatin porogen-leaching method and used as the orbital implant in this study. The silicone scaffolds exhibited desired microstructure and simulated mechanical properties, including high porosity of ~90%, suitable pore size of 280-450 μm, reduced modulus of 50.1 ± 11.7 KPa, and excellent elasticity. in vitro results showed that the porous silicone scaffolds did not exhibit noticeable cytotoxicity and were favorable for both adhesion and proliferation of human vascular ECs. The porous silicone scaffold was easy to be manipulated when implanted into the anophthalmic sockets of rabbits. The implanted scaffolds provided satisfactory volume replacement and induced extensive fibro-vascularization, showing desirable orbital reconstruction effects. Therefore, our novel porous silicone scaffolds may be promising substitutes for current orbital implants.

A peritoneal defect covered by intraperitoneal mesh prosthesis effects an increased and distinctive foreign body reaction in a minipig model

BACKGROUND

The incidence of incisional hernia is with up to 30% one of the frequent long-term complication after laparotomy. After establishing minimal invasive operations, the laparoscopic intraperitoneal onlay mesh technique (lap. IPOM) was first described in 1993. Little is known about the foreign body reaction of IPOM-meshes, which covered a defect of the parietal peritoneum. This is becoming more important, since IPOM procedure with peritoneal-sac resection and hernia port closing (IPOM plus) is more frequently used.

METHODS

In 18 female minipigs, two out of three Polyvinylidene-fluoride (PVDF) -meshes (I: standard IPOM; II: IPOM with modified structure [bigger pores]; III: IPOM with the same structure as IPOM II + degradable hydrogel-coating) were placed in a laparoscopic IPOM procedure. Before mesh placement, a 2x2cm peritoneal defect was created. After 30 days, animals were euthanized, adhesions were evaluated by re-laparoscopy and mesh samples were explanted for histological and immunohistochemichal investigations.

RESULTS

All animals recovered after implantation and had no complications during the follow-up period. Analysing foreign body reaction, the IPOM II mesh had a significant smaller inner granuloma, compared to the other meshes (IPOM II: 8.4 µm ± 1.3 vs. IPOM I 9.1 µm ± 1.3, p < 0.001). The degradable hydrogel coating does not prevent adhesions measured by Diamond score (p = 0.46). A peritoneal defect covered by a standard or modified IPOM mesh was a significant factor for increasing foreign body granuloma, the amount of CD3+ lymphocytes, CD68+ macrophages and decrease of pore size.

CONCLUSION

A peritoneal defect covered by IPOM prostheses leads to an increased foreign body reaction compared to intact peritoneum. Whenever feasible, a peritoneal defect should be closed accurately before placing an IPOM-mesh to avoid an excessive foreign body reaction and therefore inferior biomaterial properties of the prosthesis.

A tarsus construct of a novel branched polyethylene with good elasticity for eyelid reconstruction in vivo

Branched polyethylene (B-PE) elastomer was investigated for its potential medical application as a tarsus construct. The in vitro results showed that the B-PE and processed B-PE films or scaffolds did not exhibit noticeable cytotoxicity to the NIH3T3 fibroblasts and human vascular endothelial cells (ECs). The B-PE scaffolds with a pore size of 280–480 µm were prepared by using a gelatin porogen-leaching method. The porous scaffolds implanted subcutaneously in rats exhibited mild inflammatory response, collagen deposition and fast fibrovascularization, suggesting their good biocompatibility. Quantitative real-time PCR analysis showed low expression of pro-inflammatory genes and up-regulated expressions of collagen deposition and vascularization-related genes, validating the results of historical evaluation in a molecular level. The B-PE scaffolds and Medpor controls were transplanted in rabbits with eyelid defects. The B-PE scaffolds exhibited a similar elastic modulus and provided desirable repair effects with mild fibrous capsulation, less eyelid deformities, and were well integrated with the fibrovascular tissue compared with the Medpor controls.

Improved tissue integration of a new elastic intraperitoneal stoma mesh prosthesis

Parastomal herniation is a frequent complication in colorectal surgery, occurring with a prevalence of 30-80%. The aim of the study was to create a new intraperitoneal colostoma mesh prosthesis (IPST) with enhanced elastic properties made with thermoplastic polyurethane (TPU) monofilaments. We performed open terminal sigmoid colostomies reinforced with either a 10 cm by 10 cm polyvinylidene fluoride (PVDF) or a new TPU/PVDF composite mesh in a total of 10 minipigs. Colostoma was placed paramedian in the left lower abdomen and IPST meshes were fixed intraperitoneal. After 8 weeks, the animals were euthanized after laparoscopic exploration and specimen were explanted for histological investigations. Implantation of a new IPST-mesh with enhanced elastic properties was feasible in a minipig model within an observation period of 8 weeks. Immunohistochemically, Collagen I/III ratio as a marker of tissue integration was significantly higher in TPU-group versus PVDF group (9.4 ± 0.5 vs. 8.1 ± 0.5, p = 0.002) with a significantly lower inflammatory reaction measured by a smaller inner granuloma at mesh-colon interface (17.6 ± 3.3 μm vs. 23 ± 5 μm, p < 0.001). A new TPU/PVDF composite mesh with enhanced elastic properties as IPST was created. Stoma surgery and especially the evaluation of the new stoma mesh prosthesis are feasible with reproducible results in an animal model. Tissue integration expressed by Collagen I/III ratio seems to be improved in comparison to standard-elastic PVDF-IPST meshes.

Scaffold strategies for modulating immune microenvironment during bone regeneration

Implanted bone scaffolds often fail to successfully integrate with the host tissue because they do not elicit a favorable immune reaction. Properties of bone scaffold not only provide mechanical and chemical signals to support cell adhesion, migration, proliferation and differentiation, but also play a pivotal role in determining the extent of immune response during bone regeneration. Appropriate design parameters of bone scaffold are of great significance in the process of developing a new generation of bone implants. Herein, this article addresses the recent advances in the field of bone scaffolds for immune response, particularly focusing on the physical and chemical properties of bone scaffold in manipulating the host response. Furthermore, incorporation of bioactive molecules and cells with immunoregulatory function in bone scaffolds are also presented. Finally, continuing challenges and future directions of scaffold-based strategies for modulating immune microenvironment are discussed.

Prevention of incisional hernia using different suture materials for closing the abdominal wall: a comparison of PDS, Vicryl and Prolene in a rat model

Purpose

An incisional hernia occurs frequently after a midline incision with an incidence of 12.8%. The choice in suture material used for abdominal wall closure is not straightforward and the conflicting literature focuses on clinical outcomes. This study compares a non-absorbable, slow-absorbable and fast-absorbable suture in a rat model, focusing on histological outcomes predicting better fascia healing.

Methods

33 male Wistar rats, divided over three groups, each received two separate 1 cm incisions closed with either Prolene 4/0, PDS 4/0 or Vicryl 4/0. At 7 days and 21 days, one of the incisions was explanted. Tissue was semi-quantitatively scored regarding inflammatory cells and collagen fibres present. Using qPCR macrophage polarisation, fibroblast activity and vascularisation were evaluated. Data were analysed by Kruskal–Wallis test with Mann–Whitney U post hoc test. A p value of 0.017 was considered significant after Bonferroni correction.

Results

All animals recovered without complications and completed the 21 days of follow-up. The Vicryl group showed a higher presence of macrophages after 21 days in comparison with Prolene (p = 0.003) and PDS (p = 0.006) and more foreign body giant cells compared to Prolene at 7 days (p = 0.010) and PDS at 21 days (p < 0.001). qPCR showed 2.5-fold higher expression of clec10A in PDS compared to Prolene after 7 days (p = 0.007).

Conclusions

The results of this study carefully support the use of PDS suture, compared to Prolene and Vicryl, in abdominal wall closure based on a favourable macrophage response. The heterogeneity and variability in the data might be explained by the spectrum of the macrophage subtype paradigm.

Electronic supplementary material

The online version of this article (10.1007/s10029-019-01941-9) contains supplementary material, which is available to authorized users.

Biomechanical Behaviour and Biocompatibility of Ureidopyrimidinone-Polycarbonate Electrospun and Polypropylene Meshes in a Hernia Repair in Rabbits

Although mesh use has significantly improved the outcomes of hernia and pelvic organ prolapse repair, long-term recurrence rates remain unacceptably high. We aim to determine the in vivo degradation and functional outcome of reconstructed abdominal wall defects, using slowly degradable electrospun ureidopyrimidinone moieties incorporated into a polycarbonate backbone (UPy-PC) implant compared to an ultra-lightweight polypropylene (PP) textile mesh with high pore stability. Twenty four New-Zealand rabbits were implanted with UPy-PC or PP to either reinforce a primary fascial defect repair or to cover (referred to as gap bridging) a full-thickness abdominal wall defect. Explants were harvested at 30, 90 and 180 days. The primary outcome measure was uniaxial tensiometry. Secondary outcomes were the recurrence of herniation, morphometry for musculofascial tissue characteristics, inflammatory response and neovascularization. PP explants compromised physiological abdominal wall compliance from 90 days onwards and UPy-PC from 180 days. UPy-PC meshes induced a more vigorous inflammatory response than PP at all time points. We observed progressively more signs of muscle atrophy and intramuscular fatty infiltration in the entire explant area for both mesh types. UPy-PC implants are replaced by a connective tissue stiff enough to prevent abdominal wall herniation in two-thirds of the gap-bridged full-thickness abdominal wall defects. However, in one-third there was sub-clinical herniation. The novel electrospun material did slightly better than the textile PP yet outcomes were still suboptimal. Further research should investigate what drives muscular atrophy, and whether novel polymers would eventually generate a physiological neotissue and can prevent failure and/or avoid collateral damage.

Evaluation of resorbable polydioxanone and polyglycolic acid meshes in a rat model of ventral hernia repair

The objective of this study was to evaluate physical, mechanical, and biological properties of the polydioxanone (PDO) monofilament meshes and polyglycolide (PGA) polyfilament meshes in comparison with Permacol^® implants. In rat experimental model, a 1.5 × 2.0 cm defect in abdominal wall was reconstructed by using the Permacol surgical implant or knitted meshes produced from either PDO monofilament, or PGA multifilament. The implant sites were assessed for the tensile strength and the extents of material resorption, host inflammatory response and host tissue replacement on days 3, 10, 30, or 60 after the surgery. The PDO and PGA meshes were rapidly pervaded by the host connective tissue with elements of skeletal muscle histogenesis. The degree of adhesions was significantly higher in the Permacol group. All of the prostheses underwent resorption, which correlated with gradual decreases in the overall tensile strength of the site and the Col1a1 gene expression level. Elevated expression of Fgf2 gene maintained longer in the PDO group, and the Mmp9 gene expression level in this group was higher than in the other groups. Gene expression levels of inflammatory cytokines were higher in the Permacol group. The foreign body giant cell numbers were lower in the PDO and Permacol groups than in the PGA group. Minimal macrophage infiltration with predominance of M2 cells was observed in the PDO group. Overall, the PDO prosthesis turned out to be significantly better than the PGA or Permacol prostheses by a number of indicators of biocompatibility and efficacy. © 2018 The Authors Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 00B: 000-000, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 652-663, 2019.

Biomaterial Implants in Abdominal Wall Hernia Repair: A Review on the Importance of the Peritoneal Interface

Biomaterials have long been used to repair defects in the clinical setting, which has led to the development of a wide variety of new materials tailored to specific therapeutic purposes. The efficiency in the repair of the defect and the safety of the different materials employed are determined not only by the nature and structure of their components, but also by the anatomical site where they will be located. Biomaterial implantation into the abdominal cavity in the form of a surgical mesh, such as in the case of abdominal hernia repair, involves the contact between the foreign material and the peritoneum. This review summarizes the different biomaterials currently available in hernia mesh repair and provides insights into a series of peculiarities that must be addressed when designing the optimal mesh to be used in this interface.

Characterization of the T-cell response to polypropylene mesh in women with complications

BACKGROUND

Polypropylene mesh is used widely for surgical treatment of pelvic organ prolapse and stress urinary incontinence. Although these surgeries demonstrate favorable functional and anatomic outcomes, their use has been limited by complications, the 2 most common being exposure and pain. Growing evidence suggests that T lymphocytes play a critical role in the regulation of the host response to biomaterials.

OBJECTIVE

The purpose of this study was to define and characterize the T-cell response and to correlate the response to collagen deposition in fibrotic capsules in mesh tissue complexes that are removed for the complications of pain vs exposure.

STUDY DESIGN

Patients who were scheduled to undergo a surgical excision of mesh for pain or exposure at Magee-Women's Hospital were offered enrollment. Forty-two mesh-vagina tissue complexes were removed for the primary complaint of exposure (n=24) vs pain (n=18). Twenty-one patients agreed to have an additional vaginal biopsy away from the site of mesh that served as control tissue. T cells were examined via immunofluorescent labeling for cell surface markers CD4+ (T_h), CD8+ (cytotoxic) and foxp3 (T-regulatory cell). Frozen sections were stained with hematoxylin-eosin for gross morphologic condition and picrosirius red for collagen fiber analysis. Interrupted sodium-dodecyl sulfate gel electrophoresis was used to quantify the content of collagens type I and III, and the collagen III/I ratio. Transforming growth factor-β and connective tissue growth factor, which are implicated in the development of fibrosis, were measured via enzyme-linked immunosorbent assays. Data were analyzed with the Student's t tests, mixed effects linear regression, and Spearman's correlation coefficients.

RESULTS

Demographic data were not different between groups, except for body mass index, which was 31.7 kg/m² for the exposure group and 28.2 kg/m² for pain (P=.04). Tissue complexes demonstrated a marked, but highly localized, foreign body response. We consistently observed a teardrop-shaped fibroma that encapsulated mesh fibers in both pain and exposure groups, with the T cells localized within the tip of this configuration away from the mesh-tissue interface. All 3 T-cell populations were significantly increased relative to control: CD4⁺ T helper (P<.001), foxp3⁺ T regulatory (P<.001), and CD8⁺ cytotoxic T cell (P=.034) in the exposure group. In the pain group, only T-helper (P<.001) and T-regulatory cells (P<.001) were increased, with cytotoxic T cells (P=.520) not different from control. Picrosirius red staining showed a greater area of green (thin) fibers in the exposure group (P=.025) and red (thick) fibers in the pain group (P<.001). The ratio of area green/(yellow + orange + red) that represented thin vs thick fibers was significantly greater in the exposure group (P=.005). Analysis of collagen showed that collagen type I was increased by 35% in samples with mesh complications (exposure and pain) when compared with control samples (P=.043). Strong correlations between the profibrosis cytokine transforming growth factor-β and collagen type I and III were found in patients with pain (r≥0.833; P=.01) but not exposure (P>.7).

CONCLUSION

T cells appear to play a critical role in the long-term host response to mesh and may be a central pathway that leads to complications. The complexity of this response warrants further investigation and has the potential to broaden our understanding of mesh biology and clinical outcomes.

Meshes in a mess: Mesenchymal stem cell-based therapies for soft tissue reinforcement

Surgical meshes are frequently used for the treatment of abdominal hernias, pelvic organ prolapse, and stress urinary incontinence. Though these meshes are designed for tissue reinforcement, many complications have been reported. Both differentiated cell- and mesenchymal stem cell-based therapies have become attractive tools to improve their biocompatibility and tissue integration, minimizing adverse inflammatory reactions. However, current studies are highly heterogeneous, making it difficult to establish comparisons between cell types or cell coating methodologies. Moreover, only a few studies have been performed in clinically relevant animal models, leading to contradictory results. Finally, a thorough understanding of the biological mechanisms of mesenchymal stem cells in the context of foreign body reaction is lacking. This review aims to summarize in vitro and in vivo studies involving the use of differentiated and mesenchymal stem cells in combination with surgical meshes. According to preclinical and clinical studies and considering the therapeutic potential of mesenchymal stem cells, it is expected that these cells will become valuable tools in the treatment of pathologies requiring tissue reinforcement. STATEMENT OF SIGNIFICANCE: The implantation of surgical meshes is the standard procedure to reinforce tissue defects such as hernias. However, an adverse inflammatory response secondary to this implantation is frequently observed, leading to a strong discomfort and chronic pain in the patients. In many cases, an additional surgical intervention is needed to remove the mesh. Both differentiated cell- and stem cell-based therapies have become attractive tools to improve biocompatibility and tissue integration, minimizing adverse inflammatory reactions. However, current studies are incredibly heterogeneous and it is difficult to establish a comparison between cell types or cell coating methodologies. This review aims to summarize in vitro and in vivo studies where differentiated and stem cells have been combined with surgical meshes.

Polypropylene mesh implantation for hernia repair causes myeloid cell-driven persistent inflammation

Polypropylene meshes that are commonly used for inguinal hernia repair may trigger granulomatous foreign body reactions. Here, we show that asymptomatic patients display mesh-associated inflammatory granulomas long after surgery, which are dominated by monocyte-derived macrophages expressing high levels of inflammatory activation markers. In mice, mesh implantation by the onlay technique induced rapid and strong myeloid cell accumulation, without substantial attenuation for up to 90 days. Myeloid cells segregated into distinct macrophage subsets with separate spatial distribution, activation profiles, and functional properties, showing a stable inflammatory phenotype in the tissue surrounding the biomaterial and a mixed, wound-healing phenotype in the surrounding stromal tissue. Protein mass spectrometry confirmed the inflammatory nature of the foreign body reaction, as characterized by cytokines, complement activation, and matrix-modulating factors. Moreover, immunoglobulin deposition increased over time around the implant, arguing for humoral immune responses in association with the cell-driven inflammation. Intravital multiphoton microscopy revealed a high motility and continuous recruitment of myeloid cells, which is partly dependent on the chemokine receptor CCR2. CCR2-dependent macrophages are particular drivers of fibroblast proliferation. Thus, our work functionally characterizes myeloid cell-dependent inflammation following mesh implantation, thereby providing insights into the dynamics and mechanisms of foreign body reactions to implanted biomaterials.