Biologic meshes are not superior to synthetic meshes in ventral hernia repair: an experimental study with long-term follow-up evaluation.

BACKGROUND: In laparoscopic incisional hernia repair, direct contact between the prosthesis and the abdominal viscera is inevitable, which may lead to an inflammatory reaction resulting in abdominal adhesion formation. This study compared five different synthetic and biologic meshes in terms of adhesion formation, shrinkage, incorporation, and histologic characteristics after a period of 30 and 90 days. METHODS: In 85 rats, a mesh was positioned intraperitoneally in direct contact with the viscera. Five different meshes were implanted: Prolene (polypropylene), Parietex composite (collagen-coated polyester), Strattice (porcine dermis, non-cross-linked), Surgisis (porcine small intestine submucosa, non-cross-linked), and Permacol (porcine dermis, cross-linked). The meshes were tested in terms of adhesion formation, shrinkage, and incorporation after a period of 30 and 90 days. Additionally, collagen formation after 90 days was determined. RESULTS: Significantly less adhesion formation was observed with Parietex composite (5 %; interquartile range [IQR], 2-5 %) and Strattice (5 %; IQR, 4-10 %) in the long term. In contrast, organs were attached to Permacol with four of seven meshes (57 %), and adhesion coverage of Surgisis mesh was present in 66 % (IQR, 0-100 %) of the cases. After 90 days, the best incorporation was seen with the Parietex composite mesh (79 %; IQR, 61-83 %). After 90 days, major alterations in adhesion formation were seen compared with 30 days. Histologically, Strattice and Parietex composite showed a new mesothelial layer on the visceral side of the mesh. Microscopic degradation and new collagen formation were seen in the Surgisis group. CONCLUSIONS: Parietex composite mesh demonstrated the best long-term results compared with all the other meshes. The biologic non-cross-linked mesh, Strattice, showed little adhesion formation and moderate shrinkage but poor incorporation. Biologic meshes are promising, but varying results require a more detailed investigation and demonstrate that biologic meshes are not necessarily superior to synthetic meshes. The significant changes that take place between 30 and 90 days should lead to careful interpretation of short-term experimental results.

Experimental study on synthetic and biological mesh implantation in a contaminated environment.

BACKGROUND: Implantation of meshes in a contaminated environment can be complicated by mesh infection and adhesion formation. METHODS: The caecal ligation and puncture model was used to induce peritonitis in 144 rats. Seven commercially available meshes were implanted intraperitoneally: six non-absorbable meshes, of which three had an absorbable coating, and one biological mesh. Mesh infection, intra-abdominal abscess formation, adhesion formation, incorporation and shrinkage were evaluated after 28 and 90 days. Histological examination with haematoxylin and eosin and picrosirius red staining was performed. RESULTS: No mesh infections occurred in Sepramesh(®) , Omyramesh(®) and Strattice(®) . One mesh infection occurred in Parietene(®) and Parietene Composite(®) . Significantly more mesh infections were found in C-Qur(®) (15 of 16; P ≤ 0·006) and Dualmesh(®) (7 of 15; P ≤ 0·035). Sepramesh(®) showed a significant increase in adhesion coverage from 12·5 per cent at 28 days to 60·0 per cent at 90 days (P = 0·010). At 90 days there was no significant difference between median adhesion coverage of Parietene Composite(®) (35·0 per cent), Omyramesh(®) (42·5 per cent), Sepramesh(®) (60·0 per cent) and Parietene(®) (72·5 per cent). After 90 days the adhesion coverage of Strattice(®) was 5·0 per cent, and incorporation (13·4 per cent) was significantly poorer than for other non-infected meshes (P ≤ 0·009). Dualmesh(®) showed shrinkage of 63 per cent after 90 days. CONCLUSION: Parietene Composite(®) and Omyramesh(®) performed well in a contaminated environment. Strattice(®) had little adhesion formation and no mesh infection, but poor incorporation. Some synthetic meshes can be as resistant to infection as biological meshes.

Postoperative adhesion prevention with a new barrier: an experimental study.

INTRODUCTION: Postoperative adhesion formation remains a major clinical problem. The aim of this study was to test the effect of a new hydrogel on adhesion formation in a rat model. MATERIALS AND METHODS: A reproducible rat model was used to induce standardized adhesion formation in three experiments. In experiment 1, a cross-linked polyvinyl alcohol (PVA) and carboxymethylcellulose (CMC) hydrogel (PVA/CMC, A-Part®; B. Braun Aesculap, Germany) was tested in different dosages. In experiment 2, PVA/CMC gel was compared to icodextrin 4% (Adept®; Baxter USA). In both groups, animals were sacrificed after 2 weeks. In experiment 3, histological examination after 4 and 6 weeks was performed. The percentage of adhesions to the defect was measured and the density was determined according to the Zühlke scale. During histological examination of the abdominal wall, the formation of neoperitoneum and potential residues of the agents were assessed. RESULTS: In experiment 1, a significant reduction in amount as well as density of the adhesions was visible with all dosages of PVA/CMC gel. In experiment 2, again quantity and density of the adhesions were diminished by PVA/CMC hydrogel compared to the control group. Icodextrin 4% showed no significant reduction in adhesion formation. In experiment 3, no residues of PVA/CMC gel or icodextrin 4% were found during histological examination after 4 and 6 weeks and neoperitoneum was present in all cases. CONCLUSION: PVA/CMC hydrogel appears to be a novel effective adhesion prevention agent. Together with an upcoming safety study, these data encourage to start clinical efficacy studies.

The antiapoptotic activity of insect IAPs requires activation by an evolutionarily conserved mechanism.

Apoptosis represents a fundamental biological process that relies on the activation of caspases. Inhibitor of apoptosis (IAP) proteins represent a group of negative regulators of both caspases and cell death. The current model dictates that IAPs suppress apoptosis by blocking the catalytic pocket of effector caspases thereby preventing substrate entry. Here, we provide evolutionary evidence for the functional interplay between insect IAPs and the N-end rule-associated ubiquitylation machinery in neutralising effector caspases and cell death. We find that IAPs require 'priming' in order to function as antiapoptotic molecules. Consistently, we demonstrate that the antiapoptotic activity of diverse insect IAPs is activated by effector caspases, providing the cell with a sensitive strategy to monitor and neutralise active caspases. Almost 300 million years of evolutionary selection pressure has preserved a caspase cleavage site in insect IAPs that, following processing by a caspase, exposes a binding motif for the N-end-rule-associated degradation machinery. Recruitment of this ubiquitylation machinery into the 'cleaved-IAP:caspase' complex provides a mechanism to negatively regulate effector caspases and block apoptosis. Furthermore, comparisons between cellular and several viral IAPs suggest differences in their modes of action, as OpIAP3, CpGV-IAP3 and HcNPV-IAP3 fail to associate with several effector caspases. Evolutionary conservation of the N-end-rule degradation pathway in IAP-mediated regulation of apoptosis further corroborates the physiological relevance of this ubiquitylation-associated process.

What patients and surgeons should know about the consequences of appendectomy for acute appendicitis after long-term follow-up: factors influencing the incidence of chronic abdominal complaints.

INTRODUCTION: Abscess formation and perforation are complications of acute appendicitis that lead to localized or generalized peritonitis. The long-term implications of complicated appendectomy remain largely unknown. MATERIALS AND METHODS: In the present study, it was investigated whether patients with complicated appendicitis experienced more abdominal complaints after long-term follow-up when compared to uncomplicated cases. In addition, the influence of operation technique (open versus laparoscopic) was studied. A retrospective analysis of 1,481 appendectomies for acute appendicitis was performed in two centers from January 2000 until January 2006. Demographic data, operative reports, intraoperatively adhesions and complications, abdominal pain, and satisfaction were monitored. In total, 1,433 patients were invited to fill out a questionnaire with a median follow-up of 7.1 years. Questionnaires of 526 (37 %) patients were suitable for analysis. RESULTS: Perforation, abdominal abscesses, or adhesions at initial operation did not result in more abdominal complaints when compared to appendectomy for uncomplicated acute appendicitis. Additionally, no significant differences in abdominal complaints were seen between laparoscopic and open techniques. CONCLUSION: In conclusion, the results of our study show that after follow-up of 7 years, the incidence of abdominal complaints was not influenced by operative technique or whether acute appendicitis was complicated or not. This finding does not support a causative role for adhesions with regard to chronic abdominal complaints. Our data enables surgeons to inform their patients about the long-term results of appendectomy, whether it was complicated or not.