Antibacterial Efficacy of a Chitosan-Based Hydrogel Modified With Epsilon-Poly-l-Lysine Against Pseudomonas aeruginosa in a Murine-Infected Burn Wound Model.

INTRODUCTION: Because antibiotic resistance is increasing worldwide and the leading cause of death in burn patients is an infection, an urgent need exists for nonantibiotic approaches to eliminate multidrug-resistant bacteria from burns to prevent their systemic dissemination and sepsis. We previously demonstrated the significant antibiofilm activity of a chitosan (CS) hydrogel containing the antimicrobial peptide epsilon-poly-l-lysine (EPL) against multidrug-resistant Pseudomonas aeruginosa using ex vivo porcine skin. In this study, we evaluated the in vivo antibacterial efficacy of a CS/EPL hydrogel against P. aeruginosa in a murine burn wound infection model. MATERIALS AND METHODS: Full-thickness burns were created on the dorsum using a heated brass rod and were inoculated with bioluminescent, biofilm-forming P. aeruginosa (Xen41). Mice were treated with CS/EPL, CS, or no hydrogel applied topically 2 or 24 hours after inoculation to assess the ability to prevent or eradicate existing biofilms, respectively. Dressing changes occurred daily for 3 days, and in vivo bioluminescence imaging was performed to detect and quantitate bacterial growth. Blood samples were cultured to determine systemic infection. In vitro antibacterial activity and cytotoxicity against human primary dermal fibroblasts, keratinocytes, and mesenchymal stem cells were also assessed. RESULTS: CS/EPL treatment initiated at early or delayed time points showed a significant reduction in bioluminescence imaging signal compared to CS on days 2 and 3 of treatment. Mice administered CS/EPL had fewer bloodstream infections, lower weight loss, and greater activity than the untreated and CS groups. CS/EPL reduced bacterial burden by two orders of magnitude in vitro and exhibited low cytotoxicity against human cells. CONCLUSION: A topical hydrogel delivering the antimicrobial peptide EPL demonstrates in vivo efficacy to reduce but not eradicate established P. aeruginosa biofilms in infected burn wounds. This biocompatible hydrogel shows promise as an antimicrobial barrier dressing for the sustained protection of burn wounds from external bacterial contamination.

Access to Care: End-to-End Digital Response for COVID-19 Care Delivery.

The coronavirus disease 2019 pandemic disrupted health care, requiring organizational leaders to act quickly to manage the health-related concerns of individuals and communities. The ability to offer a variety of digitally enabled telehealth services with 24/7 access to nurse practitioners and physician assistants allowed us to care for patients in their homes. It reduced the spread of the virus, protected our employees from further disease spread, and provided early interventions to those in need. The roles of nurse practitioner leaders, the enacted strategies, and patient outcomes demonstrate the impact of an innovative digital care delivery model on care across the continuum.

Priming With Toll-Like Receptor 3 Agonist Poly(I:C) Enhances Content of Innate Immune Defense Proteins but Not MicroRNAs in Human Mesenchymal Stem Cell-Derived Extracellular Vesicles.

Mesenchymal stem cells (MSCs) help fight infection by promoting direct bacterial killing or indirectly by modulating the acute phase response, thereby decreasing tissue injury. Recent evidence suggests that extracellular vesicles (EVs) released from MSCs retain antimicrobial characteristics that may be enhanced by pretreatment of parent MSCs with the toll-like receptor 3 (TLR3) agonist poly(I:C). Our aim was to determine whether poly(I:C) priming can modify EV content of miRNAs and/or proteins to gain insight into the molecular mechanisms of their enhanced antimicrobial function. Human bone marrow-derived MSCs were cultured with or without 1 µg/ml poly(I:C) for 1 h and then conditioned media was collected after 64 h of culture in EV-depleted media. Mass spectrometry and small RNA next-generation sequencing were performed to compare proteomic and miRNA profiles. Poly(I:C) priming resulted in 49 upregulated EV proteins, with 21 known to be important in host defense and innate immunity. In contrast, EV miRNA content was not significantly altered. Functional annotation clustering analysis revealed enrichment in biological processes and pathways including negative regulation of endopeptidase activity, acute phase, complement and coagulation cascades, innate immunity, immune response, and Staphylococcus aureus infection. Several antimicrobial peptides identified in EVs remained unaltered by poly(I:C) priming, including dermcidin, lactoferrin, lipocalin 1, lysozyme C, neutrophil defensin 1, S100A7 (psoriasin), S100A8/A9 (calprotectin), and histone H4. Although TLR3 activation of MSCs improves the proteomic profile of EVs, further investigation is needed to determine the relative importance of particular functional EV proteins and their activated signaling pathways following EV interaction with immune cells.

Antibiofilm activity of chitosan/epsilon-poly-L-lysine hydrogels in a porcine ex vivo skin wound polymicrobial biofilm model.

As antibiotic resistance continues to increase globally, there is an urgency for novel, non-antibiotic approaches to control chronic drug-resistant infections, particularly those associated with polymicrobial biofilm formation in chronic wounds. Also needed are clinically relevant polymicrobial biofilm models that can be utilized to assess the efficacy of innovative therapeutics against mature biofilms. We successfully developed a highly reproducible porcine ex vivo skin wound polymicrobial biofilm model using clinical isolates of multidrug-resistant Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, and Candida albicans. This ex vivo biofilm model was then used to assess the antimicrobial and antibiofilm properties of an easily fabricated chitosan hydrogel incorporating the natural antimicrobial peptide epsilon-poly-L-lysine. Antimicrobial activity was evaluated against planktonic cultures in vitro and against mature biofilms ex vivo. The antibiofilm efficiency of the hydrogels was especially pronounced against Pseudomonas aeruginosa, whose counts were reduced by 99.98% after 2 hours in vitro and by 99.94% after treatment for 24 hours when applied to 24 hour ex vivo polymicrobial wound biofilms. The activity of the hydrogels was lower against Staphylococcus aureus and ineffective against Candida albicans. Gram, Hucker-Twort staining of paraffin sections revealed balanced polymicrobial communities in mature 48 hour untreated biofilms. Treatment of 48 or 72 hour biofilms for 2 or 3 days with hydrogels that were applied within 5 hours after inoculation resulted in an impressive 96% and 97% reduction in biofilm thickness compared to untreated biofilms, respectively (P < .001). Likewise, topical gel treatment for 24 hours reduced biofilm thickness by 84% and 70%, respectively, when applied to mature biofilms at 24 and 48 hours after inoculation (P < .001). Thus, this ex vivo wound biofilm model provides a useful means to assess the efficacy of novel treatments to prevent and eradicate polymicrobial biofilms consisting of multidrug-resistant Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, and Candida albicans.

Transitioning an Advanced Practice Fellowship Curriculum to eLearning During the COVID-19 Pandemic.

BACKGROUND: The COVID-19 global pandemic brought mandatory shelter-in-place orders, disrupting traditional face-to-face teaching methods for advanced practice fellowship programs nationally, creating a challenge for fellowship program directors to preserve curriculum using nontraditional methods. METHOD: Using a variety of both web-based and app-based virtual platforms, a nationally accredited fellowship program converted traditional in-seat learning modalities to elearning platforms using both synchronous and asynchronous education. RESULTS: Preliminary data indicate that knowledge acquisition and perceived fellow satisfaction are preserved despite the abrupt change to program delivery. Programmatic modifications were submitted to the American Nurse Credentialing Center for compliance and deemed as creative, innovative, and collaborative. CONCLUSION: Curriculum for advanced practice fellowship programs can be favorably converted to elearning using virtual platforms during a crisis. Through prompt reevaluation and restructuring, virtual platforms can replace in-seat didactic lectures, patient case studies, mentoring, and even simulation, while ensuring program continuation and compliance with accreditation standards. [J Nurs Educ. 2020;59(9):514-517.].

Inhibition of microRNA-124-3p as a novel therapeutic strategy for the treatment of Gulf War Illness: Evaluation in a rat model.

Gulf War Illness (GWI) is a chronic, multisymptom illness that continues to affect up to 30% of veterans deployed to the Persian Gulf during the 1990-1991 Gulf War. After nearly 30 years, useful treatments for GWI are lacking and underlying cellular and molecular mechanisms involved in its pathobiology remain poorly understood, although exposures to pyridostigmine bromide (PB) and pesticides are consistently identified to be among the strongest risk factors. Alleviation of the broad range of symptoms manifested in GWI, which involve the central nervous system, the neuroendocrine system, and the immune system likely requires therapies that are able to activate and inactivate a large set of orchestrated genes. Previous work in our laboratory using an established rat model of GWI identified persistent elevation of microRNA-124-3p (miR-124) levels in the hippocampus whose numerous gene targets are involved in cognition-associated pathways and neuroendocrine function. This study aimed to investigate the broad effects of miR-124 inhibition in the brain 9 months after completion of a 28-day exposure regimen of PB, DEET (N,N-diethyl-3-methylbenzamide), permethrin, and mild stress by profiling the hippocampal expression of genes known to play a critical role in synaptic plasticity, glucocorticoid signaling, and neurogenesis. We determined that intracerebroventricular infusion of a miR-124 antisense oligonucleotide (miR-124 inhibitor; 0.05-0.5 nmol/day/28 days), but not a negative control oligonucleotide, into the lateral ventricle of the brain caused increased protein expression of multiple validated miR-124 targets and increased expression of downstream target genes important for cognition and neuroendocrine signaling in the hippocampus. Off-target cardiotoxic effects were revealed in GWI rats receiving 0.1 nmol/day as indicated by the detection in plasma of 5 highly elevated protein cardiac injury markers and 6 upregulated cardiac-enriched miRNAs in plasma exosomes determined by next-generation sequencing. Results from this study suggest that in vivo inhibition of miR-124 function in the hippocampus is a promising, novel therapeutic approach to improve cognition and neuroendocrine dysfunction in GWI. Additional preclinical studies in animal models to assess feasibility and safety by developing a practical, noninvasive drug delivery system to the brain and exploring potential adverse toxicologic effects of miR-124 inhibition are warranted.

Oxidative Stress Alters Angiogenic and Antimicrobial Content of Extracellular Vesicles and Improves Flap Survival.

Extracellular vesicles (EVs) secreted from adipose-derived mesenchymal stem cells (ADSCs) (ADSC-EVs) improve flap survival after ischemia-reperfusion injury. Exposure of parent ADSCs to oxidative stress has been shown to enhance this effect, but mechanisms are unclear. We aimed to determine whether angiogenesis-promoting protein and microRNA (miRNA) content is altered in EVs after preconditioning with hydrogen peroxide (H2O2 ADSC-EVs) and whether H2O2 ADSC-EVs can increase viability of random pattern skin flaps. METHODS: EVs secreted by human ADSCs were isolated after culture in EV-depleted medium ± H2O2. Nanoparticle tracking analysis determined size and concentration of purified EVs. Mass spectrometry and small RNA next-generation sequencing were performed to compare proteomic and miRNA profiles. ADSC-EVs, H2O2 ADSC-EVs, or vehicle were injected into random pattern skin flaps of BALB/c mice (4-5 mice per group). Viable and necrotic areas were measured on day 7, and tissues underwent histologic analysis. RESULTS: Angiogenic and antimicrobial protein content of EVs was altered with H2O2 preconditioning. Functional enrichment analysis identified constitutive photomorphogenesis 9 signalosome (known to direct vascular endothelial growth factor production) as the major enriched Gene Ontology term unique to H2O2 ADSC-EVs. Two miRNAs were increased, and 12 (including 10 antiangiogenic miRNAs) were reduced in H2O2 ADSC-EVs. Enhanced viability (P < 0.05) of flaps treated with H2O2 ADSC-EVs compared with vehicle corresponded to increased capillary density in the H2O2 group (P < 0.001). CONCLUSION: Altered protein and miRNA content in ADSC-EVs after H2O2 pretreatment likely contributes to enhanced therapeutic effects on flap survival observed in preclinical models.

Evaluation of a Novel Hybrid Viable Bioprosthetic Mesh in a Model of Mesh Infection.

BACKGROUND: The reported incidence of mesh infection in contaminated operative fields is as high as 30% regardless of material used. Our laboratory previously showed that augmenting acellular bioprosthetic mesh with allogeneic mesenchymal stem cells (MSC) enhances resistance to bacterial colonization in vivo and preserves mesh integrity. This study's aim was to determine whether augmentation of non-crosslinked porcine dermis (Strattice) with commercially available, cryopreserved, viable MSC-containing human placental tissue (Stravix) similarly improves infection resistance after inoculation with Escherichia coli (E. coli) using an established mesh infection model. METHODS: Stravix was thawed per manufacturer's instructions and 2 samples were tested for cell viability using a Live/Dead Cell assay at the time of surgery. Rats (N = 20) were implanted subcutaneously with 1 piece of Strattice and 1 piece of hybrid mesh (Strattice + Stravix sutured at the corners). Rats were inoculated with either sterile saline or 106 colony-forming units of E. coli before wound closure (n = 10 per group). At 4 weeks, explants underwent microbiologic and histologic analyses. RESULTS: In E. coli-inoculated animals, severe or complete mesh degradation concurrent with abscess formation was observed in 100% (10/10) hybrid meshes and 90% (9/10) Strattice meshes. Histologic evaluation determined that meshes inoculated with E. coli exhibited severe acute inflammation, which correlated with bacterial recovery (P < 0.001). Viability assays performed at the time of surgery failed to verify the presence of numerous live cells in Stravix. CONCLUSIONS: Stravix cryopreserved MSC-containing human umbilical tissue does not improve infection resistance of a bioprosthetic mesh in vivo in rats after inoculation with E. coli.

Bone Marrow-Derived Mesenchymal Stem Cells Enhance Bacterial Clearance and Preserve Bioprosthetic Integrity in a Model of Mesh Infection.

BACKGROUND: The reported incidence of mesh infection in contaminated operative fields is as high as 30% regardless of the material used. Recently, mesenchymal stem cells (MSCs) have been shown to possess favorable immunomodulatory properties and improve tissue incorporation when seeded onto bioprosthetics. The aim of this study was to evaluate whether seeding noncrosslinked bovine pericardium (Veritas Collagen Matrix) with allogeneic bone marrow-derived MSCs improves infection resistance in vivo after inoculation with Escherichia coli (E. coli). METHODS: Rat bone marrow-derived MSCs at passage 3 were seeded onto bovine pericardium and cultured for 7 days before implantation. Additional rats (n = 24) were implanted subcutaneously with MSC-seeded or unseeded mesh and inoculated with 7 × 10(5) colony-forming units of E. coli or saline before wound closure (group 1, unseeded mesh/saline; group 2, unseeded mesh/E. coli; group 3, MSC-seeded mesh/E. coli; 8 rats per group). Meshes were explanted at 4 weeks and underwent microbiologic and histologic analyses. RESULTS: MSC-seeded meshes inoculated with E. coli demonstrated superior bacterial clearance and preservation of mesh integrity compared with E. coli-inoculated unseeded meshes (87.5% versus 0% clearance; p = 0.001). Complete mesh degradation concurrent with abscess formation was observed in 100% of rats in the unseeded/E. coli group, which is in contrast to 12.5% of rats in the MSC-seeded/E. coli group. Histologic evaluation determined that remodeling characteristics of E. coli-inoculated MSC-seeded meshes were similar to those of uninfected meshes 4 weeks after implantation. CONCLUSIONS: Augmenting a bioprosthetic material with stem cells seems to markedly enhance resistance to bacterial infection in vivo and preserve mesh integrity.

Long-term epigenetic alterations in a rat model of Gulf War Illness.

Gulf War Illness (GWI) is a chronic, multisymptom illness that affects 25% of the 700,000 US veterans deployed to the Persian Gulf during the 1990-1991 Gulf War. Central nervous system impairments are among the most common symptoms reported, including memory dysfunction and depression. After 25 years, the diagnosis remains elusive, useful treatments are lacking, and the cause is poorly understood, although exposures to pyridostigmine bromide (PB) and pesticides are consistently identified to be among the strongest risk factors. Epigenetic changes including altered microRNA (miRNA) expression and DNA methylation play an important role in learning, memory, and emotion regulation and have been implicated in various neurological disorders. In this study, we used an established rat model of GWI to determine whether 1) chronic alterations in miRNA expression and global DNA methylation and DNA hydroxymethylation are mechanisms involved in the pathobiology of GWI, and 2) plasma exosome small RNAs may serve as potential noninvasive biomarkers of this debilitating disease. One year after a 28-day exposure regimen of PB, DEET (N,N-diethyl-3-methylbenzamide), permethrin, and mild stress, expression of 84 mature miRNAs and global 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) content were analyzed in the brains of GWI rats and vehicle controls by PCR array and enzyme-linked immunosorbent assay, respectively. Plasma exosome RNA next-generation sequencing analysis was performed in pooled samples to discover potential noninvasive biomarkers. We found that combined exposure to low doses of GW-related chemicals and mild stress caused epigenetic modifications in the brain that persisted one year after exposure, including increased expression of miR-124-3p and miR-29b-3p in the hippocampus and regional alterations in global 5mC and 5hmC content. GW-relevant exposures also induced the differential expression of two piwi-interacting RNAs (piRNAs) in circulation (piR-007899 and piR-019162). Results from this study implicate a role for epigenetic alterations in GWI. Evaluation of the diagnostic potential of plasma exosome RNAs in veterans with GWI is warranted.

An experimental comparison of the effects of bacterial colonization on biologic and synthetic meshes.

PURPOSE: Biologic meshes are being used with increasing frequency to repair contaminated abdominal wall defects despite high long-term recurrence and infection rates associated with their use. Recent clinical reports describing the success of lightweight, macroporous synthetic meshes in contaminated ventral hernia repairs have led some surgeons to challenge the belief that synthetics are contraindicated in contaminated fields. We aimed to determine whether a frequently used biologic mesh (Strattice(TM)) is more resistant to bacterial colonization than macroporous synthetic mesh (Parietex(TM) Progrip(TM)) after inoculation with two common pathogens. METHODS: Rats (n = 48) were implanted subcutaneously with Strattice(TM) or Progrip(TM). Meshes were inoculated with sterile saline or a suspension containing 10(6) colony-forming units of Staphylococcus aureus or Escherichia coli prior to wound closure (n = 8 per subgroup). Meshes were explanted at 4 weeks and underwent microbiologic and histologic analyses. RESULTS: Progrip(TM) demonstrated superior bacterial clearance compared to Strattice(TM) (E. coli, 88 vs. 17% clearance, p = 0.03; S. aureus, 75 vs. 50%, p = 0.61; combined bacterial strains, 81 vs. 36%, p = 0.02; respectively). In the Strattice(TM) group, severely degraded meshes were observed in 100% of animals inoculated with E. coli (but 0% inoculated with S. aureus). In contrast, all Progrip(TM) meshes remained intact regardless of inoculum. Scores for neovascularization were higher in the synthetic group irrespective of contamination (p < 0.05). CONCLUSIONS: Biologic meshes may not be more resistant to bacterial colonization than reduced-weight synthetics, and their resistance may differ in response to different pathogens. The routine use of biologics in contaminated ventral hernia repair should be questioned, particularly in the presence of E. coli.

Evaluation of Six Split-thickness Skin Graft Donor-site Dressing Materials in a Swine Model.

BACKGROUND: Numerous dressings for split-thickness skin graft donor sites are commercially available with no conclusive evidence-based consensus regarding the optimal dressing choice. This study was conducted to identify which of 5 commonly used materials promotes wound healing most effectively for use on split-thickness donor sites in comparison with our standard dressing, Xeroform (petrolatum gauze). METHODS: Twenty-four partial-thickness wounds were created on the backs of 4 pigs using a dermatome. Wounds (n = 4 per dressing type per pig) were treated with Xeroform, Opsite (polyurethane film), Kaltostat ( calcium sodium alginate), DuoDERM (hydrocolloid), Aquacel (hydrofiber), and Mepilex (silicone foam). Full-thickness skin samples were excised at 3 or 5 days and evaluated histologically for reepithelialization and inflammation. Comparisons also included incidence of infection, ease of use, and cost analyses. RESULTS: DuoDERM elicited the greatest percent reepithelialization (81%) and Mepilex the lowest (33%) after 3 days (P = 0.004). All dressings demonstrated complete reepithelialization except Mepilex (85%) at 5 days. There were no infections and inflammation was mild among all treatments. Mepilex was easiest to use, whereas Aquacel, Kaltostat, and Opsite were most difficult (P = 0.03). Xeroform was most cost-effective and Aquacel most expensive. Combined scoring revealed DuoDERM = Xeroform > Opsite = Mepilex > Kaltostat > Aquacel. CONCLUSIONS: DuoDERM and Xeroform were most effective overall. DuoDERM tended to outperform all dressings in reepithelialization at 3 days, while Xeroform was least expensive, easy to use, and demonstrated rapid reepithelialization. These findings suggest that Xeroform may be preferred for use on large donor-site areas. DuoDERM may be more appropriate for small donor sites when healing time is a priority.

Effect of cross-linked and non-cross-linked acellular dermal matrices on the expression of mediators involved in wound healing and matrix remodeling.

BACKGROUND: Molecular mechanisms that direct the extent of the foreign body reaction to implanted biological meshes and their subsequent incorporation are poorly understood. The purpose of this study was to compare the influence of non-cross-linked human dermis (AlloDerm) with that of cross-linked porcine dermis (Permacol) on the expression of genes critical for wound healing and tissue remodeling in a rat ventral hernia model. METHODS: Full-thickness abdominal wall defects were repaired with AlloDerm, Permacol, or suture repair with no mesh (n = 10 rats per group). Explants were harvested 90 days after repair and divided for histologic, immunohistochemical, and gene expression analyses. Real-time quantitative polymerase chain reaction arrays were used to profile the expression of 84 wound healing-associated genes at the tissue/mesh interface. RESULTS: Both meshes induced the differential expression (≥ 3-fold change relative to suture repair, p ≤ 0.01) of extracellular matrix components, remodeling enzymes, and inflammatory cytokines. Genes most markedly up-regulated included matrix metalloproteinase-9 (Permacol, 66-fold; AlloDerm, 19-fold) and chemokine (C-C motif) ligand 12 (Permacol, 24-fold; AlloDerm, 71-fold). Immunohistochemistry using antibodies against matrix metalloproteinase-9 and chemokine (C-C motif) ligand 12 confirmed differential expression at the protein level (p < 0.001). Histologically, AlloDerm demonstrated overall better remodeling characteristics than Permacol. CONCLUSIONS: Permacol elicits increased protease expression and reduced cellular and vascular infiltration compared with AlloDerm 90 days after implantation, indicative of delayed remodeling induced by cross-linking. Increased understanding of the host response to implanted materials ultimately will enable the development of improved meshes with enhanced wound healing properties and fewer graft-related complications.

Biocompatibility comparison of novel soft tissue implants vs commonly used biomaterials in a pig model.

OBJECTIVE: To develop a model to evaluate biocompatibility, integration, and substrate independence of novel porous bioscaffolds for maxillofacial and plastic reconstruction using sphere-templated angiogenic regeneration technology compared with currently available synthetic and biologic soft tissue implants. STUDY DESIGN: A prospective pilot study using animals. SETTING: Military medical center. SUBJECTS AND METHODS: Five pigs underwent dorsal subcutaneous implantation of a polypropylene-based material coated with precision pore silicone granules (sphere-templated scaffold), expanded polytetrafluoroethylene, human dermis, and porcine dermis. Sham and undissected sites were also used as controls. Specimens were harvested 7, 21, 90, and 180 days after surgery and evaluated histologically for inflammation, neovascularization, and collagen deposition. RESULTS: All materials and sham sites induced a mild to moderate inflammation that decreased over time, except for human dermis, which elicited a moderate to severe inflammatory response. The responses were varied and measurable using subjective scoring methods. The sphere-templated scaffold demonstrated numerous foreign body giant cells adjacent to the silicone granules, which were not seen in any of the other specimens. CONCLUSION: Subjective scoring of pathology slides and measurement of capsule thickness appeared to show differences between the materials, but these differences require a larger number of subjects and proper statistical analysis to assess. The robust foreign body reaction elicited by the polypropylene/silicone-based scaffold argues against the use of this material in future studies. The authors advocate using inert biodegradable substances for future bioscaffold constructs.

Influence of a new monofilament polyester mesh on inflammation and matrix remodeling.

ABSTRACT Synthetic mesh is widely used for hernia repairs, but mesh-induced chronic inflammatory responses may lead to postoperative complications. We previously showed an elevated response to multifilament polyester (PE) versus monofilament polypropylene (PP) and polytetrafluoroethylene (PTFE) meshes, but it is unclear whether this discrepancy is due to the differences in chemical composition or filament structure. This study compares the influence of a newly available monofilament PE mesh to that of multifilament PE, monofilament PP, and monofilament PTFE on the expression of genes important in inflammation and extracellular matrix remodeling in a rat model. Full thickness abdominal wall defects were corrected with onlay repair or suture repair with no mesh. Explants were harvested 7 or 90 days after repair and divided for histology and mRNA analyses using real-time quantitative polymerase chain reaction arrays to profile expression at the tissue-mesh interface. Monofilament PE elicited a reduced foreign body reaction compared to multifilament PE, corresponding with reduced mRNA expression of important inflammatory cytokines and matrix metalloproteinases (MMPs). Unexpectedly, monofilament PE also resulted in markedly reduced mRNA expression of tumor necrosis factor and MMPs 3 and 9 compared to the widely-used monofilament PP mesh. Findings from this study revealed that both chemical composition and filament structure are important mesh characteristics that may affect a patient's wound healing response and clinical outcome, and should be considered by the surgeon when choosing a particular mesh. Although clinical studies are warranted, results in a rodent model suggest that monofilament PE may be more beneficial than the multifilament form for certain hernia repairs.

Pulmonary toxicity after exposure to military-relevant heavy metal tungsten alloy particles.

Significant controversy over the environmental and public health impact of depleted uranium use in the Gulf War and the war in the Balkans has prompted the investigation and use of other materials including heavy metal tungsten alloys (HMTAs) as nontoxic alternatives. Interest in the health effects of HMTAs has peaked since the recent discovery that rats intramuscularly implanted with pellets containing 91.1% tungsten/6% nickel/2.9% cobalt rapidly developed aggressive metastatic tumors at the implantation site. Very little is known, however, regarding the cellular and molecular mechanisms associated with the effects of inhalation exposure to HMTAs despite the recognized risk of this route of exposure to military personnel. In the current study military-relevant metal powder mixtures consisting of 92% tungsten/5% nickel/3% cobalt (WNiCo) and 92% tungsten/5% nickel/3% iron (WNiFe), pure metals, or vehicle (saline) were instilled intratracheally in rats. Pulmonary toxicity was assessed by cytologic analysis, lactate dehydrogenase activity, albumin content, and inflammatory cytokine levels in bronchoalveolar lavage fluid 24h after instillation. The expression of 84 stress and toxicity-related genes was profiled in lung tissue and bronchoalveolar lavage cells using real-time quantitative PCR arrays, and in vitro assays were performed to measure the oxidative burst response and phagocytosis by lung macrophages. Results from this study determined that exposure to WNiCo and WNiFe induces pulmonary inflammation and altered expression of genes associated with oxidative and metabolic stress and toxicity. Inhalation exposure to both HMTAs likely causes lung injury by inducing macrophage activation, neutrophilia, and the generation of toxic oxygen radicals.

Alterations in pelvic floor muscles and pelvic organ support by pregnancy and vaginal delivery in squirrel monkeys.

INTRODUCTION AND HYPOTHESIS: The objective of this study was to measure the effects of pregnancy and parturition on pelvic floor muscles and pelvic organ support. METHODS: Levator ani, obturator internus, and coccygeus (COC) muscle volumes and contrast uptake were assessed by MRI of seven females prior to pregnancy, 3 days, and 4 months postpartum. Bladder neck and cervix position were measured dynamically with abdominal squeezing. RESULTS: The sides of three paired muscles were similar (p > 0.66). COC volumes were greater (p < 0.004) after parturition than before pregnancy or after recovery. COC contrast uptake increased (p < 0.02) immediately after delivery. Bladder neck position both in the relaxed state and abdominal pressure descended (p < 0.04) after delivery and descended further (p < 0.001) after recovery. Cervical position in the relaxed state before delivery was higher (p < 0.001) than postpartum but was unchanged (p = 0.50) with abdominal pressure relative to delivery. CONCLUSION: In squirrel monkeys, coccygeus muscles demonstrate the greatest change related to parturition, and parturition-related bladder neck descent seems permanent.

Inflammatory cytokine and matrix metalloproteinase expression induced by collagen-coated and uncoated polypropylene meshes in a rat model.

OBJECTIVE: The objective of the study was to compare the influence of collagen-coated vs uncoated polypropylene meshes on the expression of genes critical for wound healing. STUDY DESIGN: In 54 rats, abdominal wall defects were created, repaired by polypropylene sutures, and covered by an overlay of coated polypropylene (n = 20), uncoated polypropylene (n = 18), or no mesh (n = 16). Explants were harvested 7 or 90 days after repair and divided for histological, immunohistochemical, and messenger ribonucleic acid (mRNA) analyses. Real-time quantitative polymerase chain reaction arrays were used to profile the expression of 84 genes at the tissue-mesh interface. RESULTS: One week after implantation, coated mesh elicited a slightly greater inflammatory response and increased mRNA expression of 4 proinflammatory cytokines compared with uncoated mesh. Both materials, however, induced a comparable expression of cytokines and matrix metalloproteinases relative to suture repair 90 days after implantation. CONCLUSION: Collagen-coated polypropylene mesh induces elevated inflammatory cytokine expression compared with uncoated mesh early in the healing process, but the response to both meshes is similar 90 days after implantation.

Influence of mesh materials on the expression of mediators involved in wound healing.

The use of synthetic mesh for ventral hernia repair is widely accepted, but mesh-induced inflammatory responses may lead to postoperative complications. Molecular mechanisms that direct the extent of the foreign body reaction to implanted materials are poorly understood. This study compares the influence of three macroporous meshes on the expression of genes critical for wound healing and extracellular matrix remodeling in a rat model. Full thickness abdominal wall defects were corrected with polypropylene, polyester, polytetrafluoroethylene (PTFE), or suture repair with no mesh. Explants were harvested 7 or 90 days after repair and were divided for histological, immunohistochemical, and mRNA analyses. Real-time quantitative polymerase chain reaction arrays were used to profile the expression of 84 genes involved in angiogenesis at the tissue-mesh interface. Evaluation of gene expression profiles and histologic specimens revealed that polypropylene and polyester induced a greater and more persistent inflammatory response than PTFE, which elicited a response most similar to that induced by suture repair. Mesh implantation induced the differential expression (>3-fold change and p < .01) of genes encoding inflammatory cytokines, growth factors, and extracellular matrix proteins relative to suture repair without mesh. Genes most markedly upregulated included the neutrophil chemoattractant CXCL2 and matrix metalloproteinases 3 and 9. Polyester induced the greatest number of differentially expressed genes relative to suture repair both at 7 and 90 days after implantation. Results from this study suggest that the particular type of mesh used in a hernia repair may affect the patient's wound healing response and clinical outcome.

Effect of estrogen replacement on the histologic response to polypropylene mesh implanted in the rabbit vagina model.

OBJECTIVE: The aim of this study was to determine the effect of estrogen replacement after ovariectomy on the histologic response to polypropylene mesh implanted in rabbit vagina. STUDY DESIGN: Thirty rabbits were assigned to 5 groups: sham laparotomy, ovariectomy, ovariectomy-preoperative estrogen, ovariectomy-postoperative estrogen, or ovariectomy-preoperative and postoperative estrogen. Rabbits underwent sham surgery or ovariectomy and were infused with vehicle or 17beta-estradiol (200 microg/d) for 4 weeks ("preoperative" estrogen). Polypropylene mesh was implanted in the posterior vaginal wall, and rabbits were infused with vehicle or "postoperative" estrogen for an additional 8 weeks. Grafts were harvested and underwent histologic evaluation. RESULTS: Vaginal atrophy in ovariectomized rabbits was reversed by estrogen replacement. Scores for inflammation (P = .33) and neovascularization (P = .23) at the graft site were not different among estrogen replacement groups, but estrogen administration was associated with increased collagen deposition (P = .005). CONCLUSION: Estrogen replacement administered for 8 weeks postoperatively increases collagen deposition into polypropylene mesh.