scholarly journals Synchrony of sarcomeric movement regulates left ventricular pump function in the in vivo beating mouse heart

2021 ◽  
Vol 153 (11) ◽  
Author(s):  
Fuyu Kobirumaki-Shimozawa ◽  
Togo Shimozawa ◽  
Kotaro Oyama ◽  
Shunsuke Baba ◽  
Jia Li ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Sarcomere Length ◽  
Left Ventricular ◽  
Mouse Heart ◽  
The Novel ◽  
Passive Force ◽  
Pump Function ◽  
Average Value ◽  
Contribution Index

Sarcomeric contraction in cardiomyocytes serves as the basis for the heart’s pump functions. It has generally been considered that in cardiac muscle as well as in skeletal muscle, sarcomeres equally contribute to myofibrillar dynamics in myocytes at varying loads by producing similar levels of active and passive force. In the present study, we expressed α-actinin–AcGFP in Z-disks to analyze dynamic behaviors of sequentially connected individual sarcomeres along a myofibril in a left ventricular (LV) myocyte of the in vivo beating mouse heart. To quantify the magnitude of the contribution of individual sarcomeres to myofibrillar dynamics, we introduced the novel parameter “contribution index” (CI) to measure the synchrony in movements between a sarcomere and a myofibril (from −1 [complete asynchrony] to 1 [complete synchrony]). First, CI varied markedly between sarcomeres, with an average value of ∼0.3 during normal systole. Second, when the movements between adjacent sarcomeres were asynchronous (CI < 0), a sarcomere and the ones next to the adjacent sarcomeres and farther away moved in synchrony (CI > 0) along a myofibril. Third, when difference in LV pressure in diastole and systole (ΔLVP) was lowered to <10 mm Hg, diastolic sarcomere length increased. Under depressed conditions, the movements between adjacent sarcomeres were in marked asynchrony (CI, −0.3 to −0.4), and, as a result, average CI was linearly decreased in association with a decrease in ΔLVP. These findings suggest that in the left ventricle of the in vivo beating mouse heart, (1) sarcomeres heterogeneously contribute to myofibrillar dynamics due to an imbalance of active and passive force between neighboring sarcomeres, (2) the force imbalance is pronounced under depressed conditions coupled with a marked increase in passive force and the ensuing tug-of-war between sarcomeres, and (3) sarcomere synchrony via the distal intersarcomere interaction regulates the heart's pump function in coordination with myofibrillar contractility.

scholarly journals 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

2015 ◽  
Vol 147 (1) ◽  
pp. 53-62 ◽  
Author(s):  
Fuyu Kobirumaki-Shimozawa ◽  
Kotaro Oyama ◽  
Togo Shimozawa ◽  
Akari Mizuno ◽  
Takashi Ohki ◽  
...  
Keyword(s):  
High Speed ◽  
Sarcomere Length ◽  
Imaging System ◽  
Critical Role ◽  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Mouse Heart ◽  
Tight Coupling ◽  
Sarcomere Dynamics

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.

Abstract 5402: Two Photon Microscopy Measurements Of Sub-epicardial Sarcomere Length In Perfused Rat Hearts

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Patrizia Camelliti ◽  
Gil Bub ◽  
Daniel J Stuckey ◽  
Christian Bollensdorff ◽  
Damian J Tyler ◽  
...  
Keyword(s):  
Sarcomere Length ◽  
Left Ventricular ◽  
Model Systems ◽  
Future Research ◽  
Fundamental Parameter ◽  
Rat Hearts ◽  
Perfused Hearts ◽  
Over Time

Sarcomere length (SL) is a fundamental parameter underlying the Frank Starling relation in the heart, as it offers an absolute representation of myocardial stretch. Previous studies addressed the Frank Starling relation by measuring SL in isolated myocytes or muscle strips. Here, we report first data obtained using a novel technique to measure sub-epicardial SL in perfused hearts. Rat hearts were Langendorff perfused (normal Tyrode solution) at a constant pressure of 90mmHg, labeled with the fluorescent membrane marker di-4-ANEPPS, and then arrested with high-K + Tyrode for either 2-photon microscopy (n=4) or MRI (n=4). Image analysis software was developed to extract SL at the cell level from >1,400 2-photon images (Fig 1 ) and correct for cell angle. SL increased by 10±2 % between 30 and 80 min of perfusion (1.98±0.04 to 2.17±0.03 μm; p<0.05; Fig 1 ). Measurements of left ventricular myocardial volume (LVMV) were made in vivo and in perfused hearts using 3D MRI. LVMV increased by 24±7% from in vivo to 30 min of perfusion, and by 11±3 % between 30 and 90 min (539±35; 664±44; 737±49 mm 3 , respectively; p<0.05; Fig 1 ). We show that SL can be measured in isolated perfused hearts. The method allowed monitoring of changes in SL over time, and showed that SL and LVMV increase to a similar extent during 30–80 min perfusion with crystalloid solution, probably due to tissue oedema. This result, together with the increase in LVMV during the first 30 min, highlights the pronounced differences between in vivo , in situ , and in vitro model systems for studies of cardiac physiology and mechanics. Future research will compare changes in SL in healthy hearts and disease models involving contractile dysfunction. Figure 1: Left: 2-photon microscopy image of di-4-ANEPPS labeled myocardium. Right: SL and LVMV changes over time.

Effect of sarcomere length on total capillary length in skeletal muscle: In vivo evidence for longitudinal stretching of capillaries

1990 ◽  
Vol 40 (1) ◽  
pp. 63-72 ◽  
Author(s):  
C.G. Ellis ◽  
O. Mathieu-Costello ◽  
R.F. Potter ◽  
I.C. MacDonald ◽  
A.C. Groom
Keyword(s):  
Skeletal Muscle ◽  
Sarcomere Length ◽  
Capillary Length

Abstract 96: Inactivation of Neddylation Causes Left Ventricular Noncompaction Cardiomyopathy Through Suppressing YAP Signaling

2017 ◽  
Vol 121 (suppl_1) ◽  
Author(s):  
Jianqiu Zou ◽  
Wenxia Ma ◽  
Jie Li ◽  
Rodney Littlejohn ◽  
Il-man Kim ◽  
...  
Keyword(s):  
Cardiac Development ◽  
Heart Diseases ◽  
Left Ventricular ◽  
Late Gestation ◽  
Mouse Heart ◽  
Cardiomyocyte Proliferation ◽  
Transcription Cofactor ◽  
Wild Type Counterpart

Rationale: Cardiac development is orchestrated by a number of growth factors, transcription factors and epigenetic regulators, perturbation of which can lead to congenital heart diseases and cardiomyopathies. However, the role of novel ubiquitin-like protein modifiers, such as NEDD8 (neural precursor cells expressed developmentally downregulated 8), in cardiac development is unknown. Objectives: The objective of this study was to determine the significance of NEDD8 modification (neddylation) during perinatal cardiac development. Methods and Results: Neddylated proteins and NEDD8 enzymes were highly abundant in fetal and neonatal hearts but downregulated in adult hearts. We employed an αMHC Cre transgene to delete NAE1, a subunit of the NEDD8 E1 enzyme, in the perinatal mouse heart. Cardiac-specific deletion of NAE1 (NAE1 CKO ) significantly decreased neddylated proteins in the heart. The NAE1 CKO mice displayed cardiac hypoplasia, ventricular non-compaction and heart failure during late gestation, which became more pronounced by postnatal day 1 and led to perinatal lethality. Mechanistically, genetic deletion or pharmacological inhibition of NAE1 resulted in accumulation of Hippo kinases Mst1 and LATS1/2, which in turn phosphorylated and inactivated YAP, a transcription cofactor necessary for cardiomyocyte proliferation, leading to dysregulation of a number of cell cycle-regulatory genes and blockade of cardiomyocyte proliferation in vivo and in vitro . Reactivation of YAP signaling by overexpression of a constitutively-active YAP mutant (YAP 5SA ), but not its wild-type counterpart, overcame the blockade of cardiomyocyte proliferation induced by inhibition of NAE1. Conclusions: Our findings establish the importance of neddylation in the heart, more specifically, in ventricular chamber maturation, and identify neddylation as a novel regulator of Hippo-YAP signaling to promote cardiomyocyte proliferation.

scholarly journals Effects of myofiber isolation technique on sarcolemma biomechanics

BioTechniques ◽  
2020 ◽  
Vol 69 (5) ◽  
pp. 388-391
Author(s):  
Karla P Garcia-Pelagio ◽  
Stephen JP Pratt ◽  
Richard M Lovering
Keyword(s):  
Skeletal Muscle ◽  
Extensor Digitorum Longus ◽  
Sarcomere Length ◽  
Biomechanical Properties ◽  
Isolation Technique ◽  
Enzymatic Dissociation ◽  
Flexor Digitorum Brevis ◽  
Flexor Digitorum ◽  
Biomechanical Measurements

Isolated myofibers are commonly used to understand the function of skeletal muscle in vivo. This can involve single isolated myofibers obtained from dissection or from enzymatic dissociation. Isolation via dissection allows control of sarcomere length and preserves tendon attachment but is labor-intensive, time-consuming and yields few viable myofibers. In contrast, enzymatic dissociation is fast and facile, produces hundreds of myofibers, and more importantly reduces the number of muscles/animals needed for studies. Biomechanical properties of the sarcolemma have been studied using myofibers from the extensor digitorum longus, but this has been limited to dissected myofibers, making data collection slow and difficult. We have modified this tool to perform biomechanical measurements of the sarcolemma in dissociated myofibers from the flexor digitorum brevis.

scholarly journals Troponin and Titin Coordinately Regulate Length-dependent Activation in Skinned Porcine Ventricular Muscle

2008 ◽  
Vol 131 (3) ◽  
pp. 275-283 ◽  
Author(s):  
Takako Terui ◽  
Munguntsetseg Sodnomtseren ◽  
Douchi Matsuba ◽  
Jun Udaka ◽  
Shin'ichi Ishiwata ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Thin Filament ◽  
Left Ventricular ◽  
Ventricular Muscle ◽  
Passive Force ◽  
Active Force ◽  
Fast Skeletal Muscle ◽  
Thin Filaments ◽  
Cross Bridges ◽  
Length Dependent Activation

We investigated the molecular mechanism by which troponin (Tn) regulates the Frank-Starling mechanism of the heart. Quasi-complete reconstitution of thin filaments with rabbit fast skeletal Tn (sTn) attenuated length-dependent activation in skinned porcine left ventricular muscle, to a magnitude similar to that observed in rabbit fast skeletal muscle. The rate of force redevelopment increased upon sTn reconstitution at submaximal levels, coupled with an increase in Ca2+ sensitivity of force, suggesting the acceleration of cross-bridge formation and, accordingly, a reduction in the fraction of resting cross-bridges that can potentially produce additional active force. An increase in titin-based passive force, induced by manipulating the prehistory of stretch, enhanced length-dependent activation, in both control and sTn-reconstituted muscles. Furthermore, reconstitution of rabbit fast skeletal muscle with porcine left ventricular Tn enhanced length-dependent activation, accompanied by a decrease in Ca2+ sensitivity of force. These findings demonstrate that Tn plays an important role in the Frank-Starling mechanism of the heart via on–off switching of the thin filament state, in concert with titin-based regulation.

scholarly journals Myosin light chain 3F regulatory sequences confer regionalized cardiac and skeletal muscle expression in transgenic mice.

1995 ◽  
Vol 129 (2) ◽  
pp. 383-396 ◽  
Author(s):  
R Kelly ◽  
S Alonso ◽  
S Tajbakhsh ◽  
G Cossu ◽  
M Buckingham
Keyword(s):  
Skeletal Muscle ◽  
Transgenic Mice ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Muscle Development ◽  
Regulatory Elements ◽  
Left Ventricular ◽  
Mouse Heart ◽  
Regulatory Sequences ◽  
Enhancer Element

The myosin light chain IF/3F locus contains two independent promoters, MLC1F and MLC3F, which are differentially activated during skeletal muscle development. Transcription at this locus is regulated by a 3' skeletal muscle enhancer element, which directs correct temporal and tissue-specific expression from the MLC1F promoter in transgenic mice. To investigate the role of this enhancer in regulation of the MLC3F promoter in vivo, we have analyzed reporter gene expression in transgenic mice containing lacZ under transcriptional control of the mouse MLC3F promoter and 3' enhancer element. Our results show that these regulatory elements direct strong expression of lacZ in skeletal muscle; the transgene, however, is activated 4-5 d before the endogenous MLC3F promoter, at the time of initiation of MLC1F transcription. In adult mice, transgene activity is downregulated in muscles that have reduced contributions of type IIB fibers (soleus and diaphragm). The rostrocaudal positional gradient of transgene expression documented for MLC1F transgenic mice (Donoghue, M., J. P. Merlie, N. Rosenthal, and J. R. Sanes. 1991. Proc. Natl. Acad. Sci. USA. 88:5847-5851) is not seen in MLC3F transgenic mice. Although MLC3F was previously thought to be restricted to skeletal striated muscle, the MLC3F-lacZ transgene is expressed in cardiac muscle from 7.5 d of development in a spatially restricted manner in the atria and left ventricular compartments, suggesting that transcriptional differences exist between cardiomyocytes in left and right compartments of the heart. We show here that transgene-directed expression of the MLC3F promoter reflects low level expression of endogenous MLC3F transcripts in the mouse heart.

scholarly journals BOT-5 Chrysanthemum morifolium extract improves doxorubicin-induced cardiomyopathy by suppressing apoptosis in mouse heart

2021 ◽  
Vol 3 (Supplement_6) ◽  
pp. vi9-vi9
Author(s):  
Masaya Ono ◽  
Saho Mochizuki ◽  
Kanako Tsuchitani ◽  
Sonoka Iwashimizu ◽  
Yoichi Sunagawa ◽  
...  
Keyword(s):  
Heart Failure ◽  
Cancer Patients ◽  
Left Ventricular Systolic Dysfunction ◽  
Systolic Dysfunction ◽  
Treated Group ◽  
Chrysanthemum Morifolium ◽  
Left Ventricular ◽  
Mouse Heart ◽  
Survival Ratio

Abstract Background: Doxorubicin is widely used for the treatment of various malignant tumors. However, doxorubicin causes cumulative and dose-dependent cardiotoxicity, ranging from occult changes in myocardial structure and function to severe cardiomyopathy and congestive heart failure. Since this problem affects the QOL and survival of cancer patients, solutions for this problem are urgently needed. Recently, it has been reported that Chrysanthemum morifolium extracts (CME) have antioxidant and anti-inflammatory activities. The purpose of this study is to clarify whether CME decreases doxorubicin-induced cardiotoxicity and prevents the development of heart failure. Methods and Results: H9C2 cardiomyoblast cells were treated with CME (0.3, 1 mg/mL) for 2 hours and then stimulated with doxorubicin. After 24 hours incubation, surviving cells were evaluated by MTT assay. CME dose-dependently decreased doxorubicin-induced cardiotoxicity in H9C2 cells. Western blotting showed that CME significantly suppressed doxorubicin-induced increases in four markers of apoptosis: p53, phosphorylated p53, and cleaved caspase-9 and -3. Next, to investigate the effects of CME on doxorubicin-induced cardiomyopathy in vivo, C57BL6 mice were orally administered with CME (400 mg/kg/day) or vehicle daily from 2 days before doxorubicin treatment and then treated once intraperitoneally with doxorubicin (20 mg/kg). The survival ratio of the CME-treated group was significantly higher than that of the vehicle-treated group. Echocardiographic analysis at 7 days after doxorubicin stimulation revealed that CME had significantly improved doxorubicin-induced left ventricular systolic dysfunction. Apoptotic cells in mouse heart tissue were detected by TUNEL assay, which showed that CME significantly suppressed doxorubicin-induced apoptosis. Discussion: These results indicate that CME decreases doxorubicin-induced cardiotoxicity both in vitro and in vivo, suggesting that CME might possess the therapeutic potency to reduce doxorubicin-induced cardiotoxicity in cancer patients. Further studies are required to assess the effectiveness of CME for preventing doxorubicin-induced heart failure in clinical settings.

scholarly journals A proposed role for non-junctional transverse tubules in skeletal muscle as flexible segments allowing expansion of the transverse network

2019 ◽  
Vol 29 (2) ◽  
Author(s):  
Manuela Lavorato ◽  
Ramesh Iyer ◽  
Clara Franzini-Armstrong
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Skeletal Muscles ◽  
Sarcomere Length ◽  
Muscle Fibers ◽  
Entire Length ◽  
Small Fish ◽  
Transverse Tubules ◽  
T Tubules

Using a variety of technical approaches, we have detected the presence of continuous triads that cover the entire length of T tubules in the main white body muscles of several small fish. This is in contrast to the discontinuous association of sarcoplasmic reticulum with T tubules in the red muscles from the same fish as well as in all other previously described muscles in a large variety of skeletal muscles. We suggest that continuous triads are permissible only in muscle fibers that are not normally subject to significant changes in sarcomere length during normal in vivo activity, as is the case for white muscles in the trunk of fish.

Left ventricular volumes and function in the embryonic mouse heart

1997 ◽  
Vol 273 (3) ◽  
pp. H1368-H1376 ◽  
Author(s):  
N. Tanaka ◽  
L. Mao ◽  
F. A. DeLano ◽  
E. M. Sentianin ◽  
K. R. Chien ◽  
...  
Keyword(s):  
Left Ventricular ◽  
Fluorescent Imaging ◽  
Left Ventricular Volumes ◽  
Mouse Heart ◽  
Embryonic Mouse ◽  
End Diastolic Volume ◽  
Or Gene ◽  
The Individual ◽  
And Function

This study describes miniaturized technology for the in vivo analysis of the volume and function of the embryonic mouse heart and the application of this technology to study the normal embryonic left ventricle (LV) at two stages of development. With the use of microsurgical techniques, embryos from embryonic day (ED) 10.5 (ED10.5) to ED16 were delivered individually from litters of normal dams, and cardiac visualization was achieved with the use of intravital microscopy by transillumination, with the umbilical circulation intact. At ED10.5-11, the heart could be imaged in color in the intact embryo, whereas at ED12.5 it was necessary to open the chest; at ED13.5-14.5, fluorescent imaging with the use of microinjection of fluorescein-conjugated albumin was necessary to visualize the LV chamber. At ED10.5-11, the LV end-diastolic volumes averaged 0.16 microliter (n = 14), and at ED13.5-14.5, they averaged 0.57 microliter (n = 16). At both ages there was a positive linear relationship between the LV end-diastolic volume and the stroke volume despite substantial variations in individual heart rates, reflecting the relative uniformity of the LV ejection fractions within each age group. The average of the individual ejection fractions was 27.4% at ED10.5-11 and 58.4% at ED13.5-14.5, the latter being within the normal range for the adult rodent heart. These methods will be useful for assessing in vivo cardiac function at ED10.5 and older murine embryos in litters of transgenic or gene-targeted mice when the mutation leads to later embryonic lethality.

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