Dridi, H. | Search bioRxiv

bioRxiv2026

Validation of differentiated sinoatrial-like hiPSCs as a model of native sinus node myocytes

BackgroundHuman induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) constitute an attractive system for basic research and pharmacologic screening of new molecules of clinical interest. Numerous protocols aiming at differentiating atrial- or ventricular-like cardiomyocytes (hiPSC-CMs) are available. Conversely, only a few are available for obtaining patient-derived sinoatrial node-like pacemaker myocytes (PM-hiPSC-CMs). Here we validate a new protocol to differentiate mature PM-hiPSC-CMs as a model of native sinoatrial node (SAN) myocytes. MethodsWe generated PM-hiPSC-CMs through a 2D matrix-sandwich method promoting epithelial-to-mesenchymal transition and small molecule-based temporal modulation of Wnt signaling pathway. In addition, we treated our cells with triiodothyronine, dexamethasone and intracellular cyclic AMP (DTA) to enhance expression of proteins involved in intracellular Ca2+ handling. ResultsProteomic analyses showed expression of key SAN proteins in DTA-treated PM-hiPSC-CMs. Importantly, expression of proteins related to Ca2+ handling was increased in DTA-treated PM-hiPSC-CMs compared to untreated ones. DTA-treated PM-hiPSC-CMs displayed action potentials, ionic currents and intracellular Ca2+ dynamics typical of native SAN. In addition, pacemaker activity responded to both {beta}-adrenergic and muscarinic stimulation. ConclusionsOur data indicate that the differentiation protocol effectively generates PM-hiPSC-CMs with typical native human SAN features. This protocol may serve as a potential approach to generate PM-hiPSC-CMs from patients with history of sinoatrial node disfunction (SND) carrying different mutations in ion channels underlying pacemaking. In addition, these in vitro models of SND could be used for testing long-term vector-based gene therapeutic strategies to handle bradycardia.

cell biology↗

bioRxiv2021

Alzheimer's-like remodeling of neuronal ryanodine receptor in COVID-19

COVID-19, caused by SARS-CoV-2 involves multiple organs including cardiovascular, pulmonary and central nervous system. Understanding how SARS-CoV-2 infection afflicts diverse organ systems remains challenging1,2. Particularly vexing has been the problem posed by persistent organ dysfunction known as "long COVID," which includes cognitive impairment3. Here we provide evidence linking SARS-CoV-2 infection to activation of TGF-{beta} signaling and oxidative overload. One consequence is oxidation of the ryanodine receptor/calcium (Ca2+) release channels (RyR) on the endo/sarcoplasmic (ER/SR) reticuli in heart, lung and brains of patients who succumbed to COVID-19. This depletes the channels of the stabilizing subunit calstabin2 causing them to leak Ca2+ which can promote heart failure4,5, pulmonary insufficiency 6 and cognitive and behavioral defects7-9. Ex-vivo treatment of heart, lung, and brain tissues from COVID-19 patients using a Rycal drug (ARM210)10 prevented calstabin2 loss and fixed the channel leak. Of particular interest is that neuropathological pathways activated downstream of leaky RyR2 channels in Alzheimers Disease (AD) patients were activated in COVID-19 patients. Thus, leaky RyR2 Ca2+ channels may play a role in COVID-19 pathophysiology and could be a therapeutic target for amelioration of some comorbidities associated with SARS-CoV-2 infection.

pathology↗