Reduction of Post-surgical Pericardial Adhesions Using a Pig Model

Beyond Traditional Medicine: EVs-Loaded Hydrogels as a Game Changer in Disease Therapeutics

Extracellular vesicles (EVs), especially exosomes, have shown great therapeutic potential in the treatment of diseases, as they can target cells or tissues. However, the therapeutic effect of EVs is limited due to the susceptibility of EVs to immune system clearance during transport in vivo. Hydrogels have become an ideal delivery platform for EVs due to their good biocompatibility and porous structure. This article reviews the preparation and application of EVs-loaded hydrogels as a cell-free therapy strategy in the treatment of diseases. The article also discusses the challenges and future outlook of EVs-loaded hydrogels.

Injectable photocurable Janus hydrogel delivering hiPSC cardiomyocyte-derived exosome for post-heart surgery adhesion reduction

Postsurgical pericardial adhesions pose increased risks of sequelae, prolonged reoperation time, and reduced visibility in the surgical field. Here, we introduce an injectable Janus hydrogel, which exhibits asymmetric adhesiveness properties after photocrosslinking, sustained delivering induced pluripotent stem cell-derived cardiomyocyte exosomes (iCM-EXOs) for post-heart surgery adhesion reduction. Our findings reveal that iCM-EXOs effectively attenuate oxidative stress in hydrogen peroxide-treated primary cardiomyocytes by inhibiting the activation of the transcription factor nuclear factor erythroid 2-related factor 2. Notably, in rat cardiac postsurgery models, the Janus hydrogels loaded with iCM-EXOs demonstrate dual functionality, acting as antioxidants and antipericardial adhesion agents. These hydrogels effectively protect iCM-EXOs from GATA6+ cavity macrophage clearance by inhibiting the recruitment of macrophages from the thoracic cavity. These results highlight the promising potential of iCM-EXO-laden Janus hydrogels for clinical safety and efficacy validation in trials involving heart surgery patients, with the ultimate goal of routine administration during open-heart surgeries.

Postsurgical Adhesions: Is There Any Prophylactic Strategy Really Working?

Postoperative adhesions are a frequent complication encountered after surgical procedures, mainly after intraperitoneal interventions. To this day, the pathophysiological mechanism behind the process of adhesions formation is not completely known. There are many strategies proposed as prophylaxis methods, involving surgical techniques, drugs or materials that prevent adhesions and even state of the art technologies such as nanoparticles or gene therapy. The aim of our review is to present these innovative approaches and techniques for postoperative adhesions prevention. After a thorough scientific database query, we selected 84 articles published in the past 15 years that were relevant to our topic. Despite all the recent groundbreaking discoveries, we are at an early stage of understanding the complexity of the adhesion formation mechanism. Further investigations should be made in order to create an ideal product for safe clinical use for prevention.

A review of animal models for post-operative pericardial adhesions

Post-operative pericardial adhesions remain a serious complication after cardiac surgery that can lead to increased morbidity and mortality. Fibrous adhesions can destroy tissue planes leading to injury of surrounding vasculature, lengthening of operation time, and increased healthcare costs. While animal models are necessary for studying the formation and prevention of post-operative pericardial adhesions, a standardized animal model for inducing post-operative pericardial adhesions has not yet been established. In order to address this barrier to progress, an analysis of the literature on animal models for post-operative pericardial adhesions was performed. The animal model, method used to induce adhesions, and the time to allow development of adhesions were analyzed. Our analysis found that introduction of autologous blood into the pericardial cavity in addition to physical abrasion of the epicardium caused more severe adhesion formation in comparison to abrasion alone or abrasion with desiccation (vs. abrasion alone p = 0.0002; vs. abrasion and desiccation p = 0.0184). The most common time frame allowed for adhesion formation was 2 weeks, with the shortest time being 10 days and the longest being 12 months. Finally, we found that the difference in adhesion severity in all animal species was similar, suggesting the major determinants for the choice of model are animal size, animal cost, and the availability of research tools in the particular model. This survey of the literature provides a rational guide for researchers to select the appropriate adhesion induction modality, animal model, and time allowed for the development of adhesions.

Indomethacin Sustained-Release Anti-adhesion Membrane Composed of a Phospholipid and Polycaprolactone Blend

Background

Postoperative peritoneal adhesions are among common challenging problems in surgery. The availability of limited efficient strategies to prevent intra-abdominal adhesion reinforces the need to explore new methods. Given the favorable prolonged drug release characteristics of polycaprolactone (PCL) films and their ability to act as a biodegradable physical barrier implant, along with the anti-inflammatory and anti-adhesion properties of indomethacin and phospholipids, this study hypothesized that indomethacin sustained-release membrane composed of phosphatidylcholine (PC) and PCL blend could efficiently prevent abdominal adhesion formation.

Methods

Different polymeric and polymeric/lipidic hybrid formulations with three feeding materials to drug weight ratios were prepared, and their physicochemical characteristics and drug release kinetics were evaluated and compared. Abdominal adhesions were induced in 48 rats by the abrasion of the cecum and excision of a section of the opposite abdominal wall. Adhesion formation was evaluated by macroscopic scoring, histological, scanning electron microscopy, and polymerase chain reaction analyses.

Results

Both PCL and PCL-PC films exhibited sustained indomethacin release profiles. The X-ray diffraction and Fourier-transform infrared spectroscopy studies confirmed indomethacin incorporation in formulations in molecular dispersion form without any interaction. The films showed smooth surfaces and good mechanical properties. The treatment with indomethacin PCL-PC membrane significantly reduced the expression levels of tumor necrosis factor-alpha, transforming growth factor-beta, interleukin-1, interleukin-6, and fibrinogen in the adhesion tissues. The separation of the injured peritoneum, very low adhesion scores, and complete mesothelial cell regeneration were also achieved.

Conclusions

This study suggests that indomethacin-eluting PCL-PC membrane acting through the combination of physical barrier, anti-inflammatory agents, and controlled drug delivery warrants an effective approach to prevent intra-abdominal adhesion.

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.

Preventing post-surgical cardiac adhesions with a catechol-functionalized oxime hydrogel

Post-surgical cardiac adhesions represent a significant problem during routine cardiothoracic procedures. This fibrous tissue can impair heart function and inhibit surgical access in reoperation procedures. Here, we propose a hydrogel barrier composed of oxime crosslinked poly(ethylene glycol) (PEG) with the inclusion of a catechol (Cat) group to improve retention on the heart for pericardial adhesion prevention. This three component system is comprised of aldehyde (Ald), aminooxy (AO), and Cat functionalized PEG mixed to form the final gel (Ald-AO-Cat). Ald-AO-Cat has favorable mechanical properties, degradation kinetics, and minimal swelling, as well as superior tissue retention compared to an initial Ald-AO gel formulation. We show that the material is cytocompatible, resists cell adhesion, and led to a reduction in the severity of adhesions in an in vivo rat model. We further show feasibility in a pilot porcine study. The Ald-AO-Cat hydrogel barrier may therefore serve as a promising solution for preventing post-surgical cardiac adhesions.

Advancement of Biomaterial-Based Postoperative Adhesion Barriers

Postoperative peritoneal adhesion (PPA) is a prevalent incidence that generally happens during the healing process of traumatized tissues. It causes multiple severe complications such as intestinal obstruction, chronic abdominal pain, and female infertility. To prevent PPA, several antiadhesion materials and drug delivery systems composed of biomaterials are used clinically, and clinical antiadhesive is one of the important applications nowadays. In addition to several commercially available materials, like film, spray, injectable hydrogel, powder, or solution type have been energetically studied based on natural and synthetic biomaterials such as alginate, hyaluronan, cellulose, starch, chondroitin sulfate, polyethylene glycol, polylactic acid, etc. Moreover, many kinds of animal adhesion models, such as cecum abrasion models and unitary horn models, are developed to evaluate new materials' efficacy. A new animal adhesion model based on hepatectomy and conventional animal adhesion models is recently developed and a new adhesion barrier by this new model is also developed. In summary, many kinds of materials and animal models are studied; thus, it is quite important to overview this field's current progress. Here, PPA is reviewed in terms of the species of biomaterials and animal models and several problems to be solved to develop better antiadhesion materials in the future are discussed.

"BAX602" in Preventing Surgical Adhesion after Extracorporeal Ventricular Assist Device Implantation for Refractory Congestive Heart Failure: Study Protocol for a Multicenter Randomized Clinical Trial

BACKGROUND

The high surgical risk in redo cardiac surgery is largely attributed to adhesions around the epicardium and the great vessels. BAX602 is an adhesion prevention reagent composed of two synthetic polyethylene glycols. Spraying BAX602 over the epicardium and the great vessels reportedly contributes to adhesion prevention after pediatric cardiac surgery. The present study aims to evaluate the safety and effectiveness of BAX602 spray in patients undergoing extracorporeal ventricular assist device implantation surgery to treat refractory congestive heart failure.

METHODS AND DESIGN

This investigator-initiated, multicenter, pivotal, two-arm, open-label, randomized trial will include a total of 30 patients. The primary outcome measure is the severity of adhesions, which will be evaluated during re-sternotomy surgery performed 2-12 weeks after the primary extracorporeal ventricular assist device implantation surgery. The adhesion severity will be evaluated at five predefined sites using a four-grade adhesion evaluation score (0 = no adhesion; 1 = filmy and avascular adhesion; 2 = dense/vascular adhesion; 3 = cohesive adhesion). This measure will be summarized in two ways to evaluate the effect of BAX602: (1) the total score of the severity of adhesions at all five sites (ranging from 0 to 15), and (2) the total number of sites with dense/vascular or cohesive adhesions (ranging from 0 to 5).

ETHICS AND DISSEMINATION

The study findings will be disseminated at regional, national, and international conferences and through peer-reviewed scientific journals.

TRIAL REGISTRATION

The trial was registered in the UMIN Clinical Trials Registry (UMIN-CTR: UMIN000038998) on 6 January 2020.

Urinary Bladder Matrix Scaffolds Promote Pericardium Repair in a Porcine Model

Pericardium closure after cardiac surgery is recommended to prevent postoperative adhesions to the sternum. Synthetic materials have been used as substitutes, with limited results because of impaired remodeling and fibrotic tissue formation. Urinary bladder matrix (UBM) scaffolds promote constructive remodeling that more closely resemble the native tissue. The aim of the study is to evaluate the host response to UBM scaffolds in a porcine model of partial pericardial resection. Twelve Landrace pigs were subjected to a median sternotomy. A 5 × 7 cm pericardial defect was created and then closed with a 5 × 7 cm multilayer UBM patch (UBM group) or left as an open defect (control group). Animals were survived for 8 wk. End points included gross morphology, biomechanical testing, histology with semiquantitative score, and cardiac function. The UBM group showed mild adhesions, whereas the control group showed fibrosis at the repair site, with robust adhesions and injury to the coronary bed. Load at failure (gr) and stiffness (gr/mm) were lower in the UBM group compared with the native pericardium (199.9 ± 59.2 versus 405.3 ± 99.89 g, P = 0.0536 and 44.23 ± 15.01 versus 146.5 ± 24.38 g/mm, P = 0.0025, respectively). In the UBM group, the histology resembled native pericardial tissue, with neovascularization, neofibroblasts, and little inflammatory signs. In contrast, control group showed fibrotic tissue with mononuclear infiltrates and a lack of organized collagen fibers validated with a histologic score. Both groups had normal ultrasonography results without cardiac motility disorders. In this setting, UBM scaffolds showed appropriate features for pericardial repair, restoring tissue properties that could help reduce postsurgical adhesions and prevent its associated complications.

The Effect of Mitomycin C on Reducing Endometrial Fibrosis for Intrauterine Adhesion

<strong>BACKGROUND</strong> Intrauterine adhesion (IUA) is a common reproductive system disease in women, characterized by endometrial stromal cell proliferation, increasing fibroblasts and increasing extracellular matrix secretion. The purpose of this study was to investigate the effect of mitomycin C on reducing endometrial fibrosis for IUA. <strong>MATERIAL AND METHODS</strong> Firstly, a rat IUA model was constructed by intrauterine mechanical injury. The endometrial stromal cells and fibroblasts were isolated and treated with mitomycin C. After that, Cell Counting Kit-8 (CCK-8) assay was used to investigate the endometrial stromal cell viability. Furthermore, cell cycle and apoptosis assays of endometrial stromal cells and fibroblasts were performed, respectively. Finally, the cell viability of human endometrial cells or human uterus adhesion fibroblasts treated with mitomycin C was determined using CCK-8 assay with or without estradiol. <strong>RESULTS</strong> Endometrial stromal cells were isolated from a rat IUA model. Cell cycle assay results showed that mitomycin C inhibited cell viability and promoted G1 cell cycle arrest and apoptosis in rat IUA endometrial stromal cells. Fibroblasts were also isolated from the rat IUA model. We found that mitomycin C inhibited the synthesis and secretion of collagen type I by western blotting analysis. Furthermore, mitomycin C promoted G1 cell cycle arrest and apoptosis in IUA rat uterine fibroblasts. We found that estradiol decreased the inhibitory effects of cell viability of human endometrial cells and human uterus adhesion fibroblasts by mitomycin C. <strong>CONCLUSIONS</strong> Our findings revealed that mitomycin C could reduce endometrial fibrosis for intrauterine adhesion.

A simple mouse model of pericardial adhesions

Background

Postoperative pericardial adhesions are considered a risk factor for redo cardiac surgery. Several large- and medium-size animal models of pericardial adhesions have been reported, but small animal models for investigating the development of anti-adhesion materials and molecular mechanisms of this condition are lacking. In this study, we aimed to establish a simple mouse model of pericardial adhesions to address this gap.

Methods

We administered blood, minocycline, picibanil, and talc into the murine pericardial cavity via one-shot injection. Micro-computed tomography analyses of contrast agent-injected mice were carried out for methodological evaluation. We investigated various dosages and treatment durations for molecules identified to be inducers of pericardial adhesion. The adhesive grade was quantified by scoring the strength and volume of adhesion tissues at sacrificed time points. Histological staining with hematoxylin and eosin and Masson’s trichrome, and immunostaining for F4/80 or αSMA was performed to investigate the structural features of pericardial adhesions, and pathological features of the pericardial adhesion tissue were compared with human clinical specimens.

Results

Administration of talc resulted in the most extensive pericardial adhesions. Micro-computed tomography imaging data confirmed that accurate injection into the pericardial cavity was achieved. We found the optimal condition for the formation of strong pericardial adhesions to be injection of 2.5 mg/g talc for 2 weeks. Furthermore, histological analysis showed that talc administration led to an invasion of myofibroblasts and macrophages in the pericardial cavity and epicardium, consistent with pathological findings in patients with left ventricular assistive devices.

Conclusions

We successfully established a simple mouse model of talc-induced pericardial adhesions, which mimics human pathology and could contribute to solving the clinical issues related to pericardial adhesions.

Battling adhesions: from understanding to prevention

Adhesions represent a major burden in clinical practice, particularly following abdominal, intrauterine, pericardial and tendon surgical procedures. Adhesions are initiated by a disruption in the epithelial or mesothelial layer of tissue, which leads to fibrin adhesion sites due to the downregulation of fibrinolytic activity and an increase in fibrin deposition. Hence, the metabolic events involved in tissue healing, coagulation, inflammation, fibrinolysis and angiogenesis play a pivotal role in adhesion formation. Understanding these events, their interactions and their influence on the development of post-surgical adhesion is crucial for the development of effective therapies to prevent them. Mechanical barriers, antiadhesive agents and combination thereof are customarily used in the battle against adhesions. Although these systems seem to be effective at reducing adhesions in clinical procedures, their prevention remains still elusive, imposing the need for new antiadhesive strategies.

An Absorbable Hydrogel Spray Reduces Postoperative Mediastinal Adhesions After Congenital Heart Surgery

BACKGROUND

Adhesions encountered during reoperative cardiac surgery can prolong operative time and increase operative risk. The purpose of this clinical study was to investigate the antiadhesion property of a synthetic bioabsorbable polymer spray after cardiac reoperations in infants.

METHODS

A prospective randomized double-blinded study was designed. Forty infants requiring staged cardiac operations were randomly allocated to a study group (n = 20) or a control group (n = 20). The appropriate volume of the polymer was sprayed onto the mediastinal surfaces before chest closure after the first surgical procedure in the study group. At reoperation, adhesions were evaluated by a blinded investigator following a 5-grade scoring system. Five predetermined anatomic areas were scored. Incision to extracorporeal circulation time was also analyzed.

RESULTS

In all, 40 subjects were enrolled into the study. Four babies died before the second operation. Three others were missed for reevaluation. The control group (n = 16) had longer incision to extracorporeal circulation time (38 ± 10 minutes) than the study group (n = 17; 23 ± 6 minutes; p < 0.001). The control subjects had significantly more severe adhesions than the study group at all five mediastinal areas: (1) retrosternal (p < 0.001); (2) base of the heart (large vessels [p < 0.05]); (3) right side (p < 0.01); (4) left side (p < 0.02); and (5) diaphragmatic side of the mediastinum (p < 0.001).

CONCLUSIONS

The use of synthetic bioabsorbable polymer sealant spray at the end of primary pediatric cardiac surgery reduces the intensity of mediastinal adhesions and the reentry time in infants undergoing repeat median sternotomy.

Post-sternotomy pain syndrome following cardiac surgery: case report

Over 2 million people undergo sternotomy worldwide for heart surgery each year, and many develop post-sternotomy pain syndrome (PSPS) which persists in the anterior thorax. In some patients, PSPS lasts for many years or suddenly reappears a long time after the sternotomy. The exact etiology of PSPS is unknown. This article presents a case report of a patient with a diagnosis of PSPS (after cardiac surgery 4 years prior) for whom an osteopathic approach was used, which successfully eliminated the pain. In a previous study, we demonstrated that this osteopathic procedure could reduce sternal pain associated with a recent surgical wound. Further efforts are needed to understand the reasons for PSPS. In light of new scientific data, these osteopathic techniques could contribute to a multidisciplinary approach to solve the problem.

Effect of Temperature-Sensitive Poloxamer Solution/Gel Material on Pericardial Adhesion Prevention: Supine Rabbit Model Study Mimicking Cardiac Surgery

Objective

We investigated the mobility of a temperature-sensitive poloxamer/Alginate/CaCl₂ mixture (PACM) in relation to gravity and cardiac motion and the efficacy of PACM on the prevention of pericardial adhesion in a supine rabbit model.

Methods

A total of 50 rabbits were randomly divided into two groups according to materials applied after epicardial abrasion: PACM and dye mixture (group PD; n = 25) and saline as the control group (group CO; n = 25). In group PD, rabbits were maintained in a supine position with appropriate sedation, and location of mixture of PACM and dye was assessed by CT scan at the immediate postoperative period and 12 hours after surgery. The grade of adhesions was evaluated macroscopically and microscopically two weeks after surgery.

Results

In group PD, enhancement was localized in the anterior pericardial space, where PACM and dye mixture was applied, on immediate post-surgical CT scans. However, the volume of the enhancement was significantly decreased at the anterior pericardial space 12 hours later (P < .001). Two weeks after surgery, group PD had significantly lower macroscopic adhesion score (P = .002) and fibrosis score (P = .018) than did group CO. Inflammation score and expression of anti-macrophage antibody in group PD were lower than those in group CO, although the differences were not significant.

Conclusions

In a supine rabbit model study, the anti-adhesion effect was maintained at the area of PACM application, although PACM shifted with gravity and heart motion. For more potent pericardial adhesion prevention, further research and development on the maintenance of anti-adhesion material position are required.

Binding of Anticell Adhesive Oxime-Crosslinked PEG Hydrogels to Cardiac Tissues

Postsurgical cardiac adhesions increase the number of surgeries as well as patient mortality and morbidity. A fast gelling oxime-crosslinked PEG hydrogel with tunable gelation time, degradation, and mechanical properties is presented. This material is cytocompatible and prevents cellular adhesion. Material retention on different cardiac tissues is demonstrated ex vivo over time and that functional group ratio alters material retention on different cardiac tissues.

Assessment of the efficacy of Ankaferd blood stopper on the prevention of postoperative pericardial adhesions

Objectives

Ankaferd has been used as a blood-stopping agent and it may also have an anti-inflammatory effect. We investigated the efficacy of Ankaferd in preventing postoperative pericardial adhesions in an experimental rabbit model.

Methods

Sixteen New Zealand white rabbits were used and categorised into two groups: an Ankaferd and a control group. The Ankaferd group of rabbits was treated with a sponge impregnated with Ankaferd solution, which was applied over the abraded epicardium. A sponge impregnated with 0.9% isotonic NaCl solution was applied to the control group using the same protocol. Scores for adhesion and visibility of coronary vessels were graded by macroscopic examination, and pericardial tissues were analysed microscopically in terms of inflammation and fibrosis.

Results

In the Ankaferd group, the adhesion scores were significantly higher than in the control group (p = 0.007). When the groups were compared according to the prevalence of fibrosis and degree of inflammation, the Ankaferd group was found to be statistically significantly different from the control group in terms of prevalence of fibrosis (p = 0.028).

Conclusion

Topical application of Ankaferd to prevent postoperative pericardial adhesions increased adhesion and fibrosis scores.