An Integrated Approach to Colorectal Anastomotic Leakage

__Abstract__ Colorectal anastomotic leakage (CAL) still remains a frequent and most dangerous complication after gastrointestinal surgery, occurring in 4-33% patients and contributing to one third of postoperative mortality. CAL substantially prolongs hospital stay ? by one to two weeks - and greatly increases medical costs by as much as $24,000 within the first period of hospitalization, thereby approximately tripling the expenditure relative to that of patients without CAL. Due to the high risk of postoperative mortality, substantial efforts have been made to investigate means of preventing and detecting CAL. In recent decades, however, even with substantial improvements in surgical technique, no clear decrease in CAL rate has been achieved. Much effort has been devoted to selecting patients with higher risks of CAL, and many risk factors have been identified, such as being male, smoking, alcohol abuse, obesity, a high American Society of Anesthesiologists (ASA) score, low level (e.g. rectal) anastomosis, tumor stage, urgent operation, increased blood loss, and prolonged duration of surgery have been revealed. Previous studies by our research group also reported several novel risk factors including after-hours surgery, and long-term and preoperative administration of corticosteroids. However, these risk factors seem to cover most patients and thus may have limited value in the preoperative selection of patients

Chemically Active Rheological Modifiers for the Improved Clinical Use of Cyanoacrylates

Over 100 million surgical incisions, 50 million traumatic wounds, and 20 million minor lacerations from cuts and grazes are treated globally each year. One study determined that globally internal and external wounds occur for 40% and 37% of cases respectively for a total of 111 million patients that were treated for wounds. The remaining 23% of patients were treated for minor lacerations and trauma in the emergency room. These wounds require immediate medical attention including pressure application, sutures, clips, tissue cautery, and/or topical hemostatic agents to cease hemorrhage or the exit of other bodily fluids. With blood flow ceased, wound approximation or sealant is used temporarily to close the wound until fresh tissue is formed. There are several different approaches to close a wound with each lacking in one or more properties to achieve ideal wound healing. Tissue welding and cauterization are two methods employed; however, these methods result in the formation of necrotic tissue, which is undesirable. Sutures are the wound approximation gold standard due to their flexibility and ability to resist tensile forces, but they can result in complications such as bleeding from the holes created during the suturing application required to place them. Staples and tapes are common wound approximation devices, but unlike sutures, they lack the ability to resist large tensile forces. In addition to these mechanical closure devices, fibrin and thrombin based sealants have been employed to approximate or seal tissues. These biological sealants are very biocompatibility, but they also have a low mechanical strength especially as compared to the mechanical closure devices. This low strength has resulted in re-bleeding when this type of sealant was applied externally and also in cases when it was applied internally. In comparison, BioGlue®, a non-biological sealant has a high mechanical strength, but is limited by its poor biocompatibility. Alternatively, there have been advancements based on gecko and mussel adhesions (bioadhesion) in order to fabricate synthetic materials that mimic these naturally occurring dry and wet adhesives respectively. Studies have demonstrated that these materials have a great potential, but they still require additional research in order to render them clinically relevant for wound approximation. Cyanoacrylate adhesives is another family of wound approximation and sealant devices. As a general overview, these materials are able to penetrate into tissue due to their liquid monomer form, rapidly polymerize due to their highly electrophilic nature, and then form bonds due to the interpenetrating networks formed. They have been fabricated in many varieties by differing the side chain for the adhesive monomer during its synthesis, blending additives into the adhesive, or mixing insoluble materials into the adhesive. A myriad of studies have demonstrated that these variations can control the properties of the adhesive in its monomer and polymer forms. Several of these properties include viscosity, mechanical strength and flexibility, polymerization rate and reaction temperature, degradation rate, and biocompatibility. By controlling the side chain type and materials added to it, researchers are able to tailor cyanoacrylates for specific external and internal medical and industrial uses. These adhesives are well known for their typically successful external medical uses and industrial uses; however, their internal medical use has been slow to reach global use due to the heat released during the adhesives polymerization, and the cytotoxic formaldehyde byproduct released as the polymerized adhesive degrades. In order to overcome this issue, researchers commonly synthesize cyanoacrylates for internal use by attaching long alkane side chains (e.g. 2-octyl) to them. The resulting cyanoacrylate releases a lower amount of heat during its polymerization and minimal formaldehyde as it degrades; however, several studies have demonstrated that this degradation take years, if it degrades at all, which can result in a prolonged, chronic wound healing. Nevertheless, this material has excellent clinical usefulness when the specific cyanoacrylate types are used for their specific intended uses. There is therefore great potential to modulate the adhesive to improve its clinical usefulness. The completed research presented in this dissertation focused on using this information to formulate cyanoacrylates with potentially improved clinical usefulness. The cyanoacrylates were improved through the addition of novel chemically active polyesters (rheological modifiers). Methoxypropyl cyanoacrylate was selected for this research due to its inclusion of a short alkoxy side chain resulting in a flexible, high strength bond as well as the adhesive’s proven biocompatibility. Poly(glycolide-cocaprolactone) polymers (PGCL) were synthesized as the polyesters for this research due to the fast degrading, low pH producing ability of glycolide and slow degrading, increased flexibility of ε-caprolactone. The combination of both fast and slow degrading monomers allows one specifically to control the polyester’s degradation rate and thus resulting pH level for the eluent. Based on these properties, it was hypothesized that mixing PGCL as an amorphous polymer into cyanoacrylate, polymerizing the cyanoacrylate, and then allowing the polycyanoacrylate to degrade in water or a phosphate buffered saline will allow the adhesive modifier contained within the polycyanoacrylate to also hydrolyze and self-modulate the pH of the surrounding environment to an acidic level. When a polycyanoacrylate degrades in an acidic instead of basic solution, then the formaldehyde levels released should be minimized, and the alcohol and cyanoacrylic acid released should be less toxic; thus, rendering the polycyanoacrylate potentially safer for internal use

Major Abdominal Surgical Complications : Innovative Approaches

In this thesis the focus was on three major complications after abdominal surgery: incisional hernia (IH), prolonged postoperative ileus (PPOI), and colorectal anastomotic leakage (CAL). The results were summarized in three parts: _Part 1_ focused on prediction and detection of these surgical complications; _Part 2_ describes different methods to prevent complications; _Part 3_ analyzed also prevention of major surgical complications with a focus on patients at risk. Even anno 2017 it is still necessary to explore new strategies to prevent complications in abdominal surgery. Also with new surgical techniques, for example the use of staplers for colorectal anastomosis, prevention of CAL is still an issue. In addition, early detection of a complication is necessary to prevent from worse. This also requires more attention and research since detection of leakage is still mainly based on clinical observation and the experience of the surgeon. Research on more advanced technical and/ or digital solutions to objectively assess and quantify leakage and other complications is strongly needed. Therefore in this thesis the focus was to develop different strategies that may facilitate prevention, prediction, and diagnosis of different important abdominal surgical complications such as colorectal anastomotic leakage, postoperative ileus, incisional hernia, and infectious complications

Biomatériaux dérivés d’une matrice extracellulaire (MEC) pour l’ingénierie tissulaire et les dispositifs médicaux

Abstract: Tissue engineering involves the production of whole organ or a part of it in vitro or in vivo. Decellularized organs as scaffolds for reconstructing organs have been emerging due to the potential of the ExtraCellular Matrix (ECM). ECM is a complex structure primarily composed of proteins and glycosaminoglycans (GAGs). Most common proteins include collagens, laminins, fibronectins and elastins. Several commercial products have been derived from ECM including tissue papers, 3D-printed scaffolds, and wound dressings. Bioadhesives are currently employed alone or as adjuncts to sutures to seal leaks of air or blood from organs following surgical interventions. ECM-incorporated bioadhesives could be hypothesized to not only seal leaks, but also to regenerate tissues. This thesis aims to investigate the composition and properties of ECMs derived from different porcine organs (bladders, kidneys, livers, lungs, and pancreas) using detergent-based and detergent-free methods. The first experimental work includes the design of a cell culture system to study the effect of detergent-based and detergent-free decellularized bladders on insulin-secreting rat pancreatic cell (INS-1) proliferation and functionality. ECMs were characterized initially for conservation of ultrastructure and removal of dsDNA. CyQUANT proliferation assay indicated cell proliferation following 7 days of culture on detergent-free decellularized bladders. Glucose-stimulated insulin secretion (GSIS) and immunostaining confirmed that cells were functional. The second experimental work involved decellularization of the five porcine organs using the detergent-based and detergent-free methods. Two additional steps were added to the detergent-free approach (pH adjustment and ethylenediaminetetraacetic acid (EDTA) treatment) to aid in the removal of residual hemoglobin from the organs. ECMs were characterized by staining for the removal of cellular content and conservation of ultrastructure. Further, mass spectrometry revealed better conservation of a greater number of key proteins such as collagen IV, laminins, fibronectin, and elastin in the ECM resulting from the detergent-free methods, as compared to that produced using the detergent-based one. Collagen fibers orientation measurement indicated preservation of the fibers orientation in the ECMs as compared to that measured in the native organs. The third experimental work initially screened the INS-1 cell response on different organ ECMs. INS-1 cells were functional on certain detergent-free decellularized organs following 7 days of cell culture. Finally, mouse primary pancreatic islets were seeded on the detergent-free decellularized bladders, revealing functional islets following 48 hours of culture.Le génie tissulaire consiste à construire un organe entier ou une partie de celui-ci in vitro ou in vivo. Les organes décellularisés utilisés comme échafaudages pour la reconstruction d'organes sont de plus en plus populaires en raison, entre autres, du potentiel de la matrice extracellulaire (MEC). La MEC consiste en un ensemble complexe composé principalement de protéines et de glycosaminoglycanes (GAG). Les protéines les plus courantes comprennent les collagènes, les laminines, les fibronectines et l’élastine. Plusieurs produits commerciaux sont composés de MEC, notamment des papiers tissulaires, des encres pour l’impression 3D et des pansements pour le traitement de plaies. Les bio-adhésifs sont actuellement utilisés seuls ou en complément des sutures pour sceller les fuites d'air ou de sang à la suite d’interventions chirurgicales. On pourrait supposer, par exemple, qu’un bio-adhésif incorporant la MEC permettrait non seulement de sceller une fuite, mais qu'il contribuerait également à la régénération tissulaire. Cette thèse a pour objectif général d’évaluer la composition et les propriétés de la MEC dérivée de différents organes porcins (vessie, rein, foie, poumon et pancréas) décellularisés à l'aide de méthodes utilisant un détergent et sans détergent. Également, le projet vise à développer une nouvelle famille de biomatériaux à base de MEC pour des applications en médecine. Le premier travail expérimental comprend la conception d'un système de culture cellulaire pour étudier l'effet des vessies décellularisées, avec ou sans détergent, sur la prolifération et la fonctionnalité des cellules pancréatiques (INS-1 cellules) de rat sécrétant de l'insuline en réponse à des gradients de glucose. Les MECs ont été initialement caractérisées pour la conservation de l'ultrastructure et l'élimination de l'ADN double brin. L'analyse utilisant un test de prolifération CyQUANT a indiqué une prolifération cellulaire après 7 jours de culture sur les vessies décellularisées sans détergent. La sécrétion d'insuline stimulée par le glucose (GSIS) et l'immunomarquage ont confirmé que les cellules étaient également fonctionnelles. Le deuxième travail expérimental visait la décellularisation des cinq organes porcins à l'aide d’une méthode utilisant un détergent et de méthodes sans détergent. Deux étapes supplémentaires ont été ajoutées à la technique sans détergent (ajustement du pH et traitement par éthylènediaminetétraacétate (EDTA)) afin de réduire la présence d'hémoglobine résiduelle dans les organes décellularisés. Les MECs ont été caractérisées en histologie par différentes colorations pour investiguer l'élimination du contenu cellulaire et la conservation de l'ultrastructure. De plus, la spectrométrie de masse a révélé la conservation d'un plus grand nombre de protéines clés telles que le collagène IV, les laminines, la fibronectine et l'élastine dans les MECs produites avec des méthodes sans détergent par rapport à celles résultantes de la méthode utilisant un détergent. Les mesures de l’orientation du collagène ont indiqué une conservation de l'orientation dans les MECs par rapport à la structure native. Le troisième travail expérimental a initialement investigué la réponse des cellules INS-1 exposées aux différentes MEC d'organes. Les cellules INS-1 demeuraient fonctionnelles sur certains organes décellularisés sans détergent après 7 jours de culture. Enfin, des îlots pancréatiques primaires de souris ont été ensemencés sur des vessies décellularisées sans détergent, révélant ainsi que les îlots étaient fonctionnels après 48 heures de culture