Abstract Background Kearns-Sayre Syndrome (KSS) is a cardiac metabolic rare diseases occur due to mitochondrial DNA deletion. In this study, we modelled the mitochondrial cardiomyopathy seen in KSS with debilitating consequences affecting both males and females. KSS has a prevalence of 1.6 cases per 100,000 individuals. Although, the mitochondrial DNA deletion varies in KSS but the most common deletion seen in the population is with 4977 bp. Affected individuals have at least 1 of the following conditions like heart block, higher cerebrospinal fluid protein, cerebellar ataxia, optic neuropathy, deafness, kidney dysfunction, endocrine abnormalities and cardiomyopathy. Approved medical therapies for KSS cardiomyopathy are scarce. Currently there is no in-vitro or in-vivo model available to study KSS cardiomyopathy. This KSS cardiac organoid model will help further to delineate the pathophysiology of the disease and new therapeutic identifications. Methods In this study, we reveal the establishment of in vitro 3D models for KSS cardiomyopathy using human iPSC-derived self-organized cardiac organoid (hiPSC-SCO). Patient’s fibroblasts with the most common deletion, were reprogrammed into iPSCs and further differentiated into mature cardiac organoids. Afterwards, control and KSS cardiac organoid’s oxidative phosphorylation, beating was measured respectively by seahorse assay and calcium transient assay. Control and KSS cardiac organoid’s heteroplasmy was determined by qRT PCR. Additionally, Control and KSS cardiac organoid’s ultrastructure and mitochondrial protein content was determined by Electron microscopy and mitochondrial proteomics. RNA sequencing was performed to investigate the changes in gene expressions in control and KSS cardiac organoids. Results Mature control and KSS cardiac organoids were derived respectively from control and KSS iPSC line. Both cardiac organoids contained all relevant cell types of the human heart, such as cardiomyocytes, smooth muscle cells, fibroblasts, nerves, and macrophages. KSS cardiac organoid showed higher heteroplasmy along with higher beating frequency and less amplitude compared to control organoid. KSS cardiac organoid showed reduced OCR compared to control organoids. Mitochondrial proteomics showed less abundance of ETC complexes in KSS cardiac organoid. Further, RNA sequencing showed higher expression of cardiac fibrotic and disease marker genes. KSS cardiac organoids showed alpha actin filament disarray. Importantly, KSS cardiac organoids showed less ATP concentration and neurons compared to healthy cardiac organoids. Electron micrograph confirmed altered mitochondrial morphology in KSS cardiac organoids. Conclusion We successfully developed KSS cardiomyopathy model which replicated the disease phenotype. This disease model could be used to understand the underlying pathophysiologic mechanisms, disease development and for drug screening.
Das et al. (Sat,) studied this question.