End-diastolic force pre-activates cardiomyocytes and determines contractile force: role of titin and calcium

Aref Najafi, Martijn van de Locht, Maike Schuldt, Patrick Schönleitner, Menne van Willigenburg, Ilse Bollen, Max Goebel, Coen A. C. Ottenheijm, Jolanda van der Velden, Michiel Helmes, Diederik W. D. Kuster

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Abstract: Titin functions as a molecular spring, and cardiomyocytes are able, through splicing, to control the length of titin. We hypothesized that together with diastolic [Ca2+], titin-based stretch pre-activates cardiomyocytes during diastole and is a major determinant of force production in the subsequent contraction. Through this mechanism titin would play an important role in active force development and length-dependent activation. Mutations in the splicing factor RNA binding motif protein 20 (RBM20) result in expression of large, highly compliant titin isoforms. We measured single cardiomyocyte work loops that mimic the cardiac cycle in wild-type (WT) and heterozygous (HET) RBM20-deficient rats. In addition, we studied the role of diastolic [Ca2+] in membrane-permeabilized WT and HET cardiomyocytes. Intact cardiomyocytes isolated from HET left ventricles were unable to produce normal levels of work (55% of WT) at low pacing frequencies, but this difference disappeared at high pacing frequencies. Length-dependent activation (force–sarcomere length relationship) was blunted in HET cardiomyocytes, but the force–end-diastolic force relationship was not different between HET and WT cardiomyocytes. To delineate the effects of diastolic [Ca2+] and titin pre-activation on force generation, measurements were performed in detergent-permeabilized cardiomyocytes. Cardiac twitches were simulated by transiently exposing permeabilized cardiomyocytes to 2 µm Ca2+. Increasing diastolic [Ca2+] from 1 to 80 nm increased force development twofold in WT. Higher diastolic [Ca2+] was needed in HET. These findings are consistent with our hypothesis that pre-activation increases active force development. Highly compliant titin allows cells to function at higher diastolic [Ca2+].
Original languageEnglish
Pages (from-to)4521-4531
JournalJournal of Physiology
Volume597
Issue number17
DOIs
Publication statusPublished - 1 Sep 2019

Cite this

@article{b3e8ba4ba6c143cd9aeb4f3dcb5523bb,
title = "End-diastolic force pre-activates cardiomyocytes and determines contractile force: role of titin and calcium",
abstract = "Abstract: Titin functions as a molecular spring, and cardiomyocytes are able, through splicing, to control the length of titin. We hypothesized that together with diastolic [Ca2+], titin-based stretch pre-activates cardiomyocytes during diastole and is a major determinant of force production in the subsequent contraction. Through this mechanism titin would play an important role in active force development and length-dependent activation. Mutations in the splicing factor RNA binding motif protein 20 (RBM20) result in expression of large, highly compliant titin isoforms. We measured single cardiomyocyte work loops that mimic the cardiac cycle in wild-type (WT) and heterozygous (HET) RBM20-deficient rats. In addition, we studied the role of diastolic [Ca2+] in membrane-permeabilized WT and HET cardiomyocytes. Intact cardiomyocytes isolated from HET left ventricles were unable to produce normal levels of work (55{\%} of WT) at low pacing frequencies, but this difference disappeared at high pacing frequencies. Length-dependent activation (force–sarcomere length relationship) was blunted in HET cardiomyocytes, but the force–end-diastolic force relationship was not different between HET and WT cardiomyocytes. To delineate the effects of diastolic [Ca2+] and titin pre-activation on force generation, measurements were performed in detergent-permeabilized cardiomyocytes. Cardiac twitches were simulated by transiently exposing permeabilized cardiomyocytes to 2 µm Ca2+. Increasing diastolic [Ca2+] from 1 to 80 nm increased force development twofold in WT. Higher diastolic [Ca2+] was needed in HET. These findings are consistent with our hypothesis that pre-activation increases active force development. Highly compliant titin allows cells to function at higher diastolic [Ca2+].",
author = "Aref Najafi and {van de Locht}, Martijn and Maike Schuldt and Patrick Sch{\"o}nleitner and {van Willigenburg}, Menne and Ilse Bollen and Max Goebel and Ottenheijm, {Coen A. C.} and {van der Velden}, Jolanda and Michiel Helmes and Kuster, {Diederik W. D.}",
year = "2019",
month = "9",
day = "1",
doi = "10.1113/JP277985",
language = "English",
volume = "597",
pages = "4521--4531",
journal = "Journal of Physiology - London",
issn = "0022-3751",
publisher = "Wiley-Blackwell",
number = "17",

}

End-diastolic force pre-activates cardiomyocytes and determines contractile force: role of titin and calcium. / Najafi, Aref; van de Locht, Martijn; Schuldt, Maike; Schönleitner, Patrick; van Willigenburg, Menne; Bollen, Ilse; Goebel, Max; Ottenheijm, Coen A. C.; van der Velden, Jolanda; Helmes, Michiel; Kuster, Diederik W. D.

In: Journal of Physiology, Vol. 597, No. 17, 01.09.2019, p. 4521-4531.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - End-diastolic force pre-activates cardiomyocytes and determines contractile force: role of titin and calcium

AU - Najafi, Aref

AU - van de Locht, Martijn

AU - Schuldt, Maike

AU - Schönleitner, Patrick

AU - van Willigenburg, Menne

AU - Bollen, Ilse

AU - Goebel, Max

AU - Ottenheijm, Coen A. C.

AU - van der Velden, Jolanda

AU - Helmes, Michiel

AU - Kuster, Diederik W. D.

PY - 2019/9/1

Y1 - 2019/9/1

N2 - Abstract: Titin functions as a molecular spring, and cardiomyocytes are able, through splicing, to control the length of titin. We hypothesized that together with diastolic [Ca2+], titin-based stretch pre-activates cardiomyocytes during diastole and is a major determinant of force production in the subsequent contraction. Through this mechanism titin would play an important role in active force development and length-dependent activation. Mutations in the splicing factor RNA binding motif protein 20 (RBM20) result in expression of large, highly compliant titin isoforms. We measured single cardiomyocyte work loops that mimic the cardiac cycle in wild-type (WT) and heterozygous (HET) RBM20-deficient rats. In addition, we studied the role of diastolic [Ca2+] in membrane-permeabilized WT and HET cardiomyocytes. Intact cardiomyocytes isolated from HET left ventricles were unable to produce normal levels of work (55% of WT) at low pacing frequencies, but this difference disappeared at high pacing frequencies. Length-dependent activation (force–sarcomere length relationship) was blunted in HET cardiomyocytes, but the force–end-diastolic force relationship was not different between HET and WT cardiomyocytes. To delineate the effects of diastolic [Ca2+] and titin pre-activation on force generation, measurements were performed in detergent-permeabilized cardiomyocytes. Cardiac twitches were simulated by transiently exposing permeabilized cardiomyocytes to 2 µm Ca2+. Increasing diastolic [Ca2+] from 1 to 80 nm increased force development twofold in WT. Higher diastolic [Ca2+] was needed in HET. These findings are consistent with our hypothesis that pre-activation increases active force development. Highly compliant titin allows cells to function at higher diastolic [Ca2+].

AB - Abstract: Titin functions as a molecular spring, and cardiomyocytes are able, through splicing, to control the length of titin. We hypothesized that together with diastolic [Ca2+], titin-based stretch pre-activates cardiomyocytes during diastole and is a major determinant of force production in the subsequent contraction. Through this mechanism titin would play an important role in active force development and length-dependent activation. Mutations in the splicing factor RNA binding motif protein 20 (RBM20) result in expression of large, highly compliant titin isoforms. We measured single cardiomyocyte work loops that mimic the cardiac cycle in wild-type (WT) and heterozygous (HET) RBM20-deficient rats. In addition, we studied the role of diastolic [Ca2+] in membrane-permeabilized WT and HET cardiomyocytes. Intact cardiomyocytes isolated from HET left ventricles were unable to produce normal levels of work (55% of WT) at low pacing frequencies, but this difference disappeared at high pacing frequencies. Length-dependent activation (force–sarcomere length relationship) was blunted in HET cardiomyocytes, but the force–end-diastolic force relationship was not different between HET and WT cardiomyocytes. To delineate the effects of diastolic [Ca2+] and titin pre-activation on force generation, measurements were performed in detergent-permeabilized cardiomyocytes. Cardiac twitches were simulated by transiently exposing permeabilized cardiomyocytes to 2 µm Ca2+. Increasing diastolic [Ca2+] from 1 to 80 nm increased force development twofold in WT. Higher diastolic [Ca2+] was needed in HET. These findings are consistent with our hypothesis that pre-activation increases active force development. Highly compliant titin allows cells to function at higher diastolic [Ca2+].

UR - https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85071702854&origin=inward

UR - https://www.ncbi.nlm.nih.gov/pubmed/31314138

U2 - 10.1113/JP277985

DO - 10.1113/JP277985

M3 - Article

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EP - 4531

JO - Journal of Physiology - London

JF - Journal of Physiology - London

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ER -