Primary sclerosing cholangitis (PSC) is an idiopathic and heterogenous cholestatic
liver disease characterized by chronic
inflammation and
fibrosis of the biliary tree. Currently, no effective
therapies are available for this condition, whose incidence is rising. At present, specificity and sensitivity of current
serum markers used to diagnose PSC are limited and often unreliable. In this study, we characterize circulating extracellular vesicles and provide supporting data on their potential use as novel surrogate
biomarkers for PSC. EVs are membrane surrounded structures, 100-1000 nm in size, released by cells under various conditions and which carry a variety of bioactive molecules, including small non-coding RNAs,
lipids and
proteins. In recent years, a large body of evidence has pointed to diagnostic implications of EVs and relative cargo in various human diseases. We isolated EVs from serum of well-characterized patients with PSC or control subjects by differential centrifugation and size-exclusion chromatography. A complete characterization identified elevated levels of circulating EVs in PSC patients compared to healthy control subjects (2000 vs. 500
Calcein-FITC + EVs/μL). Tissue and cell specificity of circulating EVs was assessed by identification of liver-specific markers and cholangiocyte marker CK-19. Further molecular characterization identified 282
proteins that were differentially regulated in PSC-derived compared to healthy control-EVs. Among those, IL-13Ra1 was the most significantly and differentially expressed
protein in PSC-derived EVs and correlated with the degree of
liver fibrosis. In addition to
protein profiling, we performed a
miRNA-sequencing analysis which identified 11 among established, liver-specific (e.g., miR-122 and miR-192) and novel
miRNAs. One of the newly identified
miRNAs, miR-4645-3p, was significantly up-regulated fourfold in PSC-derived EVs compared to circulating EVs isolated from healthy controls. This study provides supporting evidence of the potential role of circulating EVs and associated
protein and
miRNA cargo as surrogate noninvasive and reliable
biomarker for PSC.