Impact of stretch on sarcomere length variability in isolated fully relaxed rat cardiac myocytes

Lookin O. Boulali N. Cazorla O. de Tombe P.
October 2023 Springer Science and Business Media Deutschland GmbH

Pflugers Archiv European Journal of Physiology
2023 #475 Issue 10 1203 - 1210 pp.

The contractility of cardiac muscle is greatly affected by preload via the Frank-Starling mechanism (FSM). It is based on preload-dependent activation of sarcomeres—the elementary contractile units in muscle cells. Recent findings show a natural variability in sarcomere length (SL) in resting cardiomyocytes that, moreover, is altered in an actively contracting myocyte. SL variability may contribute to the FSM, but it remains unresolved whether the change in the SL variability is regulated by activation process per se or simply by changes in cell stretch, i.e., average SL. To separate the roles of activation and SL, we characterized SL variability in isolated, fully relaxed rat ventricular cardiomyocytes (n = 12) subjected to a longitudinal stretch with the carbon fiber (CF) technique. Each cell was tested in three states: without CF attachment (control, no preload), with CF attachment without stretch, and with CF attachment and ~ 10% stretch of initial SL. The cells were imaged by transmitted light microscopy to retrieve and analyze individual SL and SL variability off-line by multiple quantitative measures such as coefficient of variation or median absolute deviation. We found that CF attachment without stretch did not affect the extent of SL variability nor average SL. In stretched myocytes, the averaged SL significantly increased, while the SL variability remained unchanged. This result clearly indicates that the non-uniformity of individual SL is not sensitive to the average SL itself in fully relaxed myocytes. We conclude that SL variability per se does not contribute to the FSM in the heart.

Carbon fibers , Isolated cardiomyocyte , Sarcomere , Sarcomere length variability , Stretch

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Astana, Kazakhstan
Laboratoire “Physiologie Et Médecine Expérimentale du Coeur Et Des Muscles,” Phymedexp, INSERM, CNRS, Montpellier University, CHU Arnaud de Villeneuve, Montpellier, 34295, France
Physiology and Biophysics, University of Illinois at Chicago, Chicago, 60612, IL, United States

Astana
Laboratoire “Physiologie Et Médecine Expérimentale du Coeur Et Des Muscles
Physiology and Biophysics

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