Investigating the cardiac pathology of SCO2‐mediated hypertrophic cardiomyopathy using patients induced pluripotent stem cell–derived cardiomyocytes

Abstract

Mutations in SCO2 are among the most common causes of COX deficiency, resulting in reduced mitochondrial oxidative ATP production capacity, often leading to hypertrophic cardiomyopathy (HCM). To date, none of the recent pertaining reports provide deep understanding of the SCO2 disease pathophysiology. To investigate the cardiac pathology of the disease, we were the first to generate induced pluripotent stem cell (iPSC)-derived cardiomyocytes (iPSC-CMs) from SCO2-mutated patients. For iPSC generation, we reprogrammed skin fibroblasts from two SCO2 patients and healthy controls. The first patient was a compound heterozygote to the common E140K mutation, and the second was homozygote for the less common G193S mutation. iPSC were differentiated into cardiomyocytes through embryoid body (EB) formation. To test the hypothesis that the SCO2 mutation is associated with mitochondrial abnormalities, and intracellular Ca 2+ -overload resulting in functional derangements and arrhythmias, we investigated in SCO2-mutated iPSC-CMs (compared to control cardiomyocytes): (i) the ultrastructural changes; (ii) the inotropic responsiveness to b-adrenergic stimulation, increased [Ca 2+ ] o and angiotensin-II (AT-II); and (iii) the Beat Rate Variability (BRV) characteristics. In support of the hypothesis, we found in the mutated iPSC-CMs major ultrastructural abnormalities and markedly attenuated response to the inotropic interventions and caffeine, as well as delayed afterdepolarizations (DADs) and increased BRV, suggesting impaired SR Ca 2+ handling due to attenuated SERCA activity caused by ATP shortage. Our novel results show that iPSC-CMs are useful for investigating the pathophysiological mechanisms underlying the SCO2 mutation syndrome.

Mitochondrial Transfer through Pericardium Contributes to Functional Recovery in Ischemic Cardiomyopathy

“…Regarding the pathophysiology of mitochondrial cardiomyopathy, mitochondrial protein abnormalities can cause chronic structural abnormalities in heart tissue. Thus, if transferred mitochondria activate pathological mitochondria, it may be bene cial for the subject [31][32][33][34][35]. In the present study, structural improvements, such as orientation of myocardial bers, suppression of CM hypertrophy, and suppression of brosis (remodeling suppression) were observed.…”

Functional abnormalities in induced Pluripotent Stem Cell-derived cardiomyocytes generated from titin-mutated patients with dilated cardiomyopathy

“…To evaluate the iPSC differentiation capacity in vivo , 5-day-old iPSC colonies from one 6-well plate were detached using 1 mg/ml type IV collagenase, washed 3 times in PBS and then injected into thigh muscle of severe combined immunodeficient (SCID) mice. Teratomas were observed 8–12 weeks after injection, and images were obtained from formalin-fixed (4%) and paraffin-embedded teratoma sections stained with hematoxylin and eosin (H&E) [ 14 – 16 ].…”

Cardiomyopathy phenotypes in human-induced pluripotent stem cell-derived cardiomyocytes—a systematic review

“…down, GB3 accumulation, low beating rate, arrhythmias No [ 15 ] LAMP2 Het c.129– 130insAT) Het c.64+1G>A Danon n.d. n.d. n.d. n.d. n.d. Mitochondrial abnormalities, decreased autophagic flux No Yes [ 34 ] MYBPC3 Het c.1358_1359insC HCM n.d. n.d. n.d. + 65% n.d. cMyBPC haploinsufficiency, BNP, MYH7 and others up Corrected by gene therapy No [ 76 ] PRKAG2 Het Arg302Gln HCM + WPW n.d. n.d. n.d. + 10–30% n.d. MDP, APD +/−, If +/−, AP irregularity, RR scatter + 500% Yes Yes [ 5 ] SCO2 Hom c.577G>A CpHet c.418G>A/c.17Ins19 HCM syndrome +/− (??) n.d. n.d. n.d. n.d. Mitochondrial abnormalities, no Iso or Ca 2+ response, DAD, arrhythmic response to Iso No Yes [ 31 ] MT-RNR2 m.2336T>C Mitochondrial HCM n.d. n.d. n.d. + 30% n.d. NPPA , NPPB , NFAT up, slightly increased intracellular calcium, SR store, reduced I Ca , APD prolonged, arrhythmias, RMP − 55, upstroke 5–10 v/s, DAD No Yes [ 52 ] MYL3 Het c.170C-A, Exac 0.0001154, introduced 170C-g and MYBPC3 Het p.Val321Met HCM-associated VUS n.d. n.d. n.d. +/− (also in mut) n.d. No phenotype detected in VU...…”

“…down, GB3 accumulation, low beating rate, arrhythmiasNo[15] LAMP2 Het c.129– 130insAT) Het c.64+1G>A Danonn.d.n.d.n.d.n.d.n.d.Mitochondrial abnormalities, decreased autophagic fluxNoYes[34] MYBPC3 Het c.1358_1359insCHCMn.d.n.d.n.d.+ 65%n.d.cMyBPC haploinsufficiency, BNP, MYH7 and others upCorrected by gene therapyNo[76] PRKAG2 Het Arg302GlnHCM + WPWn.d.n.d.n.d.+ 10–30%n.d.MDP, APD +/−, If +/−, AP irregularity, RR scatter + 500%YesYes[5] SCO2 Hom c.577G>ACpHet c.418G>A/c.17Ins19HCM syndrome+/− (?? )n.d.n.d.n.d.n.d.Mitochondrial abnormalities, no Iso or Ca 2+ response, DAD, arrhythmic response to IsoNoYes[31] MT-RNR2 m.2336T>CMitochondrial HCMn.d.n.d.n.d.+ 30%n.d. NPPA , NPPB , NFAT up, slightly increased intracellular calcium, SR store, reduced I Ca , APD prolonged, arrhythmias, RMP − 55, upstroke 5–10 v/s, DADNoYes[52] MYL3 Het c.170C-A,Exac 0.0001154, introduced 170C-gand MYBPC3 Het p.Val321MetHCM-associated VUSn.d.n.d.n.d.+/− (also in mut)n.d.No phenotype detected in VUS, mean cell size 1800 μm 2 , NPPA and MYH7 up in the two diseased, contraction and rel velocity slightly up, arrhythmias, good statsYesYes[57] TNNT2 Het p.Ile79AsnHCM+ 75%n.d.+ 40%+/−yesSarcomere length +/− (1.8 μm), smaller caffeine transient, higher Ca 2+ buffering, shorter APD, Ca 2+ beat to beat instability, triangulation, NCX-sensitiveYesYes[100] MYH7 and MYH6 ; Het/Hom p.Arg453Cys, frameshift KO, + MYH6 frameshiftHCM− 20% (het), − 70% (hom) − 80% (KO)+ 20%+/− or + 10% (+ MYH6 fs)+ 50%yes NPPB up, multinucleation, basal and max. respiration up, ATP production up, Ca 2+ transie...…”