Determinants and prognostic value of ischemic necrosis in early biopsies following heart transplant

Novel biomarkers useful in surveillance of graft rejection after heart transplantation

Heart transplantation (HTx) is considered the gold-standard therapy for the treatment of advanced heart failure (HF). The long-term survival in HTx is hindered by graft failure which represents one of the major limitations of the long-term efficacy of HTx. Endomyocardial biopsy (EMB) and the evaluation of donor-specific antibodies (DSA) are currently considered the essential diagnostic tools for surveillance of graft rejection. Recently, new molecular biomarkers (including cell-free DeoxyriboNucleic Acid, exosomes, gene profiling microarray, nanostring, reverse transcriptase multiplex ligation-dependent probe amplification, proteomics and immune profiling by quantitative multiplex immunofluorescence) provide useful information on mechanisms of graft rejection. The ambitious role of a similar change of perspective is aimed at a better and longer graft preservation.

Glycated ACE2 receptor in diabetes: open door for SARS-COV-2 entry in cardiomyocyte

Rationale

About 50% of hospitalized coronavirus disease 2019 (COVID-19) patients with diabetes mellitus (DM) developed myocardial damage. The mechanisms of direct SARS-CoV-2 cardiomyocyte infection include viral invasion via ACE2-Spike glycoprotein-binding. In DM patients, the impact of glycation of ACE2 on cardiomyocyte invasion by SARS-CoV-2 can be of high importance.

Objective

To evaluate the presence of SARS-CoV-2 in cardiomyocytes from heart autopsy of DM cases compared to Non-DM; to investigate the role of DM in SARS-COV-2 entry in cardiomyocytes.

Methods and results

We evaluated consecutive autopsy cases, deceased for COVID-19, from Italy between Apr 30, 2020 and Jan 18, 2021. We evaluated SARS-CoV-2 in cardiomyocytes, expression of ACE2 (total and glycosylated form), and transmembrane protease serine protease-2 (TMPRSS2) protein. In order to study the role of diabetes on cardiomyocyte alterations, independently of COVID-19, we investigated ACE2, glycosylated ACE2, and TMPRSS2 proteins in cardiomyocytes from DM and Non-DM explanted-hearts. Finally, to investigate the effects of DM on ACE2 protein modification, an in vitro glycation study of recombinant human ACE2 (hACE2) was performed to evaluate the effects on binding to SARS-CoV-2 Spike protein. The authors included cardiac tissue from 97 autopsies. DM was diagnosed in 37 patients (38%). Fourth-seven out of 97 autopsies (48%) had SARS-CoV-2 RNA in cardiomyocytes. Thirty out of 37 DM autopsy cases (81%) and 17 out of 60 Non-DM autopsy cases (28%) had SARS-CoV-2 RNA in cardiomyocytes. Total ACE2, glycosylated ACE2, and TMPRSS2 protein expressions were higher in cardiomyocytes from autopsied and explanted hearts of DM than Non-DM. In vitro exposure of monomeric hACE2 to 120 mM glucose for 12 days led to non-enzymatic glycation of four lysine residues in the neck domain affecting the protein oligomerization.

Conclusions

The upregulation of ACE2 expression (total and glycosylated forms) in DM cardiomyocytes, along with non-enzymatic glycation, could increase the susceptibility to COVID-19 infection in DM patients by favouring the cellular entry of SARS-CoV2.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-021-01286-7.

Lipid Accumulation in Hearts Transplanted From Nondiabetic Donors to Diabetic Recipients

BACKGROUND

Early pathogenesis of diabetic cardiomyopathy (DMCM) may involve lipotoxicity of cardiomyocytes in the context of hyperglycemia. There are many preclinical studies of DMCM pathogenesis, but the human evidence is still poorly understood.

OBJECTIVES

By using a nondiabetic mellitus (non-DM) heart transplanted (HTX) in diabetes mellitus (DM) recipients, this study conducted a serial study of human heart transplant recipients evaluating cardiac effects of diabetic milieu (hyperglycemia and insulin resistance) on lipotoxic-mediated injury. We evaluated cardiomyocyte morpho-pathology by seriated biopsies of healthy implanted hearts in DM recipients during 12-month follow-up from HTX. Because metformin reduces ectopic lipid accumulation, we evaluated the effects of the drug in a nonrandomized subgroup.

METHODS

The DMCM-AHEAD (Diabetes and Lipid Accumulation and Heart Transplant) prospective ongoing study (NCT03546062) evaluated 158 first HTX recipients (82 non-DM, 76 DM of whom 35 [46%] were receiving metformin). HTX recipients were undergoing clinical standard evaluation (metabolic status, echocardiography, coronary computed tomography angiography, and endomyocardial biopsies). Biopsies evaluated immune response, Oil Red-O staining, ceramide, and triacylglycerol levels. Lipotoxic factors and insulin resistance were evaluated by reverse transcriptase-polymerase chain reaction.

RESULTS

There was a significant early and progressive cardiomyocyte lipid accumulation in DM but not in non-DM recipients (p = 0.019). In the subgroup receiving metformin, independently from immunosuppressive therapy that was similar among groups, lipid accumulation was reduced in comparison with DM recipients not receiving the drug (hazard ratio: 6.597; 95% confidence interval: 2.516 to 17.296; p < 0.001). Accordingly, lipotoxic factors were increased in DM versus non-DM recipients, and, relevantly, metformin use was associated with fewer lipotoxic factors.

CONCLUSIONS

Early pathogenesis of human DMCM started with cardiomyocyte lipid accumulation following HTX in DM recipients. Metformin use was associated with reduced lipid accumulation independently of immunosuppressive therapy. This may constitute a novel target for therapy of DMCM.

A novel method of measuring cardiac preservation injury demonstrates University of Wisconsin solution is associated with less ischemic necrosis than Celsior in early cardiac allograft biopsy specimens

BACKGROUND

No consensus exists on the optimal heart preservative solution (HPS) for cardiac allograft preservation. The significance of varying degrees of acute ischemic necrosis (AIN) in early transplant biopsy specimens is unknown. We investigated the effects of HPS on early cardiac histopathology by developing a novel grading system of AIN.

METHODS

A retrospective review of our institutional database of orthotopic heart transplants (OHT) identified hearts preserved with University of Wisconsin (UW) or Celsior solutions. AIN severity was graded on early post-transplant biopsy specimens. Primary stratification was by HPS. Multivariable models examined mortality, AIN grade, primary graft dysfunction (PGD), and right heart failure (RHF).

RESULTS

From 1996 to 2010, 42 of 174 adult OHTs were preserved with UW and 132 with Celsior, from which 431 biopsy specimens were reviewed. UW and Celsior had similar 30-day (p = 0.79) and 1-year mortality (p = 0.92). Celsior was associated with significantly more AIN on the first (p = 0.02) and second (p = 0.04) specimens and persisted on multivariable analysis for the first (odds ratio, 2.93; 95% confidence interval, 1.26-6.83; p = 0.01) and second biopsy specimen (2.08; 0.99-4.34; p = 0.05). When stratified by AIN score, 30-day and 1-year mortality were similar (p > 0.05). Adjusted analysis showed increasing AIN score on the first biopsy was strongly associated with an increased incidence of PGD (1.59; 1.02-2.47; p = 0.04) and RHF (2.45; 1.14-5.27; p = 0.02).

CONCLUSIONS

Our grading system provides a simple, reproducible method for determining AIN. UW is associated with less AIN than Celsior solution. Early biopsy ischemia is associated with PGD and RHF. AIN may have prognostic significance and its routine evaluation should be considered.

Elective cardiac surgery using Celsior or St. Thomas No. 2 solution: a prospective, single-center, randomized pilot study

OBJECTIVE

Celsior is a crystalloid solution specifically designed for solid-organ transplantation. Due to its advanced combination of solutes, we wanted to evaluate its safety, efficacy, and possible benefits when used as blood cardioplegia in elective cardiac surgery in a single-center, randomized, controlled clinical trial, comparing its performance with a well-established cardioplegic solution.

METHODS

Patients programmed for aortic valve replacement were randomized to receive either St. Thomas No. 2 or Celsior as blood cardioplegia with the same administration protocol. Intraoperative and postoperative variables concerning myocardial protection were registered and compared.

RESULTS

A total of 60 patients were enrolled and randomized (Celsior, 30; St. Thomas, 30). There were no significant differences in baseline and preoperative variables. Volume of cardioplegic solution, number of administrations needed and the amount of potassium added were similar in both groups. Patients in the Celsior group showed a higher incidence of spontaneous sinus rhythm after myocardial ischemia (77% vs 40%, p=0.004) and fewer patients required defibrillation (17% vs 43%, p=0.024) for ventricular reperfusion arrhythmias. Postoperatively, there were no significant differences in troponin I release, inotropic and vasopressor drug support, ICU stay, and postoperative evolution. There were no deaths in the study.

CONCLUSIONS

Celsior solution used as blood cardioplegia is effective and seems to be safe in elective aortic valve replacement when compared in this pilot study with a standard cardioplegic solution used worldwide. Fast return to sinus rhythm and lower incidence of reperfusion arrhythmias in the Celsior group may reflect a better myocardial protection during cardioplegic arrest. More investigation is needed to elucidate its performance in elective surgery.