The role of neutrophils in peritoneal adhesion formation

Role of Substance P-Dependent Chemotactic Signaling in Postoperative Adhesion Formation

BACKGROUND

Postoperative adhesions are a potentially life-threatening complication of abdominal surgery. We previously showed that substance P (SP), acting through the neurokinin-1 receptor (NK-1R), is an important early mediator of adhesiogenesis through its regulation of the tissue plasminogen activator/plasminogen activator inhibitor-1 (PAI-1) fibrinolytic system. SP also mediates neurogenic inflammation by recruiting inflammatory leukocytes, such as neutrophils and macrophages. Our objective was to determine the role of SP-dependent chemotactic recruitment of these inflammatory cells through the CXCR2 in postsurgical adhesion formation.

MATERIALS AND METHODS

A mouse cecal cauterization model was used to generate intra-abdominal adhesions. Protein and mRNA levels of the chemokines CXCL1 and CXCL2 and their receptor CXCR2 were measured at 3 h and 6 h after surgery in peritoneal tissue and in peritoneal lavages in response to antagonists for the SP receptor and CXCR2, and in IFN-γ knockout mice.

RESULTS

Postsurgical adhesion formation was inhibited by both an antagonist to NK-1R and an antagonist to CXCR2. Expression levels of neutrophil chemokines and CXCR2 in peritoneal tissue peaked 3-6 h after surgery and partially depended on SP and IFN-γ, one of its downstream mediators. An NK-1R antagonist inhibited SP-mediated increases in the expression of the PAI-1 inhibitory component of the fibrinolytic system, but the CXCR2 antagonist had no effect.

CONCLUSIONS

Postsurgical adhesiogenesis involves upregulation of chemokine signaling that is partially SP- and IFN-γ-dependent. However, the adhesiogenic properties of chemokine signaling are not mediated through the inhibition of fibrinolysis with PAI-1, as was previously shown for SP.

Post-Operative Adhesions: A Comprehensive Review of Mechanisms

Post-surgical adhesions are common in almost all surgical areas and are associated with significant rates of morbidity, mortality, and increased healthcare costs, especially when a patient requires repeat operative interventions. Many groups have studied the mechanisms driving post-surgical adhesion formation. Despite continued advancements, we are yet to identify a prevailing mechanism. It is highly likely that post-operative adhesions have a multifactorial etiology. This complex pathophysiology, coupled with our incomplete understanding of the underlying pathways, has resulted in therapeutic options that have failed to demonstrate safety and efficacy on a consistent basis. The translation of findings from basic and preclinical research into robust clinical trials has also remained elusive. Herein, we present and contextualize the latest findings surrounding mechanisms that have been implicated in post-surgical adhesion formation.

Prevention of Post-Operative Adhesions: A Comprehensive Review of Present and Emerging Strategies

Post-operative adhesions affect patients undergoing all types of surgeries. They are associated with serious complications, including higher risk of morbidity and mortality. Given increased hospitalization, longer operative times, and longer length of hospital stay, post-surgical adhesions also pose a great financial burden. Although our knowledge of some of the underlying mechanisms driving adhesion formation has significantly improved over the past two decades, literature has yet to fully explain the pathogenesis and etiology of post-surgical adhesions. As a result, finding an ideal preventative strategy and leveraging appropriate tissue engineering strategies has proven to be difficult. Different products have been developed and enjoyed various levels of success along the translational tissue engineering research spectrum, but their clinical translation has been limited. Herein, we comprehensively review the agents and products that have been developed to mitigate post-operative adhesion formation. We also assess emerging strategies that aid in facilitating precision and personalized medicine to improve outcomes for patients and our healthcare system.

Multilayer fibroin/chitosan oligosaccharide lactate and pullulan immunomodulatory patch for treatment of hernia and prevention of intraperitoneal adhesion

This study aims to develop a novel intraperitoneal two- or three-layered patch with immunomodulatory property for treatment of hernia, regeneration of abdominal wall and prevention of intraperitoneal adhesions. Polypropylene (PP) mesh, middle layer, was intended to provide mechanical support whereas pullulan (PUL) hydrogel coating layer was designed to prevent intraperitoneal adhesions. Fibroin/chitosan oligosaccharide lactate (F/COS) layer electrospun on one side of pullulan was chosen for immunomodulation and abdominal wall regeneration. Physical and mechanical properties and regenerative capacity of intraperitoneal patches were determined. Immunomodulatory property of electrospun layer and whole patch was studied by determining nitric oxide amount produced by RAW 264.7 macrophages. 25 % (w/v) PUL hydrogel and F/COS with 90:10 (w/w) ratio yielded optimal results. Here, we report that fabricated intraperitoneal patches successfully prevented cell adhesion on one side and increased cell viability and proliferation on other side, along with immunomodulation, in vitro.

Injectable thermosensitive hydrogel containing hyaluronic acid and chitosan as a barrier for prevention of postoperative peritoneal adhesion

Peritoneal adhesion is one of the common complications after abdominal surgery. Injectable thermosensitive hydrogel could serve as an ideal barrier to prevent this postoperative tissue adhesion. In this study, poly(N-isopropylacrylamide) (PNIPAm) was grafted to chitosan (CS) and the polymer was further conjugated with hyaluronic acid (HA) to form thermosensitive HA-CS-PNIPAm hydrogel. Aqueous solutions of PNIPAm and HA-CS-PNIPAm at 10%(w/v) are both free-flowing and injectable at room temperature and exhibit sol-gel phase transition around 31°C; however, HA-CS-PNIPAm shows less volume shrinkage after gelation and higher complex modulus than PNIPAm. Cell culture studies indicate both injectable hydrogel show barrier effects to reduce fibroblasts penetration while induce little cytotoxicity in vitro. From a sidewall defect-bowel abrasion model in rats, significant reduction of postoperative peritoneal adhesion was found for peritoneal defects treated with HA-CS-PNIPAm compared with those treated with PNIPAm and untreated controls from gross and histological evaluation. Furthermore, HA-CS-PNIPAm did not interfere with normal peritoneal tissue healing and did not elicit acute toxicity from blood analysis and tissue biopsy examination. By taking advantage of the easy handling and placement properties of HA-CS-PNIPAm during application, this copolymer hydrogel would be a potentially ideal injectable anti-adhesion barrier after abdominal surgeries.

Assessment of Tissue Damage due to Mechanical Stresses

While there are many benefits to minimally invasive surgery (MIS), force feedback or touch sensation is limited in the currently available MIS tools, such as surgical robots, creating the potential for excessive force application during surgery and unintended tissue injury. The goal of this work was to develop a methodology with which to identify stress magnitudes and durations that can be safely applied with a MIS grasper to di ferent tissues, potentially improving MIS device design and reducing potentially adverse clinically relevant consequences. Using the porcine model, stresses typically applied in MIS were applied to liver, ureter and small bowel using a motorized endoscopic grasper. Acute indicators of tissue damage including cellular death and infiltration of inflammatory cells were measured using histological and image analysis techniques. Finite element analysis was used to identify approximate stress distributions experienced by the tissues. Parameters used in these finite element models specifically reflected the properties of liver, which served as an initial proxy for all tissues, as stress distributions rather than absolute values were desired. Local regions predicted to have uniform stress by the computational models were mapped to and analyzed in the tissue samples for acute damage. Analysis of variance (ANOVA) and post-hoc analyses were used to detect stress magnitudes and durations that caused significantly increased tissue damage with the goal to ultimately identify safe stress `thresholds' during grasping of the studied tissues. Preliminary data suggests a graded non-linear response between applied stress magnitude and apoptosis in liver and small bowel as well as neutrophil infiltration in the small bowel. The ureter appeared to be more resistant to injury at the tested stress levels. By identifying stress magnitudes and durations within the range of grasping loads applied in MIS, it may be possible for researchers to create a `smart' surgical robot that can guide a surgeon to manipulate tissues with minimal resulting damage. In addition, surgical simulator design can be improved to reflect more realistic tissue responses and evaluate trainees' tissue handling skills.

Comprehensive analysis of chemokines and cytokines secreted in the peritoneal cavity during laparotomy

We recently found that chemokine-driven peritoneal cell aggregation is the primary mechanism of postoperative adhesion in a mouse model. To investigate this in humans, paired samples of peritoneal lavage fluid were obtained from seven patients immediately after incision (preoperative) and before closure (postoperative), and were assayed for the presence of 27 cytokines and chemokines using multiplex beads assay. As a result, IL-6 and CCL5 showed the most striking increase during operation. Recombinant CCL5 or lavage fluid induced chemotaxis of human peripheral blood mononuclear cells. We propose that CCL5 is possibly involved in the mechanism of postoperative adhesion in humans.

Polygalacturonic acid hydrogel with short-chain hyaluronate cross-linker to prevent postoperative adhesion

The purpose of this study was to develop a poly(galacturonic acid) (PGA)-based hydrogel using a short-chain hyaluronate (sHA) cross-linker for medical applications. PGA was grafted with adipic acid dihydrazide (ADH) to yield PGA–ADH, an amine-containing PGA derivative. This PGA–ADH formed a water-insoluble hydrogel by reacting with 1,1′-carbonyldiimidazole (CDI)–grafted sHA (sHA–CDI) in aqueous solution. The sHA–cross-linked PGA hydrogel has a water content of about 94%–97% and compressive modulus of 10.7–26.9 kPa. The in vitro data indicated that the sHA–cross-linked PGA hydrogel is degradable and noncytotoxic, thus suitable for biomedical applications. Animal implant studies showed that the sHA–cross-linked PGA hydrogel membrane exhibited antiadhesion potency, significantly higher than that found in untreated rats and has great potential for future clinical applications.

Intra-abdominal administration of bevacizumab diminishes intra-peritoneal adhesions

AIM

To determine the effect of a single dose of bevacizumab on adhesion formation in the rat cecum abrasion model.

METHODS

The cecum and parietal peritoneum of 38 male Wistar rats were abraded to promote adhesion formation. The rats were randomized into 2 groups: group 1 received bevacizumab (2.5 mg/kg) intraperitoneally, and group 2 received saline. On day 30 animals were killed, adhesions scored, and histopathological samples taken.

RESULTS

There was no wound dehiscence; there were 2 incision hernias (5.3%), 1 per group. Thirty-seven animals developed adhesions (97.4%). Adhesion grade and severity scores were significantly different between groups 1 and 2 at 2.7:1.6 (P = .018) and 3.8:2.7 (P = .007), respectively. There was no difference in adhesion square area (27.7:25.0%; P = .16), location (P = 1.00), or number (2.1:1.3; P = .06). Histopathology confirmed the statistical difference between groups (P = .049), and a highly significant correlation between results was shown (r = .758; P = .0001).

CONCLUSION

A single dose of intraperitoneal bevacizumab significantly reduces grade and severity of abdominal adhesions in the cecum abrasion rat model.

Addition of nimesulide to small intestinal submucosa biomaterial inhibits postsurgical adhesiogenesis in rats

Adhesion formation is a common complication in abdominal surgery with incidence as high as 93% and small bowel obstruction a common complication. Because the extracellular matrix material, small intestinal submucosa (SIS), is commonly used in various surgical procedures, methods to inhibit adhesiogenesis are of great interest. This study was undertaken to determine if incorporation of nimesulide (NM), a selective cyclooxygenase (COX)-2 inhibitor, could reduce the extent and tenacity of intraabdominal adhesion formation associated with SIS implantation. Female Sprague-Dawley rats underwent a cecal abrasion surgical procedure to induce adhesiogenesis. Rats were either left untreated or treated by direct application over the injured cecum with polypropylene mesh (PPM); SIS; SIS containing a low dose of NM; or SIS containing a high dose of NM. Rats were euthanized 21 days later, and adhesion extent and tenacity were evaluated using standard scales (0 = minimal adhesiogenesis; 4 = severe adhesiogenesis). Addition of NM to SIS resulted in a significant (p < 0.05) reduction in adhesion extent and in a similar reduction in adhesion tenacity for SIS containing a low dose of NM. Adhesions typically extended from the abraded cecal surface to the body wall and were characterized histologically by fibrous tissue adherent to the cecal wall. In conclusion, addition of the nonsteroidal anti-inflammatory, COX-2 selective drug, NM, to SIS attenuates adhesion extent and tenacity when compared with surgical placement of SIS or PPM alone.

Functional Th1 cells are required for surgical adhesion formation in a murine model

Tissue trauma in the peritoneal and pelvic cavities following surgery or bacterial infection results in adhesions that are a debilitating cause of intestinal obstruction, chronic pelvic pain, and infertility in women. We recently demonstrated that CD4(+) alphabeta T cells are essential for development of this process. Using a murine model of experimental adhesion formation, we now demonstrate that adhesion formation is characterized by the selective recruitment of Tim-3(+), CCR5(+), CXCR3(+), IFN-gamma(+) cells, indicating the presence of a Th1 phenotype. We further demonstrate that adhesion formation is critically dependent on the function of Th1 cells because mice genetically deficient for IFN-gamma, T-bet, or treated with Abs to the Th1-selective chemoattractant IL-16 show significantly less adhesion formation than wild-type mice. In addition, disrupting the interaction of the Th1-specific regulatory molecule Tim-3, with its ligand, significantly exacerbates adhesion formation. This enhanced response is associated with increases in the level of neutrophil-attracting chemokines KC and MIP-2, known to play a role in adhesiogenesis. These data demonstrate that the CD4(+) T cells orchestrating adhesion formation are of the Th1 phenotype and delineate the central role of T-bet, Tim-3, IFN-gamma, and IL-16 in mediating this pathogenic tissue response.

A neurokinin-1 receptor antagonist that reduces intra-abdominal adhesion formation decreases oxidative stress in the peritoneum

Oxidative stress has been implicated in intra-abdominal adhesion formation. Substance P, a neurokinin-1 receptor (NK-1R) ligand, facilitates leukocyte recruitment and reactive oxygen species (ROS) generation. We have shown in a rat model of adhesion formation that intraperitoneal administration of a NK-1R antagonist at the time of abdominal operation reduces postoperative adhesion formation. Thus we determined the effects of NK-1R antagonist administration on peritoneal leukocyte recruitment and oxidative stress within 24 h of surgery. Adhesions were induced in Wistar rats randomly assigned to receive the antagonist or vehicle intraperitoneally. Peritoneal tissue was isolated at 2, 4, 6, and 24 h after surgery for analysis of the oxidative stress biomarkers 8-isoprostane (8-IP), protein carbonyl, NADPH oxidase, myeloperoxidase (MPO), and ICAM-1 and VCAM-1 mRNAs. Total antioxidant capacity of peritoneal fluid was also determined. MPO, NADPH oxidase, 8-IP, and protein carbonyl were elevated (P < 0.05) by 6 h. ICAM-1 mRNA was elevated (P < 0.05) by 2 h, whereas VCAM-1 levels decreased (P < 0.05) at 24 h. The NK-1R antagonist delayed the MPO rise and reduced (P < 0.05) 8-IP levels by 6 h and ICAM-1 mRNA, VCAM-1 mRNA, and protein carbonyl at 2 h. The antagonist also increased (P < 0.05) the antioxidant capacity of peritoneal fluid at all time points. These data further support a role for oxidative stress in adhesion formation and suggest that the NK-1R antagonist may limit adhesions, in part, by reducing postoperative oxidative stress through an inhibition of neutrophil recruitment and an increase in peritoneal fluid antioxidant capacity.

Inhibition of CCL1-CCR8 interaction prevents aggregation of macrophages and development of peritoneal adhesions

Peritoneal adhesions are a significant complication of surgery and visceral inflammation; however, the mechanism has not been fully elucidated. The aim of this study was to clarify the mechanism of peritoneal adhesions by focusing on the cell trafficking and immune system in the peritoneal cavity. We investigated the specific recruitment of peritoneal macrophages (PMphi) and their expression of chemokine receptors in murine models of postoperative and postinflammatory peritoneal adhesions. PMphi aggregated at the site of injured peritoneum in these murine models of peritoneal adhesions. The chemokine receptor CCR8 was up-regulated in the aggregating PMphi when compared with naive PMphi. The up-regulation of CCR8 was also observed in PMphi, but not in bone marrow-derived Mphi, treated with inflammatory stimulants including bacterial components and cytokines. Importantly, CCL1, the ligand for CCR8, a product of both PMphi and peritoneal mesothelial cells (PMCs) following inflammatory stimulation, was a potent enhancer of CCR8 expression. Cell aggregation involving PMphi and PMCs was induced in vitro in the presence of CCL1. CCL1 also up-regulated mRNA levels of plasminogen activator inhibitor-1 in both PMphi and PMCs. CCR8 gene-deficient mice or mice treated with anti-CCL1-neutralizing Ab exhibited significantly reduced postoperational peritoneal adhesion. Our study now establishes a unique autocrine activation system in PMphi and the mechanism for recruitment of PMphi together with PMCs via CCL1/CCR8, as immune responses of peritoneal cavity, which triggers peritoneal adhesions.

Enteric bacteria and their antigens may stimulate postoperative peritoneal adhesion formation

BACKGROUND

Intraabdominal sepsis causes exuberant inflammation, which results in dense adhesions. Translocation of enteric bacteria and/or their antigens after laparotomy may therefore also affect peritoneal healing by promoting local release of proinflammatory cytokines. Our hypothesis was that targeted counter therapy could be beneficial if such contamination was to augment postoperative adhesion formation.

METHODS

Two endotoxin-hyposensitive mouse strains (C3H/HeJ and C57BL/10ScCr) and their syngeneic counterparts (C3H/HeN and C57BL10/ScSn, respectively) underwent reproducible adhesion-inducing operation (AIO) (n=10/group) with sacrifice and blinded adhesion grading 14 days later. In addition, CD-1 mice were gavaged with fluorescein isothiocyanate labeled-lipopolysaccharide (FITC-LPS) prior to either AIO or sham laparotomy and had both peritoneal macrophages and circulating monocytes assessed by flow cytometry afterward. The cytokine-release response of resident peritoneal cells to LPS stimulation was assessed in vitro (murine peritoneal mast cell cultures) and in vivo (unoperated CD-1 mice administered LPS intraperitoneally [10 & 50 microg/mouse]). Finally, CD-1 mice (n=10/group) had AIO and received either bactericidal/permeability increasing protein (rBPI, 2 mg/mouse) or vehicle solution in the early postoperative period with assessment of adhesion formation 2 weeks later.

RESULTS

Both HeJ and ScCr mice had less adhesions than their controls (P=.0015 and .0001, respectively, Mann Whitney U test). FITC-LPS uptake by peritoneal macrophages was striking after AIO. Intraperitoneal LPS provoked significant local vascular endothelial growth factor (VEGF) release as did the process of AIO. In vitro, LPS induced significant interleukin-(IL)-6 release from isolated mast cells. Intraperitoneal administration of rBPI to CD-1 mice early after AIO markedly attenuated subsequent adhesion formation (P=.0003).

CONCLUSIONS

Peritoneal adhesion formation is exacerbated by peritoneal contamination due to translocation after laparotomy and may be attenuated by therapeutic antagonism.

The Role of Neutrophils and Oxygen Free Radicals in Post-Operative Adhesions

BACKGROUND

Postoperative intra-abdominal adhesion formation remains a major surgical problem. Surgery induces an inflammatory reaction, which is responsible for adhesion formation. Neutrophils and their oxygen-free radicals are key mediators in the early post-operative inflammatory response. The present study evaluates the effect of either blocking the influx of neutrophils or its products by scavenging oxygen-free radicals on adhesion formation.

MATERIALS AND METHODS

Reproducible rat models were used to induce post-surgical intra-abdominal adhesions. In the first experiment anti-neutrophil serum (ANS) was used to prevent neutrophils from entering the peritoneal cavity after surgery. In a second experiment superoxide dismutase (SOD), catalase, and mannitol were tested, to scavenge the superoxide, hydrogen peroxide, and hydroxyl radicals, respectively.

RESULTS

In positive control groups 69 to 76% of the area of interest contained adhesions. In all experimental groups, except for mannitol, a significant reduction in post-surgical adhesion formation could be achieved. ANS reduced adhesion formation by 38% (P < 0.001) and SOD/catalase by 42% (P < 0.01). Mannitol could not reduce adhesion formation.

CONCLUSIONS

Intra-abdominal influx of neutrophils after surgical peritoneal trauma plays an important role in post-operative adhesion formation. Preventing the intra-abdominal influx of neutrophils in the early post-operative inflammatory reaction can reduce adhesion formation, but an even more selective approach, by scavenging its products, proved as efficient.

Mast cells facilitate local VEGF release as an early event in the pathogenesis of postoperative peritoneal adhesions

BACKGROUND

Peritoneal injury sustained at laparotomy may evoke local inflammatory responses that result in adhesion formation. Peritoneal mast cells are likely to initiate this process, whereas vascular permeability/endothelial growth factor (VEGF) may facilitate the degree to which subsequent adhesion formation occurs.

METHODS

Mast cell deficient mice (WBB6F1-/-), along with their mast cell sufficient counterparts (WBB6F1+/+), underwent a standardized adhesion-inducing operation (AIS) with subsequent sacrifice and adhesion assessment 14 days later in a blinded fashion. Additional CD-1 and WBB6F1+/+, and WBB6F1-/- mice were killed 2, 6, 12, and 24 hours after operation for measurement of VEGF by ELISA in systemic serum and peritoneal lavage fluid. Two further groups of CD-1 mice underwent AIS and received either a single perioperative dose of anti-VEGF monoclonal antibody (10 mug/mouse) or a similar volume of IgG isotypic antibody and adhesion formation 2 weeks later was evaluated.

RESULTS

WBB6F1-/- mice had less adhesions then did their WBB6F1+/+ counterparts (median [interquartile range] adhesion score 3[3-3] vs 1.5[1-2] respectively; P < .003). Local VEGF release peaked 6 hours after AIS in both WBB6F1+/+ and CD-1 mice whereas levels remained at baseline in WBB6F1-/- mice. CD-1 mice treated with a single dose of anti-VEGF therapy during operation had less adhesions than controls (2[1.25-2] vs 3[2.25-3], P = .0002).

CONCLUSIONS

Mast cells and VEGF are central to the formation of postoperative intra-abdominal adhesions with mast cells being responsible, either directly or indirectly, for VEGF release into the peritoneal cavity after operation. In tandem with the recent clinical success of anti-VEGF monoclonal antibodies in oncologic practice, our observations suggest an intriguing avenue for research and development of anti-adhesion strategy.

Development of peritoneal adhesions in macrophage depleted mice

BACKGROUND

We present a new mouse model for the study of peritoneal adhesions using macrophage Fas-induced apoptosis (Mafia) transgenic mice expressing a Fas-FKBP construct under control of the murine c-fms promoter. Mafia mice allow systemic macrophage depletion by dimerization of Fas with a synthetic dimerizer, AP20187. Results demonstrate that macrophage depletion in Mafia mice induces peritoneal adhesion formation when the peritoneal cavity is also exposed to an irritant. The Mafia mouse model presents a reproducible, non-surgical approach for research in adhesion formation and prevention.

MATERIALS AND METHODS

Mafia mice were treated with AP20187 using an intravenous (i.v.) or intraperitoneal (i.p.) injection. Control groups included mock-treated Mafia mice and both AP20187 and mock-treated wild type mice. Seven days after treatment, mice were observed for the presence of adhesions.

RESULTS

After i.p. injection with AP20187, 76% of Mafia mice developed adhesions whereas none of the mock-treated Mafia or wild-type mice developed adhesions, and only one AP20187-treated wild-type mouse (5.8%) developed a mild adhesion. Mafia mice treated with AP20187 i.v. exhibited macrophage depletion not significantly different than i.p. treated mice, but did not develop adhesions. In contrast, Mafia mice treated with AP20187 i.v. developed adhesions when diluent was also injected into the peritoneal cavity, whereas i.p diluent alone had no effect.

CONCLUSION

Macrophage depletion, combined with a peritoneal irritant, results in peritoneal adhesion formation in transgenic Mafia mice. Macrophages appear to play a protective role in the development and/or repair of peritoneal adhesions.

Inhibition of chemokines prevents intraperitoneal adhesions in mice

BACKGROUND

The present study evaluates the efficacy of a broad-spectrum chemokine inhibitor, NR58-3.14.3, in the prevention of adhesion formation after i.p. surgery in mice.

METHODS

A total of 110 eight week old female Balb/c mice underwent laparotomy. Forty animals were randomly assigned to receive daily i.p. injections of either vehicle (control) or NR58-3.14.3. Time-course of adhesion formation was assessed. A titration of NR58-3.14.3 was conducted for i.p. and s.c. administrations. The effectiveness of a single intra-operative dose of NR58-3.14.3 was evaluated. Number, extent, location and type of adhesions were recorded. Immunohistochemistry of adhesions was done with leukocyte common antigen, CD45.

RESULTS

Adhesion scores peaked on post-operative days 6-8. On both days 6 and 8, there were smaller adhesion size and lower cumulative adhesion scores in NR58-3.14.3-treated group. Moreover, on day 8, there were significantly fewer adhesions in NR58-3.14.3-treated group compared to controls. The least effective dose for i.p. administration of NR58-3.14.3 was 0.45 mg/animal. Subcutaneous and single intra-operative i.p. administrations were also effective in the prevention of i.p. adhesions. Although NR58-3.14.3 decreased the number of CD45+ inflammatory cells in the adhesions by 22.5% compared to control group, this was not significant.

CONCLUSIONS

Our results show that this broad-spectrum chemokine inhibitor prevents post-operative adhesions in mice and may have a potential clinical use.

A new anti-adhesion film synthesized from polygalacturonic acid with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide crosslinker

The most commonly used anti-adhesion device for separation and isolation of wounded tissues after surgery is the polymeric film. In this study, a new anti-adhesion membrane based on polygalacturonic acid (PGA) has been synthesized, and its biocompatibility and anti-adhesion capabilities evaluated. The PGA film was reacted with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) to obtain a cross-linked PGA film with an 86% gel content and a 47% water content when immersed in aqueous solution. This PGA-EDC film did not show any evidence of cytotoxic effects since it did not induce any significant increase in cytoplasmic LDH release from the L929 cells in contact with it. When implanted into rats, the PGA-EDC film exhibited a most promising anti-adhesion potential with only 1 out of 21 rats operated not forming any tissue adhesion. This anti-adhesion potency is significantly higher than that found for Seprafilm and untreated rats where 11 out of 21 and 18 out of 21 operated rats, respectively, formed tissue adhesions. The implanted PGA-EDC film did not elicit any acute inflammatory reaction based on the results of histological examination and peritoneal fluid leukocytes analysis. The newly developed PGA-EDC film thus has a great potential for future use in clinical applications.

Thalidomide given intraperitoneally reduces the number of postoperative adhesions after large bowel resection in rabbits

OBJECTIVE

To investigate the effect of thalidomide given intraperitoneally on the formation of adhesions after colonic resection in rabbits.

DESIGN

Controlled, randomised prospective study.

SETTING

University hospital, Germany.

ANIMALS

40 female New Zealand White rabbits.

INTERVENTIONS

After an end-to-end colonic anastomosis the animals were given thalidomide 200 mg/kg in 1% carboxymethylcellulose intraperitoneally or carboxymethylcellulose alone (n = 20 in each group).

OUTCOME MEASURES

The adhesion score according to Tyrell on day 3 (n = 20) and day 7 (n = 20) postoperatively, weight, behaviour, and white cell count (WCC).

RESULTS

There was no difference in behaviour or weight. On the third postoperative day WCCs and on the seventh postoperative day WCCs and adhesion scores, were lower in the thalidomide group (p < 0.01).

CONCLUSION

The number of postoperative adhesions was reduced in the group given thalidomide intraperitoneally. Our results suggest that thalidomide may be helpful in the prevention of postoperative adhesions.

CD4+ T cells regulate surgical and postinfectious adhesion formation

The development of adhesions in the peritoneal and pelvic cavities, which commonly form after surgery or infection, cause significant morbidity and mortality. However, the pathogenesis of adhesion formation is still poorly understood. Because T cells are important in orchestrating fibrinogenic tissue disorders, we hypothesized that they play a critical role in the pathogenesis of peritoneal adhesion formation. Using a cecal abrasion surgical model in rodents, T cell depletion and adoptive transfer experiments demonstrated that this host response is dependent on CD4+ alphabeta T cells. These cells were also critical to adhesion formation associated with experimental intraabdominal sepsis. T cell transfer studies with mice deficient in signal transducer and activator of transcription (Stat)4 and Stat6 revealed that adhesion formation was dependent on a T helper 1 response. Activated T cells homed to the peritoneal cavity 6 hours after cecal abrasion surgery and predominated at this site during adhesiogenesis. Increased levels of the T cell-derived proinflammatory cytokine interleukin (IL)-17 and of neutrophil chemoattractant CXC chemokines macrophage inflammatory protein-2/CXCL8 and cytokine-induced neutrophil chemoattractant/CXCL1 were associated with adhesion formation. The production of these chemokines was dependent on T cells. Furthermore, the administration of neutralizing antibodies specific for IL-17 or the receptor that binds these CXC chemokines, CXC chemokine receptor 2, significantly reduced the degree of adhesion formation. These results demonstrate for the first time that the immunopathogenesis of adhesion formation is under the control of T cells and that T cell-derived cytokines and chemokines play important roles in the development of this deleterious host response.

The impact of conventional and laparoscopic colon resection (CO2 or helium) on intraperitoneal adhesion formation in a rat peritonitis model

BACKGROUND

Although postoperative intra-abdominal adhesion formation has been shown to be less with laparoscopic procedures than with open surgery, the extent of intraperitoneal adhesion formation after open and laparoscopic colon resection in patients with intra-abdominal infection remains unclear.

METHODS

A standardized fecal inoculum was intraperitoneally applied in 72 rats to induce peritonitis. The rats were randomized into four groups. The three experimental groups underwent laparoscopic resection of the cecum with carbon dioxide (n = 20) or helium (n = 20) insufflation at a pressure of 8 mmHg, or conventional open cecum resection (n = 20). In the control group, no further manipulations were performed after induction of the peritonitis (n = 12). Blood samples were taken during the perioperative course to determine the plasma levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10). The number of intraperitoneal adhesions and the bacterial species of peritoneal swabs were determined in each animal.

RESULTS

The adhesions were increased in all operation groups as compared with the control group. The number of adhesions was significantly greater after conventional resection than after laparoscopic approaches (p < 0.01). The overall adhesion score was significantly lower in the helium group (p < 0.05) than in the two other operation groups. There was no difference between the laparotomy and carbon dioxide groups. Whereas postoperative TNF-alpha plasma levels were decreased, IL-10 levels were significantly greater in the helium group than in the other three groups.

CONCLUSIONS

Intraperitoneal infection is reducing the benefit of laparoscopic surgery regarding postoperative adhesions. Although laparoscopic resection showed an advantage in the number of adhesions with both gases, the total adhesion score was lowest in the helium group.

The effect of tenoxicam on intraperitoneal adhesions and prostaglandin E2 levels in mice

We determined whether tenoxicam administered intraperitoneally in the preoperative period had an effect on the development of postoperative intraabdominal adhesions (IAA). For this purpose, 100 albino mice were divided into four random groups. Mice in Group 1 were given only 1 mL of 0.9% NaCl intraperitoneally, whereas in Group 2, 1 mL of tenoxicam (150 microg = 5 mg/kg) was administered. After the induction of anesthesia, a median laparotomy was performed, and the bowels were traumatized by touching them with powdered gloves before the incision was closed in Groups 3 and 4. Intraperitoneal tenoxicam was administered to mice in Group 4 after skin closure. All mice were killed after 14 days to determine macroscopic and microscopic IAA; prostaglandin E2 levels were also measured. Postoperative evaluation revealed a reduced IAA formation and a parallel decrease in tissue prostaglandin E2 levels in Group 1 and 2 mice. We conclude that intraperitoneal tenoxicam decreased IAA formation with no peritoneal reaction in the postoperative period.

IMPLICATIONS

Postoperative intraabdominal adhesions can cause intestinal obstruction, pelvic pain, or infertility. In this study, we showed that intraperitoneally administered tenoxicam decreases tissue prostaglandin E2 levels and intraabdominal adhesions in mice.

Effects of granulocyte-macrophage colony-stimulating factor on incisional wound healing in an experimental diabetic rat model

The exact nature of poor wound healing in diabetes is uncertain. Neutrophils play a critical role in the host defense mechanism, and it is suggested that impaired neutrophil functions cause healing difficulties with or without infections in diabetic patients. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is used clinically when given systematically to increase the circulating neutrophils, but its wound-healing effects have not been systematically studied. This study was undertaken to examine the effects of GM-CSF on incisional wound healing in an experimental diabetic rat model. Forty rats were randomly divided into three groups, group I receiving saline as control, diabetes-induced group II receiving saline and diabetes-induced group III receiving GM-CSF. The anesthetized rats in all groups were wounded 21 days after diabetes induction by streptozotocin. Blood neutrophil counts and neutrophil fractions were also determined three days after wounding. Tensile strengths of wounded skin and the hydroxyproline (hyp) level of the wound were determined and wound healing processes were evaluated by light and electron microscopy, fourteen days after wounding. Neutrophil counts and phagocytosis were significantly increased in group III and neutrophil counts decreased in group II (p < 0.05). Although the hydroxyproline level of wound tissue significantly decreased in group II as compared with group III (p < 0.05), there was no differences of tensile strength between group II and III (p < 0.05). Wound score in group II was less than that in groups I and III (p < 0.05). It is concluded that PMN may have a role in modulating wound healing. GM-CSF may be useful for creating better wound healing healing. GM-CSF may be useful for creating better wound healing in risky patients such as diabetics.