Abstract
Tendon injuries in both the human and horse represent a challenge due to persistent inflammation combined with inadequate reparative cells and a poorly organised extracellular matrix. The potential of mesenchymal stem cells (MSCs) in regenerating tendon injuries remains to be fully realised. The main mechanism of action by MSCs is considered to be primarily mediated via paracrine mechanisms. This may involve the production and release of extracellular vesicles (EVs) by stem cells with a sub-fraction of these EVs (<100 nm diameter) called exosomes that appear to be the main paracrine effectors. EVs can be readily prepared from MSCs and offer a clinically relevant therapy. However, EVs for tendon repair need to be fully characterised. The horse represents a highly relevant model of tendon and ligament injuries as it shares many features of mechanical loading, function and aetiopathology with the human. We have isolated and characterised EVs from equine MSCs for modulating tendon cell phenotype in an in vitro tendon injury model using IL-1ß. EVs can be isolated from IL-1ß stimulated MSCs although their levels are not significantly increased over controls suggesting that the nature of the stimulated EV cargo may be more important than absolute levels of released EVs.
