Diverse Expression of Extracellular Matrix Proteins in Human Muscle Spindles

Abstract

Sensory transduction in muscle spindle involves distortion of the intrafusal fibres and of their sensory endings. In the equatorial region, where the sensory endings are found, the muscle spindle capsule is dilated and filled with fluid. It is generally accepted that the spindle capsule acts as a diffusion barrier and that the fluid-filled periaxial space provides both mechanical protection and a special internal millieu. Given these data, one would expect the extracellular matrix (ECM) to play an important role in muscle spindle function. In recent years, the number of ECM proteins and their proposed functions have expanded tremendously but data on the ECM of mammalian intrafusal fibres are scarse. We have therefore studied adult human muscle spindles with antibodies against the following ECM proteins: laminin, fibronectin and tenascin.