The use of polymeric meshes for pelvic organ prolapse: Current concepts, challenges, and future perspectives.

Pelvic organ prolapse (POP) is one of the most common chronic disorders in women, impacting the quality of life of millions of them worldwide. More than 100 surgical procedures have been developed over the decades to treat POP. However, the failure of conservative strategies and the number of patients with recurrence risk have increased the need for further adjuvant treatments. Since their introduction, surgical synthetic meshes have dramatically transformed POP repair showing superior anatomic outcomes in comparison to traditional approaches. Although significant progress has been attained, among the meshes in clinical use, there is no single mesh appropriate for every surgery. Furthermore, due to the risk of complications including acute and chronic infection, mesh shrinkage, and erosion of the tissue, the benefits of the use of meshes have recently been questioned. The aim of this work is to review the evolution of POP surgery, analyzing the current challenges, and detailing the key factors pertinent to the design of new mesh systems. Starting with a description of the pelvic floor anatomy, the article then presents the traditional treatments used in pelvic organ disorders. Next, the development of synthetic meshes is described with an insight into how their function is dependent on both mesh design variables (i.e., material, structure, and functional treatment) and surgical applications. These are then linked to common mesh-related complications, and an indication of current research aiming to address these issues.

MYC competes with MiT/TFE in regulating lysosomal biogenesis and autophagy through an epigenetic rheostat.

Coordinated regulation of the lysosomal and autophagic systems ensures basal catabolism and normal cell physiology, and failure of either system causes disease. Here we describe an epigenetic rheostat orchestrated by c-MYC and histone deacetylases that inhibits lysosomal and autophagic biogenesis by concomitantly repressing the expression of the transcription factors MiT/TFE and FOXH1, and that of lysosomal and autophagy genes. Inhibition of histone deacetylases abates c-MYC binding to the promoters of lysosomal and autophagy genes, granting promoter occupancy to the MiT/TFE members, TFEB and TFE3, and/or the autophagy regulator FOXH1. In pluripotent stem cells and cancer, suppression of lysosomal and autophagic function is directly downstream of c-MYC overexpression and may represent a hallmark of malignant transformation. We propose that, by determining the fate of these catabolic systems, this hierarchical switch regulates the adaptive response of cells to pathological and physiological cues that could be exploited therapeutically.

Surgical outcomes of primary and revision augmentation rhinoplasty using a processed fascia lata.

BACKGROUND: Dorsal augmentation is the most commonly performed procedure in rhinoplasty for Asian patients. Due to the anatomic features of the Asian nose, the use of nonautologous materials to obtain a proper degree of augmentation is inevitable in most cases. Because the use of nonautologous materials possesses a higher risk of complications, surgeons are concerned about selecting suitable materials for the procedure, especially in revision rhinoplasty. Therefore, this study was designed to evaluate the suitability and usefulness of a homologous material, Tutoplast-processed fascia lata (TPFL), in revision augmentation rhinoplasty. METHODS: Retrospective analysis of 104 rhinoplasty patients (primary, 86; revision, 18) who had undergone dorsal augmentation using TPFL was conducted. The comparison of surgical outcomes between primary and revision surgery was made using objective [dorsal height (DH) and radix height (RH), complication rate] and subjective (patient satisfaction) parameters. RESULTS: The degree of augmentation represented by DH and RH was comparable between primary and revision rhinoplasty using TPFL. In comparing the rate of postoperative complications, only minor incidents were noted, in six cases after primary surgery and in one case after revision surgery. Patient satisfaction was measured in both primary and revision augmentation, with a significant difference observed between the two groups (40.57 ± 9.25 versus 31.48 ± 7.59; p < 0.05). CONCLUSION: TPFL is a feasible implant material that delivers suitable augmentation and patient satisfaction with minimal morbidity in both primary and revision rhinoplasty.

Immobilization of actively thromboresistant assemblies on sterile blood-contacting surfaces.

Rapid one-step modification of thrombomodulin with alkylamine derivatives such as azide, biotin, and PEG is achieved using an evolved sortase (eSrtA) mutant. The feasibility of a point-of-care scheme is demonstrated herein to site-specifically immobilize azido-thrombomodulin on sterilized commercial ePTFE vascular grafts, which exhibit superior thromboresistance compared with commercial heparin-coated grafts in a primate model of acute graft thrombosis.

Peptide derived from Pvfp-1 as bioadhesive on bio-inert surface.

Surface property is one important characteristic of materials, especially for ones that are bio-inert but designed for bio-medical application. In this study, we designed a series of peptides and compared their capacities as bioadhesive to improve the surface bioactivity of bio-inert material. The peptides were designed according to the sequence of Perna viridis foot protein 1 (Pvfp-1), one of the Mfp-1s (mussel foot protein 1) which play key roles in wet adhesion of mussel byssus. And the Teflon (PTFE) was chosen as a model of bio-inert material. With adsorption, adhesion and coating analysis, it was found that peptide C2 (M) (derived from the non-repeating region of Pvfp-1, contains modified DOPA) has superior coating and adhesion abilities especially on the bio-inert surface of PTFE. After coating with peptide C2 (M), the cell adhesion and spreading of osteoblast MC3T3-E1 cells on PTFE were significantly improved compared with those on non-coated surface, and the peptide-coating did not show any cell toxicity. Therefore, peptide C2 (M) is effective for improving the bioactivity of bio-inert PTFE, and could be potentially used as a bioadhesive on other bio-inert materials for biomedical application. Moreover, this study also provided new insights in designing other peptide-based bioadhesive materials.

Nano-TiO 2 enriched polymeric powder coatings support human mesenchymal cell attachment and growth.

The objective of this study was to utilize ultrafine powder coating technology to prepare (PPC) that can support human mesenchymal cell attachment and growth. Resins were modified with titanium dioxide and polytetrafluoroethylene (PTFE), and enriched with either SiO(2) or TiO(2) nanoparticles (nSiO(2) or nTiO(2)) to create continuous PPC. Scanning electron microscopy (SEM) revealed complex surface topographies with nano features, and energy dispersive X-ray (EDX) analysis with Ti mapping confirmed a homogenous dispersion of the material. SEM and inverted fluorescence microscopy showed that human embryonic palatal mesenchymal (HEPM) cells attached and spread out on the PPC surfaces, particularly those enriched with nTiO( 2). Cell counts were higher, and the MTT assay measured more metabolic activity from the nTiO(2) enriched PPCs. Furthermore, these cellular responses were enhanced on PPC surfaces that were enriched with a higher concentration of nTiO(2) (2% vs. 0.5%), and appeared comparable to that seen on commercially pure titanium (cpTi). Therefore the nTiO( 2) enrichment of PPC was shown to favor human mesenchymal cell attachment and growth. Indeed, this modification of the materials created continuous surface coatings that sustained a favorable cellular response.

Encapsulation of ePTFE in prevascularized collagen leads to peri-implant vascularization with reduced inflammation.

During the typical healing response to an implanted biomaterial, vascular-rich granulation tissue forms around the implant and later resolves into a relatively avascular, fibrous capsule. We have previously shown that a microvascular construct (MVC) consisting of isolated microvessel fragments suspended in a collagen I gel forms a persistent microcirculation in lieu of avascular scar when implanted. The current study evaluated the potential for microvascular constructs to maintain a vascularized tissue environment around an implanted biomaterial. An analysis of the peri-implant tissue around bare expanded polytetrafluoroethylene (ePTFE), ePTFE embedded within a microvascular construct, or ePTFE embedded within collagen alone revealed that the presence of the MVC, but not collagen alone, promoted vascular densities comparable to that of the granulation tissue formed around bare ePTFE. The vessels within the microvascular construct surrounding the ePTFE were perfusion competent, as determined by India ink perfusion casting, and extended into the interstices of the polymer. In contrast to bare ePTFE, the presence of the MVC or collagen alone significantly reduced the number of activated macrophages in association with ePTFE. Similar results were observed for ePTFE modified to increase cellularity and prevent the formation of an avascular scar. The microvascular construct may prove effective in forming vascularized tissue environments and limiting the number of activated macrophages around implanted polymers thereby leading to effective implant incorporation.

Biomaterial topography alters healing in vivo and monocyte/macrophage activation in vitro.

The effect of biomaterial topography on healing in vivo and monocyte/macrophage stimulation in vitro was assessed. A series of expanded polytetrafluoroethylene (ePTFE) materials were characterized by increasing average intranodal distance of 1.2 µm (1.2-ePTFE), 3.0 µm (3.0-ePTFE), and 4.4 µm (4.4-ePTFE), but presented consistent surface chemistry with nonporous PTFE (np-PTFE). Subcutaneous implantation of 4.4-ePTFE into mice resulted in a statistically thinner capsule that appeared less organized and less dense than the np-PTFE response. In vitro, isolated monocytes/macrophages cultured on np-PTFE produced low levels of interleukin 1-beta (IL-1ß), 1.2-ePTFE and 3.0-ePTFE stimulated intermediate levels, and 4.4-ePTFE stimulated a 15-fold increase over np-PTFE. Analysis of cDNA microarrays demonstrated that additional proinflammatory cytokines and chemokines, including IL-1ß, interleukin 6, tumor necrosis factor alpha, monocyte chemotactic protein 1, and macrophage inflammatory protein 1-beta, were expressed at higher levels by monocytes/macrophages cultured on 4.4-ePTFE at 4 and 24 h, respectively. Expression ratios for several genes were quantified by RT-PCR and were consistent with those from the cDNA array results. These results demonstrate the effect of biomaterial topography on early proinflammatory cytokine production and gene transcription by monocytes/macrophages in vitro and decreased fibrous capsule thickness in vivo.

Friction transfer of polytetrafluoroethylene (PTFE) to produce nanoscale features and influence cellular response in vitro.

A large number of cell types are known to respond to chemical and topographical patterning of substrates. Friction transfer of polytetrafluoroethylene (PTFE) onto substrates has been shown to produce continuous, straight, parallel nanofibres. Ammonia plasma treatment can be used to defluorinate the PTFE, decreasing the dynamic contact angle. Fibroblast and epithelial cells were elongated and oriented with their long axis parallel to the fibres, both individually and in clusters. The fibres restricted cell migration. Cell alignment was slightly reduced on the plasma-treated fibres. These results indicated that although surface topography can affect cellular response, surface chemistry also mediates the extent of this response.

Platelet and endothelial adhesion on fluorosurfactant polymers designed for vascular graft modification.

A prominent failure mechanism of small diameter expanded polytetrafluoroethylene (ePTFE) vascular grafts is platelet-mediated thrombosis. We have designed a surface modification for ePTFE consisting of a self-assembling fluorosurfactant polymer (FSP) bearing biologically active ligands, including adhesive peptides and polysaccharide moieties. The goal of this biomimetic construct is to improve graft hemocompatibility by promoting rapid surface endothelialization, whereas minimizing platelet adhesion. Here we present a direct comparison of platelet and endothelial cell (EC) adhesion to FSPs containing one of three cell-adhesion peptides: cyclic Arg-Gly-Asp-D-Phe-Glu (cRGD), cyclic *Cys-Arg-Arg-Glu-Thr-Ala-Trp-Ala-Cys* (cRRE, *denotes disulfide bond cyclization), linear Gly-Arg-Gly-Asp-Ser-Pro-Ala (RGD), or a polysaccharide moiety: oligomaltose (M-7), later designed to prevent nonspecific protein adhesion. Measurements of soluble peptide-integrin binding indicated that cRRE exhibits very low affinity for the alpha(IIb)beta(3) platelet fibrinogen receptor. Static and dynamic adhesion of washed, activated platelets on FSP-modified surfaces revealed that M-7 and cRRE promote significantly less platelet adhesion compared to RGD and cRGD FSPs, whereas EC adhesion was similar on all peptide FSPs and minimal on M-7 FSP. These results illustrate the potential for ligands presented in a FSP surface modification to selectively adhere ECs with limited platelet attachment.

Adsorbed serum albumin is permissive to macrophage attachment to perfluorocarbon polymer surfaces in culture.

Monocyte/macrophage adhesion to biomaterials, correlated with foreign body response, occurs through protein-mediated surface interactions. Albumin-selective perfluorocarbon (FC) biomaterials are generally poorly cell-conducive because of insufficient receptor-mediated surface interactions, but macrophages bind to albumin-coated substrates and also preferentially to highly hydrophobic fluorinated surfaces. Bone marrow macrophages (BMMO) and IC-21, RAW 264.7, and J774A.1 monocyte/macrophage cells were cultured on FC surfaces. Protein deposition onto two distinct FC surfaces from complex and single-component solutions was tracked using fluorescence and time-of-flight secondary ion mass spectrometry (ToF-SIMS) methods. Cell adhesion and growth on protein pretreated substrates were compared by light microscopy. Flow cytometry and integrin-directed antibody receptor blocking were used to assess integrins critical for monocyte/macrophage adhesion in vitro. Albumin predominantly adsorbs onto both FC surfaces from 10% serum. In cultures preadsorbed with albumin or serum-dilutions, BMMO responded similar to IC-21 at early time points. Compared with Teflon AF, plasma-polymerized FC was less permissive to extended cell proliferation. The beta(2) integrins play major roles in macrophage adhesion to FC surfaces: antibody blocking significantly disrupted cell adhesion. Albumin-mediated cell adhesion mechanisms to FC surfaces could not be clarified. Primary BMMO and secondary IC-21 macrophages behave similarly on FC surfaces, regardless of preadsorbed protein biasing, with respect to adhesion, cell morphology, motility, and proliferation.

In vitro study of cell-promoting multiple-armed peptides.

The purpose of this study was to compare the effectiveness of several linear and branch cell-binding peptides to promote cell growth in prosthetic vascular grafts. In this in vitro study, the peptides were covalently immobilized onto expanded polytetrafluoroethylene (ePTFE) vascular grafts. Cell-growth properties were studied using primary human umbilical vein endothelial cells (HUVECs) and primary human umbilical artery smooth muscle cells (HUASMCs). Linear peptides (P15 and P15') and multiple-armed peptides (MAP4-I and MAP4-II) were covalently bonded onto ePTFE grafts by an atmospheric plasma coating method. X-ray photoelectron spectroscopy and amino acid analysis were used to analyze the surface characteristics of the peptide-coated samples. Cell adhesion, proliferation, and morphology were evaluated by culturing HUVECs and HUASMCs onto the surfaces of different samples: ePTFE control, chemically activated ePTFE, P15-coated ePTFE, and MAP4-coated ePTFE. The cell culture experiments were repeated several times to obtain statistically reliable cell-growth data. Cell-growth data were statistically analyzed by the two-way statistical analysis of variance. The study showed that multiple-armed MAP4 peptides were significantly more effective in promoting endothelial cells than the structurally similar linear P15 peptides. There were 800% more HUVECs proliferated on the MAP4-coated ePTFE samples compared with the ePTFE control. MAP4 peptides were 80% more effective for promoting HUVECs than P15 peptides. In contrast, MAP4 peptides were significantly less effective for promoting HUASMCs than HUVECs. There were only about 100% more HUASMCs proliferated on the MAP4-coated ePTFE samples compared with the ePTFE control. MAP4 and P15 peptides had similar cell-promoting characteristics for SMCs.

Polydimethylsiloxane versus polytetrafluoroethylene for vocal fold medialization: histologic evaluation in a rabbit model.

The objective is to study the tissue reaction of the paralyzed vocal cord in response to the injection of particulate plastics in a rabbit model. Forty-five New Zealand rabbits with surgical vocal-fold paralysis were used in the study. Histologic reactions of the larynx and the regional lymph nodes were analyzed by a single blinded pathologist at 6 weeks and 6 months after a vocal-cord injection of Teflon or of silicone elastomer. Macroscopic studies of the liver, lungs, spleen, kidney, and brain were performed. The histological study showed a greater proportion of chronic granulomatous inflammation in animals injected with silicone than in those injected with Teflon. The immunohistochemical study showed a higher degree of phagocytosis of Teflon particles than of the silicone particles. The silicone group presented a more severe fibrous reaction than the Teflon group, but the difference was not significant. No migration particles were found. It is concluded that silicone, having a greater viscosity than Teflon because of the size of its particles, induces more fibrosis and a larger proportion of foreign giant cells in the host. Due to this histological reaction, silicone particles present greater anchorage and stability.

Modulation of angiogenic functions in human macrophages by biomaterials.

We examined the ability of polyvinylchloride (PVC), polytetrafluorethylene (PTFE) and tissue culture polystyrene (TCPS) to affect angiogenic functions in human monocyte-derived macrophages by measuring the mRNA expression of genes encoding angiogenic and anti-angiogenic molecules including basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), angiopoietin-1 (Ang-1) and thrombospondin-1 (Tsp-1). The angiogenic activity of the corresponding macrophage conditioned media (CM) was measured by the proliferation of endothelial cells and the sprouting of new capillaries from fragments of human placental blood vessels. We determined that bFGF was not expressed in macrophages while VEGF and Tsp-1 mRNAs were expressed constitutively. Ang-1 was expressed in macrophages cultured up to 7 days on PTFE and TCPS independent of the culture stage. In contrast, macrophages cultured on PVC did not produce detectable amounts of Ang-1 mRNA after 7 days. CM from macrophages cultured either on PTFE or TCPS stimulated angiogenesis whereas CM from macrophages cultured on PVC inhibited it. The results demonstrate that polymers can cause differential expression of the angiogenic molecule Ang-1 in macrophages. They also induce different phenotypes of macrophages, which can either stimulate or inhibit angiogenesis suggesting a material-dependent influence on neovascularization.

Biomembranes enriched with TGFbeta1 favor bone matrix protein expression by human osteoblasts in vitro.

The use of growth factors in oral tissue regeneration is currently under investigation. When growth factors are combined with commercial materials, the in vitro mechanisms of action still remain unclear. The present study first evaluated the capacity of barrier membranes, used in oral surgery, to sequester TGFbeta(1). Resorbable HYAFF, paroguide, poly DL-lactide and nonresorbable PTFE membranes were immersed in MEM containing 0.2 ng (125)I-TGFbeta(1) for different periods of time. It was found that HYAFF membrane and paroguide sequestered the most TGFbeta(1), which was then released in its active form (as shown by the CCL64 cell line bioassay). Untreated membranes and membranes enriched with TGFbeta(1) were then used as substrate for human bone cells to evaluate the synthesis of the osteoblast phenotype, as indicated by specific parameters. Results showed that membranes enriched with TGFbeta(1) increased alkaline phosphatase activity, collagen, and osteocalcin production more than untreated membranes. HYAFF and paroguide membranes, which sequestered the most of TGFbeta(1), were the most suitable for stimulating bone matrix proteins.

Postoperative complications after laparoscopic incisional hernia repair. Incidence and treatment.

BACKGROUND: The popularity of laparoscopic repair of incisional hernias is increasing due to the apparent advantages of laparoscopy. PATIENTS AND METHODS: A group of 150 consecutive patients with incisional hernias were treated by laparoscopic IPOM technique with a Goretex Dualmesh between September 1999 and September 2001 and subsequently followed up. Some minor and major complications could clearly identify advantages as well as drawbacks of the technique. RESULTS: No primary mesh infection were observed but 4 recurrences, 3 of them due to technical mistakes, and 1 case with ileus due to a volvolus at day 4 p.o. were recorded. Further major complications included 2 early and 2 later stage trocar hernias, which needed surgical correction. Two patients developed secondary bowel perforation after thermal injury and after primary enterotomy which was closed by laparotomy. CONCLUSIONS: All complications, except one recurrence due to failure of the material, were surgical mistakes and cannot be attributed to the laparoscopic procedure. Consequently, after taking into account the surgical mistakes and possible technical errors, the low recurrence rate justifies further application of laparoscopic ventral hernia repair.

The neuropeptide Y monomer in solution is not folded in the pancreatic-polypeptide fold.

Fluorescence-labelled analogs of NPY, a 36-amino acid peptide amide, were synthesized by solid-phase peptide synthesis and used for fluorescence-resonance energy transfer studies to investigate the conformation. Energy-transfer efficiency measurements in different media at the concentration of 10 microM are in agreement with a model of the NPY structure proposed by NMR studies (performed at millimolar concentration) in which the C-terminal part of the molecule adopts an alpha-helical conformation while the N-terminal part is flexible. According to this model, the alpha-helix is stabilized by intermolecular hydrophobic interactions because of the formation of dimers. The decrease of the peptide concentration causes a shift of the dimerization equilibrium toward the monomeric form. Energy-transfer efficiency measurements performed at lower concentrations do not support the hypothesis of the folding back of the N-terminal tail onto the C-terminal alpha-helix to yield the so-called "PP-fold" conformation. This structure is observed in the crystal structure of avian pancreatic polypeptide, a member of the NPY peptide hormone family, and it has been considered to be the bioactive one. Our results complete the structural characterization of NPY in solution at concentration ranges in which NMR experiments are not feasible. Furthermore, these results open the way to study the conformation of the receptor-bound ligand.

Treatment of aortocoronary vein graft lesions with membrane-covered stents: A multicenter surveillance trial.

BACKGROUND: Stent implantation in lesions of degenerated aortocoronary vein grafts is associated with a high risk of periprocedural thrombus embolization and in-stent restenosis. METHODS AND RESULTS: In a multicenter study, we followed up 109 consecutive patients (mean age 66+/-8 years, 12% female) who received polytetrafluoroethylene (PTFE) membrane-covered stents for 125 de novo stenoses in vein grafts 11+/-5 years after bypass surgery. Stent deployment was successful in all but 1 patient; 1 patient suffered from subacute stent thrombosis. Six-month cardiac mortality was 7% (8 patients), 3 patients (3%) underwent repeat bypass surgery, and 9 patients (8%) required target-lesion PTCA. Repeat angiography revealed vessel occlusions in 9% and in-stent restenosis in 8% of patients by the end of follow-up. CONCLUSIONS: Membrane-covered stents appear to be a safe and efficient treatment strategy associated with a low incidence of restenosis and target-vessel revascularization. Compared with previous studies, the investigated device is not associated with an increase in mortality or late vessel occlusions.

Structural and functional role of the disulfide bridges in the hydrophobin SC3.

Hydrophobins function in fungal development by self-assembly at hydrophobic-hydrophilic interfaces such as the interface between the fungal cell wall and the air or a hydrophobic solid. These proteins contain eight conserved cysteine residues that form four disulfide bonds. To study the effect of the disulfide bridges on the self-assembly, the disulfides of the SC3 hydrophobin were reduced with 1,4-dithiothreitol. The free thiols were then blocked with either iodoacetic acid (IAA) or iodoacetamide (IAM), introducing eight or zero negative charges, respectively. Circular dichroism and infrared spectroscopy showed that after opening of the disulfide bridges SC3 is initially unfolded. IAA-SC3 did not self-assemble at the air-water interface upon shaking an aqueous solution. Remarkably, after drying down IAA-SC3 or after exposing it to Teflon, it refolded into a structure similar to that observed for native SC3 at these interfaces. Iodoacetamide-SC3 on the other hand, which does not contain extra charges, spontaneously refolded in water in the amyloid-like beta-sheet conformation, characteristic for SC3 assembled at the water-air interface. From this we conclude that the disulfide bridges of SC3 are not directly involved in self-assembly but keep hydrophobin monomers soluble in the fungal cell or its aqueous environment, preventing premature self-assembly.

Exposure of plasma proteins on Dacron and ePTFE vascular graft material in a perfusion model.

OBJECTIVES: to compare the exposure of plasma proteins adsorbed onto three vascular graft materials (polytetrafluoroethylene ePTFE and two modifications of polyethyleneterephthalate Dacron). METHODS: surface exposure of fibronectin, vitronectin, thrombospondin, antithrombin III, IgG, high molecular-weight kininogen, fibrinogen, albumin and plasminogen was studied by incubation with radiolabelled antibodies in a perfusion model. Perfusion times with human plasma were 1, 4, 24 and 48 hours. RESULTS: all proteins could be detected at 1, 4, 24 and 48 hours after the start of perfusion. Overall, the least amount of proteins adsorbed onto ePTFE. CONCLUSIONS: the low adsorption of proteins onto ePTFE may be one of the reasons for the lower incidence of infections reported with this material.