Systematic review of experimental studies on intestinal anastomosis

The Effectiveness of Adipose Tissue-Derived Mesenchymal Stem Cells Mixed with Platelet-Rich Plasma in the Healing of Inflammatory Bowel Anastomoses: A Pre-Clinical Study in Rats

Introduction: Multiple factors have been linked with increased risk of anastomotic leak in bowel surgery, including infections, inflammatory bowel disease, patient comorbidities and poor surgical technique. The aim of this study was to investigate the positive effect, if any, of adipose derived mesenchymal stem cells (MSCs) mixed with platelet-rich plasma (PRP) in the healing of bowel anastomoses, in an inflammatory environment after establishment of experimental colitis. Materials and Methods: Thirty-five male Wistar rats were divided into five groups of seven animals: normal controls, colitis controls, PRP, MSCs, and PRP+MSCs. All groups underwent laparotomy, one-cm segmental colectomy and anastomosis in situ. In the colitis group, colectomy was performed at the affected area. Colitis was previously established by transrectal administration of 2,4,6-trinitrobenzene sulfonic acid (TNBS) except for the normal controls. Post-mortem histopathological, tissue hydroxyproline and anastomotic bursting pressure (ABP) assessments were performed. The Mann-Whitney U test was used to assess statistical significance differences between groups. Results: No perioperative mortality was noted. Tissue hydroxyproline and ABP were significantly increased in the group of PRP+MSCs compared to colitis controls (p = 0.0151 and p = 0.0104, respectively). Inflammatory cell infiltration was lower and fibroblast activity higher in PRP+MSCs group, but not statistically significant (p > 0.05). Neoangiogenesis (p = 0.0073) and anastomotic area epithelialization (p = 0.0182) were significantly higher in PRP + MSCs group compared to colitis controls. Discussion: The synergistic effect of the PRP and MSCs is apparently responsible for the improved healing markers in bowel anastomoses even on inflammatory bowel. This gives hope for primary anastomoses and stoma saving in many emergency and/or elective circumstances, especially in immunocompromised or malnourished patients, even in cases with inflammation or peritonitis. Clinical studies should follow in order to support the clinical application of PRP+MSCs in gastrointestinal anastomoses.

Reinforcement of colon anastomosis healing with leukocyte platelet-rich fibrin in rabbit model

AIM

This study investigated the regenerative efficacy of leukocyte platelet-rich fibrin (L-PRF) on colon anastomotic healing in rabbits.

MAIN METHODS

Thirty-six healthy male white New Zealand rabbits were subjected to complete transactions of the ascending colon. The rabbits were equally divided into two groups: the control group, where the transected colon ends were anastomosed by a simple interrupted suture pattern, and the L-PRF-treated group, in which L-PRF was wrapped entirely around the anastomotic line. The postoperative acute pain scale was assessed using the Bristol Rabbit Pain Scale before surgery and at each four-hour interval post-operatively. After euthanizing the rabbits, the adhesion degree score, anastomotic bursting pressure, and stenosis degree of the anastomotic colon were assessed, and histopathological examination at the 7th, 14th, and 28th days postoperatively.

KEY FINDINGS

Rabbits in both groups showed a significant increase in pain scores compared to baseline. Postoperatively, the L-PRF group exhibited significantly lower pain scores, adhesion scores, and stenosis degrees than the control group. However, the anastomotic bursting pressure was significantly higher in the L-PRF group. Re-epithelialization, polymorphonuclear neutrophil infiltration, granulation tissue formation, and collagen deposition scores were improved considerably in the L-PRF group compared to the control group. Immunostaining of growth factor expression was significantly lower in the control than in the L-PRF group.

SIGNIFICANCE

The L-PRF can augment collagen deposition, re-epithelialize the mucosa, promote angiogenesis, reduce adhesions, and diminish the stenosis degree scores. Therefore, it can be considered a promising aid in healing bowel anastomoses.

The 3Ranker: An AI-based Algorithm for Finding Non-animal Alternative Methods

The search for existing non-animal alternative methods for use in experiments is currently challenging because of the lack of both comprehensive structured databases and balanced keyword-based search strategies to mine unstructured textual databases. In this paper we describe 3Ranker, which is a fast, keyword-independent algorithm for finding non-animal alternative methods for use in biomedical research. The 3Ranker algorithm was created by using a machine learning approach, consisting of a Random Forest model built on a dataset of 35 million abstracts and constructed with weak supervision, followed by iterative model improvement with expert curated data. We found a satisfactory trade-off between sensitivity and specificity, with Area Under the Curve (AUC) values ranging from 0.85-0.95. Trials showed that the AI-based classifier was able to identify articles that describe potential alternatives to animal use, among the thousands of articles returned by generic PubMed queries on dermatitis and Parkinson's disease. Application of the classification models on time series data showed the earlier implementation and acceptance of Three Rs principles in the area of cosmetics and skin research, as compared to the area of neurodegenerative disease research. The 3Ranker algorithm is freely available at www.open3r.org; the future goal is to expand this framework to cover multiple research domains and to enable its broad use by researchers, policymakers, funders and ethical review boards, in order to promote the replacement of animal use in research wherever possible.

Evaluating and developing sealants for the prevention of pulmonary air leakage: A systematic review of animal models

Sealants may provide a solution for pulmonary air leakage (PAL), but their clinical application is debatable. For sealant comparison, standardized animal models are lacking. This systematic review aims to assess methodology and quality of animal models for PAL and sealant evaluation. All animal models investigating lung sealing devices (e.g., staplers, glues, energy devices) to prevent or treat PAL were retrieved systematically from Embase, Pubmed and Web of science. Methodological study characteristics, risk of bias, reporting quality and publication bias were assessed. A total of 71 studies were included (N  =  75 experiments, N  =  1659 animals). Six different species and 18 strains were described; 92% of experiments used healthy animals, disease models were used in only six studies. Lesions to produce PAL were heterogenous, and only 11 studies used a previously reported technique, encompassing N  =  5 unique lesions. Clinically relevant outcomes were used in the minority of studies (imaging 16%, air leak 10.7%, air leak duration 4%). Reporting quality was poor, but revealed an upward trend per decade. Overall, high risk of bias was present, and only 18.7% used a negative control group. All but one study without control groups claimed positive outcomes (95.8%), in contrast to 84.3% using positive or negative control groups, which also concluded equivocal, adverse or inconclusive outcomes. In conclusion, animal studies evaluating sealants for prevention of PAL are heterogenous and of poor reporting quality. Using negative control groups, disease models and quantifiable outcomes seem important to increase validity and relevance. Further research is needed to reach consensus for model development and standardization.

The comparison of anastomosis strength and leakage between double-layer full-thickness and single-layer extramucosal intestine anastomosis

Various intestine anastomosis techniques have been studied and used, but which is best is still debated. In our center, double-layer full-thickness intestine anastomosis was still considered as standard. However, a single-layer extramucosal intestine anastomosis has shown favorable results. This study created an anastomotic model to compare the anastomosis strength and leakage between double-layer full-thickness and single-layer extramucosal intestine anastomosis.

METHODS

This experimental study was performed in 20 randomized healthy male pigs, to be included either in Group A (Single-layer extramucosal intestine anastomosis) or Group B (Double-layer full-thickness intestine anastomosis). Enterotomy followed by an end-to-end anastomosis suture was performed in the jejunum. Fourteen days after the operation, any anastomosis leakage and its location was documented. The anastomosis strength was evaluated using manometry. Data were compared between groups using the Mann-Whitney U and Fischer Exact test, considering a significance level of P<0.05.

RESULTS

The overall mean intraluminal anastomotic bursting pressure was 4,257±1,185. Group A had a higher intraluminal anastomotic bursting pressure but was not statistically significant compared to group B (4.726±0.952 vs. 3.787±1.252 kilopascals, P=0.063). One leakage (5%, antimesenteric area) occurred in Group A and three leakages (15%, antimesenteric and mesenteric area) occurred in Group B. However, statistical analysis with Fischer exact showed no significant difference of leakage rate between those groups (P=0.291).

CONCLUSIONS

The anastomosis strength and leakage did not differ significantly between the single-layer extramucosal intestine anastomosis group and the double-layer full-thickness anastomosis group. However, the location of leakage was most common in the antimesenteric area in the double-layer full-thickness anastomosis group.

Enhancing intestinal anastomotic healing using butyrate: Systematic review and meta-analysis of experimental animal studies

BACKGROUND

Despite advancements in surgical technique and perioperative care, intestinal anastomoses still have a 10-15 per cent risk of leakage, which results in considerable morbidity and/or mortality. Recent animal studies have suggested that administration of butyrate to the anastomotic site results in enhanced anastomotic strength, which may prevent leakage. This systematic review and meta-analysis summarises current evidence concerning the effect of butyrate administration on anastomotic healing and will form a scientific basis for the development of new research into this subject.

METHODS

Animal studies on the effect of butyrate-based interventions in models of intestinal anastomotic healing were systematically retrieved from online databases. Bibliographical data, study characteristics and outcome data were extracted, and internal validity of the studies was assessed. Outcomes studied through meta-analysis concerned: anastomotic strength, anastomotic leakage, collagen metabolism and general histologic parameters of wound healing.

RESULTS

A comprehensive search and selection identified 19 relevant studies containing 41 individual comparisons. Design and conduct of most experiments were poorly reported resulting in an unclear risk of bias. Meta-analyses showed that butyrate administration significantly increases anastomotic strength (SMD 1.24, 0.88 to 1.61), collagen synthesis (SMD 1.44, 0.72 to 2.15) and collagen maturation, making anastomoses less prone to leakage in the early postoperative period (OR 0.37, 0.15 to 0.93).

CONCLUSION

This systematic review and meta-analysis shows that there is potential ground to investigate the use of butyrate in clinical trials to prevent anastomotic leakage in intestinal surgery. However, more research is necessary to define the best application form, dosage and administration route.

Fusobacterium nucleatum induces colon anastomosis leak by activating epithelial cells to express MMP9

Background

Despite advances in anastomotic techniques and perioperative care, the incidence of anastomotic leak (AL) has not substantially decreased over time. Although it is known that AL etiology is multifactorial and the mechanisms involved remain unclear, there is accumulating evidence pointing at AL related to gut microbiota.

Method

We firstly performed a clinical study to analyze the gut microbiota between colorectal cancer patients who developed AL and those who did not (nAL) using 16S-rRNA sequencing and quantitative real-time PCR to identify AL risk bacterial taxa. Then we built a rat anastomosis model and performed a bacteria transplantation to ensure the cause-effect relationship. The anastomotic healing score was used to evaluate the healing of anastomosis. In addition, we assessed the adhesion ability of bacteria by staining with fluorescein isothiocyanate and attachment assay. The expression of matrix metalloproteinase 9 (MMP9) was detected by western blot, and the activity was detected by gelatin zymography.

Results

We found that the abundance and positive rate of Fusobacterium nucleatum (Fn) were higher in the AL patients. Exposure of the rat's colon anastomosis to Fn contributes to the loss of submucosa collagen I and III, leading to AL's pathogenesis. Fn can attach to the gut epithelial cells and stimulate intestinal MMP9 expression in vitro and in vivo. We further confirmed that these effects of Fn depended on the E-cadherin/β-catenin signaling pathway.

Conclusion

This work demonstrates that Fn attaches and then stimulates the expression of epithelial cells MMP9 by the E-cadherin/β-catenin signaling pathway. These effects contribute to collagen break down in the intestinal tissue, finally leading to AL.

New understanding of gut microbiota and colorectal anastomosis leak: A collaborative review of the current concepts

Anastomotic leak (AL) is a life-threatening postoperative complication following colorectal surgery, which has not decreased over time. Until now, no specific risk factors or surgical technique could be targeted to improve anastomotic healing. In the past decade, gut microbiota dysbiosis has been recognized to contribute to AL, but the exact effects are still vague. In this context, interpretation of the mechanisms underlying how the gut microbiota contributes to AL is significant for improving patients' outcomes. This review concentrates on novel findings to explain how the gut microbiota of patients with AL are altered, how the AL-specific pathogen colonizes and is enriched on the anastomosis site, and how these pathogens conduct their tissue breakdown effects. We build up a framework between the gut microbiota and AL on three levels. Firstly, factors that shape the gut microbiota profiles in patients who developed AL after colorectal surgery include preoperative intervention and surgical factors. Secondly, AL-specific pathogenic or collagenase bacteria adhere to the intestinal mucosa and defend against host clearance, including the interaction between bacterial adhesion and host extracellular matrix (ECM), the biofilm formation, and the weakened host commercial bacterial resistance. Thirdly, we interpret the potential mechanisms of pathogen-induced poor anastomotic healing.

Preparation of healing promotive alanyl-glutamine-poly(p-dioxanone) electrospun membrane integrated with gentamycin and its application for intestinal anastomosis in rats

Anastomosis surgery at the intestinal site is performed on millions of individuals every year. However, several persistent complications, such as anastomotic leakage, abnormal adhesion, and anastomotic stenosis, have been observed after the surgery. For promoting anastomotic healing and to overcome the challenges mentioned above, re-epithelialization at anastomotic sites is crucial. In this study, an epithelialization-promoting macromolecular prodrug Ala-Gln-PPDO was prepared and processed into fibrous membranes by electrospinning. Ala-Gln and gentamicin were sustainably released from the electrospun membranes with degradation of these membranes to promote the proliferation of rat intestinal epithelial cells and suppress the proliferation of Staphylococcus aureus and Escherichia coli. The comprehensive repair effects of Ala-Gln-PPDO membranes have been evaluated in rat models of intestinal anastomosis in this study. Application of Ala-Gln-PPDO membranes, especially the gentamicin-incorporated Ala-Gln-PPDO ones, could prevent adhesion between the injured intestine and surrounding intestinal tissues. In addition, they did not affect the healing strength of anastomotic stoma negatively and could promote re-epithelialization at the anastomotic sites. Furthermore, the gentamicin-incorporated Ala-Gln-PPDO membranes could relieve stenosis at anastomotic sites. The gentamicin-incorporated Ala-Gln-PPDO electrospun membrane is a promising, comprehensive implantable material for promoting healing after gastrointestinal anastomosis owing to its effects involving the promotion of re-epithelialization, prevention of adhesion, and relieving of anastomotic stenosis.

Intestinal Anastomotic Healing: What do We Know About Processes Behind Anastomotic Complications

Colorectal surgery has developed rapidly in the recent decades. Nevertheless, colorectal anastomotic leakage continues to appear postoperatively in unpleasant rates and leads to life-threatening conditions. The development of valid complication-preventing methods is inefficient in many aspects as we are still lacking knowledge about the basics of the process of anastomotic wound healing in the gastrointestinal tract. Without the proper understanding of the crucial mechanisms, research for prevention of anastomotic leakage is predestined to be unsuccessful. This review article discusses known pathophysiological mechanisms together with the most lately found processes to be further studied. The aim of the article is to facilitate the orientation in the topic, support the better understanding of known mechanisms and suggest promising possibilities and directions for further research.

Novel Elastic Threads for Intestinal Anastomoses: Feasibility and Mechanical Evaluation in a Porcine and Rabbit Model

Gastrointestinal anastomoses are an important source of postoperative complications. In particular, the ideal suturing material is still the subject of investigation. Therefore, this study aimed to evaluate a newly developed suturing material with elastic properties made from thermoplastic polyurethane (TPU); Polyvinylidene fluoride (PVDF) and TPU were tested in two different textures (round and a modified, “snowflake” structure) in 32 minipigs, with two anastomoses of the small intestine sutured 2 m apart. After 90 days, the anastomoses were evaluated for inflammation, the healing process, and foreign body reactions. A computer-assisted immunohistological analysis of staining for Ki67, CD68, smooth muscle actin (SMA), and Sirius red was performed using TissueFAXS. Additionally, the in vivo elastic properties of the material were assessed by measuring the suture tension in a rabbit model. Each suture was tested twice in three rabbits; No major surgical complications were observed and all anastomoses showed adequate wound healing. The Ki67+ count and SMA area differed between the groups (F (3, 66) = 5.884, p = 0.0013 and F (3, 56) = 6.880, p = 0.0005, respectively). In the TPU-snowflake material, the Ki67+ count was the lowest, while the SMA area provided the highest values. The CD68+ count and collagen I/III ratio did not differ between the groups (F (3, 69) = 2.646, p = 0.0558 and F (3, 54) = 0.496, p = 0.686, respectively). The suture tension measurements showed a significant reduction in suture tension loss for both the TPU threads; Suturing material made from TPU with elastic properties proved applicable for intestinal anastomoses in a porcine model. In addition, our results suggest a successful reduction in tissue incision and an overall suture tension homogenization.

Stem cell therapy applied for digestive anastomosis: Current state and future perspectives

BACKGROUND

Digestive tract resections are usually followed by an anastomosis. Anastomotic leakage, normally due to failed healing, is the most feared complication in digestive surgery because it is associated with high morbidity and mortality. Despite technical and technological advances and focused research, its rates have remained almost unchanged the last decades. In the last two decades, stem cells (SCs) have been shown to enhance healing in animal and human studies; hence, SCs have emerged since 2008 as an alternative to improve anastomoses outcomes.

AIM

To summarise the published knowledge of SC utilisation as a preventative tool for hollow digestive viscera anastomotic or suture leaks.

METHODS

PubMed, Science Direct, Scopus and Cochrane searches were performed using the key words “anastomosis”, “colorectal/colonic anastomoses”, “anastomotic leak”, “stem cells”, “progenitor cells”, “cellular therapy” and “cell therapy” in order to identify relevant articles published in English and Spanish during the years of 2000 to 2021. Studies employing SCs, performing digestive anastomoses in hollow viscera or digestive perforation sutures and monitoring healing were finally included. Reference lists from the selected articles were reviewed to identify additional pertinent articles.

Given the great variability in the study designs, anastomotic models, interventions (SCs, doses and vehicles) and outcome measures, performing a reliable meta-analysis was considered impossible, so we present the studies, their results and limitations.

RESULTS

Eighteen preclinical studies and three review papers were identified; no clinical studies have been published and there are no registered clinical trials. Experimental studies, mainly in rat and porcine models and occasionally in very adverse conditions such as ischaemia or colitis, have been demonstrated SCs as safe and have shown some encouraging morphological, functional and even clinical results. Mesenchymal SCs are mostly employed, and delivery routes are mainly local injections and cell sheets followed by biosutures (sutures coated by SCs) or purely topical. As potential weaknesses, animal models need to be improved to make them more comparable and equivalent to clinical practice, and the SC isolation processes need to be standardised. There is notable heterogeneity in the studies, making them difficult to compare. Further investigations are needed to establish the indications, the administration system, potential adjuvants, the final efficacy and to confirm safety and exclude definitively oncological concerns.

CONCLUSION

The future role of SC therapy to induce healing processes in digestive anastomoses/sutures still needs to be determined and seems to be currently far from clinical use.

The use of mesenchymal stem cells in animal models for gastrointestinal anastomotic leak: A systematic review

AIM

Anastomotic leak is the most feared complication of gastrointestinal surgery. Mesenchymal stem cell technology is used clinically to promote wound healing; however, the safety and efficacy of this technology on anastomotic healing has yet to be defined. The aim of this study was to investigate whether mesenchymal stem cells confer any benefit when applied to animal models for gastrointestinal anastomotic leak, identify the methodology and how efficacy is assessed.

METHODS

The MEDLINE, EMBASE, WebofScience and Cochrane Library databases were interrogated between 1 January1947 to 1 May 2020. All studies where mesenchymal stem cells were applied to laboratory animal leak models to demonstrate a healing effect were considered. All experimental and histological outcomes were examined. Compliance to ARRIVE and current International Consensus was assessed.

RESULTS

A total of 1205 studies were screened. Twelve studies reported on 438 gastrointestinal anastomoses in four species using 11 models; seven in the colon. No studies utilised a model with a known leak rate. Significant variance was observed in histological outcomes with efficacy demonstrated in five out of 12 studies. One study demonstrated a benefit in leak rate. Colorectal studies had a greater median ARRIVE compliance, 60.8% (IQR 63.2-64.5) compared to noncolorectal 45.4% (IQR 43.8-49.0).

CONCLUSIONS

Mesenchymal stem cell delivery to an animal anastomosis is safe and feasible. Use may confer benefit but findings are currently limited to surrogate histological outcomes. There is consistency in outcome measures reported but variance in how this is assessed. Poor compliance to ARRIVE but good compliance to current international consensus in leak models of the colon was observed.

Impact of Deserosalization on Small Bowel Anastomosis Healing in Swine: A Pilot Study

BACKGROUND

Healing is related to gastrointestinal anastomotic leak, which is a severe and common complication. This study aimed to investigate the feasibility and the impact of deserosalization on healing of jejuno-jejunal anastomoses in an animal model.

MATERIALS AND METHODS

Seven swine underwent three types of side-to-side jejuno-jejunal anastomosis twice and survived seven days. Three different types of jejuno-jejunal side-to-side anastomoses were performed twice at 20-cm distance from each other in each animal: no serosa removal, one-sided, and two-sided serosa removal, respectively. Bursting pressure, tissue hydroxyproline concentration, and pathology scores were evaluated.

RESULTS

Hydroxyproline tissue concentration was a mean±standard deviation of 0.37±0.09, 0.38±0.08, and 0.30±0.05 nmoI/ml respectively (p<0.05). Bursting pressure was a mean±standard deviation of 59.02±8.60, 73.20±11.09, and 100.01±7.49 mmHg, respectively (p<0.001). The histopathological assessment did not find any statistically significant differences.

CONCLUSION

Deserosalization in jejuno-jejunal anastomosis was technically feasible and seemed to improve mechanical strength and collagen deposition in this experimental porcine model. Further investigation is warranted.

Reviewing the animal literature: how to describe and choose between different types of literature reviews

Before starting any (animal) research project, review of the existing literature is good practice. From both the scientific and the ethical perspective, high-quality literature reviews are essential. Literature reviews have many potential advantages besides synthesising the evidence for a research question. First, they can show if a proposed study has already been performed, preventing redundant research. Second, when planning new experiments, reviews can inform the experimental design, thereby increasing the reliability, relevance and efficiency of the study. Third, reviews may even answer research questions using already available data. Multiple definitions of the term literature review co-exist. In this paper, we describe the different steps in the review process, and the risks and benefits of using various methodologies in each step. We then suggest common terminology for different review types: narrative reviews, mapping reviews, scoping reviews, rapid reviews, systematic reviews and umbrella reviews. We recommend which review to select, depending on the research question and available resources. We believe that improved understanding of review methods and terminology will prevent ambiguity and increase appropriate interpretation of the conclusions of reviews.

Double-layered Nanofibrous Patch for Prevention of Anastomotic Leakage and Peritoneal Adhesions, Experimental Study

BACKGROUND/AIM

Anastomotic leakage is a feared complication in colorectal surgery. Postoperative peritoneal adhesions can also cause life-threatening conditions. Nanofibrous materials showed their pro-healing properties in various studies. The aim of the study was to evaluate the impact of double-layered nanofibrous materials on anastomotic healing and peritoneal adhesions formation.

MATERIALS AND METHODS

Two versions of double-layered materials from polycaprolactone and polyvinyl alcohol were applied on defective anastomosis on the small intestine of healthy pigs. The control group remained with uncovered defect. Tissue specimens were subjected to histological analysis and adhesion scoring after 3 weeks of observation.

RESULTS

The wound healing was inferior in the experimental groups, however, no anastomotic leakage was observed and the applied material always kept covering the defect. The extent of adhesions was larger in the experimental groups.

CONCLUSION

Nanofibrous materials may prevent anastomotic leakage but delay healing.

Intestinal anastomotic healing models during experimental colitis

BACKGROUND

Anastomotic leakage represents a major complication following resections in colorectal surgery. Among others, intestinal inflammation such as in inflammatory bowel disease is a significant risk factor for disturbed anastomotic healing. Despite technical advancements and several decades of focused research, the underlying mechanisms remain incompletely understood. Animal experiments will remain the backbone of this research in the near future. Here, instructions on a standardized and reproducible murine model of preoperative colitis and colorectal anastomosis formation are provided to amplify research on anastomotic healing during inflammatory disease.

METHODS

We demonstrate the combination of experimental colitis and colorectal anastomosis formation in a mouse model. The model allows for monitoring of anastomotic healing during inflammatory disease through functional outcomes, clinical scores, and endoscopy and histopathological examination, as well as molecular analysis.

DISCUSSION

Postoperative weight loss is used as a parameter to monitor general recovery. Functional stability can be measured by recording bursting pressure and location. Anastomotic healing can be evaluated macroscopically from the luminal side by endoscopic scoring and from the extraluminal side by assessing adhesion and abscess formation or presence of dehiscence. Histologic examination allows for detailed evaluation of the healing process.

CONCLUSION

The murine model presented in this paper combines adjustable levels of experimental colitis with a standardized method for colorectal anastomosis formation. Extensive options for sample analysis and evaluation of clinical outcomes allow for detailed research of the mechanisms behind defective anastomotic healing.

Innovative approaches for induction of gastrointestinal anastomotic healing: an update on experimental and clinical aspects

PURPOSE

In most cases, traditional techniques to perform an anastomosis following gastrointestinal resections lead to successful healing. However, despite focused research in the field, in certain high-risk situations leakage rates remain almost unchanged. Here, additional techniques may help the surgeon to protect the anastomosis and prevent leakage. We give an overview of some of the latest developments on experimental and clinical techniques for induction of anastomotic healing.

METHODS

We performed a review of the current literature on approaches to improve anastomotic healing.

RESULTS

Many promising approaches with a high clinical potential are in the developmental pipeline. Highly experimental approaches like inhibition of matrix metalloproteinases, stem cell therapy, hyperbaric oxygen therapy, induction of the hypoxic adaptive response, and the administration of growth factors are still in the preclinical phase. Other more clinical developments aim to strengthen the anastomotic suture line mechanically while shielding it from the influence of the microbiome. Among them are gluing, seaming the staple line, attachment of laminar biomaterials, and temporary intraluminal tubes. In addition, individualized bowel preparation, selectively reducing certain detrimental microbial populations could become the next stage of bowel preparation. Compression anastomoses are evolving as an equivalent technique additional to established hand-sewn and stapled anastomoses. Fluorescence angiography and flexible endoscopy could complement intraoperative quality control additionally to the air leak tests. Virtual ileostomy is a concept to prepare the bowel for the easy formation of a stoma in case of leakage.

CONCLUSION

A variety of promising diagnostic and prophylactic measures that may support the surgeon in identifying high-risk anastomoses and support them according to their potential deficits is currently in development.

Systematic Review on the Influence of Tissue Oxygenation on Gut Microbiota and Anastomotic Healing

BACKGROUND

Anastomotic leak rates have not improved over several decades despite improvements in surgical techniques and patient care. The gut microbiome has been implicated in the development of leaks. The exact mechanisms by which tissue oxygenation affects gut microbial composition and anastomotic healing physiology are unclear. Also, commonly used carbon dioxide (CO₂) is a known vasodilator that improves tissue oxygen tension. We performed a systematic review to determine the influence of hyperoxia, hypoxia, and hypercapnia on the gut microbiome and anastomotic healing.

METHODS

A literature search was performed in MEDLINE, EMBASE, and COCHRANE to identify studies investigating the effects of hyperoxia, hypoxia, and hypercapnia on anastomotic healing and gut microbiota published between 1998 and 2018. Two reviewers screened the articles for eligibility and quality. Fifty-three articles underwent full text review, and a narrative synthesis was undertaken.

RESULTS

Hyperoxia is associated with better anastomotic healing, increased gastrointestinal oxygen tension, and may reduce gut anaerobes. Hypoxia is associated with poor healing and increased gut anaerobes. However, it is unclear if hypoxia is the most important predictor of anastomotic leaks. Low pressure CO₂ pneumoperitoneum and mild systemic hypercapnia are both associated with increased gastrointestinal oxygen tension and may improve anastomotic healing. We found no studies which investigated the effect of hypercapnia on gut microbiota in the context of anastomotic healing.

CONCLUSIONS

Tissue oxygenation influences gut anastomotic healing, but little evidence exists to demonstrate the influence on the gut microbiome in the context of healing. Further studies are needed to determine if anastomotic microbiome changes with altered tissue oxygenation and if this affects healing and leak rates. If confirmed, altering tissue oxygenation through hyperoxia or hypercapnia could be feasible means of altering the microbiome such that anastomotic leak rates reduce.

Anti-Adhesive, Platelet Gathering Effects of c-RGD Modified Poly(p-dioxanone-co-l-Phe) Electrospun Membrane and Its Comprehensive Application in Intestinal Anastomosis

Intestinal resection and anastomosis are performed in over a million people with various bowel diseases annually. Excessive fibrosis and anastomotic site leakage are the main complications of anastomosis surgery, despite great improvements in operative technique and equipment in recent years. In this study, cRGD modified poly(p-dioxanone-co-l-Phe) (PDPA) membranes are designed and applied in intestinal anastomosis to simultaneously solve the two aforementioned complications. cRGD is modified onto PDPA membranes through both physical absorption and π-π accumulation between d-Phe of cRGD and l-Phe of PDPA. Although cRGD modification enhanced the biocompatibility of PDPA membranes, cRGD modified PDPA membrane suppresses fibroblast proliferation both in vitro and in vivo as a result of degradation and subsequent release of fibroblast suppressive l-Phe from PDPA. Meanwhile, platelets are entrapped by cRGD modified PDPA membranes through the specific binding of cRGD and platelet GP_IIbIIIa . cRGD modified PDPA membranes are applied in rat intestinal anastomosis, and both adhesion and stenosis are successfully prevented at anastomotic sites. At the same time, bursting pressure, which represents healing intensity at anastomotic sites, is promoted. The gathering and activation of platelets on PDPA membranes induce secretion of autologous PDGF and VEGF to facilitate angiogenesis and subsequent healing of anastomotic sites.

How Can Systematic Reviews Teach Us More about the Implementation of the 3Rs and Animal Welfare?

Simple Summary

The three Rs stand for Replacement, Reduction, and Refinement of animal studies and were published for the first time in 1959 by Russell and Burch. Replacement refers to avoiding the use of (non-human) animals in research. Reduction implies using fewer animals, for example, by better statistical methods and better literature studies, and Refinement means reducing the discomfort and improving the welfare of animals used in experiments. The three Rs have gained more interest and popularity since the 1970s, and have now become the crucial central element in the revised legislation in Europe, the EU Directive 2010/63EU, controlling the proper use of animals in experiments in the European member states. Animals are used in order to improve the health and welfare of other non-human animals, in veterinary medicine, and of humans, for toxicological purposes and in clinical medicine. Using animals in experiments has always been subject to ethical and societal debate. At Syrcle, we have introduced the methodology of systematic reviews for preclinical animal studies since 2012. This methodology comes from the clinical field and is a key element in evidence-based medicine, as systematic reviews summarise the scientific evidence as objectively as possible. A systematic review (SR) is defined as a literature review focused on a single question that tries to identify, appraise, select, and synthesise all high-quality research evidence relevant to that question. Introducing this methodology for the preclinical animal studies seems very logical, as animal studies in clinical medicine are performed for protecting humans from ineffective or unsafe treatments. Systematic reviews thus lead to summarising evidence from preclinical studies before entering clinical trials. In addition to protecting humans, systematic reviews can also be used to implement the three Rs. Examples of how systematic reviews contribute to implementing the three Rs are provided in the following article, thus demonstrating the value for protecting animals as well.

Abstract

This paper describes the introduction of the systematic review methodology in animal-based research and the added value of this methodology in relation to the 3Rs and beyond. The 3Rs refer to Replacement, Reduction, and Refinement of animal studies. A systematic review (SR) is defined as a literature review focused on a single question that tries to identify, appraise, select, and synthesise all high-quality research evidence relevant to that question. Examples are given on how SRs lead to the implementation of the 3Rs and better science. Additionally, a broader context is given regarding societal, political, and scientific developments. Various examples of systematic reviews are given to illustrate the current situation regarding reporting, quality, and translatability of animal-based research. Furthermore, initiatives that have emerged to move further towards more responsible and sustainable research is of benefit for both animals and humans.

Adhesion reformation and the limited translational value of experiments with adhesion barriers: A systematic review and meta-analysis of animal models

Today, 40-66% of elective procedures in general surgery are reoperations. During reoperations, the need for adhesiolysis results in increased operative time and a more complicated convalescence. In pre-clinical evaluation, adhesion barriers are tested for their efficacy in preventing 'de novo' adhesion formation, However, it is unknown to which extent barriers are tested for prevention of adhesion reformation. The aim of this systematic review and meta-analysis is to assess the efficacy of commercially available adhesion barriers and laparoscopic adhesiolysis in preventing adhesion reformation in animal models. Pubmed and EMBASE were searched for studies which assessed peritoneal adhesion reformation after a standardized peritoneal injury (in the absence of an intra-peritoneal mesh), and reported the incidence of adhesions, or an adhesion score as outcome. Ninety-three studies were included. No study met the criteria for low risk of bias. None of the commercially available adhesion barriers significantly reduced the incidence of adhesion reformation. Three commercially available adhesion barriers reduced the adhesion score of reformed adhesions, namely Seprafilm (SMD 1.38[95% CI]; p < 0.01), PEG (SMD 2.08[95% CI]; p < 0.01) and Icodextrin (SMD 1.85[95% CI]; p < 0.01). There was no difference between laparoscopic or open adhesiolysis with regard to the incidence of adhesion reformation (RR 1.14[95% CI]; p ≥ 0.05) or the adhesion score (SMD 0.92[95% CI]; p ≥ 0.05). Neither currently commercially available adhesion barriers, nor laparoscopic adhesiolysis without using an adhesion barrier, reduces the incidence of adhesion reformation in animal models. The methodological quality of animal studies is poor.

Adaptation of the Systematic Review Framework to the Assessment of Toxicological Test Methods: Challenges and Lessons Learned with the Zebrafish Embryotoxicity Test

Systematic review methodology is a means of addressing specific questions through structured, consistent, and transparent examinations of the relevant scientific evidence. This methodology has been used to advantage in clinical medicine, and is being adapted for use in other disciplines. Although some applications to toxicology have been explored, especially for hazard identification, the present preparatory study is, to our knowledge, the first attempt to adapt it to the assessment of toxicological test methods. As our test case, we chose the zebrafish embryotoxicity test (ZET) for developmental toxicity and its mammalian counterpart, the standard mammalian prenatal development toxicity study, focusing the review on how well the ZET predicts the presence or absence of chemical-induced prenatal developmental toxicity observed in mammalian studies. An interdisciplinary team prepared a systematic review protocol and adjusted it throughout this piloting phase, where needed. The final protocol was registered and will guide the main study (systematic review), which will execute the protocol to comprehensively answer the review question. The goal of this preparatory study was to translate systematic review methodology to the assessment of toxicological test method performance. Consequently, it focused on the methodological issues encountered, whereas the main study will report substantive findings. These relate to numerous systematic review steps, but primarily to searching and selecting the evidence. Applying the lessons learned to these challenges can improve not only our main study, but may also be helpful to others seeking to use systematic review methodology to compare toxicological test methods. We conclude with a series of recommendations that, if adopted, would help improve the quality of the published literature, and make conducting systematic reviews of toxicological studies faster and easier over time.

Enhanced anastomotic healing by Daikenchuto (TJ-100) in rats

Daikenchuto (DKT), a traditional Japanese medicine, is widely used to treat various gastrointestinal disorders. This study aimed to investigate whether DKT could promote the anastomotic healing in a rat model. Pedicled colonic segments were made in left colon by ligation of the feeding arteries, and then intestinal continuity was restored. Colonic blood flow was analyzed by using ICG fluorescence imaging: Fmax, Tmax, T1/2, and Slope were calculated. Anastomotic leakage (AL) was found in 6 of 19 rats (31.6%) in the control group, whereas in 1 of 16 rats (6.2%) in the DKT group. The Fmax and Slope of DKT group were significantly higher than those of control group. DKT could promote the anastomotic healing, with the higher bursting pressure on postoperative day (POD) 2 and 5, the larger granulation thickness on POD 5, and neoangiogenesis on POD 5. Histological examination showed DKT exhibited a decreased inflammatory cell infiltration, enhanced fibroblast infiltration, and enhanced collagen density on POD 5. In the DKT group, the levels of TGFβ1 on POD 2 and VEGFα on POD5 were significantly higher, whereas the level of TNFα on POD 2 was significantly lower. Therefore, DKT could be effective for the prevention of AL following colorectal surgery.

Modelling side to side intestinal anastomosis

Side-to-side intestinal anastomosis is a surgical procedure where an incision is performed between two parallel segments of gut and then they are sutured together. The purpose of this paper is to investigate if the standard surgical practice diameter used in anastomosis leads to undesirable closed circulatory flows which may be harmful to the gut tissue. A finite element model for the chyme flow in a side by side anastomosis with realistic user configurable parameters is developed and solved in a wide range of situations. We analyze the flow crossing the anastomosis, the normalized pressure difference in the gut section and the streamlines that show the presence or absence of closed flow regions for a set of surgically feasible anastomosis diameter values. In contrast with the findings of simpler analytical models, closed flows do not appear in any of these cases. The study shows that the current standard surgical practice where the anastomosis diameter is similar to the gut diameter does not lead to undesirable effects predicted by some simple analytical models.

A collaborative review of the current concepts and challenges of anastomotic leaks in colorectal surgery

The reduction of the incidence, detection and treatment of anastomotic leakage (AL) continues to challenge the colorectal surgical community. AL is not consistently defined and reported in clinical studies, its occurrence is variably reported and its impact on longterm morbidity and health-care resources has received relatively little attention. Controversy continues regarding the best strategies to reduce the risk. Diagnostic tests lack sensitivity and specificity, resulting in delayed diagnosis and increased morbidity. Intra-operative fluorescence angiography has recently been introduced as a means of real-time assessment of anastomotic perfusion and preliminary evidence suggests that it may reduce the rate of AL. In addition, concepts are emerging about the role of the rectal mucosal microbiome in AL and the possible role of new prophylactic therapies. In January 2016 a meeting of expert colorectal surgeons and pathologists was held in London, UK, to identify the ongoing controversies surrounding AL in colorectal surgery. The outcome of the meeting is presented in the form of research challenges that need to be addressed.

Morphine Promotes Colonization of Anastomotic Tissues with Collagenase - Producing Enterococcus faecalis and Causes Leak

BACKGROUND

Despite ever more powerful antibiotics, newer surgical techniques, and enhanced recovery programs, anastomotic leaks remain a clear and present danger to patients. Previous work from our laboratory suggests that anastomotic leakage may be caused by Enterococcus faecalis strains that express a high collagenase phenotype (i.e., collagenolytic). Yet the mechanisms by which the practice of surgery shifts or selects for collagenolytic phenotypes to colonize anastomotic tissues remain unknown.

METHODS

Here, we hypothesized that morphine, an analgesic agent universally used in gastrointestinal surgery, promotes tissue colonization with collagenolytic E. faecalis and causes anastomotic leak. To test this, rats were administered morphine in a chronic release form as would occur during routine surgery or vehicle. Rats were observed for 6 days and then underwent exploratory laparotomy for anastomotic inspection and tissue harvest for microbial analysis. These results provide further rationale to enhanced recovery after surgery (i.e., ERAS) programs that suggest limiting or avoiding the use of opioids in gastrointestinal surgery.

RESULTS

Results demonstrated that compared to placebo-treated rats, morphine-treated rats demonstrated markedly impaired anastomotic healing and gross leaks that correlated with the presence of high collagenase-producing E. faecalis adherent to anastomotic tissues. To determine the direct role of morphine on this response, various isolates of E. faecalis from the rats were exposed to morphine and their collagenase activity and adherence capacity determined in vitro. Morphine increased both the adhesiveness and collagenase production of four strains of E. faecalis harvested from anastomotic tissues, two that were low collagenase producers at baseline, and two that were high collagenase producers at baseline.

CONCLUSION

These results provide further rationale to enhanced recovery after surgery (i.e., ERAS) programs that suggest limiting or avoiding the use of opioids in gastrointestinal surgery.

Prevention of Perioperative Anastomotic Healing Complications: Anastomotic Stricture and Anastomotic Leak

The anastomotic healing complications of postoperative leak and stricture continue to plague surgeons despite many broadly targeted interventions. Evaluation of preventive measure efficacy is difficult due to inconsistent definitions and reporting of these complications. Few interventions have been shown to impact rates of leakage or stricture. However, new evidence is emerging that the intestinal microbiota can play an important role in the development of anastomotic complications. A more holistic approach to understanding the mechanisms of anastomotic complications is needed in order to develop tailored interventions to reduce their frequency. Such an approach may require a more complete definition of the role of the microbiota in anastomotic healing.

Therapeutic improvement of colonic anastomotic healing under complicated conditions: A systematic review

AIM: To identify therapeutic agents for the prophylaxis of gastrointestinal anastomotic leakage (AL) under complicated conditions.

METHODS: The PubMed and EMBASE databases were searched for English articles published between January 1975 and September 2014. Studies with the primary purpose of improving anastomotic healing in the colon or rectum under complicated preoperative and/or intraoperative conditions were included. We excluded studies investigating the adverse effects or risk assessment of an active intervention. Furthermore, investigations of biophysical materials, sealants, electrical stimulation and nutrients were excluded. The primary study outcome was biomechanical anastomotic strength or AL. The meta-analysis focused on therapeutic agents that were investigated in one animal model using the same outcome by at least three independent research groups.

RESULTS: The 65 studies included were divided into 7 different complicated animal models: Bowel ischemia, ischemia/reperfusion, bowel obstruction, obstructive jaundice, peritonitis, chemotherapy and radiotherapy. In total, 48 different therapeutic compounds were examined. The majority of investigated agents (65%) were reported as beneficial for anastomotic healing. Twelve of the agents (25%) were tested more than once in the same model, whereas 13 (27%) of the agents were tested in two or more models of complicated healing. Two therapeutic agents met our inclusion criteria for the meta-analysis. Postoperative hyperbaric oxygen therapy significantly increased anastomotic bursting pressure in ischemic colon anastomoses by a mean of 28 mmHg (95%CI: 17 to 39 mmHg, P < 0.00001). Granulocyte macrophage-colony stimulating factor failed to show a significant increase in anastomotic bursting pressure (95%CI: -20 to 21 mmHg, P = 0.97) vs controls in experimental chemotherapeutic models.

CONCLUSION: This systematic review identified potential therapeutic agents, but more studies are needed before concluding that any of these are useful for AL prophylaxis.

International consensus statement regarding the use of animal models for research on anastomoses in the lower gastrointestinal tract

PURPOSE

This project aimed to reach consensus on the most appropriate animal models and outcome measures in research on anastomoses in the lower gastrointestinal tract (GIT). The physiology of anastomotic healing remains an important research topic in gastrointestinal surgery. Recent results from experimental studies are limited with regard to comparability and clinical translation.

METHODS

PubMed and EMBASE were searched for experimental studies investigating anastomotic healing in the lower GIT published between January 1, 2000 and December 31, 2014 to assess currently used models. All corresponding authors were invited for a Delphi-based analysis that consisted of two online survey rounds followed by a final online recommendation survey to reach consensus on the discussed topics.

RESULTS

Two hundred seventy-seven original articles were retrieved and 167 articles were included in the systematic review. Mice, rats, rabbits, pigs, and dogs are currently being used as animal models, with a large variety in surgical techniques and outcome measures. Forty-four corresponding authors participated in the Delphi analysis. In the first two rounds, 39/44 and 35/39 participants completed the survey. In the final meeting, 35 experts reached consensus on 76/122 items in six categories. Mouse, rat, and pig are considered appropriate animal models; rabbit and dog should be abandoned in research regarding bowel anastomoses. ARRIVE guidelines should be followed more strictly.

CONCLUSIONS

Consensus was reached on several recommendations for the use of animal models and outcome measurements in research on anastomoses of the lower GIT. Future research should take these suggestions into account to facilitate comparison and clinical translation of results.

Colorectal anastomotic healing: why the biological processes that lead to anastomotic leakage should be revealed prior to conducting intervention studies

BACKGROUND

Anastomotic leakage (AL) remains the most dreaded complication after colorectal surgery and causes high morbidity and mortality. The pathophysiology of AL remains unclear, despite numerous studies that have been conducted on animals and humans, probably due to the undetermined healing process of colorectal anastomoses. Increasing basic knowledge on this healing process may shed more light on causal factors of AL, and additionally reduce the quantity and accelerate the quality of experimental studies. In this debate article, our aim was to provide different perspectives on what is known about the colorectal healing process in relation to wound healing and AL.

DISCUSSION

Since knowledge on anastomotic healing is lacking, it remains difficult to conclude which factors are essential in preventing AL. This is essential information in the framework of humane animal research, where the focus should lie on Replacement, Reduction and Refinement (3Rs). While many researchers compare anastomotic healing with wound healing in the skin, there are substantial recognized differences, e.g. other collagen subtypes and different components involved. Based on our findings in literature as well as discussions with experts, we advocate stop considering anastomotic healing in the gastrointestinal tract and cutaneous healing as a similar process. Furthermore, intervention studies should at least address the anastomotic healing process in terms of histology and certain surrogate markers. Finally, the anastomotic healing process ought to be further elucidated - with modern techniques to achieve 3Rs in animal research--to provide starting points for potential interventions that can prevent AL.