Validation of circulating extracellular vesicle diagnostic and prognostic biomarker candidates for amyotrophic lateral sclerosis

Abstract

Amyotrophic Lateral Sclerosis (ALS), the most common form of Motor Neuron Disease (MND), is a neurodegenerative disease resulting in progressive muscular weakness, bulbar dysfunction and respiratory impairment with a typical survival of 2-5 years from symptom onset. The incidence of MND is predicted to rise due to the ageing population. To date, there are no definitive diagnostic or prognostic tests for this disease, impeding the search for effective therapeutic options.

This thesis firstly evaluates the epidemiology and survival trends of MND in NI from 2015-2019, identifying that the incidence and prevalence have increased from previous studies. We identify that younger age at onset, longer time to diagnosis, attendance at the MND multidisciplinary clinic and first presentation to neurology as an outpatient are clinical factors associated with improved survival. We then describe the development of the NI MND biobank, a repository of samples from people with MND and other neurological diseases in NI. Samples from the NI MND biobank are used to investigate the utility of serum neurofilament light (NFL) and heavy (NFH) chains in aiding the diagnosis of MND and their ability to differentiate ALS from the more slowly progressive forms of MND, progressive muscular atrophy (PMA) and primary lateral sclerosis (PLS). NFL and NFH levels were raised in MND, NFL levels were able to differentiate ALS from PMA and PLS and also correlated with measures of disease severity and rate of disease progression.

The thesis subsequently evaluates circulating extracellular vesicle (EV) biomarkers in ALS and other types of MND- spinal bulbar muscular atrophy (SBMA) and spinal muscular atrophy (SMA). We describe an immunoprecipitation based method for isolating circulating EVs from skeletal muscle origin (MuVs) which will allow for non-invasive investigation of skeletal muscle health in neuromuscular conditions. The thesis progresses to investigate serum EV sphingomyelins (SM) in ALS, SBMA and SMA. We identify that the EV SMs are dysregulated in these MNDs and show that a panel of 15 EV SMs has excellent utility in differentiating ALS and SBMA with the potential to be developed as a diagnostic biomarker for ALS. Finally, we show that the EV SM profile is also dysregulated in SMA, correlates with disease severity and use a murine SMA model to show that disease modifying therapy partially corrects the EV SM profile having potential as a prognostic and disease tracking biomarker in SMA.

Date of Award	Sept 2023
Original language	English
Sponsors	Association of British Neurologists & Guarantors of Brain
Supervisor	William Duddy (Supervisor) & Stephanie Marie Duguez (Supervisor)