Nanocarriers Loaded with Oxygen to Improve the Protection of the Heart to be Transplanted

: In the case of serious cardiovascular diseases, such as refractory heart failure, heart transplantation is the only possible intervention. Currently, the modes of organ transport in hypothermic cardioplegic solution do not allow the implantation of the heart beyond 4-5 hours from the explant. The heart being an organ with a greater consumption of oxygen and high metabolism than the brain, its transport in hypothermic cardioplegic solutions presents critical issues in terms of time and conservation. An ambitious goal of many researchers and clinicians is to minimize the hypoxia of the explanted heart and extend the permanence time in cardioplegic solution without damage from hypoxia. Adequately oxygenating the explanted organs may extend the usability time of the explanted organ. This challenge has been pursued for years with approaches that are often expensive, risky, and/or difficult to use. We propose to consider oxygenated nanocarriers realizing oxygen for a long time. In this way, it will also be possible to use organs from distant countries with respect to the recipient, thus exceeding the canonical 4-5 hours tolerated up to now. In addition to the lack of oxygen, the transplanted organ can undergo the accumulation of catabolites due to the lack of perfusion during transport. Therefore, nanocarriers can also be perfused in adequate solution during organ transportation. A better oxygenation improving the postoperative recovery of the transplanted heart will improve the recipient's quality of life.

Cardiac radiotherapy induces electrical conduction reprogramming in the absence of transmural fibrosis

Cardiac radiotherapy (RT) may be effective in treating heart failure (HF) patients with refractory ventricular tachycardia (VT). The previously proposed mechanism of radiation-induced fibrosis does not explain the rapidity and magnitude with which VT reduction occurs clinically. Here, we demonstrate in hearts from RT patients that radiation does not achieve transmural fibrosis within the timeframe of VT reduction. Electrophysiologic assessment of irradiated murine hearts reveals a persistent supraphysiologic electrical phenotype, mediated by increases in NaV1.5 and Cx43. By sequencing and transgenic approaches, we identify Notch signaling as a mechanistic contributor to NaV1.5 upregulation after RT. Clinically, RT was associated with increased NaV1.5 expression in 1 of 1 explanted heart. On electrocardiogram (ECG), post-RT QRS durations were shortened in 13 of 19 patients and lengthened in 5 patients. Collectively, this study provides evidence for radiation-induced reprogramming of cardiac conduction as a potential treatment strategy for arrhythmia management in VT patients.

A challenging case of arrhythmogenic right ventricular cardiomyopathy presenting as fulminant myocarditis

ABSTRACT Arrhythmogenic right ventricular cardiomyopathy (ARVC) is known as a primary genetic heart disease that leading to the myocardial deposition of fibrofatty tissue in right ventricular (RV) wall. Sometimes, it occurs in the left ventricular (LV) subepicardial wall. This study introduces a child referred to our hospital with influenza-like symptoms and ventricular tachyarrhythmia, followed by cardiac failure. However, in our subsequent evaluation, there was evidence of severe LV and RV dysfunction based on the echocardiography. Moreover, cardiac magnetic resonance showed not only the major criteria of ARVC but also those of Lake Luise seen in myocarditis. Regarding the deteriorating condition during the hospital course, he was later scheduled for heart transplantation. Finally, the histopathological study of explanted heart revealed RV myocyte atrophy with the infiltration of fibrofatty tissue in myocardium diagnostic of ARVC, resolving dilemma between ARVC and myocarditis.

Cryo-EM reveals structural breaks in a patient-derived amyloid fibril from systemic AL amyloidosis

Systemic AL amyloidosis is a debilitating and potentially fatal disease that arises from the misfolding and fibrillation of immunoglobulin light chains (LCs). The disease is patient-specific with essentially each patient possessing a unique LC sequence. In this study, we present two ex vivo fibril structures of a λ3 LC. The fibrils were extracted from the explanted heart of a patient (FOR005) and consist of 115-residue fibril proteins, mainly from the LC variable domain. The fibril structures imply that a 180° rotation around the disulfide bond and a major unfolding step are necessary for fibrils to form. The two fibril structures show highly similar fibril protein folds, differing in only a 12-residue segment. Remarkably, the two structures do not represent separate fibril morphologies, as they can co-exist at different z-axial positions within the same fibril. Our data imply the presence of structural breaks at the interface of the two structural forms.

Dual Functional States of R406W-Desmin Assembly Complexes Cause Cardiomyopathy With Severe Intercalated Disc Derangement in Humans and in Knock-In Mice

Background: Mutations in the human desmin gene cause myopathies and cardiomyopathies. This study aimed to elucidate molecular mechanisms initiated by the heterozygous R406W-desmin mutation in the development of a severe and early-onset cardiac phenotype. Methods: We report an adolescent patient who underwent cardiac transplantation as a result of restrictive cardiomyopathy caused by a heterozygous R406W-desmin mutation. Sections of the explanted heart were analyzed with antibodies specific to 406W-desmin and to intercalated disc proteins. Effects of the R406W mutation on the molecular properties of desmin were addressed by cell transfection and in vitro assembly experiments. To prove the genuine deleterious effect of the mutation on heart tissue, we further generated and analyzed R405W-desmin knock-in mice harboring the orthologous form of the human R406W-desmin. Results: Microscopic analysis of the explanted heart revealed desmin aggregates and the absence of desmin filaments at intercalated discs. Structural changes within intercalated discs were revealed by the abnormal organization of desmoplakin, plectin, N-cadherin, and connexin-43. Next-generation sequencing confirmed the DES variant c.1216C>T (p.R406W) as the sole disease-causing mutation. Cell transfection studies disclosed a dual behavior of R406W-desmin with both its integration into the endogenous intermediate filament system and segregation into protein aggregates. In vitro, R406W-desmin formed unusually thick filaments that organized into complex filament aggregates and fibrillar sheets. In contrast, assembly of equimolar mixtures of mutant and wild-type desmin generated chimeric filaments of seemingly normal morphology but with occasional prominent irregularities. Heterozygous and homozygous R405W-desmin knock-in mice develop both a myopathy and a cardiomyopathy. In particular, the main histopathologic results from the patient are recapitulated in the hearts from R405W-desmin knock-in mice of both genotypes. Moreover, whereas heterozygous knock-in mice have a normal life span, homozygous animals die at 3 months of age because of a smooth muscle-related gastrointestinal phenotype. Conclusions: We demonstrate that R406W-desmin provokes its severe cardiotoxic potential by a novel pathomechanism, where the concurrent dual functional states of mutant desmin assembly complexes underlie the uncoupling of desmin filaments from intercalated discs and their structural disorganization.

Myocardial iron depletion exacerbates end-stage heart failure by promoting adverse remodeling and worsening mitochondrial function

Background Heart failure (HF) is highly associated with systemic iron deficiency (ID) yet its association with myocardial iron depletion (MID) remains barely unveiled. Similarly, it has been unclear whether and how MID deteriorates the progression to advanced HF. Furthermore, neither the underlying pathophysiology nor the negative impact of unmet iron availability to the failing heart, at the molecular level, is elucidated. Purpose We aim to integrate clinical information and experimental data from human explanted heart tissues: 1) to establish the defining criterion of MID in advanced HF population; 2) to recapitulate the pathophysiological role MID plays in the progression of HF; and 3) to identify novel HF molecular signatures or potential cures to correct MID status underestimated in the failing hearts. Methods Adult failing hearts (N=143), including dilated (n=76) and ischemic (n=67) cardiomyopathies, and non-failing control hearts (NFC, N=46) were collected per Human Explanted Heart Program. Iron levels were measured directly from both ventricles, which were re-evaluated by cardiac magnetic resonance imaging (CMR) mapping sequences (e.g. T1, T2*, etc.). Mitochondrial metabolic, reactive oxygen species (ROS) and ROS-scavenging profiles were assessed spectrophotometrically. Tissue remodeling and ultrastructure characteristics were captured by confocal and electron microscopies respectively. Meanwhile, the patients' clinical profiles were integrated into the analysis of molecular regulatory mechanism. Results Myocardial iron content in LV was significantly lower in HF versus NFC [121.4 (88.1–150.3) vs. 137.4 (109.2–165.9) μg/g dry weight, p<0.05], while both RVs showed no difference. With a cutoff of 86.1 μg/g iron level in LV, it screened ∼23% HF patients with MID (HF-MID). Compared with non-MID HF patients, depleted iron store weakly correlated with systemic hemoglobin concentration (r=−0.27, p=0.13) but highly with T2* and magnetic susceptibility proving CMR as an exceptional surrogate for non-invasive diagnosis. And it was noted that MID independently predicted ominous endpoints as NYHA grade increased and LV dysfunctions worsened (all p<0.05). Cardiac respiratory chain enzymatic activities from complex I to V (except for COX III) were further suppressed in the iron-deficient failing hearts, indicating altered myocardial metabolism and excessive ROS production. Moreover, the whole anti-ROS defense were severely impaired, consistent with remarkably inverse tissue remodeling and ultrastructure disintegrity in HF-MID. Mechanistically, two iron-regulatory proteins (IRP-1/2) and following iron trafficking pathways were inactivated possibly determine the restricted iron availability to advanced failing hearts. Conclusions MID worsens HF progression primarily mediated by mitochondrial dysfunction and collapsed oxidative protection in LV, independently predicting an inferior prognosis. CMR demonstrates clinical potential to monitor MID. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Canadian Institutes for Health Research (CIHR); Heart & Stroke Foundation (HSF)

Cryo-EM reveals structural breaks in a patient-derived amyloid fibril from systemic AL amyloidosis

Systemic AL amyloidosis is a debilitating and potentially fatal disease that arises from the misfolding and fibrillation of immunoglobulin light chains (LCs). The disease is patient-specific with essentially each patient possessing a unique LC sequence. In this study, we present the first ex vivo fibril structures of a λ3 LC. The fibrils were extracted from the explanted heart of a patient (FOR005) and consist of 115 residues, mainly from the LC variable domain. The fibril structures imply that a 180° rotation around the disulfide bond and a major unfolding step are necessary for fibrils to form. The two fibril structures show highly similar fibril protein folds, differing in only a 12-residue segment. Remarkably, the two structures do not represent separate fibril morphologies, as they can co-exist at different z-axial positions within the same fibril. Our data imply the presence of structural breaks at the interface of the two structural forms.

Chondroid and Osseous Metaplasia of the Central Fibrous Body in Adolescent Hearts with Mutations in TNNI3 and TNNT2 genes

The histological spectrum of the central fibrous body (CFB) of the heart, particularly in humans, is not fully characterized. Herein, we describe the presence of cartilage and bone within the CFB of 2 explanted heart specimens from patients with known mutation-driven cardiomyopathy involving the TNNI3 and TNNT2 genes, review the existing literature on the identified variants particularly TNNI3 (p.Asn185Thrfs*14) and TNNT2 (p.Arg141Trp), and provide insights into the plausible nature of such histopathological observation based on animal studies and the few reported cases in humans.