Abstract
Exosomes are extracellular vesicles with a size of 40–150 nm that are released from a multitude of cell types and are present in biological fluids, which are particularly rich in membrane proteins. These vesicles are present in the bile, where they function as a special regulator of the digestive system; however, their source and characteristics in normal gallbladders have never been discovered. Bile, liver, and gallbladder were obtained from healthy turtles after starvation treatment. Biliary exosomes were extracted and their morphology, particle sizes, and specific proteins were characterized by transmission electron microscope (TEM), nanoparticle tracking analysis (NTA), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) staining, and Western blotting. Furthermore, immunohistochemistry and TEM were used to investigate the distribution of exosomes in both liver and gallbladder. Biliary exosomes had a round or oval shape with apparent bilayer membranes. Biliary exosomes were uniform in size, with a range from 40 to 180 nm in diameter. Immunohistochemistry showed that the CD63 exosome marker was positive and primarily distributed in the hepatocyte junction, while the free surface of gallbladder tested negative. In addition, exosomes were present in bile but absent on the apical free surface of gallbladder. This study provides direct evidences that biliary exosomes are secreted by hepatocytes into bile canaliculus and flow with bile into the gallbladder. The source and the isolated protocol of biliary exosomes may provide technical support and a theoretical basis for the exploration of potential antiviral or anti-inflammatory properties of biliary exosomes.
Highlights
Exosomes are membrane vesicles of endosomal origin that are released into the extracellular medium from various cells (Ding et al, 2018)
The protein CD81 in serum exosomes is increased in patients with chronic hepatitis C virus (HCV) (Welker et al, 2012), and CD10 protein levels were increased in urinary exosomes of a mouse model for chronic liver injury (Conde-Vancells et al, 2010)
To determine whether biliary exosomes can be marked via the exosomal protein, biliary exosomes were labeled with CD63
Summary
Exosomes are membrane vesicles (with a size of 40–150 nm) of endosomal origin that are released into the extracellular medium from various cells (Ding et al, 2018). Various cells can secrete exosomes; exosomes are widely present in biological fluids, such as serum (Rekker et al, 2014), breast milk (Admyre et al, 2007), sweat (Wu and Liu, 2018), and bile (Ge et al, 2017). The internal conserved proteins of exosomes include four transmembrane proteins such as CD63, heat shock proteins such as HSP70 (Théry et al, 2002), and the host protein lysosomal associated membrane protein-1 (LAMP-1) (Giri et al, 2010). CD63, HSP-70, and LAMP-1 are often used as positive biomarkers in studies of exosomes. Exosomes are considered as diagnostic and prognostic biomarkers of liver diseases (Masyuk et al, 2013). It is possible to speculate on the pathological changes of exosomes secreted by cells or organs by tracking the source of exosomes in bile
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
