Influence of a new monofilament polyester mesh on inflammation and matrix remodeling.

ABSTRACT Synthetic mesh is widely used for hernia repairs, but mesh-induced chronic inflammatory responses may lead to postoperative complications. We previously showed an elevated response to multifilament polyester (PE) versus monofilament polypropylene (PP) and polytetrafluoroethylene (PTFE) meshes, but it is unclear whether this discrepancy is due to the differences in chemical composition or filament structure. This study compares the influence of a newly available monofilament PE mesh to that of multifilament PE, monofilament PP, and monofilament PTFE on the expression of genes important in inflammation and extracellular matrix remodeling in a rat model. Full thickness abdominal wall defects were corrected with onlay repair or suture repair with no mesh. Explants were harvested 7 or 90 days after repair and divided for histology and mRNA analyses using real-time quantitative polymerase chain reaction arrays to profile expression at the tissue-mesh interface. Monofilament PE elicited a reduced foreign body reaction compared to multifilament PE, corresponding with reduced mRNA expression of important inflammatory cytokines and matrix metalloproteinases (MMPs). Unexpectedly, monofilament PE also resulted in markedly reduced mRNA expression of tumor necrosis factor and MMPs 3 and 9 compared to the widely-used monofilament PP mesh. Findings from this study revealed that both chemical composition and filament structure are important mesh characteristics that may affect a patient's wound healing response and clinical outcome, and should be considered by the surgeon when choosing a particular mesh. Although clinical studies are warranted, results in a rodent model suggest that monofilament PE may be more beneficial than the multifilament form for certain hernia repairs.

Inflammatory cytokine and matrix metalloproteinase expression induced by collagen-coated and uncoated polypropylene meshes in a rat model.

OBJECTIVE: The objective of the study was to compare the influence of collagen-coated vs uncoated polypropylene meshes on the expression of genes critical for wound healing. STUDY DESIGN: In 54 rats, abdominal wall defects were created, repaired by polypropylene sutures, and covered by an overlay of coated polypropylene (n = 20), uncoated polypropylene (n = 18), or no mesh (n = 16). Explants were harvested 7 or 90 days after repair and divided for histological, immunohistochemical, and messenger ribonucleic acid (mRNA) analyses. Real-time quantitative polymerase chain reaction arrays were used to profile the expression of 84 genes at the tissue-mesh interface. RESULTS: One week after implantation, coated mesh elicited a slightly greater inflammatory response and increased mRNA expression of 4 proinflammatory cytokines compared with uncoated mesh. Both materials, however, induced a comparable expression of cytokines and matrix metalloproteinases relative to suture repair 90 days after implantation. CONCLUSION: Collagen-coated polypropylene mesh induces elevated inflammatory cytokine expression compared with uncoated mesh early in the healing process, but the response to both meshes is similar 90 days after implantation.

Incidence of postoperative intraabdominal abscesses in open versus laparoscopic appendectomies.

BACKGROUND: Risk for intraabdominal abscess (IAA) after laparoscopic appendectomy (LA) remains controversial. A 2008 Cochrane Review suggests almost a threefold increase in the incidence of IAA after LA compared with open appendectomy (OA). METHODS: The authors conducted a retrospective chart review of all appendicitis patients 18 years and older undergoing appendectomy from 1996 to 2007 at one military treatment facility and one civilian hospital in Hawaii. Data collection included demographics, procedure, presence of complicated appendicitis (defined as perforated or gangrenous appendicitis at surgical or pathologic assessment), and presence of postoperative IAA on computed axial tomography (CAT) scan. RESULTS: The review identified 2,464 patients with appendicitis. A total of 1,924 LAs (78%) and 540 OAs (22%) were performed. The comparison of laparoscopic and open appendectomies showed no significant differences in the number of postoperative abscesses (2.2% vs 1.9%; p = 0.74). The patients with a diagnosis of complicated appendicitis were significantly associated with a higher incidence of postoperative abscess formation (67% vs 25%; p < 0.01), which had an unadjusted odds ratio of 6.1 (95% confidence interval [CI], 3.4-11.0; p < 0.01). No significant difference in the development of abscess in patients with complicated appendicitis could be found between LA and OA (5.9% vs 4.1%; p = 0.44). CONCLUSIONS: No significant difference in the occurrence of IAA after LA versus OA was found. The patients with complicated appendicitis experienced a greater number of IAA than the patients with uncomplicated appendicitis.

Influence of mesh materials on the expression of mediators involved in wound healing.

The use of synthetic mesh for ventral hernia repair is widely accepted, but mesh-induced inflammatory responses may lead to postoperative complications. Molecular mechanisms that direct the extent of the foreign body reaction to implanted materials are poorly understood. This study compares the influence of three macroporous meshes on the expression of genes critical for wound healing and extracellular matrix remodeling in a rat model. Full thickness abdominal wall defects were corrected with polypropylene, polyester, polytetrafluoroethylene (PTFE), or suture repair with no mesh. Explants were harvested 7 or 90 days after repair and were divided for histological, immunohistochemical, and mRNA analyses. Real-time quantitative polymerase chain reaction arrays were used to profile the expression of 84 genes involved in angiogenesis at the tissue-mesh interface. Evaluation of gene expression profiles and histologic specimens revealed that polypropylene and polyester induced a greater and more persistent inflammatory response than PTFE, which elicited a response most similar to that induced by suture repair. Mesh implantation induced the differential expression (>3-fold change and p < .01) of genes encoding inflammatory cytokines, growth factors, and extracellular matrix proteins relative to suture repair without mesh. Genes most markedly upregulated included the neutrophil chemoattractant CXCL2 and matrix metalloproteinases 3 and 9. Polyester induced the greatest number of differentially expressed genes relative to suture repair both at 7 and 90 days after implantation. Results from this study suggest that the particular type of mesh used in a hernia repair may affect the patient's wound healing response and clinical outcome.