Dysregulation of iron metabolism-linked genes at myocardial tissue and cell levels in dilated cardiomyopathy
Authors: Massaiu I , Campodonico J , Mapelli M , Salvioni E , Valerio V , Moschetta D , Myasoedova V , Cappellini M , Pompilio G , Poggio P , Agostoni P 
Published: May 2023

Abstract

Funding Acknowledgements
Type of funding sources: Public Institution(s). Main funding source(s): Fondazione Gigi & Pupa Ferrari ONLUS Italian Ministry of Health-Ricerca Corrente.

Background
Heart failure (HF) is defined as one of the main clinical and public health burdens with multifactorial symptoms and high worldwide prevalence. Dilated cardiomyopathy (DCM) is one of the leading causes of HF and is responsible for over half of all left ventricular assist device implantations and heart transplantations. DCM is regarded as a multiple disease entity linked to a number of genetic, nutritional, inflammatory, infective, metabolic, and environmental causes. Among the metabolic processes associated with HF, iron metabolism disorders, ranging from iron deficiency to iron overload, are gaining attention. However, the understanding of iron mechanisms, at cardiac level, involved in HF and particularly in DCM, remains elusive.

Purpose
We aim to evaluate the possible dysregulation of iron metabolism-linked genes in DCM, through a quantitative analysis of public myocardial gene expression data at tissue and cell levels.

Methods
Bulk RNA sequencing (RNA-seq) and single-nucleus RNA-seq (snRNA-seq) datasets, respectively of 436 and 38 left ventricle samples from adult non-failed (NF) and DCM subjects, were retrieved from public studies. We defined a list of 272 genes directly related to intramyocardial iron metabolism and performed the differential gene expression analysis both at whole cardiac tissue level and in cardiomyocytes, fibroblasts, myeloid, endocardial, and endothelial cells.

Results
In the overall myocardial tissue, we found 44 iron-linked genes differentially expressed between DCM and NF subjects. To better understand iron genes abnormalities in the myocardium of DCM patients we deepened the analysis from tissue to single-cell level. Among the five considered cell types (cardiomyocytes, fibroblasts, myeloid, endocardial, and endothelial cells) at least 9% of iron-linked expressed genes were significantly regulated in DCM when compared to NF. Specifically, the iron metabolism in DCM cardiomyocytes is altered at several levels (Figure 1), including: 1) imbalance of Fe3+ internalization (SCARA5 down-regulation) and reduction of internal conversion from Fe3+ to Fe2+ (STEAP3 down-regulation), 2) increase of iron consumption to produce hemoglobin (HBA1/2 up-regulation), 3) higher heme synthesis and externalization (ALAS2 and ABCG2 up-regulation), 4) lower cleavage of heme to Fe2+, biliverdin and carbon monoxide (HMOX2 down-regulation), and 5) positive regulation of hepcidin (BMP6 up-regulation).

Conclusions
In conclusion, the present study provides significant progress in knowledge of iron metabolism changes in DCM disease, which likely have a clinical meaning. Indeed, our data show that regulation of intracellular iron homeostasis is dysfunctional in DCM patients’ cardiac tissues, supporting, but not providing, the hypothesis of a direct effect of iron in the disease progression.