TNX-1500, a crystallizable fragment-modified anti-CD154 antibody, prolongs nonhuman primate cardiac allograft survival.

Blockade of the CD40/CD154 T cell costimulation pathway is a promising approach to supplement or replace current clinical immunosuppression in solid organ transplantation. We evaluated the tolerability and activity of a novel humanized anti-CD154 monoclonal antibody, TNX-1500 (TNX), in a nonhuman primate heterotopic cardiac allogeneic (allo) transplant model. TNX-1500 contains a rupluzimab fragment antigen-binding region and an immunoglobin G4 crystallizable fragment region engineered to reduce binding to the crystallizable fragment gamma receptor IIa and associated risks of thrombosis. Recipients were treated for 6 months with standard-dose TNX (sTNX) monotherapy, low-dose TNX monotherapy (loTNX), or loTNX with mycophenolate mofetil (MMF) (loTNX + MMF). Results were compared with historical data using chimeric humanized 5c8 monotherapy dosed as for loTNX but discontinued at 3 months. Median survival time was similar for humanized 5c8 and both loTNX groups, but significantly longer with sTNX (>265 days) than with loTNX (99 days) or loTNX + MMF (88 days) (P < 0.05 for both comparisons against sTNX). Standard-dose TNX prevented antidonor alloantibody elaboration, inhibited chronic rejection, and was associated with a significantly reduced effector T cells/regulatory T cells ratio relative to loTNX with MMF. No thrombotic complications were observed. This study demonstrated that TNX was well tolerated, prolongs allograft survival, and prevents alloantibody production and cardiac allograft vasculopathy in a stringent preclinical nonhuman primate heart allotransplant model.

Increased human complement pathway regulatory protein gene dose is associated with increased endothelial expression and prolonged survival during ex-vivo perfusion of GTKO pig lungs with human blood.

INTRODUCTION: Expression of human complement pathway regulatory proteins (hCPRP's) such as CD46 or CD55 has been associated with improved survival of pig organ xenografts in multiple different models. Here we evaluate the hypothesis that an increased human CD46 gene dose, through homozygosity or additional expression of a second hCPRP, is associated with increased protein expression and with improved protection from injury when GTKO lung xenografts are perfused with human blood. METHODS: Twenty three GTKO lungs heterozygous for human CD46 (GTKO.heteroCD46), 10 lungs homozygous for hCD46 (GTKO.homoCD46), and six GTKO.homoCD46 lungs also heterozygous for hCD55 (GTKO.homoCD46.hCD55) were perfused with human blood for up to 4 h in an ex vivo circuit. RESULTS: Relative to GTKO.heteroCD46 (152 min, range 5-240; 6/23 surviving at 4 h), survival was significantly improved for GTKO.homoCD46 (>240 min, range 45-240, p = .034; 7/10 surviving at 4 h) or GTKO.homoCD46.hCD55 lungs (>240 min, p = .001; 6/6 surviving at 4 h). Homozygosity was associated with increased capillary expression of hCD46 (p < .0001). Increased hCD46 expression was associated with significantly prolonged lung survival (p = .048),) but surprisingly not with reduction in measured complement factor C3a. Hematocrit, monocyte count, and pulmonary vascular resistance were not significantly altered in association with increased hCD46 gene dose or protein expression. CONCLUSION: Genetic engineering approaches designed to augment hCPRP activity - increasing the expression of hCD46 through homozygosity or co-expressing hCD55 with hCD46 - were associated with prolonged GTKO lung xenograft survival. Increased expression of hCD46 was associated with reduced coagulation cascade activation, but did not further reduce complement activation relative to lungs with relatively low CD46 expression. We conclude that coagulation pathway dysregulation contributes to injury in GTKO pig lung xenografts perfused with human blood, and that the survival advantage for lungs with increased hCPRP expression is likely attributable to improved endothelial thromboregulation.

Knock-out of N-glycolylneuraminic acid attenuates antibody-mediated rejection in xenogenically perfused porcine lungs.

BACKGROUND: Antibody-mediated rejection has long been known to be one of the major organ failure mechanisms in xenotransplantation. In addition to the porcine α1,3-galactose (α1,3Gal) epitope, N-Glycolylneuraminic acid (Neu5Gc), a sialic acid, has been identified as an important porcine antigen against which most humans have pre-formed antibodies. Here we evaluate GalTKO.hCD46 lungs with an additional cytidine monophospho-N-acetylneuraminic acid hydroxylase (CMAH) gene knock-out (Neu5GcKO) in a xenogeneic ex vivo perfusion model METHODS: Eleven GalTKO.hCD46.Neu5GcKO pig lungs were perfused for up to 6 h with fresh heparinized human blood. Six of them were treated with histamine (H) blocker famotidine and 1-thromboxane synthase inhibitor Benzylimidazole (BIA) and five were left untreated. GalTKO.hCD46 lungs without Neu5GcKO (n = 18: eight untreated and 10 BIA+H treated) served as a reference. Functional parameters, blood, and tissue samples were collected at pre-defined time points throughout the perfusion RESULTS: All but one Neu5GcKO organs maintained adequate blood oxygenation and "survived" until elective termination at 6 h whereas two reference lungs failed before elective termination at 4 h. Human anti-Neu5Gc antibody serum levels decreased during the perfusion of GalTKO.hCD46 lungs by flow cytometry (∼40% IgM, 60% IgG), whereas antibody levels in Neu5GcKO lung perfusions did not fall (IgM p = .007; IgG p < .001). Thromboxane elaboration, thrombin generation, and histamine levels were significantly reduced with Neu5GcKO lungs compared to reference in the untreated groups (p = .007, .005, and .037, respectively); treatment with BIA+H masked these changes. Activation of platelets, measured as CD62P expression on circulating platelets, was lower in Neu5GcKO experiments compared to reference lungs (p = .023), whereas complement activation (as C3a rise in plasma) was not altered. MCP-1 and lactotransferin level elevations were blunted in Neu5GcKO lung perfusions (p = .007 and .032, respectively). Pulmonary vascular resistance (PVR) rise was significantly attenuated and delayed in untreated GalTKO.hCD46.Neu5GcKO lungs in comparison to the untreated GalTKO.hCD46 lungs (p = .003) CONCLUSION: Additional Neu5GcKO in GalTKO.hCD46 lungs significantly reduces parameters associated with antibody-mediated inflammation and activation of the coagulation cascade. Knock-out of the Neu5Gc sialic acid should be beneficial to reduce innate immune antigenicity of porcine lungs in future human recipients.

Three-Dimensional-Evaluation of Aortic Changes after Frozen Elephant Trunk (FET) in Zone 0 vs. Zone 2 in Acute Type A Aortic Dissection.

Introduction: The management of aortic dissection has evolved significantly over the decades, with the frozen elephant trunk (FET) procedure emerging as a key technique for treating complex aortic pathologies. Recent practices involve deploying the FET prosthesis more proximally in the aorta (Zone 0) to reduce complications, leading to questions about its impact on long-term aortic remodeling compared to traditional Zone 2 deployment. Methods: This retrospective analysis utilized 3D segmentation software to assess the volumetric changes in aortic remodeling after acute Type A aortic dissections, comparing FET stent graft deployment in Zone 0 and Zone 2. The study included 27 patients operated on between 2020 and 2022, with volumetric measurements taken from postoperative and 6-month follow-up CT scans. Statistical analyses were performed to evaluate the differences in the aortic true lumen (TL) and the perfused false lumen (PFL) between the two groups. Results: Both Zone 0 and Zone 2 deployments resulted in significant true lumen (TL) increases (Z0 p = 0.001, Z2 p < 0.001) and perfused false lumen (PFL) decreases (Z0 p = 0.02, Z2 p = 0.04), with no significant differences in volumetric changes between the groups (p = 0.7 post op and p = 0.9 after 6 months). The distal anastomosis in Zone 0 did not compromise the aortic remodeling outcomes and was associated with reduced distal ischemia and cerebral perfusion times (p = 0.041). The angle measurements in Zone 0 did not show any significant changes after the 6-month control (p = 0.2). However, in Zone 2, a significant change was detected. (p = 0.022). The part comparison analyses did not indicate significant differences in aortic deviation between the groups (p = 0.62), suggesting comparable effectiveness in aortic remodeling. Conclusions: Performing the distal anastomosis more proximally in Zone 0 offers technical advantages without compromising the effectiveness of aortic remodeling compared to the traditional Zone 2 deployment. This finding supports the continued recommendation of Zone 0 deployment in the management of acute Type A aortic dissections, with ongoing studies being needed to confirm the long-term outcomes and survival benefits.

Future of Lung Transplantation: Xenotransplantation and Bioengineering Lungs.

Xenotransplantation promises to alleviate the issue of donor organ shortages and to decrease waiting times for transplantation. Recent advances in genetic engineering have allowed for the creation of pigs with up to 16 genetic modifications. Several combinations of genetic modifications have been associated with extended graft survival and life-supporting function in experimental heart and kidney xenotransplants. Lung xenotransplantation carries specific challenges related to the large surface area of the lung vascular bed, its innate immune system's intrinsic hyperreactivity to perceived 'danger', and its anatomic vulnerability to airway flooding after even localized loss of alveolocapillary barrier function. This article discusses the current status of lung xenotransplantation, and challenges related to immunology, physiology, anatomy, and infection. Tissue engineering as a feasible alternative to develop a viable lung replacement solution is discussed.

Pig heart and lung xenotransplantation: Present status.

The recent pig heart transplant in a patient at the University of Maryland Medical Center has stimulated renewed interest in the xenotransplantation of organs from genetically engineered pigs. The barriers to the use of pigs as sources of organs have largely been overcome by 2 approaches - (1) the deletion of expression of the three known pig carbohydrate xenoantigens against which humans have preformed antibodies, and (2) the transgenic introduction of human 'protective' proteins, such as complement-regulatory proteins. These gene modifications, coupled with immunosuppressive therapy based on blockade of the CD40/CD154 costimulation pathway, have resulted in survival of baboons with life-supporting pig heart grafts for almost 9 months. The initial clinical success at the University of Maryland reinforces encouraging preclinical results. It suggests that pig hearts are likely to provide an effective bridge to an allotransplant, but their utility for destination therapy remains uncertain. Because of additional complex immunobiological problems, the same approach has been less successful in preclinical lung xenograft transplantation, where survival is still measured in days or weeks. The first formal clinical trials of pig heart transplantation may include patients who do not have access to an allotransplant, those with contraindications for mechanical circulatory support, those in need of retransplantation or with a high level of panel-reactive antibodies. Infants with complex congenital heart disease, should also be considered.

Training Cardiac Surgeons: Safety and Requirements.

To analyze whether cardiac surgical residents can perform their first surgeries without compromising patients' safety or outcomes, by comparing their performance and results to those of senior surgeons. All documented CABGs conducted between 2002 and 2020 were included. Surgeries were divided according to the experience level of the main surgeon (defined by the number of CABG conducted by him/her) using the following thresholds: 1000; 150; 80 and 35. This resulted in 5 groups: senior surgeons (the reference group); attending surgeons; fellow surgeons; advanced residents and new residents. Primary endpoint was 30 day mortality. Secondary endpoints included a list of intra and post-operative parameters (including in-hospital complications). A multivariable analysis was conducted. 16,486 CABG were conducted by 66 different surgeons over a period of 18 years. Multivariable analysis did not find significant differences between both the primary and the secondary endpoints. Skin-to-skin time correlated significantly with experience level, as new residents needed almost 30% more time than senior surgeons (234 vs 180 minutes). With a suitable supervision by experienced surgeons, patient selection and sufficient resources (longer duration of surgery), surgical residents can perform CABGs with good results and without compromising the patient's outcome.

Negative effect of high-level infrasound on human myocardial contractility: In-vitro controlled experiment.

BACKGROUND: Human exposure to infrasound is increasing due to man-made factors, such as occupational conditions, wind farms and transportation. The concern among the public regarding the safety of infrasound exposure is growing. AIMS: To evaluate whether exposure to infrasound interferes directly with human cardiac function and contributes to pathological processes. SETTING: The University Hospital of Mainz, Germany. METHODS: Human myocardial tissues, obtained from patients undergoing cardiac surgery, were prepared in small muscle samples and stimulated electrically in-vitro for a period of almost two hours under physiological conditions to induce continuous pulsatile contractions and simulating a working human heart. Two samples were obtained from each donor: one was subjected to infrasound for 60 min and the other served as a control. Their contraction forces (CF) and durations (CD) were measured before and after each testing period and their relative changes (CF% and CD%) were calculated and introduced in a multilinear regression model. The following three infrasound levels of exposure were used in this study: 100, 110 and 120 dBz. RESULTS: The measured CF% corresponded negatively with the infrasound level measured in dBz (R2 = 0.631; P = 0.018). The decrease measured almost -11% at 110 dBz and -18% at 120 dBz, after correction for control. The CD on the other hand remained unchanged. CONCLUSIONS: Exposure to high levels of infrasound (more than 100 dBz) interferes with cardiac muscle contractile ability, as early as one hour after exposure. There are numerous additional studies which support this conclusion. These results should be taken into account when considering environmental regulations.

Disturbed Lipid Metabolism in Diabetic Patients with Manifest Coronary Artery Disease Is Associated with Enhanced Inflammation.

BACKGROUND: Diabetic vasculopathy plays an important role in the pathophysiology of coronary artery disease (CAD) with oxidative stress as a strong mediator. This study aims to elucidate the underlying pathomechanisms of diabetic cardiac vasculopathy leading to coronary disease with an emphasis on the role of oxidative stress. Therefore, novel insights into antioxidant pathways might contribute to new strategies in the treatment and prevention of diabetic CAD. METHODS: In 20 patients with insulin-dependent or non-insulin dependent diabetes mellitus (IDDM/NIDDM) and 39 non-diabetic (CTR) patients, myocardial markers of oxidative stress, vasoactive proteins, endothelial nitric oxide synthase (eNOS), activated phosphorylated eNOS (p-eNOS), and antioxidant enzymes, e.g., tetrahydrobiopterin generating dihydrofolate reductase (DHFR), heme oxygenase (HO-1), as well as serum markers of inflammation, e.g., E-selectin, interleukin-6 (IL-6), and lipid metabolism, e.g., high- and low-density lipoptrotein (HDL- and LDL-cholesterol) were determined in specimens of right atrial tissue and in blood samples from type 2 diabetic and non-diabetic patients undergoing coronary artery bypass graft (CABG) surgery. RESULTS: IDDM/NIDDM increased markers of inflammation (e.g., E-selectin, p = 0.005 and IL-6, p = 0.051), decreased the phosphorylated myocardial p-eNOS (p = 0.032), upregulated the myocardial stress response protein HO-1 (p = 0.018), and enhanced the serum LDL-/HDL-cholesterol ratio (p = 0.019). However, the oxidative stress markers in the myocardium and the expression of vasoactive proteins (eNOS, DHFR) showed only marginal adverse changes in patients with IDDM/NIDDM. CONCLUSION: Dyslipidemia and myocardial inflammation seem to be the major determinants of diabetic CAD complications. Dysregulation in pro-oxidative enzymes might be attributable to the severity of CAD and oxidative stress levels in all included patients undergoing CABG.

Experimental determination of the suture behavior of aortic tissue in comparison to 3D printed silicone modelling material.

The imitation of biological tissue in a synthetic physical model can benefit many medical applications, e.g. pre surgical planning or education. For a quantitative validation of the model's mechanical behavior, standardized testing on both, the biological original and the artificial material, is necessary. In four parts, this study focuses on the biomechanical analysis of the impact of sutures for aortic modelling using 3D printed silicone. Testing methods are developed and executed on biological and synthetic samples. The first part is the determination of the pullout strength of a single stitch. The second part is the investigation of the reduction of the tensile strength and elongation of tensile bars due to stitching. Third, the tensile testing of biological and artificial vessels repaired with an anastomosis gives information about the transferability to real surgical applications. A qualitative feedback study with surgical experts concludes the evaluation. The study reveals that the pullout strength is independent from the fiber or notch direction, but that repaired aortic tensile bars show a dependency on the fiber direction of the tissue. Additionally, the circular seam of the anastomosis provides a more stable connection than multiple single stitches. For the artificial models, the mechanical behavior mainly depends on the mechanical properties of the base silicone, here represented by the Shore A hardness, rather than the manufacturing process. When compared to the biological original the most similar material varies depending on the mechanical property in focus.

Body Mass Index (BMI) and Its Influence on the Cardiovascular and Operative Risk Profile in Coronary Artery Bypass Grafting Patients: Impact of Inflammation and Leptin.

BACKGROUND: Obesity is related to coronary artery disease (CAD) and worse outcomes in coronary artery bypass graft (CABG) patients. Adipose tissue itself is an endocrine organ that secretes many humoral mediators, such as adipokines, which can induce or reduce inflammation and oxidative stress. OBJECTIVES: We investigate the relationship between the body mass index (BMI), inflammation, and oxidative stress by measuring serum levels of leptin, interleukin-6, and 3-nitrotyrosine in CABG patients and correlate their levels to the cardiovascular and operative risk profiles. METHODS AND RESULTS: 45 men (<75 years) with a median BMI of 29 (21-51) kg/m2, who were diagnosed with CAD and scheduled for elective CABG, were included after applying the following exclusion criteria: prior myocardial infarction, reoperation, female gender, and smoking. Patients' blood samples were taken preoperatively. Several markers were measured. We found significant correlations between leptin and BMI (p < 0.0001) as well as between leptin and 3-nitrotyrosine (p = 0.006). Interleukin-6 was correlated with C-reactive protein (p < 0.0001) and with the incidence of insulin-dependent diabetes mellitus (p = 0.036), arterial hypertension (p = 0.044), reduced left ventricular function (p = 0.003), and severe coronary calcification (p = 0.015). It was also associated with significantly longer extracorporeal bypass time (p = 0.009). Postoperative deep sternal wound infections could be predicted by a higher BMI (p = 0.003) and leptin level (p = 0.001). CONCLUSIONS: There seems to be a correlation between inflammatory processes and cardiovascular morbidity in our cohort. Further, the incidence of deep sternal wound infections is related to a higher BMI and leptin serum level.

The Effect of Ivabradine on the Human Atrial Myocardial Contractility in an In Vitro Study.

PURPOSE: Ivabradine has emerged as a new antiarrhythmic agent that could compete with the traditional ones, such as beta-blockers. This experimental study aims to ascertain whether ivabradine directly interferes with the myocardial contractility in an in vitro environment. METHODS: Myocardial tissues from the right atrial appendages of patients undergoing cardiac surgery were dissected to obtain 40 specimens from 20 patients (length: 3 mm), which were exposed to electrical impulses at a frequency of 75 bpm for 30 min to reach a steady state. Specimens were then categorised into four groups (each including five patients). The first group was the control, whereas the second, third, and fourth were treated with 60 nM, 200 nM, and 2 µM ivabradine, respectively. We assessed five different contraction parameters before and after a 15 min treatment and calculated their relative changes, which were then compared to the control group. RESULTS: Ivabradine has affected the force of contraction significantly in vitro (p=0.009). However, force of contraction decreased in both the control group (93.5 ± 4.7%) and the second group (94.1 ± 4.5%, p=0.8) and force of contraction remained unchanged in the third group (101.0 ± 4.1%, p=0.24) and increased significantly in the fourth group (108.9 ± 11.6%, p=0.008). There was no change in other contraction parameters, such as passive tension force (97.1 ± 5.1%, p=0.368), duration of contraction (99.1 ± 4.3%, p=0.816), time to peak (96.6 ± 3.0%, p=0.536), and time to relaxation (101.2 ± 7.0%, p=0.564). CONCLUSIONS: Ivabradine did not interfere with the contractile behaviour of human atrial tissue when it was used in therapeutic dosages in vitro. However, it increased the contractility slightly, when it was used in supratherapeutic dosage.

In vitro effect of leptin on human cardiac contractility.

Leptin, a hormone produced by adipose tissue, has been linked to many regulatory pathways. Its role in the complex relationship between obesity and CVD is not yet clear. The aim of the present study was to evaluate whether leptin interferes directly with cardiac function regulation, altering its contractile force character, and hence contributing to different pathological processes. Muscle samples were obtained from human atrial myocardium. Each trial included two samples from the same patient. They were simultaneously electrically stimulated under sustained perfusion to perform isometric contractions. One sample was treated with a high concentration of human recombinant leptin (1 µg/ml). The other was treated with placebo and served as a control. The exhibited contraction forces (CF) and the contraction duration (CD) after 20 min of treatment were normalised by dividing them by the values before the treatment and reported as a percentage. A total of ten successful trials were conducted. Exposure to leptin did not yield a statistically significant variation in both CF and CF. In the treatment group, CF% measured 108 (95 % CI 91, 125) % and CD% measured 95 (95 % CI 90, 101) % after 20 min. In the control group, CF% measured 105 (90 % CI 84, 126) % and CD% measured 92 (95 % CI 80, 105) % after 20 min. We concluded that leptin does not alter the contractile character of human atrial tissues, even in supraphysiological dosage. These results suggest that leptin does not play a role in short-term cardiac regulation.

Septic cardiomyopathy: evidence for a reduced force-generating capacity of human atrial myocardium in acute infective endocarditis.

BACKGROUND: This study analyzes the myocardial force-generating capacity in infective endocarditis (IE) using an experimental model of isolated human atrial myocardium. In vivo, it is difficult to decide whether or not alterations in myocardial contractile behavior are due to secondary effects associated with infection such as an altered heart rate, alterations of preload and afterload resulting from valvular defects, and altered humoral processes. Our in vitro model using isolated human myocardium, in contrast, guarantees exactly defined experimental conditions with respect to preload, afterload, and contraction frequency, thus not only preventing confounding by in vivo determinants of contractility but also excluding effects of other factors associated with sepsis, hemodynamics, humoral influences, temperature, and medical treatment. METHODS: We analyzed right atrial trabeculae (diameter 0.3-0.5 mm, initial length 5 mm) from 32 patients undergoing aortic and/or mitral valve replacement for acute valve incompetence caused by IE and 65 controls receiving aortic and/or mitral valve replacement for nonendocarditic valve incompetence. Isometric force amplitudes and passive resting force values measured at optimal length in the two groups were compared using Student's t-test. RESULTS: There were no significant differences between the groups in terms of the passive resting force. The isometric force amplitude in the endocarditis group, however, was significantly lower than in the nonendocarditis group (p=0.001). In the endocarditis group, the calculated active force, defined as the isometric force amplitude minus the resting force, was significantly lower (p<0.0001) and the resting force/active force ratio was significantly higher (p<0.0001). Using linear regression to describe the function between resting force and active force, we identified a significant difference in slope (p<0.0001), with lower values found in the endocarditis group. CONCLUSION: Our data suggest that the force-generating capacity of atrial myocardium is significantly reduced in patients with IE. In these patients, an elevated resting force is required to achieve a given force amplitude. It remains unclear, however, whether this is due to calcium desensitization of the contractile apparatus, presence of myocardial edema, fibrotic remodeling, disruption of contractile units, or other mechanisms.