Are late hernia mesh complications linked to Staphylococci biofilms?

PURPOSE: The purpose of this study was to investigate the link between bacterial biofilms and negative outcomes of hernia repair surgery. As biofilms are known to play a role in mesh-related infections, we investigated the presence of biofilms on hernia meshes, which had to be explanted due to mesh failure without showing signs of bacterial infection. METHODS: In this retrospective observational study, 20 paraffin-embedded tissue sections from explanted groin hernia meshes were analysed. Meshes have been removed due to chronic pain, hernia recurrence or mesh shrinkage. The presence and bacterial composition of biofilms were determined. First, specimens were stained with fluorescence in situ hybridisation (FISH) probes, specific for Staphylococcus aureus and coagulase-negative staphylococci, and visualised by confocal laser scanning microscopy. Second, DNA was extracted from tissue and identified by S. aureus and S. epidermidis specific PCR. RESULTS: Confocal microscopy showed evidence of bacterial biofilms on meshes in 15/20 (75.0%) samples, of which 3 were positive for S. aureus, 3 for coagulase-negative staphylococci and 9 for both species. PCR analysis identified biofilms in 17/20 (85.0%) samples, of which 4 were positive for S. aureus, 4 for S. epidermidis and 9 for both species. Combined results from FISH/microscopy and PCR identified staphylococci biofilms in 19/20 (95.0%) mesh samples. Only 1 (5.0%) mesh sample was negative for bacterial biofilm by both techniques. CONCLUSION: Results suggest that staphylococci biofilms may be associated with hernia repair failure. A silent, undetected biofilm infection could contribute to mesh complications, chronic pain and exacerbation of disease.

Biofilms and effective porosity of hernia mesh: are they silent assassins?

PURPOSE: The purpose of this paper is to communicate two new concepts with the potential to cause major morbidity in hernia repair, effective porosity and biofilm. These 2 concepts are interrelated and have the potential to result in mesh-related complications. Effective porosity is a term well described in the textile industry. It is best defined as the changes to pore morphology after implantation of mesh in situ. It is heavily dependent on mesh construct and repair technique and has the potential to impact hernia repair by reducing mesh tissue integration and promoting fibrosis. Bacterial biofilm is a well-described condition affecting prosthesis in breast and join replacement surgery with catastrophic consequences. There is a paucity of information on bacterial biofilm in mesh hernia repair. We speculate that bacterial biofilm has the potential to reduce the effective porosity of mesh, resulting in non-suppurative mesh-related complications as well as the potential for late suppurative infections. We describe the aetiology, pathogenesis, diagnosis, treatment and preventative measures to address bacterial biofilm in mesh hernia surgery. Hernia surgeons should be familiar with these two new concepts which have the potential to cause major morbidity in hernia repair and know how to address them. METHODS: Ovid Medline and PubMed were searched for communications on "effective porosity" and "bacterial biofilm". RESULTS: There is a paucity of information in the literature of these conditions and their impact on outcomes following mesh hernia repair. CONCLUSIONS: We discuss the two concepts of effective porosity and biofilm and propose potential measures to reduce mesh-related complications. This includes choosing mesh with superior mesh construct and technical nuances in implanting mesh to improve effective porosity. Furthermore, measures to reduce bacterial biofilm and its consequences are suggested.

Characterisation of the cellular infiltrate in the foreign body granuloma of textile meshes with its impact on collagen deposition.

PURPOSE: As part of the foreign body reaction, mesh filaments are surrounded by an infiltrate of inflammatory cells. Though macrophages are considered as being predominant, little is known about the origin of other cells. METHODS: On 55 meshes explanted from humans, we characterised the cells in the inflammatory infiltrate of the granuloma by immunohistochemistry using 10 cellular markers: CD3+ lymphocytes, CD4+ T helper cells, CD8+ cytotoxic T cells, CD20+ B lymphocytes, CD34+ stem cells, CD45R0+ leucocytes, CD68+ macrophages, Mib1 for proliferation, Vimentin for mesenchymal origin, and Desmin for myocytes. Collagen deposits were analysed after staining with Sirius Red. RESULTS: More than 80 % of the cells in the infiltrate showed a positive expression of CD68, CD8, CD45R0 and Vimentin. CD4 and Desmin were seen in 30-80 % of the cells, unaffected by material or time. A score summarising the expression of all markers positively correlated significantly with an increased percentage of collagen type III (green) in the mesh wound. The analysis of collagen deposits was only affected to a small degree by size of area for investigation. CONCLUSIONS: At the vicinity of the mesh filaments, the accumulated inflammatory cells represent a mixture of cells of various origins. The high expression of at least four markers requires co-expression of different surface markers and thus confirms the existence of multiple transition forms instead of dominance of just macrophages. This offers new options for interventions to attenuate the inflammatory reaction of mesh implants.

Retrieval study at 623 human mesh explants made of polypropylene - impact of mesh class and indication for mesh removal on tissue reaction.

Textile meshes frequently are implanted in the abdominal wall to reinforce a hernia repair. However, revisions for mesh associated complications confirm that these devices are not completely free of risk. Explanted devices offer an opportunity to define the impact of mesh structure on tissue response. This retrieval study analyses the tissue reaction to 623 polypropylene mesh samples (170 class 1 with large pores, and 453 class 2 with small pores) explanted for pain, infection, or recurrence. Histopathological assessment included morphometry of inflammatory infiltrate (IF) and connective tissue (CT), and of collagen 1/3 ratio. Half of the meshes were removed after more than 23 month. Despite large inter-individual differences removal for infection showed more IF than for pain or recurrence with significant correlation of IF with CT. Class 1 meshes with large pores showed less IF, CT, fistula formation, calcification, and bridging than class 2 meshes with small pores. Meshes removed for recurrence showed a lowered collagen 1/3 ratio in 70%. Large pore class 1 meshes showed an improved tissue response and may be considered as favorable to prevent inflammatory side effects. The presence of lowered collagen 1/3 ratio in most of the samples with recurrences stresses the relevance of an intact healing process. Late manifestation of complications demands long-lasting follow-up. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2013.

Retrieval study at 623 human mesh explants made of polypropylene--impact of mesh class and indication for mesh removal on tissue reaction.

Textile meshes frequently are implanted in the abdominal wall to reinforce a hernia repair. However, revisions for mesh associated complications confirm that these devices are not completely free of risk. Explanted devices offer an opportunity to define the impact of mesh structure on tissue response. This retrieval study analyses the tissue reaction to 623 polypropylene mesh samples (170 class 1 with large pores, and 453 class 2 with small pores) explanted for pain, infection, or recurrence. Histopathological assessment included morphometry of inflammatory infiltrate (IF) and connective tissue (CT), and of collagen 1/3 ratio. Half of the meshes were removed after more than 23 month. Despite large inter-individual differences removal for infection showed more IF than for pain or recurrence with significant correlation of IF with CT. Class 1 meshes with large pores showed less IF, CT, fistula formation, calcification, and bridging than class 2 meshes with small pores. Meshes removed for recurrence showed a lowered collagen 1/3 ratio in 70%. Large pore class 1 meshes showed an improved tissue response and may be considered as favorable to prevent inflammatory side effects. The presence of lowered collagen 1/3 ratio in most of the samples with recurrences stresses the relevance of an intact healing process. Late manifestation of complications demands long-lasting follow-up.

Modified classification of surgical meshes for hernia repair based on the analyses of 1,000 explanted meshes.

BACKGROUND: It is an undisputable fact that meshes have become standard for repair of abdominal wall hernias. Whereas in the late eighties there were only a couple of different devices available, today we have to choose among some hundreds, with lots of minor and major variations in polymer and structure. As most of the minor variations may not lead to significant change in clinical outcome and may be regarded as less relevant, we should focus on major differences. Eventually, this is used to structure the world of mesh by forming groups of textile devices with distinct biological response. Many experimental and some clinical studies have underlined the outstanding importance of porosity, which fortunately, in contrast to other biomechanical quanlities, is widely unaffected by the anisotropy of meshes. METHODS: In accordance with the major manufacturers of meshes, a classification of meshes was derived from a huge pool of textile data based briefly on the following: (1) large pores, (2) small pores, (3) additional features, (4) no pores, (5) 3D structure and (6) biological origin. At 1,000 explanted meshes the value of this classification was evaluated by group-specific assessment of inflammatory and connective tissue reaction. RESULTS: Application of this classification to common products has proved feasable, and each of the six different classes includes devices that in clinical trials failed to show relevant differences in patients' outcome when comparing products within the same group. Furthermore, histological analysis confirmed significant differences in tissue reactions between but not within the different classes. CONCLUSIONS: Classifying implants according to a similar response enables grouping patients into comparable cohorts despite implantation of different devices. Furthermore, it enables the examination of the impact of mesh classes for the various indications even from heterogenous data of registries. Finally and not the least, any grouping supports the surgeon to select the best device to meet the individual need and to tailor patients therapy.

[The "ideal" mesh--more than a mosquito net]. / Das "ideale" Mesh - mehr als ein Mosquitonetz.

Modern meshes permit a radical treatment of hernias, an expectation that Billroth articulated already more than 100 years ago. Because clinical trials are insufficient to evaluate the distinct effects of modified mesh materials in regard to tissue biocompatibility and functionality, a basic understanding of the physico-chemical properties is essential for a rational selection of the most appropriate device. Experimental data indicate that particularly the mesh's porosity is of outstanding importance, resulting from the demanded tensile strength as well as the employed fibre material. Considering that different operation techniques require different mesh materials, specific requirements are discussed using the example of intraabdominal meshes, of parastomal meshes, of meshes in areas with bacterial contamination and of meshes in the hiatus region. Considering the late manifestation of some complications even after many years, any thorough quality control should include an assessment of explanted implant failures in addition to clinical experience.

Hernia repair: the search for ideal meshes.

BACKGROUND: Effective repair of hernia is a difficult task. There have been many advances in hernia repair techniques over the past 50 years, but new strategies must be considered to enhance the success of herniorrhaphy. DISCUSSION: At the 30th International Congress of the European Hernia Society, nine experts in hernia repair and experimental mesh evaluation participated in a roundtable discussion about today's unmet needs in hernia repair, including what constitutes an "ideal" hernia repair and the portfolio of "ideal" mesh prostheses. Defining characteristics of lightweight mesh, mesh alternatives, the surgeon's role in hernia repair, adverse events, the unmet requirements for today's hernia repair, and optimized animal models were among the topics discussed. CONCLUSION: The ideal mesh's construction is still in progress, but greater understanding of its critical characteristics was explored. It is hoped that these suggestions will lead to the development of improved hernia treatments and a maximally effective portfolio of hernia mesh prostheses.

[Metastasis of medullary plasmocytoma as the cause of acute cholecystitis]. / Metastase eines medullären Plasmozytoms als Ursache einer akuten Cholezystitis.

HISTORY AND ADMISSION FINDINGS: A 66-year-old man was found to have a medullary plasmocytoma the year before admission, after sustaining a pathological fracture of the femur. During treatment for sciatica his general condition deteriorated and he developed abdominal pain. Laboratory tests suggested a septic process. INVESTIGATIONS: The clinical and sonographic findings and computed tomography suggested an acute cholecystitis. TREATMENT AND COURSE: A cholecystectomy was performed. Microscopic examination revealed metastatic infiltration of the gall bladder by a medullary plasmocytoma. CONCLUSION: Secondary tumours of the gallbladder considered are thought to be rare. Since 1863 only 95 cases have been reported. The case discussed here is only the second one in which the metastatic tumor was a medullary plasmocytoma. But a search for published and confirmed cases indicates that secondary tumors of the gall bladder are not so rare. Metastatic tumors of the gall bladder should be kept in mind in the differential diagnosis of acute cholecystitis, especially in patients with an advanced primary tumor.

Biomaterial-dependent MMP-2 expression in fibroblasts from patients with recurrent incisional hernias.

With regard to the pathogenesis of recurrent incisional hernia, an impaired connective tissue quality leading to an aberrant scarring process has been proposed. For the matrix metalloproteinase (MMP-2) a pathogenetic involvement in direct inguinal hernia development is reported. With mesh implantation as the gold standard treatment for incisional hernias, the aim of the present study was to investigate the MMP-2 expression in patients with recurrent incisional hernias with and without mesh-materials. In primary fibroblast cultures obtained from skin scars in patients with and without recurrent incisional hernias, MMP-2 synthesis and gene expression were investigated. Furthermore, MMP-2 synthesis and gene expression of fibroblasts were compared after incubation with two different mesh materials: polypropylene and absorbable polyglactin filaments. MMP-2 enzyme activity was determined by semiquantitative zymography and mRNA synthesis by quantitative RT-PCR. Both MMP-2 enzyme activity and mRNA expression were similar in hernia and control fibroblasts in vitro. In control fibroblasts mesh incubation did not significantly affect MMP-2 expression, whereas polypropylene mesh contact of fibroblasts from patients with recurrent incisional hernias led to a major decrease of MMP-2 activity and of mRNA expression. In the absence of biomaterials fibroblasts from recurrent incisional hernia, patients have no alterations of their MMP-2 synthesis compared to control fibroblasts, whereas a specific response was found after biomaterial contact hereby indicating differences in fibroblast phenotype.

[High-resolution T1-weighted MR-lymphography of inguinal lymph nodes after interstitial application of Gadomer-17 in animal experiments]. / Hochauflösende T1-gewichtete MR-Lymphographie inguinaler Lymphknoten nach interstitieller Applikation von Gadomer-17 im Tierexperiment.

PURPOSE: To evaluate the microstructural anatomy of inguinal lymph nodes in pigs after interstitial MR-lymphography with the dendritic contrast agent Gadomer-17. MATERIAL AND METHODS: High-resolution T1-weighted MR-lymphography was performed in inguinal lymph nodes of 10 domestic pigs (39 - 46 kg) after subcutaneous injection of 10 mumol/kg body weight Gadomer-17 in the hind legs of the animals. A 1.5T MR scanner and a ring-shaped surface coil were used. Two different high-resolution gradient-echo sequences with additionally reconstructed maximum-intensity projections were evaluated in a total of 20 lymph nodes. The high-resolution MR-findings were correlated with the histologic sections of the excised inguinal lymph nodes. RESULTS: Coronal T1-weighted 3D gradient-echo images (TR = 20 msec, TE = 6.1 - 8.3 msec, FA = 20 degrees ) with a slice thickness of 1 mm, a field-of-view of 120 mm and a matrix size of 256 x 256 (reconstructed to 1024 x 1024 voxels) yielding a reconstructed in-plane resolution of 117 x 117 microm (2) were best suited for the high-resolution MR lymphography of inguinal lymph nodes and enabled the differentiation of the hyperintense lymph node sinuses and hypointense lymphoid parenchyma of each lymph node (100 %). Even dilated lymphatic vessels evident in the histologic specimen were best demonstrated on the MIP images. CONCLUSION: High-resolution interstitial MR lymphography with Gadomer-17 allows the visualization of different tissue compartments of inguinal lymph nodes. This new technique is feasible on a routine 1.5T scanner and may offer potential for the detection of micrometastases in lymph nodes of cancer patients.

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.

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.

Analysis of local complications following explantation of silicone breast implants.

A study was undertaken to analyse local complications in patients with breast implants and the total number of implant-related interventions when silicone breast implants were explanted. We studied 53 patients who had received breast implants for cosmetic augmentation or breast reconstruction following surgery for breast cancer at the time of explantation. The clinical records of all these patients were analysed, and clinical information on reason for implantation, implant properties, number and kind of implant-related interventions and reason for explantation was elicited. A complication was defined as a surgical procedure performed for any of the following reasons: capsular contracture, loss of implant integrity, haematoma or seroma, infection of the implant site, extrusion or wound dehiscence, and dissatisfaction with the result. The mean numbers of implant-related operations were 3.1 in patients who had undergone breast reconstruction and 2.3 in patients who had cosmetic augmentation (P < 0.03). We found a total of 35 complications in 28 patients, 21 patients (75%) each had one complication, five patients (18%) had two and two patients (7%) had three complications. A significantly higher incidence of early complications in patients who had undergone breast reconstruction (P < 0.03) marks the difference from complications in the cosmetic group, most of which arose after a longer time (P < 0.02). A complication analysis is presented. At the time of explantation, 78% of the patients decided to have a new implant, while 12% requested permanent removal of the implant without replacement. In the present study we saw no patients with connective tissue or other autoimmune disorders. When breast reconstruction or augmentation with silicone devices is considered, patients must be informed of the possible complications and of the potential choices in later implant-related revision surgery.

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.

[Ileocecal invagination due to a benign small intestine tumor. A case report]. / Ileozökale Invagination aufgrund eines benignen Dünndarmtumors. Ein Fallbericht.

We report a case of postoperative ileocecal invagination in a 63-year-old male. Forty-six days after esophageal resection and gastric tube reconstruction with cervical anastomosis for an esophageal carcinoma, the patient suffered from colicky pain in the right abdomen. The diagnostics showed an ileocecal invagination up to the right flexure of the colon. The invagination was based on a leiomyoma of the terminal ileum. Because of necrosis of the mucous membrane, an ileocecal resection with ileoascendostomy could not be avoided. We discuss this case on the basis of the existing literature.

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.

Caecal-diverticulitis: a rare differential diagnosis for right-sided lower abdominal pain.

OBJECTIVE: There are several differential diagnoses for acute abdominal discomfort with pain referred to the right lower quadrant region. The objective of this report is to outline our experience with diverticulitis of the caecum, which is a rare condition that is particularly difficult to diagnose correctly pre-operatively. METHODS: A retrospective analysis of acute diverticulitis of the caecum was performed over the period from January 1992 to December 2000 within the Surgical Department of the RWTH Aachen, Germany. The progress of each patient was assessed by interviewing the patient and by telephone contact with the patient's general practitioner. RESULTS: Seven patients with isolated infective diverticulitis of the caecum were encountered in the course of this study. In five of these cases, the pre-operative diagnosis was either unclear or incorrect. Four patients underwent surgery for suspected appendicitis. In one patient, the diverticulitis was diagnosed during laparoscopic surgery undertaken for presumed adnexal disease. Intestinal continuity was restored in all cases. The postoperative course was uneventful. CONCLUSIONS: Right-sided caecal diverticulitis is rare in comparison to diverticulitis of the sigmoid or descending colon. Nevertheless, it should be actively considered in the differential diagnosis of patients with acute tenderness in the right lower abdominal region.

Mesh implants in hernia repair. Inflammatory cell response in a rat model.

BACKGROUND: In the reinforcement of the abdominal wall with mesh implants, various complications including hernia recurrence, abdominal pain, seroma formation and infection are discussed to depend on the biocompatibility of the alloplastic prosthesis. Particularly macrophages, T-cells and mast cells have been shown to play a major role in the inflammatory response to biomaterials. To approach biocompatibility of surgical meshes we therefore examined the infiltrate of these cells as well as the proliferation rate in response to different clinically applied materials. MATERIALS AND METHODS: Three mesh materials (polypropylene: PP, Prolene; polyethylene terephthalate: PET, Mersilene, and polypropylene/polyglactin: PP + PG, Vypro) were compared after inlay implantation in a standardized rodent animal model. A suture-closed laparotomy served as control. After 7 and 90 days of implantation, histochemical analysis of the inflammatory response to all biomaterials was performed: macrophages (ED3), T-cells (CD3), proliferating cells (PCNA) and mast cells (Giemsa) were investigated. RESULTS: In all groups a persisting T-cell response was observed. Colonization of the interface with macrophages showed a pronounced reduction in the PP + PG-mesh group. Infiltration of mast cells at the tissue graft interface showed a time-dependent decrease in the PET- and PP + PG-mesh groups, whereas in contrast, index of mast cells increased in the PP-mesh group. At both time points, indices of proliferation were highest in the PP-mesh group. CONCLUSION: The present data confirm the development of a biomaterial-dependent chronic inflammatory response to surgical meshes with macrophages as the predominant cell type. Further research on the recruitment of inflammatory cells and in particular on the role of mast cells and their granular products should be encouraged.