Contraction Bands at Short Sarcomere Length in Chick Muscle

Hagopian, Martin

doi:10.1083/jcb.47.3.790

Cited by 24 publications

(9 citation statements)

References 9 publications

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“…Overall, nuclei number, myogenic index, and sarcomere index were similar across substrates and cell types, indicating that all substrates had a similar impact on cell adhesion, viability, and fusion. Sarcomere length was significantly higher in C2C12 myotubes compared to primary chick myotubes, which is consistent with values previous reported for C2C12 myotubes [ 25 ], ex vivo chick muscle [ 40 , 41 ], and in vitro chick myotubes [ 42 , 43 ]. Therefore, gelatin-MTG hydrogels within these ranges are highly suitable for engineering relatively mature skeletal muscle tissues from multiple types of myoblasts.…”

Section: Discussionsupporting

confidence: 92%

Characterization of Gelatin Hydrogels Cross-Linked with Microbial Transglutaminase as Engineered Skeletal Muscle Substrates

2021

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Engineered in vitro models of skeletal muscle are essential for efficiently screening drug safety and efficacy. However, conventional culture substrates poorly replicate physical features of native muscle and do not support long-term culture, which limits tissue maturity. Micromolded gelatin hydrogels cross-linked with microbial transglutaminase (gelatin-MTG hydrogels) have previously been shown to induce C21C2 myotube alignment and improve culture longevity. However, several properties of gelatin-MTG hydrogels have not been systematically characterized, such as changes in elastic modulus during incubation in culture-like conditions and their ability to support sarcomere maturation. In this study, various gelatin-MTG hydrogels were fabricated and incubated in ambient or culture-like conditions. Elastic modulus, mass, and transmittance were measured over a one- or two-week period. Compared to hydrogels in phosphate buffered saline (PBS) or ambient air, hydrogels in Dulbecco’s Modified Eagle Medium (DMEM) and 5% CO2 demonstrated the most stable elastic modulus. A subset of gelatin-MTG hydrogels was micromolded and seeded with C2C12 or primary chick myoblasts, which aligned and fused into multinucleated myotubes with relatively mature sarcomeres. These data are important for fabricating gelatin-MTG hydrogels with predictable and stable mechanical properties and highlight their advantages as culture substrates for engineering relatively mature and stable muscle tissues.

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Section: Discussionsupporting

confidence: 92%

Characterization of Gelatin Hydrogels Cross-Linked with Microbial Transglutaminase as Engineered Skeletal Muscle Substrates

2021

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“…Our simple muscle model effortlessly explains the stunning linearity of the segments of the classic force -length relationship (FLR) of striated muscle (figure 5, prediction I). It is based on the idea that myosin filaments slide through the Z-disc [21] (figure 2) instead of being compressed or folded at the Z-disc as commonly assumed. By this elegant mechanism, the muscle can maintain its highly organized structure at short lengths (figure 5, range B) occurring regularly during daily activities [34].…”

Section: Discussionmentioning

confidence: 99%

“…It is based on the idea that myosin filaments slide through the Z-disc [21] (figure 2) instead of being compressed or folded at the Z-disc as commonly assumed. By this elegant mechanism, the muscle can maintain its highly organized structure at short lengths (figure 5, range B) occurring regularly during daily activities [34].…”

Section: Discussionmentioning

confidence: 99%

“…The core of the model developed here is the idea that myosin filaments slide through the meshed Z-disc (figure 2 [21]) instead of being compressed or folded at short sarcomere lengths as typically assumed. This leads to several new types of actin-myosin filament overlap (figure 3b-e) affecting force production.…”

Section: Myosin Filament Sliding Through the Z-discmentioning

confidence: 99%

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Myosin filament sliding through the Z-disc relates striated muscle fibre structure to function

et al. 2016

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Striated muscle contraction requires intricate interactions of microstructures. The classic textbook assumption that myosin filaments are compressed at the meshed Z-disc during striated muscle fibre contraction conflicts with experimental evidence. For example, myosin filaments are too stiff to be compressed sufficiently by the muscular force, and, unlike compressed springs, the muscle fibres do not restore their resting length after contractions to short lengths. Further, the dependence of a fibre's maximum contraction velocity on sarcomere length is unexplained to date. In this paper, we present a structurally consistent model of sarcomere contraction that reconciles these findings with the well-accepted sliding filament and crossbridge theories. The few required model parameters are taken from the literature or obtained from reasoning based on structural arguments. In our model, the transition from hexagonal to tetragonal actin filament arrangement near the Z-disc together with a thoughtful titin arrangement enables myosin filament sliding through the Z-disc. This sliding leads to swivelled crossbridges in the adjacent half-sarcomere that dampen contraction. With no fitting of parameters required, the model predicts straightforwardly the fibre's entire force-length behaviour and the dependence of the maximum contraction velocity on sarcomere length. Our model enables a structurally and functionally consistent view of the contractile machinery of the striated fibre with possible implications for muscle diseases and evolution. BackgroundAs motors of life, muscles convert chemical energy into mechanical energy and heat. Muscles transport substances within the body, stabilize the skeleton and enable locomotion. The first property characterizing the mechanical function of striated muscles to be described [1] was the active isometric force-length relationship (FLR). This property shows the maximal forces the striated muscle fibre can produce by electrical stimulation at different constant lengths. The classic FLR (figure 1, straight lines) [2] with its strikingly linear segments has been described not only up to the fibre level but also for the whole muscle [7,8]. Despite the fact that this relationship represents basic textbook knowledge for life science students, to date a convincing structural model explaining the shape of the entire FLR does not exist.According to the sliding filament [4,5] and crossbridge [6] theories, actin and myosin filaments slide relative to each other in response to forces generated by temporary crossbridges formed by myosin heads-projecting from the myosin filaments-and actin filaments. This yields straightforward geometric explanations for the plateau region and for the region of decreasing isometric force based on filament lengths ( figure 1, black lines) [2]. The slope change (figure 1, black circle) in the range of increasing isometric force (ascending limb) is typically related to myosin filaments hitting the Z-disc, a thinmeshed filament structure [9] defining the sarcomere bounda...

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“…In the electron micrographs shown produced by Hagopian (; Fig. ), a parallel collection of sarcomeres attached to two dark bands, known as Z‐discs, are visible.…”

Section: Mathematical Description Of Anatomy and Physiologymentioning

confidence: 99%

Development of a computational biomechanical model of the human upper‐airway soft‐tissues toward simulating obstructive sleep apnea

Pelteret

Reddy

2013

Clinical Anatomy

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Numerous challenges are faced in investigations aimed at developing a better understanding of the pathophysiology of obstructive sleep apnea (OSA). The anatomy of the tongue and other upper-airway tissues, and the ability to model their behavior, are central to such investigations. We present details of the construction and development of a soft-tissue model of the human upper airway, with the ultimate goal of simulating obstructive sleep apnea. The steps taken to produce a representative anatomical geometry, of which the associated muscle histology is also captured, are documented. An overview of the mathematical models used to describe tissue behavior, both at a macro- and microscopic level, is given. A neurological model, which mimics the proprioceptive capabilities of the body, is described as it is applies to control of the active dynamics of the tongue. A simplified scenario, which allows for the manipulation of several environmental influences, is presented. It is demonstrated that the response of the genioglossus is qualitatively similar to that determined through experimental techniques. Furthermore, insights into the stress distribution developed within the tongue are discussed. It is shown that changes in almost any aspect of the breathing or physiological conditions invoke a significant change in the response of the airway dilators. The results of this study provide further evidence of the importance of modeling and simulation techniques as an aid in understanding the complex behavior of the human body.

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Contraction Bands at Short Sarcomere Length in Chick Muscle

Cited by 24 publications

References 9 publications

Characterization of Gelatin Hydrogels Cross-Linked with Microbial Transglutaminase as Engineered Skeletal Muscle Substrates

Characterization of Gelatin Hydrogels Cross-Linked with Microbial Transglutaminase as Engineered Skeletal Muscle Substrates

Myosin filament sliding through the Z-disc relates striated muscle fibre structure to function

Development of a computational biomechanical model of the human upper‐airway soft‐tissues toward simulating obstructive sleep apnea

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