Titanium coating of a polypropylene mesh for hernia repair: Effect on biocompatibilty

Titanium and its alloys are used worldwide in surgery. The favorable characteristics that make this material desirable for implantation are corrosion resistance and biocompatibility. Concerning hernia repair, a mesh modification has been developed using titanium layering of a polypropylene mesh implant, which is said to lead to an improved biocompatibility compared to commercially available mesh materials. To analyze the pure effect of titanium coating, two different mesh structures were studied using a standardized animal model. The titanium-coated monofilamentous, large porous, and lightweight mesh made of polypropylene and coated with titanium (PP+T) was compared to a pure polypropylene mesh manufactured with a similar structure and amount of material serving as a control (PP). In Sprague-Dawley rats, mesh samples were placed in a subcutaneuous position. Then 56, 84, and 182 days after mesh implantation, three animals from each group were sacrificed for morphological observations (amount of inflammatory and connective tissue formation, percentages of proliferating and apoptotic cells, percentage of macrophages). Both mesh modifications investigated showed an overall good biocompatibility. Macroscopic clinical observation after implantation of up to 182 days was uneventful. The tissue response to the PP as well as to the PP+T mesh was characterized by a moderate inflammatory tissue reaction limited to the perifilamentary region as is known for low weight, large porous, and monofilamentous mesh structures. No significant improvement of biocompatibility was found when analyzing the effect of titanium coating compared to the pure polypropylene mesh structure.     

Use of carbon fibers for repair of abdominal-wall defects in rats

Carbon in the form of 8-micron fibers induces growth of connective tissue. The purpose of this study was to measure and histologically characterize tissue ingrowth occurring in carbon fibers implanted for up to 12 months in abdominal-wall defects in rats, compared with polypropylene mesh. Carbon fibers induced significantly more tissue ingrowth than polypropylene mesh at 6 to 12 months postoperatively. The predominant tissues associated with carbon fibers and polypropylene mesh were dense connective tissue and fat, respectively. Fragmentation of the implants did not occur, and implant debris was not found in the regional lymph nodes. Carbon fibers are potentially useful for reinforcing abdominal-wall defects.     

Vypro II mesh in hernia repair: impact of polyglactin on long-term incorporation in rats

BACKGROUND: To the Vypro II mesh, a large-pore-sized multifilamentous polypropylene mesh for hernia repair, supplementary polyglactin 910 multifilaments were added to improve intraoperative handling. As it has been suggested that polyglactin induces fibroplastic reactions and wound complications, this study was designed to evaluate the long-term tissue reaction to polyglactin in the Vypro II mesh. MATERIALS AND METHODS: Two mesh materials, the Vypro II composite mesh (PP + PG) and the pure polypropylene variant (PP), were compared after inlay implantation in a standardized rodent animal model. After 14, 28, 42, 56, 84 and 112 days of implantation, histological analysis of the inflammatory response was performed: material absorption, inflammatory tissue reaction, fibrosis and granuloma formation were investigated. RESULTS: Total absorption of polyglactin filaments of the Vypro II mesh occurred between 56 and 84 days of implantation. Both the inflammatory and the fibrotic reaction were initially increased in the PP + PG mesh group. These differences disappeared in the following implantation period. After 112 days, inflammation was even less pronounced in the PP + PG mesh group. CONCLUSION: The present data confirm a short-term polyglactin-induced increase in inflammation and fibrosis around implanted Vypro II meshes in rats. With regard to the long-term tissue response, even an anti-inflammatory property of polyglactin multifilaments in low-weight and large-pored polypropylene meshes cannot be ruled out.     

Functional and Morphologic Properties of a Modified Mesh for Inguinal Hernia Repair

Inguinal hernia repair is one of the most frequently performed operations. Next to conventional techniques, open and laparoscopic tension-free methods using mesh implants to reinforce the abdominal wall are increasingly carried out, even becoming the standard procedure in many countries. Because of the benefits of material-reduced meshes for incisional hernia repair, a new mesh modification for tension-free inguinal hernia repair has been developed. In the present study this new low-weight mesh (Vypro II) made of polypropylene and polyglactin multifilaments was compared to a common heavy-weight polypropylene mesh (Prolene) regarding their functional consequences and the morphologic tissue response. After implantation in rats as an inlay, abdominal wall mobility was recorded by three-dimensional photogrammetry and the tensile strength of the suture zone and the mesh itself was measured at 3, 21, and 90 days. Explanted tissue samples have been investigated for their histologic reaction in regard to the inflammatory infiltrate, vascularization, and connective and fat tissue ingrowth. Numbers of granulocytes, macrophages, fibroblasts, lymphocytes, and foreign giant body cells have been evaluated to reflect the quality of the tissue response. The cellular response was assessed by measuring DNA strand breaks and apoptosis (TUNEL), proliferation (Ki67), and cell stress (HSP70). The results indicated that restriction of abdominal wall mobility was significantly reduced with Vypro II compared to that seen with heavy-weight mesh modification, and the inflammatory reaction and connective tissue formation were markedly diminished. Apoptosis and cell proliferation showed considerably lowered levels, and expression of cytoprotective HSP70 was significantly increased. The present study thus confirms the benefits of material-reduced mesh modifications. The new low-weight mesh (Vypro II) could be advantageous in inguinal hernia repair.     

Non-absorbable prosthetic meshes: which is the best option in the repair of abdominal wall defects?

The mechanical properties and macroscopic behaviour of non-absorbable materials have been widely studied. Nevertheless, biological tissue response to contact with these prostheses is not well-known. Our purpose was to compare the microscopic behaviour of two non-absorbable materials. Polypropylene and mersilene meshes were implanted on 36 female Wistar rats each (PPL and ME groups) . Six animals per group were sequentially sacrificed at 1, 2, 3, 5, 10 and 15 weeks. Global cell density and number of polymorphonuclear leukocytes, giant cells, fibroblasts and histiocytes were compared for every studied phase. The polypropylene group showed higher cell density and polymorphonuclear response in the initial phases, while scores for giant cells were higher in the mersilene group. Fibrohistiocytic reaction was increased in the polypropylene group. Polypropylene tends to provoke higher acute inflammatory reaction and connective tissue formation than mersilene. The latter induces higher foreign body reaction.     

In vivo tissue reaction to different prosthetic materials in abdominal wall hernia repair

Summary Several well tolerated materials are currently available for the treatment of hernias. Polyester (Dacron) and polypropylene (PPL) are currently the most frequently used materials. Experimental work has highlighted the biological response of laboratory animals treated with a range of prostheses. Authors agree that an inflammatory response rarely occurs, although materials generate a range of responses. In the years 1996–2000, hystological tests were performed to assess thein vivo response to the range of materials. Thirty-five prostheses were examined in 34 patients. Twenty-six were men and 8 were women with an average age of 59.3 years (range 35 to 89). Samples were fixed in formalin, de-hydrated and placed in paraffin. Four micron sections were dyed with hematoxylin and eosin and then underwent microscopy. The type and the amount of prosthesis-englobin connective tissue was evaluated, as was the number of giant cells, of inflammatory elements and of vessels. Evaluation scores ranged from-to ++. The microscope highlighted a range of patterns according to the implant: a) Dacron prostheses were surrounded by a large amount of thick connective tissue, with scarce fibroblastic elements, engendering a lively response with polynucleate giant cells in relatively large quantities, b) PPL plug prostheses were englobed in a looser connective tissue, rich in fibroblasts and with a scarce amount of inflammatory elements and giant cells, c) PPL patches were surrounded by thicker connective tissue, appear to be more inert, and were often surrounded by adipose tissue. The type of prostheses, as well as its form, may engender different tissue responses.     

Polydioxanone and polypropylene suture material in free internal mammary artery graft anastomoses

An experimental study with six beagle dogs was conducted to evaluate a new monofilamentous absorbable suturing material--polydioxanone. Free internal mammary artery grafts, 3 cm long, were harvested via a median sternotomy and were implanted as arterial bypasses in femoral arteries (12 end-to-end anastomoses) and as arteriovenous shunts in the carotid artery-contralateral jugular vein position (12 end-to-side anastomoses). Twenty-four anastomoses were made with monofilamentous nonabsorbable suturing material, polypropylene (12 arterial, 12 shunts), to serve as control grafts. At 6 months the grafts and anastomoses were explanted and studied with light and scanning electron microscopes. Macroscopically, the polydioxanone sutures had disappeared. The major histologic finding was the foreign body reaction around the polypropylene sutures. In the electron microscopic study the endothelial line covered the anastomotic site and in the polypropylene anastomoses the suture material was bulging up from the anastomoses. No aneurysms or dilatations were seen. According to this study, polydioxanone is a suitable suturing material for small luminal arterial anastomoses and is superior to polypropylene suturing material because it causes no tissue or other late changes on the flow surfaces.     

Functional and morphologic properties of a modified mesh for inguinal hernia repair

Inguinal hernia repair is one of the most frequently performed operations. Next to conventional techniques, open and laparoscopic tension-free methods using mesh implants to reinforce the abdominal wall are increasingly carried out, even becoming the standard procedure in many countries. Because of the benefits of material-reduced meshes for incisional hernia repair, a new mesh modification for tension-free inguinal hernia repair has been developed. In the present study this new low-weight mesh (Vypro II) made of polypropylene and polyglactin multifilaments was compared to a common heavy-weight polypropylene mesh (Prolene) regarding their functional consequences and the morphologic tissue response. After implantation in rats as an inlay, abdominal wall mobility was recorded by three-dimensional photogrammetry and the tensile strength of the suture zone and the mesh itself was measured at 3, 21, and 90 days. Explanted tissue samples have been investigated for their histologic reaction in regard to the inflammatory infiltrate, vascularization, and connective and fat tissue ingrowth. Numbers of granulocytes, macrophages, fibroblasts, lymphocytes, and foreign giant body cells have been evaluated to reflect the quality of the tissue response. The cellular response was assessed by measuring DNA strand breaks and apoptosis (TUNEL), proliferation (Ki67), and cell stress (HSP70). The results indicated that restriction of abdominal wall mobility was significantly reduced with Vypro II compared to that seen with heavy-weight mesh modification, and the inflammatory reaction and connective tissue formation were markedly diminished. Apoptosis and cell proliferation showed considerably lowered levels, and expression of cytoprotective HSP70 was significantly increased. The present study thus confirms the benefits of material-reduced mesh modifications. The new low-weight mesh (Vypro II) could be advantageous in inguinal hernia repair.     

In vivo study of meshes implanted over the inguinal ring and external iliac vessels in uncastrated pigs

Background: The effects of placing a prosthesis directly on the internal inguinal ring and external iliac vessels in inguinal hernia repair are unknown. We compared tissue responses to five prostheses implanted in this position in uncastrated male pigs. Methods: Three types of polypropylene and two types of expanded polytetrafluoroethylene (ePTFE) mesh were implanted in 20 pigs (n= 8 for each prosthesis type). Specimens of the implants and surrounding tissue were obtained 30 and 90 days after implantation and assessed histologically. Results: The polypropylene implants had more adhesions, more surface area covered by adhesions, and more tenacious adhesions than did the ePTFE implants. Perivascular cuffing was observed in eight polypropylene and one ePTFE specimen; ossification, necrosis, and testicular venous congestion were seen in polypropylene specimens. Conclusions: Abnormal healing processes after implantation of polypropylene mesh may increase complications of the transabdominal preperitoneal and total extraperitoneal approaches in laparoscopic inguinal hernia repair, whereas the minimal response to ePTFE meshes may make them safer for use in the preperitoneal space. Received: 2 April 1997/Accepted: 8 August 1997     

Ultrastructure of periprosthetic Dacron knee ligament tissue. Two cases of ruptured anterior cruciate ligament reconstruction.

Light- and electron-microscopic investigations were performed on two failed Dacron ligaments that had been removed from 2 patients shortly after failure of the implant 2-3 years after reconstruction of the anterior cruciate ligament. Two different cell populations and matrices were correlated with closeness to the Dacron threads. Fibroblasts surrounded by connective tissue with collagen fibrils were located far from the Dacron threads. Roundish cells, appearing to be myofibroblasts surrounded by a more lax connective tissue and elastic fibers, were found close to the Dacron threads. The presence of myofibroblasts and the matrix differentiation could be attributed to the different mechanical forces acting on the Dacron and on the connective tissue because of their different coefficients of elasticity. The sparse occurrence of inflammatory cells in the synovial membrane and in the connective tissue surrounding the Dacron supports the biologic inertness of this artificial material. However, the repair tissue was not structured to resist tension stresses.     

Tissue response to polyester mesh for hernia repair: An ultramicroscopic study in man

Summary We studied by ultramicroscopy the tissue response after mesh hernia repair. 11 patients, bearing dacron mesh from 7 days to 9 years, were biopsied during later operations. There were two groups of patients: 6 with a normal tissue response and 5 with rejection of the mesh. We observed that mesh repair was characterised by development of a foreign-body giant cell layer around the fibres, the presence of macrophages in an intermediate layer and fibroblasts in the outer layer. Collagen fibres and bundles ran between the giant cells and the host tissues. When the mesh was rejected, there were no chronic inflammatory cells and collagen bundles were reabsorbed. In the peripheral areas where the mesh-integrated tissue still persisted, there was a considerable reduction in the numbers of the giant cells and there were red blood cells and acute inflammatory cells instead of macrophages and epithelioid cells. Collagen was reduced to fibrils. From our results, mesh-tissue repair seems to be a dynamic and unstable process characterised by chronic inflammation and continuous collagen maturation. During the development, the tissue response to the mesh, as with any inflammatory condition, makes colorisation by hematogenic bacteria easier. Infection can destroy the capsule around the mesh and causes its rejection.     

Comparison of nerve regeneration through different types of neural prostheses

Rat sciatic nerve regeneration through three synthetic neural prostheses was compared with regeneration through nerve allografts. The synthetic prostheses were either nonpermeable nonabsorbable (Silastic), permeable absorbable (polyglactin mesh), or permeable nonabsorbable (polypropylene mesh). Animals were evaluated at 10, 24, and 90 days. Functional analysis of nerve regeneration was performed by noninvasive methods: electromyography and walking tracks. Nerve tissue was examined with routine histologic and immunofluorescent techniques. A compressive neuropathy developed with the use of the Silastic implant. A neutrophilic inflammatory infiltrate was consistently associated with implantation of the polyglactin mesh. A strong connective tissue response was noted around the polypropylene mesh. Early recovery of nerve function was seen with the Silastic implants, however, overall nerve function was best in the nerve allograft and polypropylene mesh groups. Polyglactin implantation increases the local inflammatory response and should not be used for nerve anastomoses. If Silastic entubulation is used, it should be removed between 24 and 90 days.     

Foreign body reaction to meshes used for the repair of abdominal wall hernias.

OBJECTIVE: To investigate the local tissue reactions to meshes that had been removed from humans. DESIGN: Open study SETTING: Surgical department of the technical University, Aachen, Germany. MATERIAL: Samples of 17 non-absorbable meshes (1 polyester, 10 polypropylene, 2 reduced polypropylene, and 4 polytetrafluorethylene, PTFE) and 1 absorbable mesh (polyglactin 910) that had been implanted for repair of abdominal wall defects. INTERVENTIONS: Light and transmission electron microscopy, immunohistochemistry, and histological examination. MAIN OUTCOME MEASURES: Signs of inflammatory response. RESULTS: Light microscopy showed chronic inflammatory tissue reaction, even after years, with pronounced differences among materials. Partial volume of inflammatory cells (%) varied from 32 in polypropylene, to 12 in expanded PTFE, 8 in polyester, and 7 in reduced polypropylene. Formation of connective tissue correlated significantly with the extent of the inflammatory reaction (p<0.01). In meshes implanted for long periods there were still numerous macrophages at the interface between tissue and polypropylene (45%), polyester (45%), expanded PTFE (25%), and reduced polypropylene (22%). There was no difference in time dependent tissue reactions (p = 0.19). CONCLUSION: Inflammation around alloplastic materials used to repair defects in the abdominal wall persists for many years. There was evidence of long term wound complications as a result of persistent foreign body reactions. Further studies are required to evaluate the long term tissue response to these materials.     

Trevira: a new polyester implant for the treatment of incisional hernia. Results of an experimental study

OBJECTIVE: The synthetic implant meshes in clinical use for the treatment of abdominal hernias are generally made of polyester in France and of polypropylene in Germany. Serving as an implant material for the replacement of the cruciate ligament, the Trevira is another polymer of polyester in clinical use with excellent results. This animal trial was performed to ascertain whether it offers any advantages over polypropylene for abdominal incisional hernia repair. MATERIAL [corrected] AND METHODS: In 12 pigs 10 x 10 cm of the abdominal wall preserving the peritoneum was resected and subsequently implanted a 15 x 15 cm synthetic mesh of polyethylene terephthalate (Trevira) in half of them and of polypropylene (Prolene) in the other half using a sublay technique. After two and six month the implant size was measured and the extend of the foreign body reaction determined by the microscopically presence of foreign body giant cells. RESULTS: No significant differences concerning the implant size were shown between the two groups at any of the time periods. The acute inflammatory reaction observed was significantly higher at the polypropylene than at the polyethylene terephthalate implant (number of giant cells after 2 month: Prolene 2.2 +/-0.4, Trevira: 0.8 +/-0.2, after six month: Prolene: 4.6 +/-1.3, Trevira: 1.1 +/-0.5). In contrast to the polyethylene terephthalate all polypropylene samples showed calcification areas after six month. CONCLUSION: In this animal trial Trevira mesh showed a high biocompatibility with a low foreign body reaction. It appears to be a promising new implant for the treatment of hernia.     

Persistent extracellular matrix remodelling at the interface to polymers used for hernia repair

On the one hand, recurrence rates and postoperative complications following hernia repair are supposed to be influenced by the kind of mesh material used. On the other hand, an impaired collagen metabolism and cleavage within connective tissue has been suggested as decisive factor in the pathogenesis of recurrent hernia formation. The aim of our study was, therefore, to analyze the impact of commonly used mesh materials on quality of collagen deposition, expression of collagenases (matrix metalloproteinases; MMP-1/MMP-13), and specific tissue inhibitors of MMPs (TIMPs) in an animal study. Four different mesh materials were used (Prolene = polypropylene, Mersilene = polyester, and Vypro and Vypro II = combinations of polypropylene and polyglactin) and implanted as abdominal wall replacement in 60 male Wistar rats. Mesh samples were explanted after 3, 21, and 90 days and investigated using immunohistochemistry (expression of MMP-1/MMP-13 and TIMP-1) and cross-polarization microscopy (percentage of collagen type III to overall collagen). Besides an insufficient collagen composition with an increased percentage of collagen type III, we found a complex expression of collagenases and their inhibitors combined with a persistent chronic foreign-body reaction even 90 days after implantation. Except for TIMP-1 expression, which was significantly related to a lowered amount of inflammatory (r = -0.980, p = 0.02) and connective tissue formation (r = -0.951, p = 0.049), there was no relation to the expression of collagenases (MMP-1/MMP-13) with regard to the amount of inflammatory and connective tissue formation despite partly significant differences between implanted polymers.     

Tissue reactions of 5 sling materials and tissue material detachment strength of 4 synthetic mesh materials in a rabbit model

PURPOSE: We evaluated tissue reactions to 5 sling materials used in tension-free vaginal tape (TVT), intravaginal slingplasty (IVS), polypropylene mesh hernia repair, the suprapubic approach to suburethral polypropylene tape (SPARC) and cadaveric fascia lata procedures. We also compared the mesh-to-tissue attachment strength of 4 sling mesh materials (TVT, IVS, surgical polypropylene mesh and SPARC) at on days 2, 7, 15 and 30 after implantation. MATERIALS AND METHODS: A total of 20 female New Zealand White rabbits were randomized to group 1-2 days, group 2-7 days, group 3-15 days and group 4-30 days. After the rabbits were anesthetized an 8 cm midline incision was made for rectus muscle access, and 0.5 x 1 cm pieces of TVT, IVS, SPARC, surgical polypropylene mesh and cadaveric fascia lata were sewn to the rectus muscle with direct contact. At the same time 4 subfascial tunnels in the medial surface of the upper extremities were prepared, and 1.0 x 0.5 cm strips of TVT, IVS, SPARC and polypropylene mesh were implanted in each tunnel. On days 2, 7, 15 and 30 after implantation mechanical testing was performed to define tissue detachment strength. The strips of 5 sling materials were then harvested with the surrounding tissue. Specimens were studied by light microscopy. RESULTS: Mean detachment strength, that is the minimum weight needed to move the mesh, of the synthetic meshes from days 2 to 30 were 291.6 to 2,390.0 gm for TVT, 178.4 to 2,160.0 gm for SPARC, 188.4 to 1,850.0 gm for hernia mesh and 92.8 to 1,510.0 gm for IVS (at all data points TVT vs IVS p < 0.05). Light microscopy revealed a quite uniform tissue reaction with a sign of marked acute inflammation in and around the mesh fibers on days 2 and 7 after implantation. All meshes showed stable fibrosis and muscle infiltration on day 30. CONCLUSIONS: All 5 synthetic sling materials produce similar tissue reactions beginning soon after implantation. Cadaveric fascia lata persisted in tissue with remarkable perifascial fibrosis at day 30. When comparing the 4 polypropylene mesh materials; the attachment capacity of TVT was superior and that of IVS was the least of the 4. TVT was statistically better than IVS at all data points. SPARC and hernia mesh provided results similar to those of TVT.     

Erosion,defective healing and extrusion after tension-free urethropexy for the treatment of stress urinary incontinence

A case-control study was performed in two departments performing tension-free urethropexy for the treatment of stress urinary incontinence. During a period of 4.5 years, 127 cases of tension-free vaginal tape operations (TVT) and 42 cases of intravaginal slingplasty (IVS) were performed. In the TVT group one case of urethral erosion was observed, but in the IVS group six cases of defective healing, erosion or extrusion were observed. It is considered that the complications might be due to the multifilamentous nature of the IVS tape in contrast to the monofilamentous nature of the TVT tape. Editorial Comment: I compliment the authors for honestly presenting their complications. Such reporting helps our understanding of the safest sling material in an effort to optimize patient safety and care. In our experience, all of the recent urethral erosions, which we have cared for, have involved a monofilament polypropylene mesh that was on excessive tension. The majority of vaginal erosions we have experienced have healed spontaneously with estrogen cream. I would concur with the authors that we must be diligent with patient follow-up and always consider the possibility of some form of erosion when a patient presents with dysparunia, a vaginal discharge, microscopic or gross hematuria, recurrent urinary tract infections, or worsening stress or urge incontinence     

Influence of polyglecaprone 25 (Monocryl) supplementation on the biocompatibility of a polypropylene mesh for hernia repair

Background: Supplementary polyglecaprone 25 (Monocryl) monofilaments were added to a lightweight pure monofilament polypropylene mesh (PP mesh) to improve intraoperative handling (PP+M mesh). This study was designed to evaluate the influence of this additional supplementation on the biocompatibility in a rodent animal model. Methods: Two mesh materials, a composite mesh (PP+M) and the pure polypropylene variant (PP), were compared after subcutaneous implantation in a standardized rat model. Histological analysis of the inflammatory response was performed after 28, 56 and 84 days of implantation. Material absorption, inflammatory tissue reaction, fibrosis and granuloma formation were investigated, as well as the percentage of proliferating and apoptotic cells at the interface. Results: Both mesh materials showed a slight foreign body reaction involving mainly macrophages and foreign body giant cells. Total absorption of the Monocryl filaments of the PP+M mesh occurred between 56 and 84 days of implantation. Both the inflammatory and the fibrotic reaction were decreased (n.s.) in the PP+M mesh group compared to the pure PP mesh. Whereas the percentage of proliferating cells showed no significant difference, the rate of apoptotic cells was significantly decreased in the PP+M mesh group over the whole implantation period. Conclusion: Compared to the pure polypropylene mesh, our data confirm that the use of a polypropylene mesh supplemented with absorbable Monocryl filaments is feasible without additional short-term mesh-related complications in the experimental model or negative side effects on biocompatibility.     

Experimental Comparison of Monofile Light and Heavy Polypropylene Meshes: Less Weight Does Not Mean Less Biological Response

Background Mesh implantation is a standard procedure in hernia repair. It provides low recurrence rate but increases complication rate due to foreign-body reaction induced by alloplastic materials in surrounding tissues. It is believed that biocompatibility of meshes may be improved by reducing their weight per meter squared (m²) and altering the implant structure. Aim The aim of this study was to evaluate the effect of weight and structure as determinants of mesh biocompatibility. Method Thirty-six Wistar rats were studied. In 12 animals, conventional polypropylene (heavy) meshes (HM) were implanted; in other 12, material-reduced (light) microporous polypropylene meshes (LM); and the remaining 12 served as a sham-operated control group. Meshes were explanted after 21 and 90 days (6 animals per group). All samples were examined by light and electron microscopies. Integration of meshes in surrounding tissue, inflammatory response, fibrotic reactions, and structural changes were recorded. Quantification of the inflammatory response was achieved by CD-68 marking of macrophages and counting their number per surface unit. Results After 21 days, there was no significant difference in thickness of surrounding connective tissue between meshes in all groups studied. After 90 days, thickness of connective tissue decreased in both groups, and fibrotic reaction in the mesh bed was significantly less in the HM group. Total amount of macrophages per millimeter squared (mm²) decreased with time in HM and LM samples but was significantly lower in the HM group on day 21 (43.5%) and day 90 (46.7%). Conclusion This study found worse biocompatibility of LM compared with HM. Thus, the amount of implanted mesh was not the main determinant of biocompatibility (expressed as successful incorporation and diminished foreign-body reaction) but the size of the pores.     

Early tissue reactions in the rat bladder wall after contact with three different synthetic mesh materials

OBJECTIVES: To investigate bladder tissue reactions to three types of implanted mesh material, i.e. polypropylene, polyglactin and polypropylene-polyglactin combined. MATERIALS AND METHODS: Forty-eight adult female Wistar albino rats were randomized to four equal groups, i.e. group 1 (sham-operated controls), group 2 (polypropylene mesh), group 3 (polyglactin mesh) and group 4 (polypropylene-polyglactin mesh). A laparotomy incision was made to access the bladder and fix a 0.5 x 1 cm piece of mesh directly on the bladder wall. Each group was randomly divided into two subgroups of six animals, killed at 7 and 14 days after mesh implantation, respectively, to study mesh and tissue features with time. Bladders were harvested for histological and immunohistochemical investigation. Microvessels that developed around the mesh were detected with the avidin-biotin peroxidase system, using antibody to Factor VIII-related antigen as an endothelial marker. Vessels were counted in the most intensely stained area of one section from each animal's bladder. RESULTS: Compared with the other groups, group 4 had more inflammatory reaction at 7 days but the tissue reactions to all mesh materials were similar at 14 days; the mesh penetrated the bladder muscularis propria at 14 days in all six rats in group 2, in one in group 3, and two in group 4. Group 4 tended to have a greater microvessel density at 14 than at 7 days. In contrast, groups 2 and 3 had lower microvessel densities at 14 than at 7 days. CONCLUSION: The rat bladder wall had a similar early response to all three types of mesh materials. Penetration was more marked with polypropylene mesh than with the other materials. This nonabsorbable material persists in tissue and is currently widely used for clinical applications. These results for penetration suggest that the use of polypropylene mesh risks serious postoperative complications, e.g. urethral tissue erosion.