Papers of the Year
Mechanical Regulation of Actin Network Dynamics in Migrating Cells
Cell migration is fundamental to various physiological processes, including metastasis, wound healing and tissue development. The complex processes involved in cell migration; polymerization, adhesion, and retraction, are mediated by highly orchestrated structure-function interactions that occur within the actin cytoskeletal structure. Thus understanding how migrating cells regulate the global dynamics of their cytoskeletal components, which result from rather localized protein-protein interactions, is fundamental to elucidating the mechanisms of cell motility. The objective of this review is to explore the mechanical regulation of actin network dynamics in migrating cells, and to discuss its regulatory role in cell migration. Specifically, we examine the various mechanical forces involved in cell migration, and how they couple with biomechanical factors to spatiotemporally regulate the dynamics of the actin cytoskeleton during cell motility. Two aspects of actin network dynamics are addressed, namely, network turnover by polymerization and depolymerization, and network flow resulting from actomyosin activity. We begin by highlighting the fundamental features of actin network dynamics in migrating cells. We then examine the coupling relationship between actin network flow and traction forces, as well as the mechanism underlying the regulation of traction forces by actin network flow. Finally, we integrate the various motility processes into a mechanical pathway in order to elucidate the importance of mechanical regulation of actin network dynamics to cell migration.
- Cell Migration, Actin Network Dynamics, Mechanical Forces, Spatiotemporal Regulation, Cell Biomechanics, Mechanobiology
- Paper information
- Kennedy Omondi OKEYO, Taiji ADACHI and Masaki HOJO, “Mechanical Regulation of Actin Network Dynamics in Migrating Cells”, Journal of Biomechanical Science and Engineering, Vol. 5, No. 3 (2010), pp.186-207 . doi:10.1299/jbse.5.186
Biomechanical Contribution of Cytoskeletal Structures to Traction Forces in Cultured Smooth Muscle Cells
- Release Date :
Cellular traction forces were measured by using a microfabricated substrate, particularly exploring how cytoskeletal structures such as actin filaments and microtubules contribute to traction forces. Smooth muscle cells isolated from bovine aortas were cultured and transfected with fluorescence proteins to visualize cell microstructures and then plated on a micropatterned elastomer substrate with arrays of micropillars. Cell spreading on the substrates produced deflection of micropillars which was used for estimation of cellular traction forces, and was closely associated with organization of stress fibers of actin filaments. Traction forces varied considerably among cells, showing the order of several 10 nN. After disruption of microtubules with nocodazole, traction forces significantly increased and there was no detectable change in formation of stress fibers. To inhibit the ROCK pathway, a signaling pathway of myosin light chain phosphorylation, possibly being induced by disruption of microtubules, significantly depressed the increase in traction forces after the disruption of microtubules. This result indicates that microtubules disassembly may regulate the actomyosin-based contractile system mainly through the ROCK pathway. The present study suggests that formation of stress fibers are mainly involved in cellular traction forces and a contribution of microtubules should include not only a force balance but also rather a modulator of the actomyosin contractile system in actin stress fibers.
- Traction Forces, Stress Fibers, Microtubules, Actomyosin Force Generation, Intracellular Stress Balance
- Paper information
- Toshiro OHASHI, Norifumi KAMEDA, Shouji NAKAMURA and Masaaki SATO, “Biomechanical Contribution of Cytoskeletal Structures to Traction Forces in Cultured Smooth Muscle Cells”, Journal of Biomechanical Science and Engineering, Vol. 5, No. 3 (2010), pp.262-271 . doi:10.1299/jbse.5.262
Patient-specific Morphological and Blood Flow Analysis of Pulmonary Artery in the Case of Severe Deformations of the Lung due to Pneumothorax
- Author :
- Jean-Joseph CHRISTOPHETakuji ISHIKAWANoriaki MATSUKIYohsuke IMAIKei TAKASEMarc THIRIETTakami YAMAGUCHI
- Release Date :
Pneumothorax is characterized by lung collapse. Its effect on hemodynamics, especially on pulmonary arterial blood flow, remains unclear. This patient-specific study investigated the effects of lung deformation on pulmonary blood flow during acute phase and after recovery. Arterial geometry was extracted up to the fifth generation from computed tomography images in three patients and reconstructed. Different geometrical parameters (artery bores, area ratios, and between-branch angles) were computed. The shapes of the pulmonary trunk and its branches were affected strongly by pneumothorax. To clarify the effect of geometrical perturbations on blood flow, the Navier--Stokes equations for a steady laminar flow of Newtonian incompressible fluid were solved in a reconstructed domain. The change in flow structure between acute phase and recovery was associated with variations in flow rate ratio between the right and left lungs. This study shows, possibly for the first time, that from a patient-specific numerical test, pneumothorax has a considerable impact on pulmonary arterial morphology and hemodynamics.
- Pneumothorax, Computational Fluid Dynamics, Morphological Analysis, Pulmonary Arteries, Patient-specific Model
- Paper information
- Jean-Joseph CHRISTOPHE, Takuji ISHIKAWA, Noriaki MATSUKI, Yohsuke IMAI, Kei TAKASE, Marc THIRIET and Takami YAMAGUCHI, “Patient-specific Morphological and Blood Flow Analysis of Pulmonary Artery in the Case of Severe Deformations of the Lung due to Pneumothorax”, Journal of Biomechanical Science and Engineering, Vol. 5, No. 5 (2010), pp.485-498 . doi:10.1299/jbse.5.485
Passive Dynamic Stability of a Hovering Fruit Fly: a Comparison between Linear and Nonlinear Methods
Insects exhibit exquisite control of their flapping flight, capable of performing precise stability and steering maneuverability. To tackle this highly nonlinear problem we have developed two simulation-based methods to investigate the dynamic passive stability of insect flight: linear and nonlinear methods. In the linear theory, the equations of body motion are linearized and the techniques of eigenvalue and eigenvector analysis are employed to obtain the natural modes. Three natural modes are identified including an unstable oscillatory mode, a stable fast subsidence mode and a stable slow subsidence mode, which indicate that the fruit fly hovering flight is dynamic unstable. While in the nonlinear theory, the equations of 6 DoF motion are solved directly by coupling with the N-S equations. The time-varying time histories of the state variables are calculated, indicating that the state of fruit fly under disturbance conditions shows a very nonlinear transient interval initially but turns to unstable eventually. However, our results also illustrate that a fruit fly does have sufficient time to apply some active mediation to sustain a steady hovering before losing body attitudes.
- Insect Flight, Fruit Fly, Passive Dynamic Stability, Flight Dynamics, NS Equation
- Paper information
- Na GAO and Hao LIU, “Passive Dynamic Stability of a Hovering Fruit Fly: a Comparison between Linear and Nonlinear Methods”, Journal of Biomechanical Science and Engineering, Vol. 5, No. 5 (2010), pp.591-602 . doi:10.1299/jbse.5.591