Background and Aims

Myositis are chronic autoimmune diseases characterized by muscular weakness, inflammation, and extra-muscular involvement. Extracellular vesicles (EVs) are heterogeneous lipid bilayer nanoparticles, ranging from 30 nm to 1000 nm, naturally released from cells. Convoying their cargo, EVs allow intercellular communication. Their role in the pathogenesis of autoimmune diseases is recognized. The study aims to investigate EVs as potential myositis biomarkers.

Methods

EVs were isolated from platelet-free plasma of myositis patients and healthy donors (HDs) through size exclusion chromatography and enriched by ultrafiltration. They were observed by transmission electron microscopy (TEM) and quantify by tunable resistive pulse sensing (TRPS).

Results

By TEM, EVs were seen more concentrated in patients (n=4) than in HDs (n=5) samples. EVs appeared intact, roundish, and heterogeneous in size, with a prevalence of smaller EVs in both groups. TRPS measurements showed an EVs concentration of 1.76e+14 [EVs/mL] and a mode diameter of 80 nm, in the patient sample (n=1). The mean EVs concentration of HDs samples (n=2) was 1.12e+14 [EVs/mL] with a mean mode diameter of 77 nm (Figure 1).

Figure 1. TRPS measurement of EVs report (qNano, Izon instruments). Quantification of a myositis patient (on the left) and HD (on the right) samples. Particles distribution graphs show particles’ concentration [EVs/mL] related to their size.

Conclusions

Preliminary data based on TEM observation and TRPS measurements showed that EVs are predominantly small in both patient and HDs samples. Moreover, the EVs concentration appeared slightly higher in the patient rather than in HDs. Further analyzed employing classical and imaging flow cytometry are ongoing.