Functional Changes in Muscle Afferent Neurones in an Osteoarthritis Model: Implications for Impaired Proprioceptive Performance

Qi Wu,James L Henry,Shawn Hochman

doi:10.1371/journal.pone.0036854

Abstract

BackgroundImpaired proprioceptive performance is a significant clinical issue for many who suffer osteoarthritis (OA) and is a risk factor for falls and other liabilities. This study was designed to evaluate weight-bearing distribution in a rat model of OA and to determine whether changes also occur in muscle afferent neurones.Methodology/Principal FindingsIntracellular recordings were made in functionally identified dorsal root ganglion neurones in acute electrophysiological experiments on the anaesthetized animal following measurements of hind limb weight bearing in the incapacitance test. OA rats but not naïve control rats stood with less weight on the ipsilateral hind leg (P = 0.02). In the acute electrophysiological experiments that followed weight bearing measurements, action potentials (AP) elicited by electrical stimulation of the dorsal roots differed in OA rats, including longer AP duration (P = 0.006), slower rise time (P = 0.001) and slower maximum rising rate (P = 0.03). Depolarizing intracellular current injection elicited more APs in models than in naïve muscle afferent neurones (P = 0.01) indicating greater excitability. Axonal conduction velocity in model animals was slower (P = 0.04).Conclusions/SignificanceThe present study demonstrates changes in hind limb stance accompanied by changes in the functional properties of muscle afferent neurones in this derangement model of OA. This may provide a possible avenue to explore mechanisms underlying the impaired proprioceptive performance and perhaps other sensory disorders in people with OA.

Highlights

For many people with lower limb osteoarthritis (OA) loss of proprioceptive performance is a significant clinical issue with potential morbidity due to falls
Conclusions/Significance: The present study demonstrates changes in hind limb stance accompanied by changes in the functional properties of muscle afferent neurones in this derangement model of OA
In a previous study recording intracellularly from dorsal root ganglion (DRG) neurones in vivo, we demonstrated that one month after model induction, when this model displays a full spectrum of histopathological and behavioural features of OA [25], significant changes are observed in the properties of evoked action potentials (AP) in a number of functionally differentiated fast conducting A-fibre mechanoreceptors but not in C- or Ad-fibre nociceptors [26]

Summary

Introduction

For many people with lower limb osteoarthritis (OA) loss of proprioceptive performance is a significant clinical issue with potential morbidity due to falls This deficit potentially impacts negatively on functional ability [1,2,3,4,5,6,7], as activities of daily living require finely-tuned integration of sensory and motor systems. It has been advocated that to promote improved functional outcomes in OA, patients’ rehabilitation strategies should be aimed at improving proprioceptive performance [14,15], in early OA [4,10,16] This evidence suggests that it may be clinically important to understand and to treat the impaired proprioceptive performance in OA patients. This study was designed to evaluate weight-bearing distribution in a rat model of OA and to determine whether changes occur in muscle afferent neurones

Methods

Results

Conclusion