Comparison of the two types of bioresorbable barriers to prevent intra-abdominal adhesions in rats

Smart hydrogels delivered by high pressure aerosolization can prevent peritoneal adhesions

Postoperative peritoneal adhesions occur in the majority of patients undergoing intra-abdominal surgery and are one of the leading causes of hospital re-admission. There is an unmet clinical need for effective anti-adhesive biomaterials, which can be applied evenly across the damaged tissues. We examined three different responsive hydrogel types, i.e. a thermosensitive PLGA-PEG-PLGA, a pH responsive UPy-PEG and a shear-thinning hexapeptide for this purpose. More specifically, their potential to be homogeneously distributed in the peritoneal cavity by high pressure nebulization and prevent peritoneal adhesions was evaluated. Solutions of each polymer type could be successfully nebulized while retaining their responsive gelation behavior in vitro and in vivo. Furthermore, none of the polymers caused in vitro toxicity on SKOV3-IP2 cells. Following intraperitoneal administration, both the PLGA-PEG-PLGA and the hexapeptide hydrogels resulted in local inflammation and fibrosis and failed in preventing peritoneal adhesions 7 days after adhesion induction. In contrast, the pH sensitive UPy-PEG formulation was well tolerated and could significantly reduce the formation of peritoneal adhesions, even outperforming the commercially available Hyalobarrier® as positive control. To conclude, local nebulization of the bioresponsive UPy-PEG hydrogel can be considered as a promising approach to prevent postsurgical peritoneal adhesions.

Oral Administration Evaluation of the Hydro-Ethanolic Extract of Ginger (Rhizome of Zingiber officinale) against Postoperative-Induced Peritoneal Adhesion: Investigating the Role of Anti-Inflammatory and Antioxidative Effects

Peritoneal adhesions (PAs) occur and develop after abdominal surgery. Abdominal adhesions are common and often develop after abdominal surgery. Currently, there are no effective targeted pharmacotherapies for treating adhesive disease. In this regard, ginger is wildly used in traditional medicine because of its anti-inflammatory and antioxidant effects and has been investigated for peritoneal adhesion treatment. This study analyzed ginger ethanolic extraction via HPLC to have a 6-gingerol concentration. Four groups induced peritoneal adhesion to evaluate ginger's effects on peritoneal adhesion. Then, ginger extract (50, 150, and 450 mg/kg) was administered by gavage in various groups of male Wistar rats (220 ± 20 g, 6-8 weeks). After scarifying the animals for biological assessment, macroscopic and microscopic parameters were determined via scoring systems and immunoassays in the peritoneal lavage fluid. Next, the adhesion scores and interleukin IL-6, IL-10, tumor necrosis factor-(TNF-) α, transforming growth factor-(TGF-) β1, vascular endothelial growth factor (VEGF), and malondialdehyde (MDA) were elevated in the control group. The results showed that ginger extract (450 mg/kg) notably decreased inflammatory (IL-6 and TNF-α), fibrosis (TGF-β1), anti-inflammatory cytokine (IL-10), angiogenesis (VEGF), and oxidative (MDA) factors, while increased antioxidant factor glutathione (GSH), compared to the control group. These findings suggest that a hydro-alcoholic extract of ginger is a potentially novel therapeutic strategy for inhibiting adhesion formation. Also, it might be considered a beneficial anti-inflammatory or antifibrosis herbal medicine in clinical trials. However, further clinical studies are required to approve the effectiveness of ginger.

The Therapeutic Potential of Targeting Key Signaling Pathways as a Novel Approach to Ameliorating Post-Surgical Adhesions

BACKGROUND

Peritoneal adhesions (PA) are a common complication of abdominal operations. A growing body of evidence shows that inhibition of inflammation and fibrosis at sites of peritoneal damaging could prevent the development of intra-abdominal adhesions.

METHODS

A search of PubMed, Medline, CINAHL and Embase databases was performed using the keywords 'postsurgical adhesion', 'post-operative adhesion', 'peritoneal adhesion', 'surgery-induced adhesion' and 'abdominal adhesion'. Studies detailing the use of pharmacological and non-pharmacological agents for peritoneal adhesion prevention were identified, and their bibliographies were thoroughly reviewed to identify further related articles.

RESULTS

Several signaling pathways, such as tumor necrosis factor-alpha, tissue plasminogen activator, and type 1 plasminogen activator inhibitor, macrophages, fibroblasts, and mesothelial cells play a key part in the development of plasminogen activator. Several therapeutic approaches based on anti-PA drug barriers and traditional herbal medicines have been developed to prevent and treat adhesion formation. In recent years, the most promising method to prevent PA is treatment using biomaterial-based barriers.

CONCLUSION

In this review, we provide an overview of the pathophysiology of adhesion formation and various agents targeting different pathways, including chemical agents, herbal agents, physical barriers, and clinical trials concerning this matter.

Spin-coated freestanding films for biomedical applications

Spin-coating is a widely employed technique for the fabrication of thin-film coatings over large areas with smooth and homogeneous surfaces. In recent years, research has extended the scope of spin-coating by developing methods involving the interface of the substrate and the deposited solution to obtain self-supported films, also called freestanding films. Thereby, such structures have been developed for a wide range of areas. Biomedical applications of spin-coated freestanding films include wound dressings, drug delivery, and biosensing. This review will discuss the fundamental physical and chemical processes governing the conventional spin-coating as well as the techniques to obtain freestanding films. Furthermore, developments within this field with a primary focus on tissue engineering applications will be reviewed.

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.

A nano chitosan membrane barrier prepared via Nanospider technology with non-toxic solvent for peritoneal adhesions' prevention

Peritoneal adhesion is one of the most common postsurgical complications and can cause bowel obstruction, pelvic pain, and infertility. Setting up a physical barrier directly between the injured site and surrounding tissues is an effective solution for preventing this adverse situation. This study investigated a chitosan electrospun membrane (CSEM) as a potent anti-adhesion barrier, which was prepared by a needleless technology called Nanospider. Scanning electron microscopy revealed that CSEM is a laminated nanofiber with good mechanical properties. The fiber is uniform with the diameter distributing in the range of 100-120 nm. The tensile strength can reach 27.45 ± 6.30 MPa with a maximum elongation at break of 18.50 ± 1.44%, which makes it stick easily to damaged parts but not to be easily damaged by tissue friction. The growth of S. aureus on CSEM was 59.18% lower than the control at 10 h, which indicates its better antibacterial property. In addition, CSEM has good coagulant and biocompatibility characteristics. It can perform hemostatic function within 10 min and the L929 mouse fibroblast viability on it was 92.18% ± 1.08% on the seventh day. In vivo experiments indicated that CSEM significantly prevented peritoneal adhesions within four weeks after surgery with wound surface coverage. These results indicate that CSEM is a promising anti-adhesion barrier material.

Peritoneal adhesions: Occurrence, prevention and experimental models

Peritoneal adhesions (PA) are a postoperative syndrome with high incidence rate, which can cause chronic abdominal pain, intestinal obstruction, and female infertility. Previous studies have identified that PA are caused by a disordered feedback of blood coagulation, inflammation, and fibrinolysis. Monocytes, macrophages, fibroblasts, and mesothelial cells are involved in this process, and secreted signaling molecules, such as tumor necrosis factor alpha (TNF-α), interleukin-10 (IL-10), tissue plasminogen activator (tPA), and type 1 plasminogen activator inhibitor (PAI-1), play a key role in PA development. There have been many attempts to prevent PA formation by anti-PA drugs, barriers, and other therapeutic methods, but their effectiveness has not been widely accepted. Treatment by biomaterial-based barriers is believed to be the most promising method to prevent PA formation in recent years. In this review, the pathogenesis, treatment approaches, and animal models of PA are summarized and discussed to understand the challenges faced in the biomaterial-based anti-PA treatments.

Postoperative peritoneal adhesion: an update on physiopathology and novel traditional herbal and modern medical therapeutics

Postoperative peritoneal adhesion (PPA) is a serious clinical condition that affects the high percentage of patients after abdominal surgery. In this review, we have tried to focus on pathophysiology and different underlying signal pathways of adhesion formation based on recent progress in the molecular and cellular mechanisms. Also, the strategies, developed based on traditional herbal and modern medicines, to prevent and treat the PPA via regulation of the molecular mechanisms were investigated. The search engines such as Google Scholar, PubMed, Scopus, and Science Direct have been used to evaluate the current literature related to the pathogenesis of adhesion formation and novel products. Recently, different mechanisms have been defined for adhesion formation, mainly categorized in fibrin formation and adhesion fibroblast function, inflammation, and angiogenesis. Therefore, the suppression of these mechanisms via traditional and modern medicine has been suggested in several studies. While different strategies with encouraging findings have been developed, most of the studies showed contradictory results and were performed on animals. The herbal products have been introduced as safe and effective agent which can be considered in future preclinical and clinical studies. Although a wide range of therapeutics based on traditional and modern medicines have been suggested, there is no agreement in the efficacy of these methods to prevent or treat adhesion formation after surgeries. Further basic and clinical researches are still needed to propose the efficiency of recommended strategies for prevention and treatment of PPA.

Prevention of Intra-abdominal Adhesions by Electrical Stimulation

The study investigated the ability of transdermal electric stimulation to prevent the formation of intra-abdominal adhesions in the combination with Seprafilm^® (anti-adhesive agent). One hundred and twenty-eight (128) rabbits were subjected to a surgical procedure to simulate the adhesion processes. After the simulation, the animals were divided into 4 groups (32 animals each), depending on the application of the methods of prevention: (1) control group (no anti-adhesives or electro-stimulation) (CG); (2) comparison group (applications of Seprafilm^®) (SF); (3) comparison group 2 (transdermal electric stimulation of the abdominal muscles) TES; (4) group (transdermal electric stimulation + Seprafilm^®) (TES + SF). We observed that the application of the Seprafilm^® alone led to a significant decrease in the adhesive process compared to the control group (CG) (p < 0.01). The adhesion process in the group underwent transdermal electrical stimulation (TES) was significantly lower compared to the Seprafilm^® group (SF) (p ≤ 0.05). The results demonstrated a significant decrease in the adhesion processes in the SF + TES group on days 1, 3, 7 and 14 in comparison with the CG group (p = 0.001), SF group (p = 0.001) and TES group (p = 0.01) group of animals. This study showed the efficacy of transdermal electrical muscle stimulation for the prevention of intra-abdominal adhesions. Moreover, the combination of Seprafilm^® anti-adhesion agent and electrical muscle stimulation resulted in the complete absence of adhesions. Our findings indicate the potential of such strategy for further clinical application.

Polysaccharide-based films for the prevention of unwanted postoperative adhesions at biological interfaces

Postoperative adhesions protect, repair, and supply nutrients to injured tissues; however, such adhesions often remain permanent and complicate otherwise successful surgeries by tethering tissues together that are normally separated. An ideal adhesion barrier should not only effectively prevent unwanted adhesions but should be easy to use, however, those that are currently available have inconsistent efficacy and are difficult to handle or to apply. A robust hydrogel film composed of alginate and a photo-crosslinkable hyaluronic acid (HA) derivative (glycidyl methacrylate functionalized hyaluronic acid (GMHA)) represents a solution to this problem. A sacrificial porogen (urea) was used in the film manufacture process to impart macropores that yield films that are more malleable and tougher than equivalent films produced without the sacrificial porogen. The robust mechanical behavior of these templated alginate/GMHA films directly facilitated handling characteristics of the barrier film. In a rat peritoneal abrasion model for adhesion formation, the polysaccharide films successfully prevented adhesions with statistical equivalence to the leading anti-adhesion technology on the market, Seprafilm®. STATEMENT OF SIGNIFICANCE: Postoperative adhesions often remain permanent and complicate otherwise successful surgeries by tethering tissues together that are normally separated and pose potentially significant challenges to patients. Therefore, the generation of adhesion barriers that are easy to deploy during surgery and effectively prevent unwanted adhesions is a big challenge. In this study robust hydrogel films composed of alginate and a photo-crosslinkable hyaluronic acid (HA) derivative (glycidyl methacrylate functionalized HA, GMHA) were fabricated and investigated for their potential to act as a solution to this problem using a rat peritoneal abrasion model for adhesion formation. We observed the polysaccharide films successfully prevented adhesions with statistical equivalence to the leading anti-adhesion technology on the market, Seprafilm®, suggesting that such films represent a promising strategy for the prevention of postoperative adhesions.

The Prevention of Hepatectomy-Induced Adhesions by Bilayer Sponge Composed of Ultrapure Alginate

BACKGROUND

Adhesion formation is a critical issue in surgery, particularly in hepatectomy. The present study aimed to develop a bilayer adhesion barrier comprising alginate (Alg) of different molecular weight (Mw). It was expected that a slowly dissolving layer remains on the cut surface, functioning as a physical barrier, whereas a rapidly dissolving layer widely distributes in the peritoneal cavity to prevent de novo adhesions.

METHODS

Bilayer Alg sponges were fabricated using low Mw Alg for the upper layer and high Mw Alg for the bottom layer. The dissolution behavior of each layer was evaluated in vitro in peritoneum-like environments. We constructed a Pean crush hepatectomy-induced adhesion model in rats. The effects of the bilayer sponge on cut surface and de novo adhesions were separately evaluated in terms of their extent and grade.

RESULTS

The Alg sponge layer with low Mw dissolved faster than that with high Mw in vitro. One week after the hepatectomy, although no significant decrease in adhesion extent on the cut surface was observed in rats that received Seprafilm and Interceed, treatment with Alg bilayer sponge significantly decreased the adhesion extent to 38% of that without treatment. Moreover, a significant decrease in de novo adhesion extent was observed in the Alg bilayer sponge compared with the Interceed group.

CONCLUSIONS

The Alg bilayer sponge was effective for preventing both cut surface and de novo adhesions in the rat Pean crush hepatectomy model. The simple yet functional design of the Alg bilayer sponge can facilitate its use in future clinical practice.

PLGA/PLCA casting and PLGA/PDPA electrospinning bilayer film for prevention of postoperative adhesion

Postoperative adhesion is a common complication and preventing adhesions during or immediately after operation is particularly important. The application of solid barrier materials represents the most successful clinical strategy to prevent postoperative adhesion. However, a simple physical barrier effect might be insufficient in preventing adhesion satisfactorily. Multilayered structures can be designed with an outer layer as the barrier and an inner layer to respond to relative drug release. In this article, bilayer film composed of a PLGA/PLCA casting layer as barrier and PLGA/PDPA electrospinning layer to respond to the release of anti-fibrosis drug l-Phe was designed and synthesized. The adhesion prevention effect of the above PLGA/PLCA/PDPA bilayer film was examined and compared with single PLGA/PLCA casting film and single PLGA/PDPA electrospinning film by applying rabbit sidewall defect-cecum abrasion model. As demonstrated by histological observation and immunohistochemical analysis, the bilayer film was the most effective of the three films in postoperative adhesion prevention in terms of both physical barrier effect and anti-fibrosis effect of the PDPA macromolecular prodrug. Besides anti-fibrosis effect, PDPA could also suppress excess proliferation of vascular endothelial cells and microvessel caused by long-term stimulation of implantation materials to the surrounding tissues. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2030-2039, 2019.

Hydroxyapatite nanobelt/polylactic acid Janus membrane with osteoinduction/barrier dual functions for precise bone defect repair

Controllable osteoinduction maintained in the original defect area is the key to precise bone repair. To meet the requirement of precise bone regeneration, a hydroxyapatite (HAp) nanobelt/polylactic acid (PLA) (HAp/PLA) Janus membrane has been successfully prepared in this study by coating PLA on a paper-like HAp nanobelt film by a casting-pervaporation method. The Janus membrane possesses dual functions: excellent osteoinduction from the hydrophilic HAp nanobelt side and barrier function originating from the hydrophobic PLA film. The cell viability and osteogenic differentiation ability of human adipose-derived stem cells (hADSCs) on the Janus membrane were assessed. The in vitro experimental results prove that the HAp nanobelt side presents high cell viability and efficient osteoinduction without any growth factor and that the PLA side can prohibit cell attachment. The in vivo repair experiments on a rat mandible defect model prove that the PLA side can prevent postoperative adhesion between bone and adjacent soft tissues. Most importantly, the HAp side has a strong ability to promote defect repair and bone regeneration. Therefore, the HAp/PLA Janus membrane will have wide applications as a kind of tissue engineering material in precise bone repair because of its unique dual osteoinduction/barrier functions, biocompatibility, low cost, and its ability to be mass-produced.

STATE OF SIGNIFICANCE

Precise bone defect repair to keeping tissue integrity and original outline shape is a very important issue for tissue engineering. Here, we have designed and prepared a novel HAp/PLA Janus membrane using a casting-pervaporation method to form a layer of PLA film on paper-like HAp nanobelt film. HAp nanobelt side of the Janus membrane can successfully promote osteogenic differentiation. PLA side of the Janus membrane exhibits good properties as a barrier for preventing the adhesion of cells in vitro. Mandible repair experiments in vivo have shown that the HAp/PLA Janus membrane can promote rat mandible repair on the HAp side and can successfully prevent postoperative adhesion on the PLA side at the same time. Therefore, the HAp/PLA Janus membrane with its osteoinduction/barrier dual functions can be applied to repair bone defect precisely.

Effect of Emodin on Preventing Postoperative Intra-Abdominal Adhesion Formation

BACKGROUND

Postoperative intra-abdominal adhesions are a major complication after abdominal surgery. Although various methods have been used to prevent and treat adhesions, the effects have not been satisfactory. Emodin, a naturally occurring anthraquinone derivative and an active ingredient in traditional Chinese herbs, exhibits a variety of pharmacological effects. In our study, we demonstrated the effect of emodin treatment on preventing postoperative adhesion formation.

MATERIALS AND METHODS

A total of 48 rats were divided into six groups. Abdominal adhesions were created by abrasion of the cecum and its opposite abdominal wall. In the experimental groups, the rats were administered daily oral doses of emodin. On the seventh day after operation, the rats were euthanized, and blood and pathological specimens were collected. Abdominal adhesion formation was evaluated by necropsy, pathology, immunohistochemistry, Western blot, and enzyme-linked immunosorbent assay analyses.

RESULTS

Abdominal adhesions were markedly reduced by emodin treatment. Compared with the control group, collagen deposition was reduced and the peritoneal mesothelial completeness rate was higher in the emodin-treated groups. Emodin had anti-inflammatory effects, reduced oxidative stress, and promoted the movement of the intestinal tract (P < 0.05).

CONCLUSION

Emodin significantly reduced intra-abdominal adhesion formation in a rat model.

The potential efficacy of Survanta (r) and Seprafilm (r) on preventing intra-abdominal adhesions in rats

PURPOSE

To investigate the potential efficacy of beractant (Survanta(r)) and Seprafilm(r) on the prevention of postoperative adhesions.

METHODS

Forty Wistar-albino female rats were used. The rats were randomly allocated into four groups of 10 rats each as control group (CG), beractant group (BG), Seprafilm(r) group (SG), and combined group (COG). All rats underwent cecal abrasion via midline laparotomy. Before abdominal closure, isotonic saline, beractant, Seprafilm, and combined agents were intraperitoneally administered. Adhesions were classified macroscopically with Canbaz Scoring System on postoperative day 10. Ceacum was resected for histopathological assessment.

RESULTS

Macroscopic adhesion scores were significantly lower in BG, SG, and COG than CG (p<0.05); (45%, 15%, 25%, and 15%; respectively). Histopathological assessment revealed a reduced inflammation and fibrosis score in the study groups than CG (p<0.05). In BG, adhesion development, inflammation and fibrosis scores were lower than SG; however, it was not statistically significant.

CONCLUSIONS

Intra-abdominal application of beractant is significantly effective for the prevention of adhesion formation with no adverse effect by covering the whole peritoneal mesothelium with excellent gliding properties in a rat model. The combination of both agents is also effective in reducing adhesion formation, however, not superior to single beractant application.

A pectin-honey hydrogel prevents postoperative intraperitoneal adhesions in a rat model

Background

Adhesions are a common postoperative surgical complication. Liquid honey has been used intraperitoneally to reduce the incidence of these adhesions. However, solid barriers are considered more effective than liquids in decreasing postoperative intra-abdominal adhesion formation; therefore, a new pectin-honey hydrogel (PHH) was produced and its effectiveness was evaluated in a rat cecal abrasion model.

Standardized cecal/peritoneal abrasion was performed through laparotomy in 48 adult Sprague-Dawley rats to induce peritoneal adhesion formation. Rats were randomly assigned to a control (C) and treatment (T) group. In group T, PHHs were placed between the injured peritoneum and cecum. Animals were euthanized on day 15 after surgery. Adhesions were evaluated macroscopically and adhesion scores were recorded and compared between the two groups. Inflammation, fibrosis, and neovascularization were histologically graded and compared between the groups.

Results

In group C, 17 of 24 (70.8%) animals developed adhesions between the cecum and peritoneum, while in group T only 5 of 24 (20.8%) did (p = 0.0012). In group C, one rat had an adhesion score of 3, sixteen had scores of 2, and seven rats had scores of 0. In group T, four rats had adhesion scores of 2, one rat had an adhesion score of 1 and nineteen have score 0 (p = 0.0003). Significantly lower grades of inflammation, fibrosis, and neovascularization were seen in group T (p = 0.006, p = 0.001, p = 0.002, respectively).

Conclusion

PHH is a novel absorbable barrier that is effective in preventing intra-abdominal adhesions in a cecal abrasion model in rats.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-0965-z) contains supplementary material, which is available to authorized users.

Evaluation of surgical anti-adhesion products to reduce postsurgical intra-abdominal adhesion formation in a rat model

Background

Adhesions frequently occur after abdominal surgery. Many anti-adhesion products have been used in clinic. However, the evidences are short for surgeons to reasonably choose the suitable anti-adhesion produces in clinical practice. This study provided such evidence by comparing the efficiency of five products to prevent abdominal adhesion formation in a rat model.

Methods

Fifty-six Sprague-Dawley rats were randomly divided into seven groups: sham-operation group, adhesion group, and five product groups (n = 8). The abdomens of rats were opened. The injuries were created on abdominal wall and cecum in the adhesion and product groups. The wounds on abdominal wall and cecum of rats in the adhesion group were not treated before the abdomens were closed. The wounds on abdominal wall and cecum of rats in the product groups were covered with anti-adhesion product: polylactic acid (PLA) film, Seprafilm^®, medical polyethylene glycol berberine liquid (PEG), medical sodium hyaluronate gel (HA), or medical chitosan (Chitosan). Fourteen days after surgery, the adhesions were evaluated by incidence, severity, adhesion area on abdominal wall and adhesion breaking strength.

Results

The application of PLA film and Seprafilm^® significantly reduced the incidence, severity, adhesion area and breaking strength of cecum-abdomen adhesion (P<0.05). HA, PEG and Chitosan failed to significantly reduce the cecum-abdomen adhesion (P>0.05). The statistical significances in the incidence and severity of abdomen-adipose adhesion between adhesion group and the product groups were not achieved. However, Seprafilm^® was more effective to reduce abdomen-adipose adhesion than PLA film. Furthermore, it was found that the products tested in this study did not effectively reduce cecum-adipose adhesion. The application of PEG could result in abdomen-small intestine adhesion.

Conclusion

Based on the results of this study, the preference order of anti-adhesion products used to reduce postsurgical intra-abdominal adhesion formation is Seprafilm > PLA >> HA > Chitosan > PEG.

Sepramesh and postoperative peritoneal adhesions in a rat model

PURPOSE

The present study aimed to investigate the safety and the anti-postoperative peritoneal adhesion (PPA) characteristics of Sepramesh^® (Davol), a composite mesh made of polypropylene covered with Seprafilm, when intraperitoneally placed in a rat model.

METHODS

Twenty male rats were randomized into a control group and a Sepramesh group. They underwent a primary surgical procedure aiming to induce a peritoneal injury in order to induce PPAs. In the Sepramesh group, the burnt peritoneum was covered with a 2-cm diameter disc of Sepramesh prosthesis. The mesh was fixed to the parietal peritoneum with four 3-0 absorbable stitches. PPAs were assessed during a second laparotomy 10 days later using quantitative and qualitative scoring systems.

RESULTS

There was no difference in terms of mean number of PPAs between both groups. All the rats from the control group developed PPAs. In the Sepramesh group, no adhesions were observed at the site of the injured peritoneum that had been covered with the Sepramesh prosthesis, but PPAs occurred at the extremities of the mesh, where there was close contact between polypropylene and viscera, or where the fixation sutures were placed. The severity and the type of adhesions were significantly higher in the control group.

CONCLUSIONS

This study demonstrated that for the Sepramesh prostheses, the Seprafilm layer might be effective in PPA prevention, but damage caused by the section and fixation of Sepramesh should be limited in order to limit PPAs.

Comparison of the effects of Mitomycin-C and sodium hyaluronate/carboxymethylcellulose [NH/CMC] (Seprafilm) on abdominal adhesions

Introduction

Intra-abdominal adhesions (IA) may occur after abdominal surgery and also may lead to complications such as infertility, intestinal obstruction and chronic pain. The aim of this study was to compare the effects of Mitomycin-C (MM-C) and sodium hyaluronate/carboxymethylcellulose [NH/CMC] on abdominal adhesions in a cecal abrasion model and to investigate the toxicity of MM-C on complete blood count (CBC) and bone marrow analyses.

Methods

The study comprised forty rats in four groups (Control, Sham, Cecal abrasion + MM-C, and Cecal abrasion + NH/CMC). On postoperative day 21, all rats except for the control (CBC + femur resection) group, were sacrificed. Macroscopical and histopathological evaluations of abdominal adhesions were performed. In order to elucidate the side effects of MM-C; CBC analyses and femur resections were performed to examine bone marrow cellularity.

Results

CBC analyses and bone marrow cellularity assessment revealed no statistically significant differences between MM-C, NH/CMC and control groups. No significant differences in inflammation scores were observed between the groups. The MM-C group had significantly lower fibrosis scores compared to the NH/CMC and sham groups. Although the adhesion scores were lower in the MM-C group, the differences were not statistically significant.

Conclusion

Despite its potential for systemic toxicity, MM-C may show some anti-fibrosis and anti-adhesive effects. MM-C is a promising agent for the prevention of IAs, and as such, further trials are warranted to study efficacy.

Hemostatic sponge effect on adhesion prevention in a porcine model

BACKGROUND

In this work, we aimed to assess the preventive effect of an absorbable hemostatic collagen sponge (HCS) on the reduction of postsurgical gynecological adhesions in a porcine model.

MATERIALS AND METHODS

Forty female pigs were subjected to a right uterine horn myotomy and left uterine horn deserosation. They were randomly divided into two groups, HCS application and control, which were rearranged into laparotomy and laparoscopy groups. Resulting adhesions were macroscopically and microscopically semiquantitatively analyzed after a 5 mo follow-up.

RESULTS

The incidence of adhesion-free animals did not significantly differ between groups, although it increased when the HCS was placed in both laparotomy (from 10%-12.5%) and laparoscopy groups (from 20%-50%). On the contrary, a significant reduction was observed in adhesion severity when the HCS was applied in the laparotomy groups (P < 0.01). Regarding microscopic study, hemostatic sponge application significantly reduced the inflammation score in the laparoscopic approach (P < 0.01). Fibrosis, unlike inflammation, differs between both approaches. In the laparoscopic group, fibrosis was reduced with application of the HCS, whereas in the laparotomy group greater fibrosis was observed within the HCS group.

CONCLUSIONS

HCS has shown to be safe for gynecological use. Although number and extent of adhesions did not decrease with HCS, inflammation and adhesions' severity were reduced in the laparoscopic and laparotomy approaches, respectively.

New hepatectomy-induced postoperative adhesion model in rats, and evaluation of the efficacy of anti-adhesion materials

PURPOSE

Repeated hepatic resections are not uncommon during the surgical management of liver tumors. Postoperative adhesions induced by hepatectomies can have a significant negative impact on subsequent surgeries. We recently developed a new hepatectomy-induced postoperative adhesion animal model to evaluate the anti-adhesion efficacy of commercially available sheet materials (Seprafilm(®) and Interceed(®)) and the recently reported hyaluronan-based in situ cross-linkable hydrogels.

METHODS

The median lobe (ML) and the left lateral lobe (LLL) of the liver (approximately 70 % of the total liver) of 43 male Sprague-Dawley rats were resected based on the classical procedure; anti-adhesion materials were then applied. A relaparotomy was performed 1 week later to evaluate the adhesions and histopathological findings.

RESULTS

The rats without the application of anti-adhesion materials (n = 14) showed the most severe adhesions (grade 3) between the cut surface of the liver and the small bowel or omentum. All the barrier materials produced slight anti-adhesion effects. Adhesions between the liver surface and the diaphragm and adhesions around the hepatic hilum were less severe, but were not remarkably reduced, by the anti-adhesion materials.

CONCLUSION

We successfully established a new hepatectomy-induced animal adhesion model, which may be useful for the development of new anti-adhesion materials.

Seprafilm® adhesion barrier: (1) a review of preclinical, animal, and human investigational studies

The aim of this study was to provide a single site resource for investigators, clinicians, and others seeking preclinical, animal, and human investigational studies concerning the postsurgical, anti-adhesion barrier Seprafilm™ (Genzyme Corporation, Cambridge, MA). All published preclinical, animal, human extra-abdominal research as of July 2011 have been summarized and included in this document. Searches of Medline and EMBASE Drugs and Pharmaceuticals databases were conducted for original preclinical, animal, and human extra-abdominal studies involving Seprafilm. Preclinical, animal, and extra-abdominal human investigational studies are the study selection for this manuscript. Intraabdominal use is discussed in the accompanying manuscript. Data extraction includes systematic manuscript review. Summary of preclinical, animal, and extra-abdominal human investigational use of Seprafilm by surgical discipline were gathered for data synthesis. The clinical use of Seprafilm, which was approved by the FDA for intra-abdominal procedures, is supported by preclinical and animal studies relating to general surgical and obstetrical/gynecological applications. Findings from preclinical, animal, and human investigational studies at other sites throughout the body raises the potential for additional human clinical trials to assess efficacy and safety following surgical procedures at non-abdominal locations.

Preventing postoperative abdominal adhesions in a rat model with PEG-PCL-PEG hydrogel

Background

Poly (ethylene glycol)-poly (ɛ-caprolactone)-poly (ethylene glycol) (PEG-PCL-PEG, PECE) hydrogel has been demonstrated to be biocompatible and thermosensitive. In this study, its potential efficacy and mechanisms of preventing postsurgical abdominal adhesions were investigated.

Results

PECE hydrogel was transformed into gel state from sol state in less than 20 seconds at 37°C. None of the animals treated with the hydrogel (n = 15) developed adhesions. In contrast, all untreated animals (n = 15) had adhesions that could only be separated by sharp dissection (P < 0.001). The hydrogel adhered to the peritoneal wounds, gradually disappeared from the wounds within 7 days, and transformed into viscous fluid, being completely absorbed within 12 days. The parietal and visceral peritoneum were remesothelialized in about 5 and 9 days, respectively. The hydrogel prevented the formation of fibrinous adhesion and the invasion of fibroblasts. Also, along with the hydrogel degradation, a temporary inflammatory cell barrier was formed which could effectively delay the invasion of fibroblasts during the critical period of mesothelial regeneration.

Conclusion

The results suggested that PECE hydrogel could effectively prevent postsurgical intra-abdominal adhesions, which possibly result from the prevention of the fibrinous adhesion formation and the fibroblast invasion, the promotion of the remesothelialization, and the hydroflotation effect.

Function of poly (lactic-co-glycolic acid) nanofiber in reduction of adhesion bands

BACKGROUND

In this study, we investigated the anti-adhesive and anti-inflammatory effects of electrospun nanofibrous membranes made of polycaprolactone (PCL), poly-L-lactide (PLLA), poly (lactic-co-glycolic acid) (PLGA), and polyethersulfune (PES) in comparison with the oxidized-regenerated cellulose (Interceed).

MATERIALS AND METHODS

Using an adhesion induction model in mice, the membranes were sutured between the abdominal wall and peritoneum after surgical operation to reveal the best membrane for prevention of postoperative adhesion bands using two scoring adhesion systems.

RESULTS

Compared with other membranes, PLGA, PCL, and Interceed membranes showed a greater ability to reduce adhesions. The lowest level of inflammation in adhesive tissues as well as cell attachment in vitro was detected for PLGA nanofibrous membranes.

CONCLUSIONS

These results suggested that in considering the FDA approved polymers, nanofibrous membranes prepared from PLGA exhibited the highest efficacy for the prevention of postoperative adhesion bands and hold promising potential for application as a new anti-adhesive agent.

Pathophysiology and prevention of postoperative peritoneal adhesions

Peritoneal adhesions represent an important clinical challenge in gastrointestinal surgery. Peritoneal adhesions are a consequence of peritoneal irritation by infection or surgical trauma, and may be considered as the pathological part of healing following any peritoneal injury, particularly due to abdominal surgery. The balance between fibrin deposition and degradation is critical in determining normal peritoneal healing or adhesion formation. Postoperative peritoneal adhesions are a major cause of morbidity resulting in multiple complications, many of which may manifest several years after the initial surgical procedure. In addition to acute small bowel obstruction, peritoneal adhesions may cause pelvic or abdominal pain, and infertility. In this paper, the authors reviewed the epidemiology, pathogenesis and various prevention strategies of adhesion formation, using Medline and PubMed search. Several preventive agents against postoperative peritoneal adhesions have been investigated. Their role aims in activating fibrinolysis, hampering coagulation, diminishing the inflammatory response, inhibiting collagen synthesis or creating a barrier between adjacent wound surfaces. Their results are encouraging but most of them are contradictory and achieved mostly in animal model. Until additional findings from future clinical researches, only a meticulous surgery can be recommended to reduce unnecessary morbidity and mortality rates from these untoward effects of surgery. In the current state of knowledge, pre-clinical or clinical studies are still necessary to evaluate the effectiveness of the several proposed prevention strategies of postoperative peritoneal adhesions.

The effect of antivascular endothelial growth factor on the development of adhesion formation in laparotomized rats: experimental study

Aims. This study determined the effects of a single dose of bevacizumab, an antiangiogenic recombinant monoclonal antibody that specifically targets vascular endothelial growth factor (VEGF), on adhesion formation in the rat cecal abrasion model. Methodology. Thirty female Wistar albino rats (200-224 g) were divided into three groups. All rats underwent laparotomy at which time cecal wall abrasion and abdominal wall injuries were induced. Group I (control) underwent only the abrasion procedure; Groups II and III received saline or bevacizumab intraperitoneally, respectively, following the abrasion. The rats were killed on postoperative day 7, and the severity of adhesions was evaluated, together with histopathological fibrosis parameters and immunohistochemical staining to identify the VEGF receptor. Results. The mean adhesion severity score in Groups I-III was 2.5 ± 0.52, 2.4 ± 0.69, and 0.7 ± 0.82, respectively; the score in Group III was significantly lower than that in Groups I (P < 0.001) and II (P < 0.001). In the histopathological evaluation, the mean fibrosis score in Group III was significantly lower that the scores in Groups I (P < 0.001) and II (P < 0.001). VEGF staining of the adhesion areas in Group III was significantly lower than that in Groups I (P < 0.001) and II (P < 0.001). Conclusion. Bevacizumab decreases adhesion formation following laparotomy in rats by blocking VEGF receptor occupancy.

Prevention of post-surgical abdominal adhesions by a novel biodegradable thermosensitive PECE hydrogel

Background

Post-operative peritoneal adhesions are common and serious complications for modern medicine. We aim to prevent post-surgical adhesions using biodegradable and thermosensitive poly(ethylene glycol)-poly(ε-caprolactone)-poly(ethylene glycol) (PEG-PCL-PEG, PECE) hydrogel. In this work, we investigated the effect of PECE hydrogel on preventing post-surgical abdominal adhesions in mouse and rat models.

Results

The PECE hydrogel in sol state could be transformed into gel in less than 20 s at 37°C. In addition, the PECE hydrogel could be easily adhered to the damaged peritoneal surfaces, and be gradually degraded and absorbed by the body within 14 days along with the healing of peritoneal wounds. A notable efficacy of the PECE hydrogel in preventing peritoneal adhesions was demonstrated in the animal models. In contrast, all untreated animals developed adhesions requiring sharp dissection. Furthermore, no significant histopathological changes were observed in main organs of the hydrogel-treated animals.

Conclusion

Our results suggested that the thermosensitive PECE hydrogel was an effective, safe, and convenient agent on preventing post-surgical intro-abdominal adhesions.

Effect of bovine amniotic fluid on intra-abdominal adhesion in male rats

BACKGROUND

A wide variety of treatments have been proposed in order to deal with prevention of postoperative adhesions formation, but, no definitive results have been achieved. In the present study, bovine amniotic fluid (BAF) has been investigated as a possible option.

MATERIALS AND METHODS

84 male Wistar rats were undergone a laparotomy. After 2 weeks, adhesions were scaled grossly. Bovine amniotic fluid (in whole combination, without cells or without cells and proteins) extracted from cows carried either male or female calves was then applied to treated groups 2 weeks later during the second laparotomy. Adhesions were rescored 2 weeks later during a third laparotomy.

RESULTS AND CONCLUSION

A significant reduction (P<0.05) in adhesions formation was observed only in rats treated with male bovine amniotic fluid without cells and proteins. Therefore, BAF could be used in treatment of adhesion formation because it is inexpensive, readily available, and has minimal side effects.

A membrane slurry reduces postoperative adhesions in rat models of abdominal surgery

BACKGROUND

Sodium hyaluronate and carboxymethylcellulose (HA-CMC) membrane is an effective barrier material for limiting postoperative adhesions, but can be difficult to apply in certain situations due to its physical properties. We tested whether HA-CMC membrane hydrated in saline (slurry) is an effective alternative to HA-CMC membrane for preventing surgical adhesions in rat models of abdominal surgery.

MATERIALS AND METHODS

All studies were performed in rat cecal abrasion or sidewall defect models of adhesion formation. Adhesions were examined 7 d after surgery. In separate studies, the effects of variations in slurry composition, volume, and site of application on anti-adhesive properties were studied and compared with untreated controls. Finally, the effectiveness of HA-CMC membrane slurry for preventing adhesions was compared with that of conventional HA-CMC membrane.

RESULTS

Application of HA-CMC membrane slurry to traumatized tissue resulted in a significant reduction in the incidence of adhesions compared with untreated controls in both rat surgery models. Slurry was equally effective when applied in low and high film-to-volume formulations, but had minimal effect when applied in a small volume or at a location distal to the injury. Comparison of HA-CMC membrane slurry and conventional HA-CMC membrane indicated similar efficacy for reducing postoperative adhesions.

CONCLUSIONS

In rat models of abdominal surgery, HA-CMC membrane slurry reduced postoperative adhesion formation and may be an effective alternative for HA-CMC membrane in situations where its use is limited by its physical properties.

Reduction of postsurgical adhesions in a rat model: a comparative study

BACKGROUND

Adhesion formation after peritoneal surgery is a major cause of postoperative bowel obstruction, infertility, and chronic pelvic pain. In this study, we compared the possible individual effects of phosphatidylcholine (PC), Seprafilm II, and tissue plasminogen activator (t-PA) and the combined effects of phosphatidylcholine and t-PA on postoperative adhesion formation in a rat surgical model.

MATERIALS AND METHODS

A total of 50 Wistar male rats underwent median laparotomy and standardized abrasion of the visceral and parietal peritoneum. phosphatidylcholine, Seprafilm II, and t-PA alone and phosphatidylcholine and t-PA in combination were applied intraperitoneally at the end of the surgical procedure. Seven days after surgery, a relaparotomy was performed for adhesion grading and histopathological examination.

RESULTS

A comparison of adhesion stages demonstrated a significant difference between the control group and the study groups (p<0.001). The adhesion grade of the combined treatment group was statistically different from that of the other groups (p<0.05). In the t-PA group and the combined group, six and two rats, respectively, developed hematomas locally on the cecum.

CONCLUSIONS

PC, t-PA, and Seprafilm II used individually reduced the adhesion grade. The t-PA and phosphatidylcholine combination was most effective in reducing adhesion formation. On the other hand, usage of t-PA alone or in combination may increase risk of bleeding. More detailed studies are needed, and future studies on the efficacy of a material for decreasing adhesion formation should include a comparison of several control materials in the same model.