Investigating serum extracellular vesicles in Cystic Fibrosis.

Background: Extracellular vesicles (EVs) are emerging as biomarkers of disease with diagnostic potential in CF. With the advent of highly effective modulator therapy, sputum production is less common and there is a need to identify novel markers of CF disease progression, exacerbation and response to therapies in accessible fluids such as serum.

Methods: We used size exclusion chromatography (SEC) to isolate and characterise EVs from the blood of PWCF of different ages and compared to ultracentrifugation (UC). We used nanoparticle tracking analysis to measure the number of EVs present in serum obtained from children and adults with CF. Mass spectrometry based proteomics was used to characterise protein expression changes between the groups.

Results: EVs were successfully isolated in SEC fractions from 250 µl serum from PWCF in greater numbers (p <0.01) than density ultracentrifugation. There was not a significant difference in EV numbers between young children with CF and controls. However, there was significantly more EVs in adults compared to children (<6yrs) (p < 0.05). EVs from PWCF before and after Kaftrio treatment were also analysed. Significant protein expression changes were observed within all 3 group. The largest changes detected were between children and adults with CF (57 proteins had a 1.5 fold change in expression with 19 significant changes p < 0.05) and PWCF taking Kaftrio (24 significant changes in EV protein expression was observed 12 months post treatment).

Conclusion: In this pilot study, we performed an initial characterisation of EVs in serum from PWCF demonstrating the potential of serum EVs for further diagnostic investigation.