Biliary exosomes influence cholangiocyte regulatory mechanisms and proliferation through interaction with primary cilia

Abstract

Exosomes are small extracellular vesicles that are thought to participate in intercellular communication. Recent work from our laboratory suggests that, in normal and cystic liver, exosome-like vesicles accumulate in the lumen of intrahepatic bile ducts, presumably interacting with cholangiocyte cilia. However, direct evidence for exosome-ciliary interaction is limited and the physiological relevance of such interaction remains unknown. Thus, in this study, we tested the hypothesis that biliary exosomes are involved in intercellular communication by interacting with cholangiocyte cilia and inducing intracellular signaling and functional responses. Exosomes were isolated from rat bile by differential ultracentrifugation and characterized by scanning, transmission, and immunoelectron microscopy. The exosome-ciliary interaction and its effects on ERK1/2 signaling, expression of the microRNA, miR-15A, and cholangiocyte proliferation were studied on ciliated and deciliated cultured normal rat cholangiocytes. Our results show that bile contains vesicles identified as exosomes by their size, characteristic "saucer-shaped" morphology, and specific markers, CD63 and Tsg101. When NRCs were exposed to isolated biliary exosomes, the exosomes attached to cilia, inducing a decrease of the phosphorylated-to-total ERK1/2 ratio, an increase of miR-15A expression, and a decrease of cholangiocyte proliferation. All these effects of biliary exosomes were abolished by the pharmacological removal of cholangiocyte cilia. Our findings suggest that bile contains exosomes functioning as signaling nanovesicles and influencing intracellular regulatory mechanisms and cholangiocyte proliferation through interaction with primary cilia.

Modularized Extracellular Vesicles: The Dawn of Prospective Personalized and Precision Medicine

“…For example, EVs offer high physicochemical and biological stability,11 which may be due to the isolating ability of the phospholipid layer, protecting the contents of EVs from exposure to the external environment ( Figure 2 ). 12 As a result, EVs can exist in almost all body fluids, including blood plasma,13 saliva,14 urine,15 bile,16 synovial fluid,17 semen,18 and breast milk 19. By expressing different surface proteins, EVs can have different targeting abilities 20.…”

Exosome: An Emerging Participant in the Development of Liver Disease

“…For example, mouse hepatocytes can secrete exosomes that contain the cytochrome P450, UDP-glucuronosyltransferases (UDPGT), and glutathione S-transferases; in humans, these exosomes may exist in the plasma and play a role in extra-hepatic detoxification (19). Exosomes derived from rat bile can suppress the proliferation of cholangiocytes by inhibiting the ERK signaling pathway and increasing the expression of miR15a (20). Prostaglandin E2-carrying exosomes from intestinal epithelial cells can inhibit the activation of liver NKT cells via α-GalCer and weaken the inflammatory responseinduced liver injury (21).…”

Physiology of Cholangiocytes

“…A G-protein-coupled nucleotide receptor, P2Y 12 , and the bile acid receptor, TGR5, are among the key elements of ciliary chemosensation (143,185). Importantly, chemosignals are delivered to cholangiocyte cilia not only as single small or large signaling molecules but also by sophisticated vesicles such as exosomes (186).…”