In Vitro Assays to Determine Skeletal Muscle Physiologic Function

Abstract

In vitro muscle contractile function assays are important to characterize the differences between different muscle types (e.g., slow vs. fast), between a diseased and non-diseased muscle, or importantly, to demonstrate the efficacy of a muscle treatment such as a drug, an overexpressed transgene, or knockout of a specific gene. Fundamental contractile properties can be assessed by twitch, tetanic, force-frequency, force-velocity, and fatigue assays. Many of these assays are conducted with the muscle at a constant length, e.g., an isometric contraction. However, to better represent the dynamic purpose of muscles in vivo (e.g., to move limbs), dynamic assays such as the force-velocity (concentric contractions) or stretch-injury (eccentric contractions) should also be obtained. Characterizing skeletal muscle function in vitro is a powerful approach to demonstrate efficacy of a treatment to rescue diseased muscle and to assess functional regeneration.

Eccentric Contraction-Induced Muscle Injury: Reproducible, Quantitative, Physiological Models to Impair Skeletal Muscle’s Capacity to Generate Force

“…Place excised EDL muscle in a petri dish with chilled, oxygenated Krebs buffer (for example recipe see Sperringer and Grange in this volume [8]); use a hemostat on each suture to keep slight tension on the muscle ( see Note 5). …”

“…The in vitro system described here is similar to that described by Sperringer and Grange in Chapter 19 of this volume [8], particularly in regard to the lever system…”

“…These muscles also have well- defined tendons making dissection and attachment to force transducers straightforward. Interfaced to equipment as described by Sperringer and Grange in Chapter 19 of this volume [8], a host of contractile tests can be performed. The in vitro section of this chapter will focus on eccentric contractions by isolated muscles and the consequent contraction-induced injury.…”

“…Others report resting tensions near 1.0 g ( see Chapter 19 by Sperringer and Grange in this volume [8]); this should be optimized in each individual lab set up. …”

“…Alternatively, a series of twitches are used to optimize contraction parameters ( see Sperringer and Grange [8]). …”