Unraveling the role of iron in the heart using 3D engineered heart tissue

Heart failure (HF) affects more than 64 million people globally. The HF prevalence is increasing due to an aging population and risk factor such as hypertension and diabetes. Although, there are various medical interventions for HF the prognosis remains grim. It has been estimated that 50% of HF patients suffer from Iron Deficiency (ID). Iron plays a key role in a variety of physiological processes including erythropoiesis, oxygen storage, and mitochondrial respiration. Hence, ID leads to a progression of HF symptoms and worsens the prognosis. Therefore, addressing the gap of knowledge on the molecular effects of ID on cardiac tissue is crucial.

This study aims to understand the pathophysiology and functional consequences of ID and iron repletion on human 3D engineered heart tissues.

State-of-the-art dynamic engineered heart tissues (Dyn-EHT) were developed with the use of human pluripotent stem cell (hPSC)-derived cardiomyocytes and cardiac fibroblasts, and subjected to an applied pre-load mimicking the human heart condition. The Dyn-EHTs were then subjected to iron depletion and repletion via the iron chelator deferoxamine (DFO) for four days and partially saturated transferrin (sTf) for two respectively. Functional contractile parameters of Dyn-EHTs were assessed by video analysis. Iron status and molecular effects will be measured using a variety of assays including PCR, ferritin measurements and mass spectrometry. Mechanistic consequences of ID will be determined by performing RNA sequencing on the Dyn-EHT.

After four days of DFO treatment, the expression of the transferrin receptor (TfRC) is significantly upregulated in a dose responsive manner. Where a dose of 10 µM DFO results in two-fold increase and a dose 90 µM and 120 µM results in an eight-fold increase in TfRC expression. Dyn-EHTs show reduced spontaneous contractions following iron depletion. Fractional shortening is significantly reduced in a dose responsive manner. Resulting in a fractional shortening fold change of 0.6 down to 0.3 for 30 µM and 120 µM DFO respectively. Moreover, These changes are partially reversable by iron repletion with sTf.

A 3D model of the heart was developed, capable of assessing the effects of ID on differentiated cardiac tissue. ID affects the contractile capabilities of Dyn-EHTs in a dose-responsive manner. Iron repletion is capable of restoring limited function contractile function of Dyn-EHTs.