Gilbert, G. | Search bioRxiv

bioRxiv2021

Human iPSC-Based Model Reveals NOX4 as Therapeutic Target in Duchenne Cardiomyopathy

Duchenne muscular dystrophy (DMD) is an X-linked progressive muscle disorder, caused by mutations in the Dystrophin gene. Cardiomyopathy is one of the major causes of early death. In this study, we used DMD patient-specific induced pluripotent stem cells (iPSCs) to model cardiomyopathic features in DMD and unravel novel pathological mechanistic insights. Cardiomyocytes (CMs) differentiated from DMD iPSCs showed enhanced premature cell death, due to significantly elevated intracellular reactive oxygen species (ROS) concentrations, as a result of depolarized mitochondria and high NADPH oxidase 4 (NOX4) protein levels. Genetic correction of Dystrophin through CRISPR/Cas9 editing restored normal ROS levels. Application of ROS reduction by N-acetyl-L-cysteine (NAC), partial Dystrophin re-expression by ataluren (PTC124) and enhancing mitochondrial electron transport chain function by idebenone improved cell survival of DMD iPSC-CMs. We show applications that could counteract the detrimental oxidative stress environment in DMD iPSC-CMs by stimulating adenosine triphosphate (ATP) production. ATP could bind to the ATP-binding domain in the NOX4 enzyme, and we demonstrate that ATP resulted in partial inhibition of the NADPH-dependent ROS production of NOX4. Considering the complexity and the early cellular stress responses in DMD cardiomyopathy, we propose to target ROS production and prevent the detrimental effects of NOX4 on DMD CMs as a promising therapeutic strategy. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=99 SRC="FIGDIR/small/460090v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@d3606borg.highwire.dtl.DTLVardef@15f1d88org.highwire.dtl.DTLVardef@18bfb9corg.highwire.dtl.DTLVardef@133c6bd_HPS_FORMAT_FIGEXP M_FIG The use of human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) from Duchenne muscular dystrophy (DMD) patients to model cardiomyopathic features in DMD and unravel novel pathological mechanistic insights. DMD iPSC-CMs showed accelerated cell death, caused by increased intracellular reactive oxygen species (ROS) levels. By intervention at different target sites, beneficial effects on the mitochondrial membrane potential ({Delta}{Psi}m) and the expression and ROS-producing activity of the cardiac-specific NADPH-oxidase 4 isoform (NOX4) were observed, resulting in an increased cell survival and function of DMD iPSC-CMs. C_FIG

developmental biology↗

bioRxiv2021

Enabling constrained spherical deconvolution and diffusional variance decomposition with tensor-valued diffusion MRI

Diffusion tensor imaging (DTI) is widely used to extract valuable tissue measurements and white matter (WM) fiber orientations, even though its lack of specificity is now well-known, especially for WM fiber crossings. Models such as constrained spherical deconvolution (CSD) take advantage of high angular resolution diffusion imaging (HARDI) data to compute fiber orientation distribution functions (fODF) and tackle the orientational part of the DTI limitations. Furthermore, the recent introduction of tensor-valued diffusion MRI allows for diffusional variance decomposition (DIVIDE), opening the door to the computation of measures more specific to microstructure than DTI measures, such as microscopic fractional anisotropy (FA). However, tensor-valued diffusion MRI data is not mathematically compatible with latest versions of CSD and the impacts of such atypical data on fODF reconstruction with CSD are yet to be studied. In this work, we lay down the mathematical and computational foundations of a tensor-valued CSD and use simulated data to explore the effects of various combinations of diffusion encodings on the angular resolution of extracted fOFDs. We also compare the combinations with regards to their performance at producing accurate and precise FA with DIVIDE, and present an optimised protocol for both methods. We show that our proposed protocol enables the reconstruction of both fODFs and FA on in vivo data.

neuroscience↗