Catherine Wang

Suppression of Murine Cardiac Allograft Arteriopathy by Long-Term Blockade of CD40-CD154 Interactions

Background—The interaction between CD40 on antigen-presenting cells and CD40L on T cells is critical in allograft rejection. CD154 blockade suppresses allograft rejection, but the role of this pathway in allograft vasculopathy remains obscure. Methods and Results—A vascularized murine heterotopic cardiac transplant model was used to test whether perioperative CD154 blockade suppresses allograft vasculopathy or whether long-term CD154 blockade is required to suppress allograft vasculopathy. Perioperative CD154 blockade consisted of MR1 given on days −1, 1, and 3; long-term blockade consisted of MR1 given on days −1, 1, and 3 and continued twice weekly for 8 weeks. Allografts treated with perioperative or long-term CD154 blockade survived indefinitely. Perioperative and long-term treatment with control antibody (Ha4/8) resulted in uniform early rejection. Perioperative CD154 blockade transiently reduced early T-cell and macrophage infiltration in parallel with a transient reduction in endothelial adhesion receptor expression. Although perioperative CD154 blockade prevented allograft failure, it did not reduce allograft vasculopathy; mean neointimal cross-sectional area in perioperative MR1-treated and Ha4/8-treated recipients was 43±7% and 50±12%, respectively (P =NS). In contrast, mean neointimal cross-sectional area in long-term, MR1-treated recipients was 19±3% (P <0.001 versus perioperative MR1). Long-term CD154 blockade also suppressed endothelial E-selectin, P-selectin, and intracellular adhesion molecule-1 expression and improved graft function 3.5-fold versus control (P <0.05). Conclusions—These data show that perioperative CD154 blockade mitigates acute rejection but long-term CD154 blockade may result in decreased allograft endothelial activation and is required to suppress allograft arteriopathy.

Reduction of retrosternal and pericardial adhesions with rapidly resorbable polymer films

BACKGROUND The formation of postoperative cardiac adhesions makes a repeat sternotomy time consuming and dangerous. Many attempts have been made to solve this problem by using either drugs to inhibit fibrinolytic activity or different types of pericardial substitutes. The results have not been satisfactory. METHODS The efficacy of bioresorbable film prototypes made of polyethylene glycol (EO) and polylactic acid (LA) (EO/LA = 1.5, 2.5, and 3.0) in the prevention of adhesions after cardiac operations in canine models was tested. After desiccation and abrasion of the epicardium, a transparent bioresorbable film was placed over the heart. The pericardium was closed to allow intrapericardial adhesions (n = 32) or left open and attached to the chest wall to induce retrosternal adhesions (n = 17). Postoperative recovery was similar among the groups. Retrosternal and pericardial adhesions were evaluated at necropsy 3 weeks later by assessing area, tenacity, and density of the adhesions. RESULTS In the control dogs, tenacious, dense adhesions were observed. In contrast, adhesion formation was reduced at all sites covered by the films. The bioresorbable films were efficacious in the reduction of adhesion formation between epicardium and pericardium or between epicardium and sternum after cardiac operation. The EO/LA 1.5 film most effectively prevented the early adhesions. CONCLUSIONS The bioresorbable films (EO/LA = 1.5, 2.5, and 3.0) significantly reduced adhesion formation, with EO/LA = 1.5 (Repel CV) being optimal. As the barrier was rapidly resorbed, the capsule formation induced by permanent barriers was avoided.

Transcriptional Control of Cardiac Allograft Vasculopathy by Early Growth Response Gene-1 (Egr-1)

Expression of the zinc finger transcription factor early growth response gene-1 (Egr-1) is triggered rapidly after mechanical vascular injury or after a precipitous drop in ambient oxygen, whereupon it induces the expression of diverse gene families to elicit a pathological response. Initially characterized as an early response transcriptional activator, the role of Egr-1 in more chronic forms of vascular injury remains to be defined. Studies were designed to examine whether Egr-1 induction may serve as a causal link between early preservation injury and delayed vascular consequences, such as coronary allograft vasculopathy (CAV). The preservation and transplantation of heterotopic murine cardiac allografts strongly induce Egr-1 expression, leading to increased expression of its downstream target genes, such as intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and platelet-derived growth factor A chain. Expression of these Egr-1–inducible gene targets is virtually obliterated in homozygous Egr-1–null donor allografts, which also exhibit attenuated parenchymal rejection and reduced CAV as long as 60 days. Congruous data are observed by treating donor hearts with a phosphorothioate antisense oligodeoxyribonucleotide directed against Egr-1 before organ harvest, which blocks subsequent expression of Egr-1 mRNA and protein and suppresses the late development of CAV. These data indicate that Egr-1 induction represents a central effector mechanism in the development of chronic rejection characterized by CAV. Blocking the expression of this proximal transcription factor solely at the time of organ harvest elicits beneficial delayed consequences for the cardiac allograft.

Interaction of Baboon Anti-α-Galactosyl Antibody with Pig Tissues

As barriers to xenotransplantation are surmounted, such as suppression of hyperacute rejection allowing improved graft survival, it becomes important to define longer-term host-xenograft interactions. To this end we have prepared in baboons high titer anti-α-Galactosyl (αGal) and anti-porcine aortic endothelial cell antibodies, similar to human natural xenoantibodies and reactive with epitopes of thyroglobulin, laminin, and heparan sulfate proteoglycans. When injected into pigs with a protocol similar to that used in the rat to show the nephritogenic potential of heterologous anti-laminin and anti-heparan sulfate proteoglycan antibodies, baboon immunoglobulins bound first to renal vascular endothelium, and later to interstitial cells, especially fibroblasts and macrophages, and to antigens in basement membranes and extracellular matrix, where they colocalized with laminin- and heparan sulfate proteoglycan-antibodies, and with bound Griffonia simplicifolia B4. A similar binding was observed in other organs. The pigs did not develop an acute complement-dependent inflammation, but rather chronic lesions of the basement membranes and the extracellular matrix. Incubation of renal fibroblasts with baboon anti-α-Galactosyl antibodies resulted in increased synthesis of transforming growth factor-β and collagen, suggesting a possible basis for the fibrotic response. The results demonstrate that in this experimental model a consequence of αGal antibody interaction with porcine tissues, is immunoreactivity with αGal on matrix molecules and interstitial cells, priming mechanisms leading to fibrosis resembling that in chronic allograft rejection. The possibility that similar lesions may develop in long-surviving pig xenografts is discussed.

Cardiac Myostatin Upregulation Occurs Immediately After Myocardial Ischemia and is Involved in Skeletal Muscle Activation of Atrophy

UNLABELLED Myostatin (MSTN), a negative regulator of muscle growth and size, is increased after acute myocardial infarction (AMI) but timing of upregulation after injury is not known. In this study, we investigated the timing of the MSTN/AKT/p38 pathway activation in heart and skeletal muscle after AMI, as well as the potential effect of cardiac injury-related MSTN endocrine signaling on skeletal muscle and other circulating growth factors. METHODS Coronary artery ligation was performed in C57BL/6 mice at age 8 weeks to induce AMI. Mice were sacrificed at different time points (10 m, 1 h, 2 h, 6 h, 12 h, 24 h, 1 week, 2 weeks, 1 months and 2 months) after surgery (n=3 per time point, n=18 total). RESULTS Cardiac and circulating MSTN upregulation occurred as early as 10 min after AMI. Two months after AMI, increased cardiac MSTN/SMAD2,3 and p38 together with decreased IGF-1/AKT signaling suggest an anti-hypertrophic profile. In skeletal muscle, an absence of local MSTN increase was accompanied by increased MSTN-dependent SMAD2,3 signaling, suggestive of paracrine effects due to cardiac-derived MSTN. Protein degradation by the ubiquitin-proteasome system in the skeletal muscle was also evident. Serum from 24h post-MI mice effectively induced a MSTN-dependent increase in atrogin1 and MuRF1. CONCLUSION Our study shows that cardiac MTSN activation occurs rapidly after cardiac ischemia and may be involved in peripheral protein degradation in the skeletal muscle by activating atrogin1 and MuRF1.

Contribution of inflammation to reperfusion injury.

Abstract Interrupting the flow of blood to an organ for even a relatively brief period disrupts multiple essential vascular homeostatic mechanisms. This results in the cardinal manifestations of reperfusion injury, which, at the tissue level, are comprised of leukocyte infiltration, thrombosis, edema, and vasoconstriction. Molecular mechanisms that are particularly relevant to post‐ischemic inflammation and reperfusion injury include induction of adhesion receptor expression at the endothelial surface, alterations in the procoagulant/anticoagulant balance to promote accumulation of intravascular thrombus, oxidant stress that directly injures cells and indirectly promotes inflammatory upregulation, loss of protective second messenger cyclic nucleotide systems, and activation of the complement cascade that causes vascular injury as well as collateral damage to innocent bystander cells with the reperfused tissue. Understanding the inflammatory mechanisms that participate in reperfusion injury may lead to reperfusion therapies designed to improve postischemic organ function.

Aortic Valve Annular SizingCLINICAL PERSPECTIVE: Intraoperative Assessment Versus Preoperative Multidetector Computed Tomography

Background— Appropriate valve sizing is critical in aortic valve replacement. We hypothesized that direct intraoperative valve sizing results in smaller aortic annular diameters compared with sizing based on systolic-phase multidetector computerized tomographic (MDCT) imaging. Methods and Results— We retrospectively analyzed 78 patients undergoing surgical aortic valve replacement for severe aortic stenosis between 2012 and 2014 at our institution. Preoperative MDCT measurements of the aortic annulus served as basis for assignment to a theoretical surgical valve size, which was then (1) compared to the implanted valve size and (2) to a theoretical transcatheter aortic valve replacement valve size. To quantify the resulting differences, geometric orifice areas (GOA) were calculated. MDCT-based sizing produced the same valve size for n=34 patients (group CT-same), a larger valve with a 25% increased GOA in n=32 patients (group CT-Lg) and a smaller GOA by 22% in n=12 patients (group CT-Sm). On the basis of MDCT measurements, 41% of valves implanted were undersized. The comparison of intraoperative implanted to a theoretical transcatheter aortic valve replacement valve size resulted in GOAs 25% larger for patients in group CT-same, 40.6% larger in group CT-Lg and 14.6% larger in group CT-Sm. Conclusions— Preoperative MDCT measurements differ substantially from direct intraoperative assessment of the aortic annulus. Implanted surgical aortic valve replacement valves were smaller relative to MDCT-based sizing in 41% of patients, and the potential GOA was between 25% and 40.6% larger if patients had undergone transcatheter aortic valve replacement.

PREOPERATIVE ANEMIA AND INTRAOPERATIVE TRANSFUSION TOGETHER PREDICT WORSENED SHORT AND LONG-TERM MORTALITY AFTER ISOLATED SURGICAL AORTIC VALVE REPLACEMENT

The combined interaction of anemia with packed red blood cell (PRBC) transfusion has not been studied in surgical aortic valve replacement (SAVR). We sought to determine whether anemia and transfusion independently predict outcomes after SAVR. All patients undergoing isolated SAVR (n=2169) from

Bicuspid aortic valve increases risk of permanent pacemaker implant following aortic root replacement

OBJECTIVES We aimed to assess the incidence and possible differences in postoperative conduction delay after aortic root replacement (ARR) in bicuspid aortic valve (BAV) patients compared with a tricuspid aortic valve (TAV). METHODS A total of 380 patients undergoing ARR at our institution between 2005 and 2013 were included in the analysis. Patients were stratified by aortic valve anatomy: BAV, n = 191 vs TAV, n = 189. Electrocardiographic and echocardiographic data were retrospectively analysed at different time points (pre-, postoperatively and at follow-up). Primary outcome of interest was permanent pacemaker (PPM) implantation within 30 days, the composite of new PPM or new left fascicular or bundle branch block (PPM or LBBB) was the secondary outcome of interest. Age range was 24-89.5 years and incidence of preoperative moderate to severe aortic stenosis was 9.7%. RESULTS BAV patients had higher incidence of PPM implantation within 30 days (5.8 vs 1.6% in TAV, P = 0.053); moreover, the composite of PPM or LBBB was also more frequent in BAV (8.4 vs 2.1%, P = 0.010). BAV was independently associated with PPM insertion (OR 4.08, P = 0.047) and also an independent predictor of PPM or LBBB in multiple regression (OR 4.96, P = 0.006). CONCLUSIONS Significantly higher incidence of PPM implantation or LBBB may exist after ARR in bicuspid patients and BAV was confirmed to be an independent predictor for postoperative conduction disturbances by multivariable regression.

MYOSTATIN INHIBITION IMPROVES CARDIAC GLUCOSE METABOLISM IN A MURINE MODEL OF HEART FAILURE

Myostatin (MSTN) is a negative regulator of muscle growth that may improve insulin sensitivity. We hypothesized that systemic MSTN inhibition would improve cardiomyocyte glucose metabolism in experimental heart failure (HF). C57BL/6J mice were subjected to left anterior descending coronary artery