title: Exploring the Role of Extracellular Vesicles in Equine Musculoskeletal Pathologies and Associated Regenerative Therapies
Creators: name: Clarke, Emily-Jayne
Publisher: name: University of Liverpool Repository
Year: 2024

description: Horses are used in a variety of disciplines, including dressage, show jumping, eventing and racing.
Thus, the equine athlete is predisposed to the development of musculoskeletal injury. Both equine
osteoarthritis and tendon injury are significant causes of pain, lameness and are equine welfare
concerns. Osteoarthritis and tendon injuries are usually diagnosed at late stage and treatment
includes biological therapies, such as mesenchymal stem cell and platelet-rich plasma therapy. These
therapeutics often produce variable clinical outcomes and their mechanistic action is not well
characterised. It is hypothesised that extracellular vesicles may be involved in mediating the effect of
biological therapies, and could offer a viable cell-free alternative therapeutic. The aims of this thesis
were as follows; (1) To investigate extracellular vesicle structure and protein cargo from a longitudinal
in vivo model of equine osteoarthritis treated with mesenchymal stem cells, in order to determine
disease-associated extracellular vesicle cargo, and their potential role in mediating mesenchymal stem
cell therapy. (2) Explore the differences in composition of extracellular vesicles from healthy horses
and those with clinically diagnosed osteoarthritis using both spectroscopic and spectrometric
techniques. (3) Explore the composition of platelet-rich plasma and platelet-rich plasma derived
extracellular vesicles using mass spectrometry proteomics. (4) Investigate the effect of platelet-rich
plasma and platelet-rich plasma derived extracellular vesicles in an in vitro model of equine tendon
injury, using mass spectrometry proteomics and gene expression analysis.
Extracellular vesicles were characterised and a range of spectroscopic and spectrometric techniques
used including mass spectrometry. This thesis has catalogued extracellular vesicle cargo from synovial
fluid in both an in vivo models of equine osteoarthritis (carpal osteochondral fragment model) and
naturally occurring disease. As some protein content can be attributed to disease progression they
could serve as potential biomarkers used in the development of diagnostic tests to aid earlier diagnosis
and intervention in osteoarthritis. Further to this, my work has identified altered cargo in association
with extracellular vesicles following mesenchymal stem cell treatment, and cellular cargo following
platelet-rich plasma derived extracellular vesicle treatment, emphasising their role as mediators of
therapy and their capacity to serve as future therapeutics. Therefore, they might be considered as a
viable therapeutic alternative that warrants further investigation in the case of mesenchymal stem
cell therapy, in order to deliver a safer more reproducible therapeutic. With respect to platelet-rich
plasma, extracellular vesicles should be considered when optimising the composition of platelet-rich
plasma for more efficacious outcomes, or considered as an alternative to platelet rich plasma.