Histologic evaluation of absorbable and non-absorbable barrier coated mesh secured to the peritoneum with fibrin sealant in a New Zealand white rabbit model.

PURPOSE: The purpose of this study is to evaluate the histologic response to fibrin sealant (FS) as an alternative fixation method for laparoscopic ventral hernia repair. METHODS: One non-absorbable barrier mesh (Composix™) and three absorbable barrier meshes (Sepramesh™, Proceed™, and Parietex™ Composite) were used for the study, with uncoated macroporous polypropylene mesh (ProLite Ultra™) as the control. Three methods of fixation were used: #0-polypropylene suture + FS (ARTISS™, Baxter Healthcare Corp.), FS alone (ARTISS™), or tacks alone (n = 10 for each group). Two pieces of mesh (of dimensions 4 × 4-cm) were secured intraperitoneally in 75 New Zealand white rabbits. After 8 weeks, hematoxylin and eosin (H&E)-stained specimens were evaluated for host tissue response. Statistical significance (P < 0.05) was determined using a one-way analysis of variance (ANOVA) with Fisher's least significant difference (LSD) post hoc test. RESULTS: Composix™ with FS only showed significantly greater cellular infiltration than with suture + FS (P = 0.0007), Proceed™ with FS only had significantly greater neovascularization than with suture + FS (P = 0.0172), and ProLite Ultra™ with suture + FS had significantly greater neovascularization than with tacks only (P = 0.046). Differences due to mesh type showed that Composix™ exhibited less extensive cellular infiltration (P ≤ 0.0032), extracellular matrix (ECM) deposition, and neovascularization, and demonstrated less inflammatory cells and more fibroblasts compared to the other meshes (P < 0.05). CONCLUSIONS: FS did not have a significant histologic effect compared to tacks when utilized for the fixation of mesh to the peritoneum of New Zealand White rabbits. However, the mesh type did have a significant histologic effect. The permanent barrier mesh (Composix™) was associated with less histologic incorporation than absorbable barrier and macroporous meshes, as evidenced by lower levels of cellular infiltration, ECM deposition, and neovascularization, independent of the fixation method used.

Histologic and biomechanical evaluation of a novel macroporous polytetrafluoroethylene knit mesh compared to lightweight and heavyweight polypropylene mesh in a porcine model of ventral incisional hernia repair.

PURPOSE: To evaluate the biocompatibility of heavyweight polypropylene (HWPP), lightweight polypropylene (LWPP), and monofilament knit polytetrafluoroethylene (mkPTFE) mesh by comparing biomechanics and histologic response at 1, 3, and 5 months in a porcine model of incisional hernia repair. METHODS: Bilateral full-thickness abdominal wall defects measuring 4 cm in length were created in 27 Yucatan minipigs. Twenty-one days after hernia creation, animals underwent bilateral preperitoneal ventral hernia repair with 8 × 10 cm pieces of mesh. Repairs were randomized to Bard(®)Mesh (HWPP, Bard/Davol, http://www.davol.com), ULTRAPRO(®) (LWPP, Ethicon, http://www.ethicon.com), and GORE(®)INFINIT Mesh (mkPTFE, Gore & Associates, http://www.gore.com). Nine animals were sacrificed at each timepoint (1, 3, and 5 months). At harvest, a 3 × 4 cm sample of mesh and incorporated tissue was taken from the center of the implant site and subjected to uniaxial tensile testing at a rate of 0.42 mm/s. The maximum force (N) and tensile strength (N/cm) were measured with a tensiometer, and stiffness (N/mm) was calculated from the slope of the force-versus-displacement curve. Adjacent sections of tissue were stained with hematoxylin and eosin (H&E) and analyzed for inflammation, fibrosis, and tissue ingrowth. Data are reported as mean ± SEM. Statistical significance (P < 0.05) was determined using a two-way ANOVA and Bonferroni post-test. RESULTS: No significant difference in maximum force was detected between meshes at any of the time points (P > 0.05 for all comparisons). However, for each mesh type, the maximum strength at 5 months was significantly lower than that at 1 month (P < 0.05). No significant difference in stiffness was detected between the mesh types or between timepoints (P > 0.05 for all comparisons). No significant differences with regard to inflammation, fibrosis, or tissue ingrowth were detected between mesh types at any time point (P > 0.09 for all comparisons). However, over time, inflammation decreased significantly for all mesh types (P < 0.001) and tissue ingrowth reached a slight peak between 1 and 3 months (P = 0.001) but did not significantly change thereafter (P > 0.09). CONCLUSIONS: The maximum tensile strength of mesh in the abdominal wall decreased over time for HWPP, LWPP, and mkPTFE mesh materials alike. This trend may actually reflect inability to adequately grip specimens at later time points rather than any mesh-specific trend. Histologically, inflammation decreased with time (P = 0.000), and tissue ingrowth increased (P = 0.019) for all meshes. No specific trends were observed between the polypropylene meshes and the monofilament knit PTFE, suggesting that this novel construction may be a suitable alternative to existing polypropylene meshes.

Early biocompatibility of crosslinked and non-crosslinked biologic meshes in a porcine model of ventral hernia repair.

PURPOSE: Biologic meshes have unique physical properties as a result of manufacturing techniques such as decellularization, crosslinking, and sterilization. The purpose of this study is to directly compare the biocompatibility profiles of five different biologic meshes, AlloDerm(®) (non-crosslinked human dermal matrix), PeriGuard(®) (crosslinked bovine pericardium), Permacol(®) (crosslinked porcine dermal matrix), Strattice(®) (non-crosslinked porcine dermal matrix), and Veritas(®) (non-crosslinked bovine pericardium), using a porcine model of ventral hernia repair. METHODS: Full-thickness fascial defects were created in 20 Yucatan minipigs and repaired with the retromuscular placement of biologic mesh 3 weeks later. Animals were euthanized at 1 month and the repair sites were subjected to tensile testing and histologic analysis. Samples of unimplanted (de novo) meshes and native porcine abdominal wall were also analyzed for their mechanical properties. RESULTS: There were no significant differences in the biomechanical characteristics between any of the mesh-repaired sites at 1 month postimplantation or between the native porcine abdominal wall without implanted mesh and the mesh-repaired sites (P > 0.05 for all comparisons). Histologically, non-crosslinked materials exhibited greater cellular infiltration, extracellular matrix (ECM) deposition, and neovascularization compared to crosslinked meshes. CONCLUSIONS: While crosslinking differentiates biologic meshes with regard to cellular infiltration, ECM deposition, scaffold degradation, and neovascularization, the integrity and strength of the repair site at 1 month is not significantly impacted by crosslinking or by the de novo strength/stiffness of the mesh.

Evaluation of fenestrated and non-fenestrated biologic grafts in a porcine model of mature ventral incisional hernia repair.

INTRODUCTION: The purpose of this study is to compare the tissue incorporation of a novel fenestrated and non-fenestrated crosslinked porcine dermal matrix (CPDM) (CollaMend™, Davol Inc., Warwick, RI) in a porcine model of ventral hernia repair. METHODS: Bilateral abdominal wall defects were created in 12 Yucatan minipigs and repaired with a preperitoneal or intraperitoneal technique 21 days after hernia creation. Animals were randomized to fenestrated or non-fenestrated CPDM for n = 6 pieces of each graft in the preperitoneal or intraperitoneal location. All animals were sacrificed at 1 month. Adhesion characteristics and graft contraction/growth were measured by the Garrard adhesion grading scale and transparent grid overlay. Histological analysis of hematoxylin and eosin (H&E)-stained slides was performed to assess graft incorporation. Tissue incorporation strength was measured by a T-peel tensile test. The strength of explanted CPDM alone and de novo CPDM was measured by a uniaxial tensile test using a tensiometer (Instron, Norwood, MA) at a displacement rate of 0.42 mm/s. Statistical significance (P < 0.05) was determined for histological analysis using a Kruskal-Wallis non-parametric test with a Bonferroni correction, and for all other analyses using a two-way analysis of variance (ANOVA) with a Bonferroni post-test or a Kruskal-Wallis non-parametric test with a Dunn's post-test. RESULTS: Intraperitoneal placement of fenestrated CPDM resulted in a significantly higher area of adhesions and adhesion score compared to the preperitoneal placement of fenestrated CPDM (P < 0.05). For both preperitoneal and intraperitoneal placement, histological findings demonstrated greater incorporation of the graft due to the fenestrations. No significant differences were detected in the uniaxial tensile strengths of the graft materials alone, either due to the graft type (non-fenestrated vs. fenestrated) or due to the placement location (preperitoneal vs. intraperitoneal). The incorporation strength (T-peel force) was significantly greater for fenestrated compared to non-fenestrated CPDM when placed in the preperitoneal location (P < 0.01). The incorporation strength was also significantly greater for fenestrated CPDM placed in the preperitoneal location compared to fenestrated CPDM placed in the intraperitoneal location (P < 0.05). CONCLUSIONS: Fenestrations in CPDM result in greater tissue incorporation strength and lower adhesion area and score when placed in the preperitoneal location. Fenestrations in CPDM allow for greater tissue incorporation without accelerating graft degradation. Fenestrations may be placed in CPDM while still allowing adequate graft strength for intraperitoneal and preperitoneal hernia repairs at 1 month in a porcine model.

Evaluation of acute fixation strength of absorbable and nonabsorbable barrier coated mesh secured with fibrin sealant.

INTRODUCTION: The purpose of this study was to evaluate the acute fixation strength of fibrin sealant as an alternative fixation method for laparoscopic ventral hernia repair (LVHR) when utilized with absorbable and nonabsorbable barrier meshes. METHODS: Representative mesh types for LVHR included one nonabsorbable barrier mesh (Bard Composix) and three absorbable barrier meshes (Sepramesh, Proceed, and Parietex Composite Mesh). Macroporous polypropylene mesh (Prolite Ultra) served as a control. An associated pilot study demonstrated that acute fixation was not achieved with C-Qur or Dualmesh, thus these meshes were not subjected to further analysis. Two fibrin sealants varying in thrombin concentration (TISSEEL 500 IU/ml or ARTISS 4 IU/ml) were each utilized to secure a 3 x 4 cm piece of mesh to the peritoneal surface of harvested abdominal wall from New Zealand white rabbits. Ten samples were prepared for each mesh and fibrin sealant combination. The resulting mesh-tissue interface (3 x 3 cm) underwent lap shear testing at a rate of 0.42 mm/s using a tensiometer (Instron 5542, Norwood, MA). The maximum load sustained by the construct was recorded as the acute fixation strength in units of Newtons (N). Data are given as means +/- SEM. Statistical significance (P < 0.05) was determined using a two-way ANOVA and Bonferroni post-test. RESULTS: There was no significant difference (P > 0.05) in the acute fixation strength achieved by ARTISS versus TISSEEL with Composix, Sepramesh, Proceed, and Parietex Composite Mesh. However, Prolite Ultra fixed with ARTISS (7.099 +/- 1.01 N) had a significantly higher tensile strength (P < 0.001) than Prolite Ultra fixed with TISSEEL (3.405 +/- 0.72 N). Among meshes fixed with TISSEEL, Parietex Composite (3.936 +/- 0.73 N) was significantly stronger than Sepramesh (1.760 +/- 0.33 N) (P < 0.05). CONCLUSIONS: Acute fixation strength is equivalent for TISSEEL and ARTISS fibrin sealants for selected nonabsorbable (Composix) and absorbable barrier-coated (Sepramesh, Proceed, and Parietex Composite Mesh) meshes. Previous evaluations in this model indicated fibrin sealant alone did not appear to be a suitable method of fixation with C-Qur or DualMesh against the peritoneum. Long-term evaluation is needed to evaluate the efficacy of this method of fixation using absorbable and nonabsorbable barrier-coated meshes in a model of LVHR.

High affinity binding of receptor-associated protein to heparin and low density lipoprotein receptor-related protein requires similar basic amino acid sequence motifs.

The 39-kDa receptor-associated protein (RAP) is a specialized chaperone for members of the low density lipoprotein receptor gene family, which also binds heparin. Previous studies have identified a triplicate repeat sequence within RAP that appears to exhibit differential functions. Here we generated a series of truncated and site-directed RAP mutants in order to define the sites within RAP that are important for interacting with heparin and low density lipoprotein receptor-related protein (LRP). We found that high affinity binding of RAP to heparin is mediated by the carboxyl-terminal repeat of RAP, whereas both the carboxyl-terminal repeat and a combination of amino and central repeats exhibit high affinity binding to LRP. Several motifs were found to mediate the binding of RAP to heparin, and each contained a cluster of basic amino acids; among them, an intact R(282)VSR(285)SR(287)EK(289) motif is required for high affinity binding of RAP to heparin, whereas two other motifs, R(203)LR(205)R(206) and R(314)ISR(317)AR(319), also contribute to this interaction. We also found that intact motifs of both R(203)LR(205)R(206) and R(282)VSR(285)SR(287)EK(289) are required for high affinity binding of RAP to LRP, with the third motif, R(314)ISR(317)AR(319), contributing little to RAP-LRP interaction. We conclude that electrostatic interactions likely contribute significantly in the binding of RAP to both heparin and LRP and that high affinity interaction with both heparin and LRP appears to require mostly overlapping sequence motifs within RAP.