Iron chelation therapy failed to improve cardiac dysfunction caused by mitochondrial injury in rats with iron overload cardiomyopathy a 7T Cardiac MR research in vivo
Authors: Fan X , Hou J , Zi L , Chen W 
Published: October 2024

Abstract

Purpose
To assess the efficacy of iron chelation therapy in improving cardiac function in iron overload cardiomyopathy (IOC) rats by using Cardiac magnetic resonance feature-tracking (CMR-FT).

Methods
The IOC rat model was induced by intraperitoneal injection of iron dextran over 2 months. Subsequently, 7 rats with IOC were assigned as IOC group to receive continued intraperitoneal injections of saline for an additional 2 months, while another group of 5 rats received intraperitoneal injections of deferoxamine (DFO) for the same duration, forming the IOC+DFO group. Meanwhile, a control group consisting of 7 healthy rats received intraperitoneal injections of saline for the entire duration of 4 months. All rats underwent a 7T CMR scan to assess cardiac function, myocardial iron overload, and myocardial fibrosis via cine, T2 mapping, and late gadolinium enhancement (LGE) scanning, respectively. The cardiac function analysis included left ventricular ejection fraction (LVEF) and left ventricular global longitudinal strain (GLS) using cine images. Following CMR scans, all rats underwent open-chest blood collection to detect serum iron levels, and cardiac gross specimens were then subjected to pathological staining, including hematoxylin and eosin (HE) for cardiomyocytes injury, Prussian blue for iron deposition , and Masson staining for myocardial fibrosis. Furthermore, the ultrastructure of cardiomyocyte was examined using transmission electron microscopy (TEM).

Results
The T2 value, measured in the septum wall at the mid-layer of the LV, and LVEF, and GLS exhibited a significant decrease in the IOC or IOC+DFO group, compared to the control group, while there were no significant difference observed between the IOC and IOC+DFO group (Fig. 1A, B, C). Myocardial fibrosis was not detected in the LGE images in both IOC and IOC+DFO group. Compared to the control group (37.5±12.5μmol/L) , serum iron levels were significantly elevated in the IOC group (368.6±181.0μmol/L) and in chelation treatment group (106.1±32.2μmol/L). Histological examination with HE staining revealed a normal arrangement of myocardial cells in all rats, without cellular degeneration or necrosis. Prussian blue staining highlighted the presence of iron particles within the myocardial interstitium in the IOC and IOC+DFO groups. Masson staining demonstrated intact myocardial muscle bundles without any evidence of myocardial fibrosis. Transmission electron microscopy (TEM) revealed myocardial mitochondria injury, characterized by ruptured outer membranes, reduced cristae, and vacuolization.

Conclusions
Following iron chelation therapy, the excessive iron burden in the bloodstream was alleviated. However, myocardial iron overload persisted in IOC rats, with no significant improvement in cardiac function observed. This persistence may be attributed to mitochondrial injury. The findings underscore the importance of monitoring cardiac dysfunction in patients with iron overload.CMR parameters analysis in IOC rats