Mechanisms Underlying Mesenchymal Stem Cell-Derived Extracellular Vesicle Modulation of Sensory Neuron Excitability

Mesenchymal stem cells (MSCs) represent a promising therapeutic approach for a range of conditions, including osteoarthritis (OA). Increasing evidence highlights the critical role of MSC-derived extracellular vesicles (EVs), which facilitate the transfer of biomolecular cargo between cells. Our previous work demonstrated that MSC-EVs alleviate pain in a murine model of OA by reducing OA-induced sensory neuron hyperexcitability, rather than altering joint pathology. These findings underscore the therapeutic potential of MSC-EVs in pain management. We further showed that MSC-EVs can directly inhibit sensitisation of dorsal root ganglion (DRG) neurons induced by nerve growth factor (NGF), a key mediator implicated in OA pathogenesis and associated pain. The present study sought to elucidate the mechanisms by which MSC-EVs prevent NGF-induced sensitisation of DRG neurons, using whole-cell patch-clamp electrophysiology. Surface proteins were first removed from MSC-EVs through proteolytic “shaving,” revealing that shaved EVs were unable to fully reproduce the effects observed with intact EVs. We then established that chronic (48-hour), but not acute (10-minute), exposure to MSC-EVs was necessary to prevent NGF-induced sensitisation. These findings suggest that EV internalisation is at least partially required and that transcriptional changes may underlie the observed effects. Consistent with this hypothesis, inhibition of transcription with actinomycin D attenuated the full protective effect of MSC-EVs. A review of the literature identified several intracellular biomolecules potentially responsible for these effects, including microRNAs (miRNAs), many of which are known to modulate pain pathways. Accordingly, small RNA sequencing was performed to characterise the miRNA cargo of MSC-EVs. Candidate miRNAs with established roles in pain were subsequently selected and assessed for their capacity to modulate NGF-induced sensitisation of DRG neurons. In addition to the central focus of this thesis, complementary studies examined the influence of OA-associated mediators on neuronal excitability. One investigation demonstrated that the sphingomyelin species N-palmitoyl-D-erythro-sphingosylphosphorylcholine (d18:1/16:0), elevated in OA synovial fluid, sensitises DRG neurons and induces inflammatory joint pain in mice. A further study revealed that the neurotrophic factor artemin sensitises sensory neurons in both OA-susceptible mice and OA-resistant naked mole-rats, although additional in vivo studies are required to determine whether these in vitro findings translate into behavioural changes. In summary, this thesis advances understanding of the mechanisms by which MSC-EVs regulate neuronal excitability and clarifies how specific OA-associated mediators contribute to sensory neuron sensitisation.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2025

Author dc:creator

• Qiu, Lanhui

Advisor dc:contributor.advisor

• Smith, Ewan St John

• Mesenchymal stem cell
• Extracellular vesicle
• Osteoarthritis
• Pain
• micro-RNA

Licence

• https://www.repository.cam.ac.uk/bitstreams/4b1a1227-8c9d-4240-8edf-4de9b49634c9/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.127702

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/399000