Reduction of adhesions with composite AlloDerm/polypropylene mesh implants for abdominal wall reconstruction

Ventral hernia repair often includes the use of structural prosthetic materials, such as polypropylene mesh, that can induce dense abdominal adhesions to peritoneal structures. AlloDerm (LifeCell Corp., Branchburg, N.J.), a commercially available decellularized human dermal analogue with its native basement membrane components intact, is gradually revascularized and replaced with autologous tissue after implantation. The authors hypothesized that AlloDerm integrated with polypropylene mesh would reduce adhesions and provide a biodegradable scaffold to generate an autologous vascularized tissue layer separating the abdominal viscera from the mesh. Ventral hernia defects (3 x 1 cm) in 19 guinea pigs were repaired using an inlay technique with polypropylene mesh alone (n = 6) or with composite implants constructed by integrating polypropylene mesh and AlloDerm with its basement membrane surface oriented toward (polypropylene/AlloIn, n = 7) or away from (polypropylene/ AlloOut, n = 6) the peritoneal cavity. At 4 weeks, the authors determined the amount of mesh implant surface area covered by adhesions, the strength of the adhesions [graded from 0 (none) to 3], and the incidence of bowel adhesions. Histologic analyses were performed on full-thickness tissue sections from the repair sites. The mean surface areas affected by adhesions and mean adhesion strength were significantly lower in the polypropylene/AlloIn (area, 12.4 percent; mean grade, 1.0) and polypropylene/AlloOut (area, 9.5 percent; mean grade, 0.5) groups than in the polypropylene group (area, 79.5 percent; mean grade, 2.9); there were no such differences between the polypropylene/AlloIn and polypropylene/AlloOut groups. The bowel was adherent to 67 percent of polypropylene repairs and 0 percent of the composite mesh repairs. The AlloDerm was remodeled to form a vascularized tissue layer beneath the mesh in composite repairs, unlike the significantly thinner, dense scar layer that formed in the polypropylene repairs. Immunohistochemical labeling for factor VIII showed neovascularization throughout the AlloDerm.The AlloDerm thus functioned as a biodegradable tissue scaffold, guiding the formation of a thick, well-vascularized tissue layer separating the polypropylene mesh from intraperitoneal structures. This significantly reduced both the amount of surface area covered by adhesions and adhesion strength. Basement membrane orientation had no effect. Composite mesh implants composed of structural prosthetic materials integrated with AlloDerm may have useful clinical applications for abdominal wall reconstruction by reducing adhesions and providing a vascularized tissue layer to separate and protect the peritoneal structures from polypropylene mesh fibers.     

Preclinical Bioassay of a Polypropylene Mesh for Hernia Repair Pretreated with Antibacterial Solutions of Chlorhexidine and Allicin: An In Vivo Study

Introduction

Prosthetic mesh infection constitutes one of the major complications following hernia repair. Antimicrobial, non-antibiotic biomaterials have the potential to reduce bacterial adhesion to the mesh surface and adjacent tissues while avoiding the development of novel antibiotic resistance. This study assesses the efficacy of presoaking reticular polypropylene meshes in chlorhexidine or a chlorhexidine and allicin combination (a natural antibacterial agent) for preventing bacterial infection in a short-time hernia-repair rabbit model.

Methods

Partial hernia defects (5 x 2 cm) were created on the lateral right side of the abdominal wall of New Zealand White rabbits (n = 21). The defects were inoculated with 0.5 mL of a 10⁶ CFU/mL Staphylococcus aureus ATCC25923 strain and repaired with a DualMesh Plus antimicrobial mesh or a Surgipro mesh presoaked in either chlorhexidine (0.05%) or allicin-chlorhexidine (900 μg/mL-0.05%). Fourteen days post-implant, mesh contraction was measured and tissue specimens were harvested to evaluate bacterial adhesion to the implant surface (via sonication, S. aureus immunolabeling), host-tissue incorporation (via staining, scanning electron microscopy) and macrophage response (via RAM-11 immunolabeling).

Results

The polypropylene mesh showed improved tissue integration relative to the DualMesh Plus. Both the DualMesh Plus and the chlorhexidine-soaked polypropylene meshes exhibited high bacterial clearance, with the latter material showing lower bacterial yields. The implants from the allicin-chlorhexidine group displayed a neoformed tissue containing differently sized abscesses and living bacteria, as well as a diminished macrophage response. The allicin-chlorhexidine coated implants exhibited the highest contraction.

Conclusions

The presoaking of reticular polypropylene materials with a low concentration of chlorhexidine provides the mesh with antibacterial activity without disrupting tissue integration. Due to the similarities found with the antimicrobial DualMesh Plus material, the chlorhexidine concentration tested could be utilized as a prophylactic treatment to resist infection by prosthetic mesh during hernia repair.     

Formation of adhesions at surgical meshes in a rat experimental model

Abdominal wall hernias are surgical problem that are easily solved with laparoscopic surgery. The determining factor for the success of the operation is the right choice and use of surgical mesh as the support material. The most common complication of surgical mesh placement is the formation of adhesions. Aim of this paper is to determine whether there is a statistic difference in formation of adhesions between different surgical meshes in lab environment. Wistar rats were used as the experimental model. After the anaesthesia a 1x1 cm defect of the abdominal wall was made, but the skin was left intact. The mesh was placed directly on the internal organs. The experiment considered four different mesh types. After set time periods of one, two or four weeks the animals were sacrificed and the amount of formed adhesions were evaluated based on the modified Diamond scale. Immediately after the first week we found a statistically significant difference in the adhesion occurrence rate between compared materials. The smallest amount of adhesions was caused by polypropylen + polydoksanon mesh, and the most by polypropilen mesh. Polypropylen + polyglactin mesh showed significant reduction of adhesion formation between the tested weeks. We can conclude that polypropylen + polydoxanon meshes are superior for ventral hernia operation, because those defects are in close contact with the internal organs and it is very important to have the smallest amount of adhesions.     

Foreign Body Reaction Associated with PET and PET/Chitosan Electrospun Nanofibrous Abdominal Meshes

Electrospun materials have been widely explored for biomedical applications because of their advantageous characteristics, i.e., tridimensional nanofibrous structure with high surface-to-volume ratio, high porosity, and pore interconnectivity. Furthermore, considering the similarities between the nanofiber networks and the extracellular matrix (ECM), as well as the accepted role of changes in ECM for hernia repair, electrospun polymer fiber assemblies have emerged as potential materials for incisional hernia repair. In this work, we describe the application of electrospun non-absorbable mats based on poly(ethylene terephthalate) (PET) in the repair of abdominal defects, comparing the performance of these meshes with that of a commercial polypropylene mesh and a multifilament PET mesh. PET and PET/chitosan electrospun meshes revealed good performance during incisional hernia surgery, post-operative period, and no evidence of intestinal adhesion was found. The electrospun meshes were flexible with high suture retention, showing tensile strengths of 3 MPa and breaking strains of 8–33%. Nevertheless, a significant foreign body reaction (FBR) was observed in animals treated with the nanofibrous materials. Animals implanted with PET and PET/chitosan electrospun meshes (fiber diameter of 0.71±0.28 µm and 3.01±0.72 µm, respectively) showed, respectively, foreign body granuloma formation, averaging 4.2-fold and 7.4-fold greater than the control commercial mesh group (Marlex). Many foreign body giant cells (FBGC) involving nanofiber pieces were also found in the PET and PET/chitosan groups (11.9 and 19.3 times more FBGC than control, respectively). In contrast, no important FBR was observed for PET microfibers (fiber diameter = 18.9±0.21 µm). Therefore, we suggest that the reduced dimension and the high surface-to-volume ratio of the electrospun fibers caused the FBR reaction, pointing out the need for further studies to elucidate the mechanisms underlying interactions between cells/tissues and nanofibrous materials in order to gain a better understanding of the implantation risks associated with nanostructured biomaterials.     

Tissue-engineered mesh for pelvic floor reconstruction fabricated from silk fibroin scaffold with adipose-derived mesenchymal stem cells

A tissue-engineered mesh fabricated with adipose-derived mesenchymal stem cells (AD-MSCs) cultured on a silk fibroin scaffold is evaluated for use in female pelvic reconstruction. Thirty-five female Sprague Dawley rats were divided into four groups. Group A (n?=?10) were implanted with polypropylene meshes, Group B (n?=?10) with silk fibroin scaffolds and Group C (n?=?10) with tissue-engineered meshes. Group D (n?=?5) acted as the tissue control. The tissue-engineered mesh was produced as follows. AD-MSCs were obtained from adipose tissue of rats designated to Group C. The cells were seeded onto a silk fibroin scaffold, cultured and then observed by scanning electron microscopy (SEM). Histological studies of these meshes were performed at 4 and 12 weeks after implantation and mechanical testing was carried out on all groups before implantation and at 12 weeks after implantation. AD-MSCs displayed fibroblast-like shapes and were able to differentiate into adipocytes or fibroblasts. SEM observation showed that AD-MSCs proliferated and secreted a matrix onto the silk fibroin scaffolds. After implantation of the scaffolds into rats, histological analysis revealed better organized newly formed tissue in Group C than in controls. Group C also had a similar failure force (2.67?±?0.15 vs 2.33?±?0.38 N) and a higher Young’s modulus (2.99?±?0.19 vs 1.68?±?0.20 MPa) than a normal vaginal wall, indicating the potential of this tissue-engineered approach. AD-MSCs were validated as seed cells for tissue engineering. The silk fibroin scaffold thus shows promise for application with AD-MSCs in the fabrication of tissue-engineered mesh with good biocompatibility and appropriate mechanical properties for pelvic floor reconstruction.     

Treatment of difficult TRAM flap hernias using intraperitoneal synthetic mesh application

The authors report the successful repair of large lower abdominal hernia defects after transverse rectus abdominis muscle (TRAM) flap breast reconstruction in 11 patients using a technique of intraperitoneal application of synthetic polypropylene (Prolene) mesh anchored to the peritoneal surface of the abdominal wall tissues. Five of these patients had previously failed hernia repairs after a unipedicle TRAM flap breast reconstruction employing the onlay mesh technique, with two of the patients having undergone three previous hernia repairs. The other six patients had developed large hernias after bipedicle TRAM flap reconstruction without previous mesh supplementation of the abdominal wall repair. After their successful hernia repairs, all of the patients healed without difficulty and demonstrated no sign of recurrence in an 8 to 36-month follow-up. Each patient returned to her activity level before breast reconstruction.     

A review of physiological and cellular mechanisms underlying fibrotic postoperative adhesion

Postoperative adhesions (PA) are fibrotic tissues that are the most common driver of long-term morbidity after abdominal and pelvic surgery. The optimal drug or material to prevent adhesion formation has not yet been discovered. Comprehensive understanding of cellular and molecular mechanisms of adhesion process stimulates the design of future anti-adhesive strategies. Recently, disruption of peritoneal mesothelial cells were suggested as the ''motor'' of PA formation, followed by a cascade of events (coagulation, inflammation, fibrinolysis) and influx of various immune cells, ultimately leading to a fibrous exudate. We showed that a variety of immune cells were recruited into adhesive peritoneal tissues in patients with small bowel obstruction caused by PA. The interactions among various types of immune cells contribute to PA development following peritoneal trauma. Our review focuses on the specific role of different immune cells in cellular and humoral mechanisms underpinning adhesion development.     

Tolerance and Long-Term MRI Imaging of Gadolinium-Modified Meshes Used in Soft Organ Repair

Background

Synthetic meshes are frequently used to reinforce soft tissues. The aim of this translational study is to evaluate tolerance and long-term MRI visibility of two recently developed Gadolinium-modified meshes in a rat animal model.

Materials and Methods

Gadolinium-poly-ε-caprolactone (Gd-PCL) and Gadolinium-polymethylacrylate (Gd-PMA) modified meshes were implanted in Wistar rats and their tolerance was assessed daily. Inflammation and biocompatibility of the implants were assessed by histology and immunohistochemistry after 30 days post implantation. Implants were visualised by 7T and 3T MRI at day 30 and at day 90. Diffusion of Gadolinium in the tissues of the implanted animals was assessed by Inductively Coupled Plasma Mass Spectrometry.

Results

Overall Gd-PMA coated implants were better tolerated as compared to those coated with Gd-PCL. In fact, Gd-PMA implants were characterised by a high ratio collagen I/III and good vascularisation of the integration tissues. High resolution images of the coated mesh were obtained in vivo with experimental 7T as well as 3T clinical MRI. Mass spectrometry analyses showed that levels of Gadolinium in animals implanted with coated mesh were similar to those of the control group.

Conclusions

Meshes coated with Gd-PMA are better tolerated as compared to those coated with Gd-PCL as no signs of erosion or significant inflammation were detected at 30 days post implantation. Also, Gd-PMA coated meshes were clearly visualised with both 7T and 3T MRI devices. This new technique of mesh optimisation may represent a valuable tool in soft tissue repair and management.     

The role of TGF-beta1 as a determinant of foreign body reaction to alloplastic materials in rat fibroblast cultures: comparison of different commercially available polypropylene meshes for hernia repair

BACKGROUND: Animal experiments on hernia repair demonstrated better biocompatibility of light-weight polypropylene meshes. However, implanted medical devices trigger a variety of adverse tissue responses, such as inflammation, fibrosis, infection and thrombosis, but the mechanisms involved in such responses remain largely unknown. This study aimed to determine the effect of transforming growth factor beta1 (TGF-beta1) on host tolerance by quantification of foreign body reaction in cultured fibroblasts depending on the amount and composition of implanted material used for hernia repair. MATERIALS AND METHODS: An NRK-49F fibroblast culture was incubated in the presence of 4 commercially available meshes approved for hernia repair. A mesh-free cell suspension served as a control group, in which the influence of TGF-beta1 on fibroblasts was evaluated. Levels of TGF-beta1 in the supernatant were dynamically measured in a time interval of 6 to 96 h and cell proliferation rates were assessed colorimetrically using MTT test. RESULTS: A dose-dependent suppression of fibroblasts proliferation by TGF-beta1 was observed. All meshes suppressed the secretion of TGF-beta1 and conversely increased significantly cell proliferation in comparison to the control group (p<0.01) in the first 24 to 48 h of incubation. That effect was more pronounced in meshes partially containing absorbable material when compared to samples of pure polypropylene meshes (p<0.05) and to the control group (p<0.001). CONCLUSION: Our experiment revealed that early biological reaction of connective tissue cells towards polypropylene meshes and their variants depended much more on the composition and type of the material than on its absolute amount. The assumption that material weight reduction alone might affect the foreign body reaction of mesh implants could not be confirmed by our in vitro study.     

The long-term effect of mesh bioprosthesis in inguinal hernia repair on testicular nitric oxide metabolism and apoptosis in rat testis

Polypropylene mesh is the most widely used material in inguinal hernia repair. Although polypropylene mesh is known as an inert material, it is experimentally proven that mesh generates a chronic inflammatory tissue reaction. The aim of the present study was to investigate the long-term effects of polypropylene mesh material used in inguinal hernia operations on testicular function, testicular nitric oxide (NO) metabolism and germ cell-specific apoptosis in rats. The study comprised 40 male rats that were randomly allocated into two groups. In group 1, the left spermatic cord was elevated and a 0.5 x 1 cm polypropylene mesh was placed behind the left inguinal spermatic cord and group 2 consisted of the sham-operated controls. Blood samples were taken at 6 months preoperatively and postoperatively after to assess luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels for hormonal evaluation. Testicular NO was evaluated by the Griess method, apoptosis by a TUNEL method and inducible nitric oxide synthase (iNOS) and endothelial NOS (eNOS) expressions by immunohistochemical staining. Mild (+) eNOS expression was observed in all specimens. Mild (+) iNOS expression was only detected in ipsilateral testis of the mesh-implanted study group. Apoptotic cells were not detected in any samples. We are of the opinion that long-term polypropylene mesh implantation has no effect on testicular hormonal function and only a limited effect on nitric oxide levels and this effect is not sufficient to cause apoptosis in testis that could lead to infertility. It seems that mesh implantation is a reliable method in inguinal hernia repair; however, further work is required by more sensitive methods to fully elucidate the potential testicular damage.     

Impacts of icodextrin on integrin-mediated wound healing of peritoneal mesothelial cells

AimsExposure to glucose and its metabolites in peritoneal dialysis fluid (PDF) results in structural alterations of the peritoneal membrane. Icodextrin-containing PDF eliminates glucose and reduces deterioration of peritoneal membrane function, but direct effects of icodextrin molecules on peritoneal mesothelial cells have yet to be elucidated. We compared the impacts of icodextrin itself with those of glucose under PDF-free conditions on wound healing processes of injured mesothelial cell monolayers, focusing on integrin-mediated cell adhesion mechanisms.Main methodsRegeneration processes of the peritoneal mesothelial cell monolayer were investigated employing an in vitro wound healing assay of cultured rat peritoneal mesothelial cells treated with icodextrin powder- or glucose-dissolved culture medium without PDF, as well as icodextrin- or glucose-containing PDF. The effects of icodextrin on integrin-mediated cell adhesions were examined by immunocytochemistry and Western blotting against focal adhesion kinase (FAK).Key findingsCell migration over fibronectin was inhibited in conventional glucose-containing PDF, while icodextrin-containing PDF exerted no significant inhibitory effects. Culture medium containing 1.5% glucose without PDF also inhibited wound healing of mesothelial cells, while 7.5% icodextrin-dissolved culture medium without PDF had no inhibitory effects. Glucose suppressed cell motility by inhibiting tyrosine phosphorylation of FAK, formation of focal adhesions, and cell spreading, while icodextrin had no effects on any of these mesothelial cell functions.SignificanceOur results demonstrate icodextrin to have no adverse effects on wound healing processes of peritoneal mesothelial cells. Preservation of integrin-mediated cell adhesion might be one of the molecular mechanisms accounting for the superior biocompatibility of icodextrin-containing PDF.     

Interactions of human ovarian tumor cells with human mesothelial cells grown on extracellular matrix : An in vitro model system for studying tumor cell adhesion and invasion

Human ovarian tumors metastasize by direct extension into the peritoneal cavity leading to tumor cell implantation onto peritoneal surfaces. Successful formation of peritoneal implants is dependent on the ability of ascitic tumor cells to infiltrate the mesothelium, and become firmly adherent to the underlying extracellular matrix (ECM). In order to investigate this process in more detail, an in vitro model system was developed employing human mesothelial cells grown on ECM-coated culture dishes. The ability of human ovarian carcinoma cells derived from ascitic fluid to attach to the mesothelial cell monolayer grown on ECM, ECM alone or plastic was quantitated with the use of 51Cr radio-labelled tumor cells. Tumor cells exhibited a more rapid and firmer attachment to ECM than to the mesothelial cells or to plastic. Using agitation to stimulate peritoneal fluid dynamics and shear forces in vivo, tumor cell arrest was found to be limited to the ECM, but it occurred at a slower rate than it did without agitation. Tumor cell attachment was also restricted to areas of exposed ECM in wounded mesothelium as assessed by phase-contrast microscopy. Morphologic alterations of the mesothelium induced by tumor cells were observed with the use of scanning electron microscopy (SEM) and immunohistochemical staining which included disruption of intercellular junctions leading to retraction of mesothelial cells, exposure of underlying ECM, subsequent attachment and proliferation on ECM. This model system would appear to be useful for elucidating mechanisms of ovarian tumor cell adhesion and proliferation, and for assessing various therapeutic modalities for their ability to block tumor cell implantation, invasion and growth on peritoneal surfaces.     

Properties of blood-contacting surfaces of clinically implanted cardiac assist devices: Gene expression,matrix composition,and ultrastructural characterization of cellular linings

The development of implantable cardiac assist devices for prolonged circulatory support has been impeded by the problem of excessive thrombogenesis on the blood–prosthetic interface, with subsequent embolization. To overcome this obstacle, a ventricular assist device has been developed with textured blood-contacting surfaces to encourage the formation of a tightly adherent, hemocompatible, biological lining. In this study, we applied molecular biological techniques, in conjunction with conventional ultrastructural and biochemical techniques, to characterize the biological linings associated with the blood-contacting surfaces of 11 of these devices, which had been clinically implanted for durations ranging from 21 to 324 days. No clinical thromboembolic events or pump-related thromboembolism occurred. Biological linings developed on the textured surfaces composed of patches of cellular tissue intermingled with areas of compact fibrinous material. In addition, islands of collagenous tissue containing fibroblast-like cells appeared after 30 days of implantation. Many of these cells contained microfilaments with dense bodies indicative of myofibroblasts. RNA hybridization analyses demonstrated that the colonizing cells actively expressed genes encoding proteins for cell proliferation (histones), adhesion (fibronectin), cytoskeleton (actin, vimentin) and extracellular matrix (types I and III collagen). Linings, which never exceeded 150 μm in thickness, remained free of pathological calcification. Textured blood-contacting surfaces induced the formation of a thin, tightly adherent, viable lining which exhibited excellent long-term hemocompatibility.     

The Influence of Reactive Oxygen Species on the Adhesion of Pancreatic Carcinoma Cells to the Peritoneum

Postoperative peritoneal carcinomatosis is a significant clinical problem after “curative” resection of pancreatic carcinoma. Peroperative surgical trauma activates a cascade of peritoneal defense mechanisms responsible for postoperative intra-abdominal tumor recurrence. Reactive oxygen species (ROS) play a pivotal role in this postoperative inflammatory reaction. This study explores the influence of ROS on adhesion of human pancreatic carcinoma cells to human mesothelial cells. Furthermore this study explores the influence of ROS on the presentation of adhesion molecules on Panc-1 and mesothelial cells. ROS were produced using the enzymatic reaction of xanthine with xanthine oxidase (X/XO). A reproducible in-vitro assay to study adhesion of human Panc-1 carcinoma tumor cells to a mesothelial cell monolayer of primary human mesothelial cells was used. Mesothelial monolayers were incubated with ROS produced prior to adhesion of the tumor cells. Incubation of the mesothelial cells with X/XO resulted in a significant increase (69.5%) in adhesion of Panc-1 in all patients. SOD/catalase, anti-oxidants, could reduce this increase by 56.7%. ROS significantly influenced the expression of the adhesion molecules ICAM-1, VCAM-1 and CD44h on mesothelial cells, but did not influence adhesion molecule expression on Panc-1. The ROS released during the post-operative inflammatory reaction may play an important role in the adhesion of pancreatic tumor cells to the mesothelium. Possibly by influencing adhesion molecule expression on mesothelial cells. Therefore ROS can partly be responsible for the enhanced post-operative intra-abdominal tumor recurrence.     

The Influence of Reactive Oxygen Species on the Adhesion of Pancreatic Carcinoma Cells to the Peritoneum

Postoperative peritoneal carcinomatosis is a significant clinical problem after “curative” resection of pancreatic carcinoma. Preoperative surgical trauma activates a cascade of peritoneal defense mechanisms responsible for postoperative intra-abdominal tumor recurrence. Reactive oxygen species (ROS) play a pivotal role in this postoperative inflammatory reaction. This study explores the influence of ROS on adhesion of human pancreatic carcinoma cells to human mesothelial cells. Furthermore this study explores the influence of ROS on the presentation of adhesion molecules on Panc-1 and mesothelial cells. ROS were produced using the enzymatic reaction of xanthine with xanthine oxidase (X/XO). A reproducible in vitro assay to study adhesion of human Panc-1 carcinoma tumor cells to a mesothelial cell monolayer of primary human mesothelial cells was used. Mesothelial monolayers were incubated with ROS produced prior to adhesion of the tumor cells. Incubation of the mesothelial cells with X/XO resulted in a significant increase (69.5%) in adhesion of Panc-1 in all patients. SOD/catalase, anti-oxidants, could reduce this increase by 56.7%. ROS significantly influenced the expression of the adhesion molecules ICAM-1, VCAM-1 and CD44h on mesothelial cells, but did not influence adhesion molecule expression on Panc-1. The ROS released during the post-operative inflammatory reaction may play an important role in the adhesion of pancreatic tumor cells to the mesothelium-possibly by influencing adhesion molecule expression on mesothelial cells. Therefore ROS can partly be responsible for the enhanced post-operative intra-abdominal tumor recurrence.Key words: reactive oxygen species, mesothelium, Panc-1     

The influence of titanium coating of mesh polypropylene endoprostheses on their biocompatibility

A comparative analysis of the proliferative activity of inflammatory infiltrate cells and the distribution of collagen type I and III in granulomas formed in the area of contact of mesh materials made of polypropylene (PP Std Light) and titanium-coated polypropylene (TiMesh) was performed via polarized microscopy and immunohistochemical detection of Ki-67 protein. Mesh materials were implanted in the soft tissues of the lumbar region of rats. The number of proliferative cells around implants made of the standard polypropylene (PP Std Light) 7 days after the operation was detected with the use of antibodies to Ki-67 protein to be less than the number of those around titanium-coated polypropylene (TiMesh) (29.1 ± 5.7 and 33.6 ± 3.1%, respectively, p < 0.001). The similar differences were revealed 1 month after the beginning of the experiment (15.9 ± 4.3 and 26.9 ± 3.6%, respectively, p < 0.001). Various types of collagen fibers in granulomas around the implanted mesh materials were detected in polarized light with the use of sections stained with Sirius Red. The ratios between collagen fibers type I and III in granulomas around PP Std Light and TiMesh materials determined 7 days after the operation were 1.085 ± 0.022 and above 1.107 ± 0.013, respectively (p = 0.017). The ratio increased to 1.174 ± 0.036 and 1.246 ± 0.102, respectively (p = 0.045) 1 month after the operation. The obtained results suggest that the titanium coating of polypropylene stimulates the formation of collagen type I and more mature connective tissue around mesh endoprostheses.     

Endothelial differentiation of human stem cells seeded onto electrospun polyhydroxybutyrate/polyhydroxybutyrate-co-hydroxyvalerate fiber mesh

Tissue engineering is based on the association of cultured cells with structural matrices and the incorporation of signaling molecules for inducing tissue regeneration. Despite its enormous potential, tissue engineering faces a major challenge concerning the maintenance of cell viability after the implantation of the constructs. The lack of a functional vasculature within the implant compromises the delivery of nutrients to and removal of metabolites from the cells, which can lead to implant failure. In this sense, our investigation aims to develop a new strategy for enhancing vascularization in tissue engineering constructs. This study's aim was to establish a culture of human adipose tissue-derived stem cells (hASCs) to evaluate the biocompatibility of electrospun fiber mesh made of polyhydroxybutyrate (PHB) and its copolymer poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHB-HV) and to promote the differentiation of hASCs into the endothelial lineage. Fiber mesh was produced by blending 30% PHB with 70% PHB-HV and its physical characterization was conducted using scanning electron microscopy analysis (SEM). Using electrospinning, fiber mesh was obtained with diameters ranging 300 nm to 1.3 μm. To assess the biological performance, hASCs were extracted, cultured, characterized by flow cytometry, expanded and seeded onto electrospun PHB/PHB-HV fiber mesh. Various aspects of the cells were analyzed in vitro using SEM, MTT assay and Calcein-AM staining. The in vitro evaluation demonstrated good adhesion and a normal morphology of the hASCs. After 7, 14 and 21 days of seeding hASCs onto electrospun PHB/PHB-HV fiber mesh, the cells remained viable and proliferative. Moreover, when cultured with endothelial differentiation medium (i.e., medium containing VEGF and bFGF), the hASCs expressed endothelial markers such as VE-Cadherin and the vWF factor. Therefore, the electrospun PHB/PHB-HV fiber mesh appears to be a suitable material that can be used in combination with endothelial-differentiated cells to improve vascularization in engineered bone tissues.     

Inhibition of Staphylococcus aureus Adhesion to the Surface of a Reticular Heavyweight Polypropylene Mesh Soaked in a Combination of Chlorhexidine and Allicin: An In vitro Study

Introduction

Presoaking meshes for hernia repair with antiseptics prior to implantation could decrease the adhesion of microorganisms to the material surface and reduce the risk of antibiotic resistances. In this work, we evaluate chlorhexidine and allicin (natural antiseptic not yet tested for these purposes) against vancomycin as antiseptics to be used in the pretreatment of a heavyweight polypropylene mesh using an in vitro model of bacterial contamination.

Methods

Solutions of saline, vancomycin (40 µg/mL), allicin (1,000 µg/mL), chlorhexidine (2%-0.05%) and the combination allicin-chlorhexidine (900 µg/mL-0.05%) were analyzed with agar diffusion tests in the presence of 10⁶ CFU Staphylococcus aureus ATCC25923. Additionally, sterile fragments of Surgipro (1 cm²) were soaked with the solutions and cultured onto contaminated agar plates for 24/48/72 h. The antimicrobial material DualMesh Plus was utilized as positive control. At every time, the inhibition zones were measured and the bacterial adhesion to the mesh surface quantified (sonication, scanning electron microscopy). Cytotoxicity of the treatments was examined (alamarBlue) using rabbit skin fibroblasts.

Results

The largest zones of inhibition were created by allicin-chlorhexidine. Chlorhexidine was more effective than vancomycin, and allicin lost its effectiveness after 24 h. No bacteria adhered to the surface of the DualMesh Plus or the meshes soaked with vancomycin, chlorhexidine and allicin-chlorhexidine. On the contrary, saline and allicin allowed adherence of high loads of bacteria. Vancomycin had no toxic effects on fibroblasts, while allicin and chlorhexidine exerted high toxicity. Cytotoxicity was significantly reduced with the allicin-chlorhexidine combination.

Conclusions

The use of antiseptics such as chlorhexidine, alone or combined with others like allicin, could represent an adequate prophylactic strategy to be used for hernia repair materials because soaking with these agents provides the mesh with similar antibacterial properties to those observed after soaking with vancomycin, similar to the effect of DualMesh Plus.     

Binding of ovarian cancer cells to immobilized hyaluronic acid

Ovarian cancer has the highest mortality rate of any gynaecological malignancy. This is caused by metastatic deposits obstructing the intestinal tract. Very little is known about the molecules involved in the initial attachment of the metastatic tumour cells to the peritoneal mesothelial lining. Previously, we showed that many ovarian tumour lines express the adhesion molecule, CD44, on their cell surface. The major ligand for CD44 is the extracellular matrix glycosaminoglycan, hyaluronic acid (HA). Because mesothelial cells have a pericellular cost that contains large amounts of HA, it was postulated that the CD44/HA interaction is an important stage in ovarian cancer spread. However, it was difficult to demonstrate this interaction in an in vitro adhesion assay with mesothelial cells as most of the HA, and presumably the bound tumour cells, were lost from the mesothelial cells during the washing steps of the assay. In order to try and clarify the situation, the adhesion of six ovarian tumour lines to immobilized HA was measured. Four lines expressed high levels of CD44 and two lines expressed negligible amounts. Preliminary experiments were carried out with one of the CD44-expressing lines. After coating a plate overnight with 3 mg ml−1 HA, the 5 min adhesion of this line varied between 2% and 73% according to the type of plate that was used. Falcon Micro Test III flexible plates gave the highest adhesion and was used for further experiments. Plates were coated with concentrations of HA between 0.001 mg ml−1 and 3 mg ml−1. All CD44 expressing lines adhered to HA, but the maximum adhesion and the adhesion strength varied with the line studied and was not closely related to the total CD44 expression. These results suggest that CD44 on ovarian tumour cells binds to HA on mesothelial cells. As much of the HA can be very easily lost from the mesothelial cell surface, additional factors such as the strength of the CD44/HA interaction, and the formation of bonds by the tumour cells with other membrane adhesion molecules, such as integrins, are also important in promoting tumour spread. This revised version was published online in November 2006 with corrections to the Cover Date.