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.

Post-Operative Adhesions: A Comprehensive Review of Mechanisms

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

Targeting Myeloid-Derived Suppressor Cells for Premetastatic Niche Disruption After Tumor Resection

Surgical resection is a common therapeutic option for primary solid tumors. However, high cancer recurrence and metastatic rates after resection are the main cause of cancer related mortalities. This implies the existence of a "fertile soil" following surgery that facilitates colonization by circulating cancer cells. Myeloid-derived suppressor cells (MDSCs) are essential for premetastatic niche formation, and may persist in distant organs for up to 2 weeks after surgery. These postsurgical persistent lung MDSCs exhibit stronger immunosuppression compared with presurgical MDSCs, suggesting that surgery enhances MDSC function. Surgical stress and trauma trigger the secretion of systemic inflammatory cytokines, which enhance MDSC mobilization and proliferation. Additionally, damage associated molecular patterns (DAMPs) directly activate MDSCs through pattern recognition receptor-mediated signals. Surgery also increases vascular permeability, induces an increase in lysyl oxidase and extracellular matrix remodeling in lungs, that enhances MDSC mobilization. Postsurgical therapies that inhibit the induction of premetastatic niches by MDSCs promote the long-term survival of patients. Cyclooxygenase-2 inhibitors and β-blockade, or their combination, may minimize the impact of surgical stress on MDSCs. Anti-DAMPs and associated inflammatory signaling inhibitors also are potential therapies. Existing therapies under tumor-bearing conditions, such as MDSCs depletion with low-dose chemotherapy or tyrosine kinase inhibitors, MDSCs differentiation using all-trans retinoic acid, and STAT3 inhibition merit clinical evaluation during the perioperative period. In addition, combining low-dose epigenetic drugs with chemokine receptors, reversing immunosuppression through the Enhanced Recovery After Surgery protocol, repairing vascular leakage, or inhibiting extracellular matrix remodeling also may enhance the long-term survival of curative resection patients.

The anti-adhesive effect of anti-VEGF agents in experimental models: A systematic review

Adhesions constitute a major problem in abdominal-pelvic and thoracic surgery with significant impact in the postoperative quality of life and healthcare services utilization. Adhesiogenesis is the result of increased fibrin formation, impaired fibrinolysis, angiogenesis, and fibrosis. Despite the recent advancements, the ideal anti-adhesive agent remains to be determined. To this end, we performed a comprehensive literature search in PubMed, EMBASE, and Scopus databases to identify studies investigating the antiadhesive role of anti-VEGF agents in peritoneal, pleural, and pericardial experimental adhesion models. Fifteen studies were eligible for inclusion with a total population of 602 animals (334 rats, 180 rabbits, and 88 mice). The majority of included studies (11/15) used bevacizumab, while three studies used other anti-VEGF antibodies and one study used an anti-VEGFR-antibody. A rat model was used in nine studies, while rabbit (n = 3) or mouse (n = 3) models were used less frequently. Eleven studies used peritoneal models, three studies used pleural models, and one study used a pericardial model. The scales (n = 12) and interval (Range: 1-42 days) used for the evaluation of adhesions varied between the studies. All studies demonstrated a significant decrease in adhesion scores between the anti-VEGF and control groups up to 42 days postprocedure. VEGF blockade resulted in decreased fibrosis in four out of five studies that used peritoneal models, while the effect on pleural models depended on the pleurodesis agent and was significant between 7 and 28 days. The effect of anti-VEGF agents on anastomosis integrity depends on the dose and the model that is used (inconclusive results).Current data support the anti-adhesive role of Anti-VEGF agents in all three serosal surfaces up to 6 weeks postprocedure. Further studies are needed to confirm the anti-adhesive role of anti-VEGF agents in pleural and pericardial adhesion experimental models and investigate any effect on anastomosis integrity in peritoneal models.