Human peritoneal membrane reduces the formation of intra-abdominal adhesions in ventral hernia repair: experimental study in a chronic hernia rat model

Different cellular and immunohistochemical abdominal wall cicatrization parameters evaluation in comparison with sublay, onlay, and ipom technique in an experimental rat model

PURPOSE

Incisional hernia (IH) occurs when there is a partial or complete solution of continuity of a fascia previously incised. Systematic reviews demonstrate that surgical treatment of IHs with the use of meshes are approximately 16%. Meta-analyses have demonstrated the superiority of mesh placement using sublay technique, but without a pathophysiological explanation. Thus, we aim to evaluate the different techniques of mesh positioning in an experimental model.

METHODS

Fifty rats were distributed into five groups; control; simulation (SM)-submitted to laparotomy only; onlay-the mesh was positioned in onlay fashion; retromuscular (SL)-the mesh was positioned in a sublay fashion; intraperitoneal (IPOM)-positioning of the mesh adjacent to the transversalis fascia, inside the cavity. After 60 days, adhesions, tensiometry, histology, and immunohistochemistry were addressed.

RESULTS

The IPOM group had the most adhesions, together with the SL group, with significantly relevant results. The SL group had higher values of tensiometric evaluation, while the IPOM group had the lowest mean in the tensiometry evaluation, being even lower than the SM group. Regarding histological and immunohistochemical findings, the SL group had a higher pixel number count compared to the groups, with statistical significance, in addition to higher expression of polymorphonuclear infiltrate and CD68 markers.

CONCLUSION

The mesh positioning in sublay compartment is associated with the development of more pronounce minimum tensile force required for detaching the surrounding abdominal wall tissues it was incorporated. The intensity of these findings correlates to the different histological and immunohistochemical profiles observed following each repair, since SL group was characterized by a higher proportion of collagen, inflammatory, and reparative elements. Characterizing these pro-healing elements and its counterparts will allow the development of new therapeutic tools which could be added to the still far-from-ideal current therapeutic options for IH treatment.

3D-Bioprinted Inflammation Modulating Polymer Scaffolds for Soft Tissue Repair

Development of inflammation modulating polymer scaffolds for soft tissue repair with minimal postsurgical complications is a compelling clinical need. However, the current standard of care soft tissue repair meshes for hernia repair is highly inflammatory and initiates a dysregulated inflammatory process causing visceral adhesions and postsurgical complications. Herein, the development of an inflammation modulating biomaterial scaffold (bioscaffold) for soft tissue repair is presented. The bioscaffold design is based on the idea that, if the excess proinflammatory cytokines are sequestered from the site of injury by the surgical implantation of a bioscaffold, the inflammatory response can be modulated, and the visceral adhesion formations and postsurgical complications can be minimized. The bioscaffold is fabricated by 3D-bioprinting of an in situ phosphate crosslinked poly(vinyl alcohol) polymer. In vivo efficacy of the bioscaffold is evaluated in a rat ventral hernia model. In vivo proinflammatory cytokine expression analysis and histopathological analysis of the tissues have confirmed that the bioscaffold acts as an inflammation trap and captures the proinflammatory cytokines secreted at the implant site and effectively modulates the local inflammation without the need for exogenous anti-inflammatory agents. The bioscaffold is very effective in inhibiting visceral adhesions formation and minimizing postsurgical complications.

Sublay repair results in superior mesh incorporation and histological fibrogenesis in comparison to onlay and primary suture in an experimental rat model

PURPOSE

To compare adhesion scores, repair strength and histological findings among sublay, onlay and primary repair incisional hernioplasty techniques. Surgical repairs were employed directly on healthy animals, without previous hernia induction, to avoid confounding factors related to hernia development.

METHODS

Forty Wistar rats were divided into four groups, control, simulation, onlay and sublay. After 42 days, adhesion intensity, tensile strength of the abdominal wall and anatomopathological histological substrate were compared.

RESULTS

SL group presented greater adhesion scores (p < 0.0001), higher tensiometric (p < 0.0001), and was characterized by more histiocytes, mononuclear cells, macrovacuolar granulomas and type I collagen on histological analysis. Pearson correlation between adhesions and tensiometry, and between tensiometry and neocollagenization showed a strong positive association (r = 0.8905 and 0.6757, respectively in SL group, p < 0.05).

CONCLUSION

Mesh positioning in sublay compartment was followed by increased adhesion development and provides a stronger mesh-tissue attachment, in addition, resulted in a different histological profile of the inflammation/repair substrate. The intensity of these findings was directly correlated, suggesting they could be the result of a common biological phenomenon. Our findings indicate that mesh placement following the retromuscular technique generates a superior repair response, and give clues to a better understanding of the superiority of sublay repair in achieving lower recurrence rates. Characterization of the cellular and molecular elements responsible for the superiority of this technique is in our view an essential prerequisite aiming for improvements in the therapeutic options for the treatment of this disease.

Systemic inflammatory cytokine analysis to monitor biomaterial augmented tissue healing

PURPOSE

Hernias can be repaired by reinforcement of damaged fascia using biomaterials to provide stabilisation. Repair materials are usually porous, through which cells infiltrate, proliferate and secrete ECM. Their efficacy relies on good tissue integration and resolution of host defence mechanisms. Therefore, understanding the dynamics by which biomaterials interact with tissue will provide knowledge to advance prosthesis design. Furthermore, determining host response in real time would provide significant advantage both clinically and scientifically over the current terminal process of histology.

METHODS

3 materials comprising synthetic and composite (synthetic materials hybridised with a resorbable biologic component) meshes were implanted into a rat full-thickness abdominal wall excision model. Their efficacy was evaluated using histopathology whilst also monitoring systemic concentrations of cytokines associated with inflammation and wound healing to predict material outcome over 12 weeks.

RESULTS

The noncomposite material (polyester) and Material B (polypropylene mesh with oligocaprone film and polydioxanone glue) stimulated the largest degree of adhesion from the 3 materials tested, although after 28 days adhesions were stronger to Material B. Histologically, all 3 materials integrated well with abdominal musculature and infiltrated completely with cells.

CONCLUSIONS

Analysis of systemic inflammation biomarkers confirmed inflammation elicited by surgeries and meshes irrespective of their composition. However, at an early postoperative endpoint (i.e., 1 week), some biomarkers, namely, IL-18 and RANTES, appeared to discriminate the noncomposite mesh from the composite materials, although in this study all materials successfully repaired the defects without recurrence or external indicators of postoperative chronic pain.

Pilot study evaluating the efficacy of AlloMEM™ for prevention of intraperitoneal adhesions and peritoneal regeneration after loop ileostomy

OBJECTIVE

This study was designed to evaluate the feasibility of AlloMEM™, a novel lyophililzed human peritoneal membrane, at peritoneal reconstitution, and decreasing adhesion formation after temporary loop ileostomy.

METHODS

In a pilot study, ten patients had AlloMEM™ used during elective formation of a temporary diverting loop ileostomy for benign or malignant colorectal disease. A blinded investigator and the operating surgeon analyzed the change in adhesion formation and peritoneal remodelling using ileostomy mobilization time and a 5-point adhesion scale grading intra-abdominally and at the subcutaneous and fascial levels.

RESULTS

The mean body mass index was 31 [standard deviation (SD) 5.6], and 40 % of patients had previous abdominal surgery. Ileostomies were reversed after a mean 14 weeks (SD 6.0). The mean ileostomy mobilization time was 27.2 min (SD 12.0). From baseline to ileostomy reversal, there were significant increases in adhesions at the subcutaneous (p = 0.0002) and fascial levels (p = 0.0024). The increased subcutaneous adhesions were associated with improved peritoneal remodeling. There was no significant increase in adhesions from baseline to ileostomy reversal at the intra-abdominal points (p = 0.9393) or around the ileostomy site (p = 0.6128). The median hospital length of stay was 2.6 days (range, 2-3). A single adverse event related to product packaging led to redesign of the packaging process.

CONCLUSIONS

Use of AlloMEM™ in ileostomy closures suggested improvement in adhesions around the fascia and promotion of peritoneal remodeling. AlloMEM™ was safe, feasible, and easy to use in this pilot study. Comparative research is needed to assess the outcomes with this novel product.

Noninvasive detection and mapping of intraabdominal adhesions: a review of the current literature

BACKGROUND

Adhesions are a well-known and very common complication to surgery. Their extent and severity varies according to type and number of surgeries, use of intraabdominal mesh, and presence of peritonitis. Adhesions cause increased morbidity and mortality, with subsequent socioeconomic consequences. This review aimed to identify existing literature on noninvasive radiologic techniques for identification of intraabdominal adhesions.

METHODS

A structured literature search of medical databases was conducted. English literature published until September 2009 and relevant references were included and assessed.

RESULTS

The search identified transabdominal ultrasonography (TAU) and cine magnetic resonance imaging (cine MRI) as relevant tools matching the search criteria. In all, 12 publications concerning TAU and 4 publications concerning cine MRI were identified. All but one of these publications had the methodologic limitation of not being blinded, which influenced the final sensitivity, specificity, and accuracy.

CONCLUSION

Both TAU and cine MRI seem able to identify intraabdominal adhesions using visceral slide with accuracy of 76% to 92%. Unfortunately, the studies are biased by being nonblinded. Accordingly, a need exists for a systematic well-conducted double-blinded comparative study to validate these radiologic techniques.