Latest developments in heart transplantation: a review

Protective effects of neutrophil serine protease inhibition against ischemia-reperfusion injury in lung or heart transplantation

Transplanted organs are inevitably exposed to ischemia-reperfusion (IR) injury, which is known to cause graft dysfunction. Functional and structural changes that follow IR tissue injury are mediated by neutrophils through the production of oxygen-derived free radicals, as well as from degranulation which entails the release of proteases and other pro-inflammatory mediators. Neutrophil serine proteases (NSPs) are believed to be the principal triggers of post-ischemic reperfusion damage. Extended preservation times for the transplanted donor organ correlate with heightened occurrences of vascular damage and graft dysfunction. Preservation with α1-antitrypsin, an endogenous inhibitor of NSPs, improves primary graft function after lung or heart transplantation. Furthermore, pre-operative pharmacological targeting of NSP activation in the recipient using chemical inhibitors suppresses neutrophilic inflammation in transplanted organs. Hence, effective control of NSPs in the graft and recipient is a promising strategy to prevent IR injury. In this review, we describe the pathological functions of NSPs in IR injury and discuss their pharmacological inhibition to prevent primary graft dysfunction in lung or heart transplantation.

Pharmacological inhibition of the cysteine protease cathepsin C improves graft function after heart transplantation in rats

BACKGROUND

Heart transplantation (HTX) is the standard treatment for end-stage heart failure. However, reperfusion following an ischemic period can contribute to myocardial injury. Neutrophil infiltration, along with the subsequent release of tissue-degrading neutrophil elastase (NE)-related serine proteases and oxygen-derived radicals, is associated with adverse graft outcomes. The inhibition of cathepsin C (CatC) has been shown to block NE-related protease activation. We hypothesized that the CatC inhibitor BI-9740 improves graft function after HTX.

METHODS

In a rat model of HTX, the recipient Lewis rats were orally administered with either a placebo (n = 12) or BI-9740 (n = 11, 20 mg/kg) once daily for 12 days. Donor hearts from untreated Lewis rats were explanted, preserved in a cardioplegic solution, and subsequently heterotopically implanted. In vivo left-ventricular (LV) graft function was assessed after 1 h of reperfusion. The proteolytic activity of neutrophil serine proteases was determined in bone marrow lysates from BI-9740-treated and control rats. Additionally, myocardial morphological changes were examined, and heart samples underwent immunohistochemistry and western blot analysis.

RESULTS

The NE-related proteolytic activity in bone marrow cell lysates was markedly decreased in the BI-9740-treated rats compared to those of the placebo group. Histopathological lesions, elevated CatC and myeloperoxidase-positive cell infiltration, and nitrotyrosine immunoreactivity with an increased number of poly(ADP-ribose) polymerase (PARP)-1-positive cells were lowered in the hearts of animals treated with BI-9740 compared to placebo groups. Regarding the functional parameters of the implanted graft, improvements were observed in both systolic function (LV systolic pressure 110 ± 6 vs 74 ± 6 mmHg; dP/dtmax 2782 ± 149 vs 2076 ± 167 mmHg/s, LV developed pressure, at an intraventricular volume of 200 µl, p < 0.05) and diastolic function in the hearts of BI-9740 treated animals compared with those receiving the only placebo. Furthermore, the administration of BI-9740 resulted in a shorter graft re-beating time compared to the placebo group. However, this study did not provide evidence of DNA fragmentation, the generation of both superoxide anions and hydrogen peroxide, correlating with the absence of protein alterations related to apoptosis, as evidenced by western blot in grafts after HTX.

CONCLUSIONS

We provided experimental evidence that pharmacological inhibition of CatC improves graft function following HTX in rats.

Hypothermia-Triggered Mesoporous Silica Particles for Controlled Release of Hydrogen Sulfide to Reduce the I/R Injury of the Myocardium

Despite the fact that heart transplantation (HTx) is a relatively mature procedure, heart ischemic and reperfusion (I/R) injury during HTx remains a challenge. Even after a successful operation, the heart will be at risk of primary graft failure and mortality during the first year. In this study, temperature-sensitive polymer poly(N-n-propylacrylamide-co-N-tert-butyl acrylamide) (PNNTBA) was coated on diallyl trisulfide (DATS)-loaded mesoporous silica nanoparticles (DATS-MSN) to synthesize hypothermia-triggered hydrogen sulfide (H₂S) releasing particles (HT-MSN). Because the PNNTBA shell dissolves in phosphate-buffered saline at 4 °C, the loaded DATS could continuously release H₂S within 6 h when activated by glutathione (GSH). Furthermore, after co-culturing biocompatible HT-MSN with cardiomyocytes, H₂S released from HT-MSN at 4 °C was found to protect cardiomyocytes from ischemic and reperfusion (I/R) injury. In detail, the rate of cell apoptosis and lactate dehydrogenase activity was decreased, as manifested by increased BCL-2 expression and decreased BAX expression. More importantly, in an isolated heart preservation experiment, HT-MSN demonstrated potent protection against cardiac I/R injury and reduced expression of inflammatory factors TNF-α and IL-1β. This study provided a new method for the controlled release of H₂S by the donor and myocardial protection from I/R injury.

A Risk Assessment Model for Stroke in the Early Post-Transplant Period in Adult Cardiac Allograft Recipients: A UNOS Database Analysis

BACKGROUND

Stroke risk in adult cardiac allograft recipients in the early postoperative period remains less defined. This study attempts to develop a risk assessment model in this population.

METHODS

Patients (≥18 years of age) between 2005 and 2015 who underwent cardiac transplantation were selected from the United Network for Organ Sharing database. The final study cohort had 20,915 patients. Risk factors were identified and multivariate logistic regression was used to test associations. SAS software was used for analyses.

RESULTS

Male recipients had a lower risk (odds ratio [OR] 0.7 [0.6-0.92]; P < .05) for stroke. Prolonged ischemic time (OR 1.2 [1.1-1.3), mechanical ventilation (OR 1.6 [1.2-1.9]), left ventricular assist device support (OR 1.8 [1.4-2.3]), black or Hispanic ethnicity (OR 1.33 [1.04-1.7]), days in status 1A (OR 1.05 [1.01-1.1]), recipient creatinine (OR 1.2 [1.02-1.4]), and type 2 diabetes (OR 1.4 [1.1-1.7]) were significant risk factors. A risk score was generated. Patients with a score of 8 had a 5-fold increase in event rate as compared with those with a score of 0. The c-statistic for this model was 0.65.

CONCLUSIONS

For the first time, a weighted risk score GIMVECH (female gender, ischemic time, mechanical ventilation, left ventricular assist device support, ethnicity, clinical history) was generated to assess stroke in the early post-transplant period.

Artesunate Restrains Maturation of Dendritic Cells and Ameliorates Heart Transplantation-Induced Acute Rejection in Mice through the PERK/ATF4/CHOP Signaling Pathway

Background

Heart transplantation (HT) is the only effective treatment for end-stage heart failure because it can effectively improve the survival rate and quality of life of patients with heart failure. Artesunate (ART) is an artemisinin derivative, with good water solubility and higher oral bioavailability. The main aim of this study was to determine the role of ART in HT mice.

Methods

In animal experiments, mice were divided into the control group, HT group, low ART+HT group, and high ART+HT group. Next, inflammatory cell infiltration, oxidative stress injury, and myocardial cell apoptosis were determined in heart tissue. The proportion of multiple lymphocytes in spleen and lymph nodes was then determined using flow cytometry. In addition, cell experiments were conducted to determine the changes in expression of surface maturation markers of BMDC and changes in intracellular reactive oxygen species after LPS stimulation. Finally, western blot analysis was performed to determine the levels of endoplasmic reticulum stress-related proteins (CHOP/ATF4/PERK).

Results

The survival time of mice in the ART treatment group was significantly prolonged and was positively correlated with the dose. In animal experiments, ART significantly reduced inflammatory cell infiltration in heart tissue and the proportion of CD4+CD8+ T cells in spleens and lymph nodes. Moreover, ART treatment lowered the 8-OHdg in hearts and myocardial apoptosis. In cell experiments, ART treatment slowed down the development and maturation of BMDCs by inhibiting the expression of endoplasmic reticulum stress-related proteins. Furthermore, the treatment alleviated the oxidative stress damage of BMDCs.

Conclusion

ART can inhibit maturation of dendritic cells through the endoplasmic reticulum stress signaling pathway, thereby alleviating acute rejection in mice after heart transplantation.

LncRNA HCP5 in hBMSC-derived exosomes alleviates myocardial ischemia reperfusion injury by sponging miR-497 to activate IGF1/PI3K/AKT pathway

Ischemia/reperfusion (I/R) injury is an inevitable process during heart transplant and suppressing I/R injury could greatly improve the survival rate of recipients. Mesenchymal stem cells (MSCs) have positive effects on I/R. We aimed to investigate the mechanisms underlying the protective roles of MSCs in I/R. Both cell model and rat model of myocardial I/R were used. MTT assay and flow cytometry were used to measure cell viability and apoptosis, respectively. QRT-PCR and western blotting were employed to measure levels of lncRNA HCP5 (HLA complex P5), miR-497, apoptosis-related proteins, and insulin-like growth factor (IGF1)/PI3K/AKT pathway. Dual luciferase assay was used to validate interactions of HCP5 and miR-497, miR-497 and IGF1. Echocardiography was performed to evaluate cardiac function of rats. Serum levels of CK-MB and LDH were measured. H&E and Masson staining were used to examine morphology of myocardial tissues. hBMSC-derived exosomes (hBMSC-Exos) increased the viability of cardiomyocytes following hypoxia/reperfusion (H/R) and decreased apoptosis. H/R diminished HCP5 expression in cardiomyocytes while hBMSC-Exos recovered the level. Overexpression of HCP5 in hBMSC-Exos further enhanced the protective effects in H/R while HCP5 knockdown suppressed. HCP5 directly bound miR-497 and miR-497 targeted IGF1. miR-497 mimics or si-IGF1 blocked the effects of HCP5 overexpression. Further, hBMSC-Exos alleviated I/R injury in vivo and knockdown of HCP5 in hBMSC-Exos decreased the beneficial effects. AntagomiR-497 blocked the effects of HCP5 knockdown. HCP5 from hBMSC-Exos protects cardiomyocytes against I/R injury via sponging miR-497 to disinhibit IGF1/PI3K/AKT pathway. These results shed light on mechanisms underlying the protective role of hBMSC-Exos in I/R.

Pre- and Postoperative Evaluation of Patients with End-Stage Heart Failure Undergoing Cardiac Transplant – a Descriptive Study

Background: Heart transplantation is still the treatment of choice in patients with end-stage heart failure, refractory to medical treatment, in NYHA class III and IV, with dilated cardiomyopathy of various etiologies, including post-myocardial infarction.

Objective: The aim of the study was to provide a descriptive analysis of the clinical, laboratory, and imaging parameters of patients undergoing heart transplantation during the pre- and postoperative period, as well as postoperative complications (including infections) and death rates.

Material and methods: The variables collected from 53 patients who underwent a heart transplant were: age at heart transplant, gender, diagnosis at hospitalization, comorbidities, pre- and postoperative virology, pre- and postoperative laboratory analyses, pre- and postoperative echocardiography, post-transplant infections, complications, and treatment before and after the surgery.

Results: Mean age at the time of transplant was 40.72 ± 14.07 years, and the majority (84.91%) of patients were males. The mean age of the donors was 31.92 ± 10.59 years. A proportion of 60.40% of patients were included in functional class NYHA IV, and 98.1% presented dilative cardiomyopathy of which 49.06% was due to previous myocardial infarction. No significant differences were observed between preand postoperative viral and bacterial serology. Left ventricular ejection fraction was significantly higher in the transplanted heart, and cardiac chamber diameters were significantly smaller after the transplant. Postoperative complications included 7 confirmed infections and 16 deaths, of which 5 had occurred during the surgical procedure.

Conclusions: The present study brings important information in regard to the pre- and postoperative evaluation of patients with end-stage heart failure undergoing cardiac transplantation, from a clinical, laboratory, and imaging point of view, as well as in regard to postoperative complications and death.

Antioxidant Solution in Combination with Angiotensin-(1-7) Provides Myocardial Protection in Langendorff-Perfused Rat Hearts

As progressive organ shortage in cardiac transplantation demands extension of donor criteria, effort is needed to optimize graft survival. Reactive oxygen and nitrogen species, generated during organ procurement, transplantation, and reperfusion, contribute to acute and late graft dysfunction. The combined application of diverse substances acting via different molecular pathways appears to be a reasonable approach to face the complex mechanism of ischemia reperfusion injury. Thus, an antioxidant solution containing α-ketoglutaric acid, 5-hydroxymethylfurfural, N-acetyl-L-methionine, and N-acetyl-selenium-L-methionine was combined with endogenous angiotensin-(1-7). Its capacity of myocardial protection was investigated in isolated Langendorff-perfused rat hearts subjected to warm and cold ischemia. The physiological cardiac parameters were assessed throughout the experiments. Effects were evaluated via determination of the oxidative stress parameters malondialdehyde and carbonyl proteins as well as immunohistochemical and ultrastructural tissue analyses. It was shown that a combination of 20% (v/v) antioxidant solution and 220 pM angiotensin-(1-7) led to the best results with a preservation of heart tissue against oxidative stress and morphological alteration. Additionally, immediate cardiac recovery (after warm ischemia) and normal physiological performance (after cold ischemia) were recorded. Overall, the results of this study indicate substantial cardioprotection of the novel combination with promising prospective for future clinical use.

Outcomes and risk factors of mechanical circulatory support by peripheral venoarterial extracorporeal membrane oxygenation in heart transplant candidates needing urgent heart transplantation

Introduction Peripheral veno-arterial extracorporeal membrane oxygenation (VA ECMO) is one of the most frequently used methods of temporary mechanical circulatory support (MCS) at patients with life-threatening circulatory derangement.

Aim: to evaluate the effectiveness and risk factors of peripheral VA ECMO in patients waiting of urgent heart transplantation (HT).

Materials and methods. The study included 149 (129 (86.6%) men and 20 (13.4%) women, age 12 to 72 (43.0 ± 1.2) years) heart transplant candidates who in the period 01.01.2011–31.12.2016 were supported by peripheral VA ECMO. These patients were 21.1% of the total waiting list (n = 706) of our institute at the same period. Indication for MCS by VA ECMO was advanced heart failure corresponding to I or II level of INTERMACS classifi cation.

Results. 135 (90.6%) from 149 patients were successfully supported to HT. 14 (9.4%) deed following MCS. Before of VA ECMO these patients (n = 14) had more severe (p < 0.05) hemodynamic disorders, organ dysfunction, electrolyte and metabolic disorders compared to patients TC successfully supported to HT. Left atrium (n = 24)/left ventricle drainage (n = 8) was performed for volume decompression of left heart (n = 32 (21.5%)). In a single-factor analysis, statistically signifi cant pre VA ECMO risk factors for the lethal outcome were: creatinine ≥ 140 mmol/l, urea ≥ 15 mmol/l, total bilirubin ≥ 80 μmol/l, ALT ≥ 300 U/l, AST ≥ 300 U/l, INR ≥ 3.0, procalcitonin ≥ 3.0 ng/ml, preexisting left ventricular thrombosis complicated thromboembolic stroke with brain death following VA ECMO (n = 3). Statistically signifi cant factors for the lethal outcome following MCS were: transthoracic left ventricle drainage (n = 8) compared to transcutaneous transfemoral transseptal left atrium drainage (n = 24) for volume decompression of left heart; hemolysis ≥ 300 mg%.

Conclusion. VA ECMO is high effi ciency method of temporary MCS in 90.6% heart transplant candidates needed at urgent HT. VA ECMO must be begin before development of potential lethal multiorgan and septic complications. Preexisting left ventricular thrombosis increase risk of lethal thromboembolic brain injury following VA ECMO. Patients with transcutaneous transfemoral transseptal left atrium drainage for left heart volume decompression had better outcome following MCS by VA ECMO. 

Metabolomics identifies metabolite biomarkers associated with acute rejection after heart transplantation in rats

The aim of this study was to identify metabolite biomarkers associated with acute rejection after heart transplantation in rats using a LC-MS-based metabolomics approach. A model of heterotopic cardiac xenotransplantation was established in rats, with Wistar rats as donors and SD rats as recipients. Blood and cardiac samples were collected from blank control rats (Group A), rats 5 (Group B) and 7 days (Group C) after heart transplantation, and pretreated rats 5 (Group D) and 7 days (Group E) post-transplantation for pathological and metabolomics analyses. We assessed International Society for Heart and Lung Transplantation (ISHLT) grades 0, 3B, 4, 1 and 1 rejection in groups A to E. There were 15 differential metabolites between groups A and B, 14 differential metabolites between groups A and C, and 10 differential metabolites between groups B and C. In addition, four common differential metabolites, including D-tagatose, choline, C16 sphinganine and D-glutamine, were identified between on days 5 and 7 post-transplantation. Our findings demonstrate that the panel of D-tagatose, choline, C16 sphinganine and D-glutamine exhibits a high sensitivity and specificity for the early diagnosis of acute rejection after heart transplantation, and LC-MS-based metabolomics approach has a potential value for screening post-transplantation biomarkers.

Risk of early, intermediate, and late rejection following heart transplantation: Trends over the past 25 years and relation to changes in medical management. Tertiary center experience: The Sheba Heart Transplantation Registry

AIM

To explore the trends in the risk for rejection following heart transplantation (HT) over the past 25 years, and their relation to changes in medical management.

METHODS

The study population comprised 216 HT patients. Rejection periods were defined as follows: 0-3 months (early), 3-12 months (intermediate), and 12+ months (late). HT era was dichotomized as follows: 1991-1999 (remote era) and 2000-2016 (recent era). Medication combination was categorized as newer (TAC, MMF, and everolimus) vs older therapies (AZA, CSA).

RESULTS

Multivariate analysis showed that patients who underwent HT during the recent era experienced a significant reduction in the risk for major rejection. These findings were consistent for early (OR = 0.44 [95% CI 0.22-0.88]), intermediate (OR = 0.02 [95% CI 0.003-0.11]), and late rejections (OR = 0.18 [95% CI 0.05-0.52]). Using the year of HT as a continuous measure showed that each 1-year increment was independently associated with a significant reduction in the risk for early, intermediate, and late rejections (5%, 21%, 18%, respectively). In contrast, the risk reduction associated with newer types of immunosuppressive therapies was not statistically significant after adjustment for the treatment period.

CONCLUSIONS

Major rejection rates following HT have significantly declined over the past 2 decades even after adjustment for changes in immunosuppressive therapies, suggesting that other factors may also play a role in the improved outcomes of HT recipients.

Heart failure therapies: new strategies for old treatments and new treatments for old strategies

Heart failure, whether acute or chronic, remains a major health care crisis affecting almost 6 million Americans and over 23 million people worldwide. Roughly half of those affected will die within 5 years, and the annual cost exceeds $30 billion in the US alone. Although medical therapy has made some modest inroads in partially stemming the heart failure tsunami, there remains a significant population for whom medication is unsuccessful or has ceased being effective; such patients can benefit from heart transplantation or mechanical circulatory support. Indeed, in the past quarter century (and as covered in Cardiovascular Pathology over those years), significant improvements in pathologic understanding and in engineering design have materially enhanced the toolkit of options for such refractory patients. Mechanical devices, whether total artificial hearts or ventricular assist devices, have been reengineered to reduce complications and basic wear and tear. Transplant survival has also been extended through a better comprehension of and improved therapies for transplant vasculopathy and antibody-mediated rejection. Here we review the ideas and treatments from the last 25 years and highlight some of the new directions in nonpharmacologic heart failure therapy.

Hp: an inflammatory indicator in cardiovascular disease

Over the past decade significant advancement has occurred in the biological and pathological role that Hp has in cardiovascular disease. Hp is an acute-phase protein with a role in the neutralization and clearance of free heme. Iron has tremendous potential for initiating vascular oxidation, inflammation and exacerbating coronary atherosclerosis. Hp genotype has been linked as a prognostic biomarker of acute myocardial infarction, heart failure, restenosis and cardiac transplant rejection. The increased understanding of Hp as a biomarker has provided new insights into the mechanisms of inflammation after cardiac injury and support the concept that Hp is not only an important antioxidant in vascular inflammation and atherosclerosis, but also an enhancer of inflammation in cardiac transplant.

Ischemic Stroke after Heart Transplantation

Cerebrovascular complications after orthotopic heart transplantation (OHT) are more common in comparison with neurological sequelae subsequent to routine cardiac surgery. Ischemic stroke and transient ischemic attack (TIA) are more common (with an incidence of up to 13%) than intracranial hemorrhage (2.5%). Clinically, ischemic stroke is manifested by the appearance of focal neurologic deficits, although sometimes a stroke may be silent or manifests itself by the appearance of encephalopathy, reflecting a diffuse brain disorder. Ischemic stroke subtypes distribution in perioperative and postoperative period after OHT is very different from classical distribution, with different pathogenic mechanisms. Infact, ischemic stroke may be caused by less common and unusual mechanisms, linked to surgical procedures and to postoperative inflammation, peculiar to this group of patients. However, many strokes (40%) occur without a well-defined etiology (cryptogenic strokes). A silent atrial fibrillation (AF) may play a role in pathogenesis of these strokes and P wave dispersion may represent a predictor of AF. In OHT patients, P wave dispersion correlates with homocysteine plasma levels and hyperhomocysteinemia could play a role in the pathogenesis of these strokes with multiple mechanisms increasing the risk of AF. In conclusion, stroke after heart transplantation represents a complication with considerable impact not only on mortality but also on subsequent poor functional outcome.