Biology subjects

Muthukumarasamy, K. M.

Publications and source records attributed to Muthukumarasamy, K. M..

2 recordsLinked to original sources

bioRxiv2025

Modeling Atrial Fibrillation through Intermittent Tachypacing-Induced Remodeling in hiPSC-Derived Atrial Cardiomyocytes and Atrial Fibroblast

BackgroundHuman in vitro models for atrial fibrillation (AF) are limited. Human-induced pluripotent stem cell-derived atrial cardiomyocytes (hiPSC-aCMs) provide a valuable tool to study AF pathophysiology by facilitating in vitro modeling. ObjectivesTo investigate the effects of an intermittent tachypacing protocol (ITPP) in matured hiPSC-aCMs co-cultured with human atrial cardiac fibroblast (haCF) to mimic AF-associated electroanatomical phenotypes. Methods and ResultshiPSC-aCMs were cultured alone or co-cultured with haCFs at 90/10 and 70/30 ratios. ITPP was applied through field stimulation, and optical mapping assessed action potentials (APs) and calcium transients (CaTs). Immunostaining was performed to quantify pro-fibrotic biomarkers (Collagen III and TGF{beta}1). ITPP led to increased spontaneous AP frequency ({Delta}=+31{+/-}7%, P<0.0001) and reduced AP duration at 80% repolarization (APD80%; {Delta}=-15{+/-}4%, P=0.001). Additionally, the upstroke slope ({Delta}=-41{+/-}11%, P=0.001) and amplitude (dF/F0; {Delta}=-51{+/-}13%, P<0.001) of intracellular CaT were significantly reduced. Co-culture at the 70/30 hiPSC-aCM/haCF ratio, showed a >100-fold increase in Collagen III expression (P<0.0001), diminished excitability ({Delta}Hz=-61{+/-}6%, P<0.0001), prolonged {Delta}APD80% ({Delta}=+130{+/-}10%, P<0.0001), prolonged AP triangulation ({Delta}APDTri=+143{+/-}13%, P<0.0001), reduced upstroke slope ({Delta}=-66{+/-}6%, P<0.0001), conduction block ({Delta}=-52{+/-}18%, P=0.0260), and diminished intracellular calcium handling (upstroke slope {Delta}=-50{+/-}8%, P<0.0001; {Delta}dF/F0=-34{+/-}9%, P=0.0003). Finally, the application of ITPP to the 70/30 co-culture model recapitulated an AF-mediated phenotype ({Delta}Hz=+25{+/-}8%, P=0.02; {Delta}APD80%=-16{+/-}6%, P=0.01) while introducing conduction block ({Delta}CV100/0 vs 70/30= -27{+/-}15%; P=0.0005). ConclusionsCo-cultures of matured hiPSC-aCMs and haCFs exhibited structural and electrophysiological remodeling, including conduction abnormalities, mirroring key AF mechanisms. This model holds potential for patient-specific therapies and drug discovery. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=177 SRC="FIGDIR/small/655123v1_ufig1.gif" ALT="Figure 1"> View larger version (61K): org.highwire.dtl.DTLVardef@1c56760org.highwire.dtl.DTLVardef@105d4a2org.highwire.dtl.DTLVardef@1cb18d4org.highwire.dtl.DTLVardef@cb3353_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO Human iPSC-Model for Atrial Fibrillation C_FIG

bioengineering↗

bioRxiv2025

Time-dependent Mitochondrial Remodeling in Experimental Atrial Fibrillation and Potential Therapeutic Relevance

BACKGROUNDChanges in mitochondria have been implicated in atrial fibrillation (AF), but their manifestations and significance are poorly understood. Here, we studied changes in mitochondrial morphology and function during AF and assessed the effect of a mitochondrial-targeted intervention in a large animal model. METHODS AND RESULTSAtrial cardiomyocytes (ACMs) were isolated from dogs in electrically-driven AF for periods of 24 hours to 3 weeks and from humans with/without longstanding persistent AF. Mitochondrial Ca2+-concentration ([Ca2+]Mito), reactive oxygen species (mtROS) production, membrane potential ({Delta}{Psi}m), permeability transition-pore (mPTP) opening and flavin adenine dinucleotide (FAD) were measured via confocal microscopy; nicotine adenine dinucleotide (NADH) under ultraviolet light. mtROS-production increased within 24 hours and superoxide-dismutase type-2 was significantly reduced from 3-day AF. [Ca2+]Mito and mPTP-opening frequency/duration increased progressively during AF. Mitochondrial depolarization was detectable 24 hours after AF-onset. NADH increased by 15% at 24-hour AF, concomitant with increased pyruvate-dehydrogenase expression, then gradually decreased. Mitochondria enlarged and elongated at 24-hour and 3-day AF, followed by progressive fragmentation, rupture and shrinkage. Mitochondrial fusion protein-1 (MFN1) was reduced from 3-day to 3-week AF and phosphorylated dynamin-related protein-1 (p-DRP1ser-616) increased after 1 week of canine AF and in human AF. Addition of the mitochondrial antioxidant MitoTempo attenuated action-potential shortening and L-type Ca2+-current (ICaL)-downregulation in canine and human AF ACMs in vitro. Administration of the orally-active mitochondrial-targeted ubiquinone mitoquinone to dogs during 3-week AF prevented mitochondrial Ca2+-overload, mtROS-overproduction, structural damage and abnormalities in {Delta}{Psi}m and respiration. Functionally, mitoquinone reduced AF-induced Ca2+-current downregulation, action-potential abbreviation, contractile dysfunction and fibrosis, preventing AF-substrate development and AF-sustainability. CONCLUSIONSMitochondria show a series of changes during AF, with early hyperfunction and enhanced ROS-generation, followed by progressive damage and dysfunction. Mitochondrial-targeted therapy prevents mitochondrial dysfunction and attenuates adverse AF-related remodeling, positioning mitochondrial protection as a potential novel therapeutic target in AF.

pathology↗