Non-invasive muscle contraction assay to study rodent models of sarcopenia

<p>Abstract</p> <p>Background</p> <p>Age-related sarcopenia is a disease state of loss of muscle mass and strength that affects physical function and mobility leading to falls, fractures, and disability. The need for therapies to treat age-related sarcopenia has attracted intensive preclinical research. To facilitate the discovery of these therapies, we have developed a non-invasive rat muscle functional assay system to efficiently measure muscle force and evaluate the efficacy of drug candidates.</p> <p>Methods</p> <p>The lower leg muscles of anesthetized rats are artificially stimulated with surface electrodes on the knee holders and the heel support, causing the lower leg muscles to push isometric pedals that are attached to force transducers. We developed a stimulation protocol to perform a fatigability test that reveals functional muscle parameters like maximal force, the rate of fatigue, fatigue-resistant force, as well as a fatigable muscle force index. The system is evaluated in a rat aging model and a rat glucocorticoid-induced muscle loss model</p> <p>Results</p> <p>The aged rats were generally weaker than adult rats and showed a greater reduction in their fatigable force when compared to their fatigue-resistant force. Glucocorticoid treated rats mostly lost fatigable force and fatigued at a higher rate, indicating reduced force from glycolytic fibers with reduced energy reserves.</p> <p>Conclusions</p> <p>The involuntary contraction assay is a reliable system to assess muscle function in rodents and can be applied in preclinical research, including age-related sarcopenia and other myopathy.</p

Quantitative MRI water content mapping of porcine intervertebral disc during uniaxial compression

International audienceBackground: Intervertebral disc (IVD) diseases are major public health problem in industrialized countries where they affect a large proportion of the population. In particular, IVD degeneration is considered to be one of the leading causes of pain consultation and sick leave. The aim of this study was to develop a new method for assessing the functionality of IVD in order to diagnose IVD degeneration. Methods: For this purpose, we have designed a specific device that enables to mechanically load porcine IVD ex vivo in the 4.7-Tesla horizontal superconducting magnet of a magnetic resonance (MR) scanner. Proton density weighted imaging (rho(H)-MRI) of the samples was acquired. Findings: The post-processing on MR images allowed (1) to reconstruct the 3D deformation under a known mechanical load and (2) to infer the IVD porosity assuming an incompressible poroelastic model. Interpretation: This study demonstrates the ability to follow the change in morphology and hydration of an IVD using MR measurements, thereby providing valued information for a better understanding of IVD function

Étude du comportement poroélastique incompressible d’un disque intervertébral sous chargement externe

Le Disque InterVertébral (DIV) est un fibrocartilage hétérogène qui assure d’une part la mobilité du rachis et d’autre part la distribution des contraintes mécaniques entre les vertèbres. Ces deux propriétés principales sont liées à la fois au contenu hydrique et à la présence des protéoglycanes (PG) dans le DIV. Les contenus en eau et en PGs diminuent selon un processus naturel durant la vie. Ce processus dégénératif est dans certains cas accéléré et conduit à des maladies dégénératives. Plusieurs études [M. Alini, S.M. Eisenstein, K. Ito, C. Little, A. Kettler, K. Masuda, J. Melrose, J. Ralphs, I. Stokes, H.J. Wilke, Eur. Spine J. 17 (2008) 2–19; E.C. Bass, N.A. Duncan, J.S. Hariharan, J. Dusick, H.U. Bueff, J.C. Lotz, Spine (Phila. Pa. 1976) 22 (1997) 2867–2876; H. Ohshima, H. Tsuji, N. Hirano, H. Ishihara, Y. Katoh, H. Yamada, Spine (Phila. Pa. 1976) 14 (1989) 1234–1244; N.D. Panagiotacopulos, Spine (Phila. Pa. 1976) 12 (1987) 912–918; N.D. Panagiotacopulos, Spine (Phila. Pa. 1976) 12 (1987) 918–924] ont montré l’importance de la teneur en eau du DIV sur son comportement biomécanique. Le but de notre étude est de suivre, avec une méthode d’Imagerie de Résonance Magnétique (IRM), les variations de morphologie et d’hydratation sous un chargement mécanique. Les campagnes de mesure complétées par un post-traitement ont permis de reconstruire la déformation volumique du DIV et d’obtenir ainsi l’évolution de la porosité au cours du chargement. Les résultats ainsi obtenus sont conformes avec la littérature et le comportement retenu adhère parfaitement avec le cadre expérimental. Ce travail d’exploration de la viabilité discale permettra d’apporter des informations importantes dans la compréhension du comportement osmotico-mécanique du DIV