Nano-imaging of the beating mouse heart in vivo: Importance of sarcomere dynamics,as opposed to sarcomere length per se,in the regulation of cardiac function |
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| Authors: | Fuyu Kobirumaki-Shimozawa Kotaro Oyama Togo Shimozawa Akari Mizuno Takashi Ohki Takako Terui Susumu Minamisawa Shin’ichi Ishiwata Norio Fukuda |
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| Affiliation: | 1.Department of Cell Physiology, and 2.Department of Anesthesiology, The Jikei University School of Medicine, Minato-ku, Tokyo 105-8461, Japan;3.Department of Physics, and 4.Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan;5.Waseda Bioscience Research Institute in Singapore, Waseda University, Helios, Singapore 138667 |
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| Abstract: | Sarcomeric contraction in cardiomyocytes serves as the basis for the heart’s pump functions in mammals. Although it plays a critical role in the circulatory system, myocardial sarcomere length (SL) change has not been directly measured in vivo under physiological conditions because of technical difficulties. In this study, we developed a high speed (100–frames per second), high resolution (20-nm) imaging system for myocardial sarcomeres in living mice. Using this system, we conducted three-dimensional analysis of sarcomere dynamics in left ventricular myocytes during the cardiac cycle, simultaneously with electrocardiogram and left ventricular pressure measurements. We found that (a) the working range of SL was on the shorter end of the resting distribution, and (b) the left ventricular–developed pressure was positively correlated with the SL change between diastole and systole. The present findings provide the first direct evidence for the tight coupling of sarcomere dynamics and ventricular pump functions in the physiology of the heart. |
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