Contractile abnormalities and altered drug response in engineered heart tissue from Mybpc3-targeted knock-in mice

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• 作者：Andrea St?hr ; Felix W. Friedrich ; Frederik Flenner ; Birgit Geertz ; Alex ; ra Eder ; Sebastian Schaaf ; Marc N. Hirt ; June Uebeler ; Saskia Schlossarek ; Lucie Carrier ; Arne Hansen ; Thomas Eschenhagen
• 关键词：Acta1 ; ¦Á-skeletal actin gene or mRNA ; Atp2a2 ; ATPase ; Ca2  ; + transporting ; cardiac mRNA ; BPM ; Beats per minute ; cMyBP-C ; Cardiac myosin-binding protein C ; EC50 ; Half maximal effective concentration ; EHT ; Engineered heart tissue ; EMD ; EMD 57033 ; HCM
• 刊名：Journal of Molecular and Cellular Cardiology
• 出版年：2013
• 出版时间：October, 2013
• 年：2013
• 卷：63
• 期：Complete
• 页码：189-198
• 全文大小：2072 K

文摘

Myosin-binding protein C (Mybpc3)-targeted knock-in mice (KI) recapitulate typical aspects of human hypertrophic cardiomyopathy. We evaluated whether these functional alterations can be reproduced in engineered heart tissue (EHT) and yield novel mechanistic information on the function of cMyBP-C. EHTs were generated from cardiac cells of neonatal KI, heterozygous (HET) or wild-type controls (WT) and developed without apparent morphological differences. KI had 70 % and HET 20 % lower total cMyBP-C levels than WT, accompanied by elevated fetal gene expression. Under standard culture conditions and spontaneous beating, KI EHTs showed more frequent burst beating than WT and occasional tetanic contractions (14/96). Under electrical stimulation (6 Hz, 37 ¡ãC) KI EHTs exhibited shorter contraction and relaxation times and a twofold higher sensitivity to external [Ca^2 +]. Accordingly, the sensitivity to verapamil was 4-fold lower and the response to isoprenaline or the Ca^2 + sensitizer EMD 57033 2- to 4-fold smaller. The loss of EMD effect was verified in 6-week-old KI mice in vivo. HET EHTs were apparently normal under basal conditions, but showed similarly altered contractile responses to [Ca^2 +], verapamil, isoprenaline and EMD. In contrast, drug-induced changes in intracellular Ca^2 + transients (Fura-2) were essentially normal. In conclusion, the present findings in auxotonically contracting EHTs support the idea that cMyBP-C's normal role is to suppress force generation at low intracellular Ca^2 + and stabilize the power-stroke step of the cross bridge cycle. Pharmacological testing in EHT unmasked a disease phenotype in HET. The altered drug response may be clinically relevant.