title: Actomyosin contractility drives bile regurgitation as an early response during obstructive cholestasis.
abstract: A wide range of liver diseases manifest as biliary obstruction, or cholestasis. However, the sequence of molecular events triggered as part of the early hepatocellular homeostatic response in obstructive cholestasis is poorly elucidated. Pericanalicular actin is known to accumulate during obstructive cholestasis. Therefore, we hypothesized that the pericanalicular actin cortex undergoes significant remodeling as a regulatory response to obstructive cholestasis.
  
  
  
  In vivo investigations were performed in a bile duct-ligated mouse model. Actomyosin contractility was assessed using sandwich-cultured rat hepatocytes transfected with various fluorescently labeled proteins and pharmacological inhibitors of actomyosin contractility.
  
  
  
  Actomyosin contractility induces transient deformations along the canalicular membrane, a process we have termed inward blebbing. We show that these membrane intrusions are initiated by local ruptures in the pericanalicular actin cortex; and they typically retract following repair by actin polymerization and actomyosin contraction. However, above a certain osmotic pressure threshold, these inward blebs pinch away from the canalicular membrane into the hepatocyte cytoplasm as large vesicles (2-8μm). Importantly, we show that these vesicles aid in the regurgitation of bile from the bile canaliculi.
  
  
  
  Actomyosin contractility induces the formation of bile-regurgitative vesicles, thus serving as an early homeostatic mechanism against increased biliary pressure during cholestasis.
  
  
  
  Bile canaliculi expand and contract in response to the amount of secreted bile, and resistance from the surrounding actin bundles. Further expansion due to bile duct blockade leads to the formation of inward blebs, which carry away excess bile to prevent bile build up in the canaliculi.
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore.
authors.forename: Kapish
authors.initials: K
authors.lastname: Gupta
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore; National University of Singapore Research Institute, Singapore.
authors.forename: Qiushi
authors.initials: Q
authors.lastname: Li
authors.affiliation: Institute of Bioengineering and Nanotechnology, Agency for Science, Technology and Research (A*STAR), Singapore; BioSyM, Singapore-MIT Alliance for Research and Technology, Singapore; Department of Orthopaedics, Xijing Hospital, Fourth Military Medical University, China.
authors.forename: Jun Jun
authors.initials: JJ
authors.lastname: Fan
authors.affiliation: Department of Physiology, National University of Singapore, Singapore; Department of Biomedical Engineering, National University of Singapore, Singapore.
authors.forename: Eliza Li Shan
authors.initials: ELS
authors.lastname: Fong
authors.affiliation: Institute of Bioengineering and Nanotechnology, Agency for Science, Technology and Research (A*STAR), Singapore.
authors.forename: Ziwei
authors.initials: Z
authors.lastname: Song
authors.affiliation: Institute of Bioengineering and Nanotechnology, Agency for Science, Technology and Research (A*STAR), Singapore.
authors.forename: Shupei
authors.initials: S
authors.lastname: Mo
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore.
authors.forename: Haoyu
authors.initials: H
authors.lastname: Tang
authors.affiliation: Department of Physiology, National University of Singapore, Singapore.
authors.forename: Inn Chuan
authors.initials: IC
authors.lastname: Ng
authors.affiliation: Department of Physiology, National University of Singapore, Singapore.
authors.forename: Chan Way
authors.initials: CW
authors.lastname: Ng
authors.affiliation: Department of Physiology, National University of Singapore, Singapore; NUS Graduate School of Integrative Sciences and Engineering, National University of Singapore, Singapore.
authors.forename: Pornteera
authors.initials: P
authors.lastname: Pawijit
authors.affiliation: BioSyM, Singapore-MIT Alliance for Research and Technology, Singapore; Fujian Normal University, Fuzhou, Fujian, China.
authors.forename: Shuangmu
authors.initials: S
authors.lastname: Zhuo
authors.affiliation: Department of Physics, National Taiwan University, Taiwan.
authors.forename: Chen-Yuan
authors.initials: CY
authors.lastname: Dong
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore; Department of Biological Sciences, National University of Singapore, Singapore.
authors.forename: Boon Chuan
authors.initials: BC
authors.lastname: Low
authors.affiliation: Department of Pathology, National University of Singapore, Singapore.
authors.forename: Aileen
authors.initials: A
authors.lastname: Wee
authors.affiliation: Division of Gastroenterology and Hepatology, National University Hospital, Singapore.
authors.forename: Yock Young
authors.initials: YY
authors.lastname: Dan
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore; Department of Biomedical Engineering, National University of Singapore, Singapore.
authors.forename: Pakorn
authors.initials: P
authors.lastname: Kanchanawong
authors.affiliation: BioSyM, Singapore-MIT Alliance for Research and Technology, Singapore.
authors.forename: Peter
authors.initials: P
authors.lastname: So
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore; CNRS UMI3639, Singapore.
authors.forename: Virgile
authors.initials: V
authors.lastname: Viasnoff
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore; Institute of Bioengineering and Nanotechnology, Agency for Science, Technology and Research (A*STAR), Singapore; BioSyM, Singapore-MIT Alliance for Research and Technology, Singapore; Department of Physiology, National University of Singapore, Singapore; Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, China. Electronic address: hanry_yu@nuhs.edu.sg.
authors.forename: Hanry
authors.initials: H
authors.lastname: Yu
mesh_terms: D000205:Actomyosin / Q000502:physiology*; D000818:Animals; D001648:Bile Canaliculi / Q000473:pathology / Q000503:physiopathology; D001652:Bile Ducts / Q000503:physiopathology*; D001655:Bile Reflux / Q000503:physiopathology; D001696:Biomechanical Phenomena; D002779:Cholestasis / Q000473:pathology / Q000503:physiopathology*; D004195:Disease Models, Animal; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D011312:Pressure; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000205:Actomyosin
keywords: Actomyosin cortex; Bile; Bile canaliculi; Blebs; Cholestasis; Hepatocytes; Vesicles