The cardiovascular system and the biochemistry of grafts used in heart surgery

Subfatin, Asprosin, Alamandine and Maresin-1 Inflammation Molecules in Cardiopulmonary Bypass

Purpose

Cardiopulmonary bypass (CPB) is a nonphysiological procedure in which inflammatory reactions and oxidative stress are induced, hormones and hemodynamic parameters are affected, and circulation is maintained outside the body. This study aimed to examine the effects of CPB on blood subfatin (SUB), asprossin (ASP), alamandine (ALA) and maresin-1 (MaR-1) levels.

Materials and Methods

Controls and patients who underwent open-heart surgery with CPB and whose age and body mass indices were compatible with each other were included in the study. Venous blood samples were collected from CPB patients (n =19) before anesthesia induction (T1), before CPB (T2), 5 min before cross-clamp removal (T3), 5 min after cross-clamp removal (T4), when taken to the intensive care unit (T5), postoperative 24th hour (T6) and 72nd hour (T7) postoperatively. Venous blood was collected from the healthy controls (n =19). The amounts of SUB, ASP, ALA, and MaR-1 in the blood samples were measured using an Enzyme-Linked Immunosorbent Assay (ELISA).

Results

The amounts of SUB and MaR-1 in the control group were significantly higher than those in CPB patients, while these parameters in T1-T3 blood gradually decreased in CPB patients (p<0.01). It was also reported that the amounts of ASP and ALA in the control group were significantly lower than those in CPB patients, whereas those parameters in the T1-T3 blood samples increased gradually in CPB patients, but started to decrease in T4-T7 blood samples.

Conclusion

These hormonal changes in the organism due to CPB demonstrate that "hormonal metabolic adaptation" mechanisms may be activated to eliminate the negative consequences of surgery. According to these data, SUB, MaR-1, anti-alamandine, and anti-asprosin could be used in CPB surgeries may come to the fore in the future to increase the safety of CPB surgeries.

Tissue-engineered collagenous fibrous cap models to systematically elucidate atherosclerotic plaque rupture

A significant amount of vascular thrombotic events are associated with rupture of the fibrous cap that overlie atherosclerotic plaques. Cap rupture is however difficult to predict due to the heterogenous composition of the plaque, unknown material properties, and the stochastic nature of the event. Here, we aim to create tissue engineered human fibrous cap models with a variable but controllable collagen composition, suitable for mechanical testing, to scrutinize the reciprocal relationships between composition and mechanical properties. Myofibroblasts were cultured in 1 × 1.5 cm-sized fibrin-based constrained gels for 21 days according to established (dynamic) culture protocols (i.e. static, intermittent or continuous loading) to vary collagen composition (e.g. amount, type and organization). At day 7, a soft 2 mm ∅ fibrin inclusion was introduced in the centre of each tissue to mimic the soft lipid core, simulating the heterogeneity of a plaque. Results demonstrate reproducible collagenous tissues, that mimic the bulk mechanical properties of human caps and vary in collagen composition due to the presence of a successfully integrated soft inclusion and the culture protocol applied. The models can be deployed to assess tissue mechanics, evolution and failure of fibrous caps or complex heterogeneous tissues in general.

Optimal Time Repair of Ventricular Septal Rupture Post Myocardial Infarction

Ventricular septal rupture (VSR) is an uncommon complication of myocardial infarction (MI). The mortality rate of VSR is high. The management of VSR is including the stabilization of the hemodynamic status and surgical closure of the rupture. In spite of the agreement of experts on the necessity of surgical repair, the timing of VSR repair management remains unclear. In this review article, we evaluate the optimal time repair of VSR. To collect the data, Pubmed, EMBASE, and Cochrane Central Registry databases were searched for potentially suitable studies. Search terms were including “Ventricular Septal Rupture”, “Myocardial Infarction”, “Timing”, and “MI”. According to the result of the studies, it seems that the time between VSR detection and its repair is a determining factor in the survival or mortality of patients in post-myocardial infraction VSR. Studies showed that earlier surgical repair in VSR increases the risk of mortality, because in the early phase after MI, infarcted myocardium is very fragile, and it is very difficult surgical repair and increases the risk of recurrent septal defects. The longer time is needed for the heart and different body systems to adapt to the hemodynamic results of the abrupt left to right shunt. It seems that the best time for the operation is after the maturation of VSR with scarring at the edges of the defect. Moreover, in a large number of patients, it is not possible to delay the operation since they are at risk of severe heart failure and organ dysfunction. In these cases operation immediately after diagnosis of VSR is recommended to prevent further hemodynamic deterioration. In hemodynamically compromised patients, it may be considered to use a ventricular assist device, requiring an intra-aortic balloon pump (IABP), or extracorporeal membrane oxygenation (ECMO) preoperative to postpone the operation which leads to higher survival in post-MI-VSD.

Role of smooth muscle cells in coronary artery bypass grafting failure

Atherosclerosis is the underlying pathology of many cardiovascular diseases. The formation and rupture of atherosclerotic plaques in the coronary arteries results in angina and myocardial infarction. Venous coronary artery bypass grafts are designed to reduce the consequences of atherosclerosis in the coronary arteries by diverting blood flow around the atherosclerotic plaques. However, vein grafts suffer a high failure rate due to intimal thickening that occurs as a result of vascular cell injury and activation and can act as 'a soil' for subsequent atherosclerotic plaque formation. A clinically-proven method for the reduction of vein graft intimal thickening and subsequent major adverse clinical events is currently not available. Consequently, a greater understanding of the underlying mechanisms of intimal thickening may be beneficial for the design of future therapies for vein graft failure. Vein grafting induces inflammation and endothelial cell damage and dysfunction, that promotes vascular smooth muscle cell (VSMC) migration, and proliferation. Injury to the wall of the vein as a result of grafting leads to the production of chemoattractants, remodelling of the extracellular matrix and cell-cell contacts; which all contribute to the induction of VSMC migration and proliferation. This review focuses on the role of altered behaviour of VSMCs in the vein graft and some of the factors which critically lead to intimal thickening that pre-disposes the vein graft to further atherosclerosis and re-occurrence of symptoms in the patient.

Long-term graft patency after coronary artery bypass grafting: Effects of morphological and pathophysiological factors

OBJECTIVE

The aim of the present study was to identify morphological and pathophysiological factors associated with long-term patency of grafts used in coronary artery bypass grafting (CABG).

METHODS

A total of 127 patients who underwent CABG between 2000 and 2006 and presented for computed tomography evaluation of graft patency at 139.78±36.64 months post-CABG were analyzed. Patients received 340 grafts (2.68 grafts/patient), 399 distal anastomoses (3.14 anastomoses/ patient), 220 (55.14%) performed using arterial grafts, and 179 (44.86%) using saphenous vein grafts (SVGs).

RESULTS

Graft patency varied according to vessel type and coronary territory. Overall graft patency was 90.16% for the left internal thoracic artery (LITA), 75.55% for the right internal thoracic artery (RITA), 79.25% for the radial artery (RA), and 74.3% for the SVG. The maximum patency rate was obtained with the RA (80.65%) for the right coronary territory, RITA (92.86%) for the anterolateral territory, and SVG (82.54%) for the circumflex territory. The LITA-left anterior descending artery graft occluded in 13 (7.93%) cases, 7 due to competitive flow. The influence of graft length on patency rates after indexing to height was not significant. The target vessel degree of stenosis influenced arterial graft patency rates with an occlusion odds ratio (OR) of 3.02 when anastomosed to target vessels with <90% stenosis. Target vessel caliber also influenced patency rates with occlusion ORs of 2.63 for SVGs and 2.31 for arterial grafts when anastomosed to ≤1.5 mm target vessels.

CONCLUSION

Morphological parameters, such as graft type, target territory, target vessel caliber, and degree of stenosis, are important factors conditioning long-term graft patency.

Computationally optimizing the compliance of multilayered biomimetic tissue engineered vascular grafts

Coronary artery bypass grafts used to treat coronary artery disease often fail due to compliance mismatch. In this study, we have developed an experimental/computational approach to fabricate an acellular biomimetic hybrid tissue engineered vascular graft composed of alternating layers of electrospun porcine gelatin/polycaprolactone (PCL) and human tropoelastin/PCL blends with the goal of compliance-matching to rat abdominal aorta, while maintaining specific geometrical constraints. Polymeric blends at three different gelatin:PCL (G:PCL) and tropoelastin:PCL (T:PCL) ratios (80:20, 50:50 and 20:80) were mechanically characterized. The stress-strain data was used to develop predictive models, which were used as part of an optimization scheme that was implemented to determine the ratios of G:PCL and T:PCL and the thickness of the individual layers within a tissue engineered vascular graft that would compliance match a target compliance value. The hypocompliant, isocompliant, and hypercompliant grafts had target compliance values of 0.000256, 0.000568 and 0.000880 mmHg-1, respectively. Experimental validation of the optimization demonstrated that the hypercompliant and isocompliant grafts were not statistically significant from their respective target compliance values (p-value=0.37 and 0.89, respectively). The experimental compliance value of the hypocompliant graft was statistically significant than their target compliance value (p-value=0.047). We have successfully demonstrated a design optimization scheme that can be used to fabricate multilayered and biomimetic vascular grafts with targeted geometry and compliance.

Long-term graft patency after coronary artery bypass grafting: Effects of surgical technique

The aim of the current study was to identify surgical factors associated with long-term patency of grafts used in coronary artery bypass grafting (CABG). The present study analyzed data from 127 patients who underwent CABG at our institute between 2000 and 2006 and presented for ambulatory examination and coronary computed tomography angiography evaluation of graft patency in 2016 (139.78±36.64 months post-CABG). The 127 patients received 340 grafts (2.68 grafts/patient) and 399 distal anastomoses (3.14 anastomoses/patient), 220 (55.14%) with arterial grafts and 179 (44.86%) with saphenous vein grafts. Graft patency varied according to coronary territory, proximal anastomosis type (in situ graft, composite graft, graft anastomosed to the ascending aorta), Y anastomosis angle (47.21° for patent arterial grafts vs. 56° for occluded), and distal anastomosis angle (in sequential anastomoses irrespective to graft type, 48.60° for patent side-to-side anastomosis vs. 53.97° for occluded, 65.12° for patent end-to-side anastomosis vs. 90.80° for occluded; in single end-to-side anastomosis of arterial grafts, 39.46° for patent and 44.94° for occluded). A single end-to-side anastomosis angle 60° or greater was associated with a 5.149 occlusion odds ratio (OR) (P<0.001) for arterial grafts. Venous grafts were not sensitive to single end-to-side anastomosis angle. In conclusion, a small anastomosis angle for proximal Y and distal anastomoses is associated with a higher long-term patency of the free graft. Radial artery grafts registered higher patency rates when anastomosed to the ascending aorta compared with composite grafting with the left internal thoracic artery, whereas in situ right internal thoracic artery (RITA) anastomosed to the right coronary territory is associated with a lower patency rate compared with free RITA used to revascularise the anterolateral or circumflex territory in composite grafting.

Biomarkers in acute myocardial infarction: current perspectives

PURPOSE

Acute myocardial infarction (AMI) is the most common cause of death in the world. Comprehensive risk assessment of patients presenting with chest pain and eliminating undesirable results should decrease morbidity and mortality rates, increase the quality of life of patients, and decrease health expenditure in many countries. In this study, the advantages and disadvantages of the enzymatic and nonenzymatic biomarkers used in the diagnosis of patients with AMI are given in historical sequence, and some candidate biomarkers - hFABP, GPBB, S100, PAPP-A, RP, TNF, IL6, IL18, CD40 ligand, MPO, MMP9, cell-adhesion molecules, oxidized LDL, glutathione, homocysteine, fibrinogen, and D-dimer procalcitonin - with a possible role in the diagnosis of AMI are discussed.

METHODS

The present study was carried out using meta-analyses, reviews of clinical trials, evidence-based medicine, and guidelines indexed in PubMed and Web of Science.

RESULTS

These numerous AMI biomarkers guide clinical applications (diagnostic methods, risk stratification, and treatment). Today, however, TnI remains the gold standard for the diagnosis of AMI. Details in the text will be given of many biomarkers for the diagnosis of AMI.

CONCLUSION

We evaluated the advantages and disadvantages of routine enzymatic and nonenzymatic biomarkers and the literature evidence of other candidate biomarkers in the diagnosis of AMI, and discuss challenges and constraints that limit translational use from bench to bedside.

Vascularisation for cardiac tissue engineering: the extracellular matrix

Cardiovascular diseases present a major socio-economic burden. One major problem underlying most cardiovascular and congenital heart diseases is the irreversible loss of contractile heart muscle cells, the cardiomyocytes. To reverse damage incurred by myocardial infarction or by surgical correction of cardiac malformations, the loss of cardiac tissue with a thickness of a few millimetres needs to be compensated. A promising approach to this issue is cardiac tissue engineering. In this review we focus on the problem of in vitro vascularisation as implantation of cardiac patches consisting of more than three layers of cardiomyocytes (> 100 μm thick) already results in necrosis. We explain the need for vascularisation and elaborate on the importance to include non-myocytes in order to generate functional vascularised cardiac tissue. We discuss the potential of extracellular matrix molecules in promoting vascularisation and introduce nephronectin as an example of a new promising candidate. Finally, we discuss current biomaterial- based approaches including micropatterning, electrospinning, 3D micro-manufacturing technology and porogens. Collectively, the current literature supports the notion that cardiac tissue engineering is a realistic option for future treatment of paediatric and adult patients with cardiac disease.

The effect of iloprost and sildenafil, alone and in combination, on myocardial ischaemia and nitric oxide and irisin levels

Aim

Insufficient oxygen supply to organs and tissues due to reduced arterial or venous blood flow results in ischaemia, during which, although ATP production stops, AMP and adenosine continue to be produced from ATP. The fate of irisin, which causes the production of heat instead of ATP during ischaemia, is unknown. Iloprost and sildenafil are two pharmaceutical agents that mediate the resumption of reperfusion (blood supply) via vasodilatation during ischaemic conditions. Our study aimed to explore the effects of iloprost and sildenafil on irisin levels in the heart, liver and kidney tissues and whether these pharmaceutical agents had any impact on serum irisin and nitric oxide levels in rats with induced experimental myocardial ischaemia.

Methods

The study included adult male Sprague-Dawley rats aged 10 months and weighing between 250 and 280 g. The animals were randomly allocated to eight groups, with five rats in each group. The groups were: sham (control), iloprost (ILO), sildenafil (SIL), ILO + SIL, myocardial ischaemia (MI), MI + ILO, MI + SIL and MI + ILO + SIL. The treatment protocols were implemented before inducing ischaemia, which was done by occluding the left coronary artery with a plastic ligature for 30 minutes. Following the reperfusion procedure, all rats were sacrificed after 24 hours, and their heart, liver and kidney tissues and blood samples were collected for analyses. An immunohistochemical method was used to measure the change in irisin levels, the ELISA method to quantify blood irisin levels, and Griess’ assay to determine nitric oxide (NO) levels in the serum and tissue. Myocardial ischaemia was confirmed based on the results of Masson’s trichrome staining, as well as levels of troponin and creatine kinase MB.

Results

Irisin levels in biological tissue and serum dropped statistically significantly in the ischaemic group (MI), but were restored with ILO and SIL administration. Individual SIL administration was more potently restorative than individual ILO administration or the combined administration of the two agents. NO level, on the other hand, showed the opposite tendency, reaching the highest level in the MI group, and falling with the use of pharmaceutical agents.

Conclusions

Individual or combined administration of ILO and SIL reduced myocardial ischaemia and NO levels, and increased irisin levels. Elevated levels of irisin obtained by drug administration could possibly contribute to accelerated wound recovery by local heat production. Sildenafil was more effective than iloprost in eliminating ischaemia and may be the first choice in offsetting the effects of ischaemia in the future.

Novel potential targets for prevention of arterial restenosis: insights from the pre-clinical research

Restenosis is the pathophysiological process occurring in 10-15% of patients submitted to revascularization procedures of coronary, carotid and peripheral arteries. It can be considered as an excessive healing reaction of the vascular wall subjected to arterial/venous bypass graft interposition, endarterectomy or angioplasty. The advent of bare metal stents, drug-eluting stents and of the more recent drug-eluting balloons, have significantly reduced, but not eliminated, the incidence of restenosis, which remains a clinically relevant problem. Biomedical research in pre-clinical animal models of (re)stenosis, despite its limitations, has contributed enormously to the identification of processes involved in restenosis progression, going well beyond the initial dogma of a primarily proliferative disease. Although the main molecular and cellular mechanisms underlying restenosis have been well described, new signalling molecules and cell types controlling the progress of restenosis are continuously being discovered. In particular, microRNAs and vascular progenitor cells have recently been shown to play a key role in this pathophysiological process. In addition, the advanced highly sensitive high-throughput analyses of molecular alterations at the transcriptome, proteome and metabolome levels occurring in injured vessels in animal models of disease and in human specimens serve as a basis to identify novel potential therapeutic targets for restenosis. Molecular analyses are also contributing to the identification of reliable circulating biomarkers predictive of post-interventional restenosis in patients, which could be potentially helpful in the establishment of an early diagnosis and therapy. The present review summarizes the most recent and promising therapeutic strategies identified in experimental models of (re)stenosis and potentially translatable to patients subjected to revascularization procedures.