Novel mitochondria-targeted therapy AP39 limits mitochondrial dysregulation and diastolic dysfunction in 2D & 3D human models of diabetic cardiomyopathy

Abstract Introduction Mitochondrial dysregulation has been implicated in many complications of diabetes. Mitochondrial-targeted therapies AP39 and SS31 are renoprotective, but their cardioprotective potential in diabetes has not been fully resolved. Purpose We investigated AP39 and SS31 in human induced pluripotent stem cell-derived cardiomyocytes (iPSC-hCM) and endothelial cells (iPSC-hEC) independently in 2D culture, as well as collectively in a 3D cardiac organoid (iPSC-hCO) model also comprising fibroblasts (iPSC-hFB), under type 2 diabetes (T2D)-like conditions. Methods Cells (iPSC-hCM, iPSC-hEC, iPSC-hFB; foreskin-2 cell line) were exposed to either 5.55mM glucose (control) or T2D conditions (20mM glucose plus fatty acids, endothelin-1 and cortisol) ± AP39 (50nM) or SS31 (1µM) for 48h. Cardiac organoids were subjected to 5.55mM glucose (control) or T2D for 4 days, with AP39 (50nM) or SS31 (1µM) added on day 2. Data are expressed as mean±SEM (fold) with n=4-6 from 2-3 independent experiments. One-way ANOVA with Dunnett`s post hoc analysis was performed with P<0.05 considered significant. Results 2D human cells: After 48h, T2D increased mitochondrial superoxide in iPSC-hCM (2.4±0.1 fold vs control) and iPSC-hEC (3.2±0.29 fold vs control), both P<0.05 (measured by MitoSOX). This was blunted by both AP39 (to 1.1±0.17) and SS31 (to 1.5±0.17) in T2D iPSC-hCM (P<0.05), with similar impact in iPSC-hEC, to 2.9±0.26 and 1.3±0.16 fold, both P<0.05. T2D increased cell death in both iPSC-hCM (1.6±0.09 fold vs control) and iPSC-hEC (1.6±0.12 fold, both P<0.05 measured by propidium iodide staining. Interestingly, AP39 selectively blunted cell death in T2D iPSC-hCM (to 1.1±0.06, P<0.05), mimicked by SS31 in T2D iPSC-hEC only (to 1.0±0.10, P<0.05). Further, T2D-induced mitochondrial hyperpolarisation in iPSC-hCM (1.5±0.09 fold vs control, assessed using TMRM), was only protected by AP39 (1.2±0.06 fold, P<0.05), but not SS31. 3D human cardiac organoids: After 4 days, T2D increased total contraction duration (1.6±0.10 fold control), time to peak (1.7±0.11) and relaxation duration (1.5±0.13, indicative of diastolic dysfunction), assessed by Olympus IX71 with a DP72 camera. All 3 contractile parameters were attenuated with AP39 (to 1.5±0.06, 1.3±0.09 and 1.0±0.04 fold, respectively) or SS31 (to 1.1±0.05, 1.2±0.15 and 1.2±0.12 fold, respectively), all P<0.05. T2D increased mitochondrial superoxide (2.7±0.16 fold control), blunted by AP39 (to 1.8±0.16) and SS31 (to 1.9±0.17), both P<0.05. Cellular injury measured by LDH was evident in T2D iPSC-hCO (2.1±0.23 fold control) was limited by AP39 (to 1.2±0.09) and SS31 (to 1.1±0.07), both P<0.05. Conclusion Our results highlight the cardioprotective potential of AP39 and SS31 to limit mitochondrial dysregulation, cell death and contractile dysfunction in human in vitro models of T2D. These findings may facilitate their clinical progression as therapeutic options for diabetic cardiomyopathy.