Filter and export

Publications

What is a Publication?
10 Publications visible to you, out of a total of 10
On the mechanisms of biliary flux

Abstract

Not specified

Authors: Nachiket Vartak, Dirk Drasdo, Fabian Geisler, Tohru Itoh, Ronald P.J. Oude Elferink, Stan F.J. van de Graaf, John Chiang, Verena Keitel, Michael Trauner, Peter Jansen, Jan G Hengstler

Date Published: 23rd Jun 2021

Publication Type: Journal

Intravital dynamic and correlative imaging reveals diffusion‐dominated canalicular and flow‐augmented ductular bile flux

Abstract (Expand)

Small‐molecule flux in tissue‐microdomains is essential for organ function, but knowledge of this process is scant due to the lack of suitable methods. We developed two independent techniques that allow … the quantification of advection (flow) and diffusion in individual bile canaliculi and in interlobular bile ducts of intact livers in living mice, namely Fluorescence Loss After Photoactivation (FLAP) and Intravital Arbitrary Region Image Correlation Spectroscopy (IVARICS). The results challenge the prevailing ‘mechano‐osmotic’ theory of canalicular bile flow. After active transport across hepatocyte membranes bile acids are transported in the canaliculi primarily by diffusion. Only in the interlobular ducts, diffusion is augmented by regulatable advection. Photoactivation of fluorescein bis‐(5‐carboxymethoxy‐2‐nitrobenzyl)‐ether (CMNB‐caged fluorescein) in entire lobules demonstrated the establishment of diffusive gradients in the bile canalicular network and the sink function of interlobular ducts. In contrast to the bile canalicular network, vectorial transport was detected and quantified in the mesh of interlobular bile ducts. In conclusion, the liver consists of a diffusion dominated canalicular domain, where hepatocytes secrete small molecules and generate a concentration gradient and a flow‐augmented ductular domain, where regulated water influx creates unidirectional advection that augments the diffusive flux.

Authors: Nachiket Vartak, Georgia Guenther, Florian Joly, Amruta Damle‐Vartak, Gudrun Wibbelt, Jörns Fickel, Simone Jörs, Brigitte Begher‐Tibbe, Adrian Friebel, Kasimir Wansing, Ahmed Ghallab, Marie Rosselin, Noemie Boissier, Irene Vignon‐Clementel, Christian Hedberg, Fabian Geisler, Heribert Hofer, Peter Jansen, Stefan Hoehme, Dirk Drasdo, Jan G. Hengstler

Date Published: 19th Jun 2020

Publication Type: Journal

Intravital dynamic and correlative imaging reveals diffusion-dominated canalicular and flow-augmented ductular bile flux

Abstract (Expand)

Small-molecule flux in tissue-microdomains is essential for organ function, but knowledge of this process is scant due to the lack of suitable methods applicable to live animals. We developed a methodology … based on dynamic and correlative imaging for quantitative intravital flux analysis. Application to the liver, challenged the prevailing ‘mechano-osmotic’ theory of canalicular bile flow. After active transport across hepatocyte membranes bile salts are transported in the canaliculi primarily by diffusion. Only in the interlobular ducts, diffusion is augmented by regulatable advection. We corroborate these observations with in silico simulations and pan-species comparisons of lobule size. This study demonstrates a flux mechanism, where the energy invested in transmembrane transport entropically dissipates in a sub-micron scale vessel network.

Authors: Nachiket Vartak, Georgia Guenther, Florian Joly, Amruta Damle-Vartak, Gudrun Wibbelt, Jörns Fickel, Simone Jörs, Brigitte Begher-Tibbe, Adrian Friebel, Kasimir Wansing, Ahmed Ghallab, Marie Rosselin, Noemie Boissier, Irene Vignon-Clementel, Christian Hedberg, Fabian Geisler, Heribert Hofer, Peter Jansen, Stefan Hoehme, Dirk Drasdo, Jan G. Hengstler

Date Published: 26th Sep 2019

Publication Type: Journal

Pipe-3D: A Pipeline Based on Immunofluorescence, 3D Confocal Imaging, Reconstructions, and Morphometry for Biliary Network Analysis in Cholestasis

Abstract

Not specified

Authors: Amruta Damle-Vartak, Brigitte Begher-Tibbe, Georgia Gunther, Fabian Geisler, Nachiket Vartak, Jan G. Hengstler

Date Published: 2019

Publication Type: Book

3D visualization of the biliary tree by X-ray phase-contrast computed tomography

Abstract

Not specified

Author: Amruta Damle-Vartak

Date Published: 1st Dec 2018

Publication Type: Not specified

Bile micro-infarcts in cholestasis are initiated by rupture of the apical hepatocyte membrane and cause shunting of bile to sinusoidal blood

Abstract

Not specified

Authors: Ahmed Ghallab, Ute Hofmann, Selahaddin Sezgin, Nachiket Vartak, Reham Hassan, Ayham Zaza, Patricio Godoy, Kai Markus Schneider, Georgia Guenther, Yasser A Ahmed, Aya A Abbas, Verena Keitel, Lars Kuepfer, Steven Dooley, Frank Lammert, Christian Trautwein, Michael Spiteller, Dirk Drasdo, Alan F Hofmann, Peter L M Jansen, Jan G Hengstler, Raymond Reif

Date Published: 13th Aug 2018

Publication Type: Not specified

Single cell polarity in liquid phase facilitates tumour metastasis.

Abstract (Expand)

Dynamic polarisation of tumour cells is essential for metastasis. While the role of polarisation during dedifferentiation and migration is well established, polarisation of metastasising tumour cells … during phases of detachment has not been investigated. Here we identify and characterise a type of polarisation maintained by single cells in liquid phase termed single-cell (sc) polarity and investigate its role during metastasis. We demonstrate that sc polarity is an inherent feature of cells from different tumour entities that is observed in circulating tumour cells in patients. Functionally, we propose that the sc pole is directly involved in early attachment, thereby affecting adhesion, transmigration and metastasis. In vivo, the metastatic capacity of cell lines correlates with the extent of sc polarisation. By manipulating sc polarity regulators and by generic depolarisation, we show that sc polarity prior to migration affects transmigration and metastasis in vitro and in vivo.

Authors: A. Lorentzen, P. F. Becker, J. Kosla, M. Saini, K. Weidele, P. Ronchi, C. Klein, M. J. Wolf, F. Geist, B. Seubert, M. Ringelhan, D. Mihic-Probst, K. Esser, M. Roblek, F. Kuehne, G. Bianco, T. O'Connor, Q. Muller, K. Schuck, S. Lange, D. Hartmann, S. Spaich, O. Gross, J. Utikal, S. Haferkamp, M. R. Sprick, A. Damle-Vartak, A. Hapfelmeier, N. Huser, U. Protzer, A. Trumpp, D. Saur, N. Vartak, C. A. Klein, B. Polzer, L. Borsig, M. Heikenwalder

Date Published: 2nd Mar 2018

Publication Type: Not specified

The ascending pathophysiology of cholestatic liver disease.

Abstract (Expand)

In this review we develop the argument that cholestatic liver diseases, particularly primary biliary cholangitis and primary sclerosing cholangitis (PSC), evolve over time with anatomically an ascending … course of the disease process. The first and early lesions are in "downstream" bile ducts. This eventually leads to cholestasis, and this causes bile salt (BS)-mediated toxic injury of the "upstream" liver parenchyma. BS are toxic in high concentration. These concentrations are present in the canalicular network, bile ducts, and gallbladder. Leakage of bile from this network and ducts could be an important driver of toxicity. The liver has a great capacity to adapt to cholestasis, and this may contribute to a variable symptom-poor interval that is often observed. Current trials with drugs that target BS toxicity are effective in only about 50%-60% of primary biliary cholangitis patients, with no effective therapy in PSC. This motivated us to develop and propose a new view on the pathophysiology of primary biliary cholangitis and PSC in the hope that these new drugs can be used more effectively. These views may lead to better stratification of these diseases and to recommendations on a more "tailored" use of the new therapeutic agents that are currently tested in clinical trials. Apical sodium-dependent BS transporter inhibitors that reduce intestinal BS absorption lower the BS load and are best used in cholestatic patients. The effectiveness of BS synthesis-suppressing drugs, such as farnesoid X receptor agonists, is greatest when optimal adaptation is not yet established. By the time cytochrome P450 7A1 expression is reduced these drugs may be less effective. Anti-inflammatory agents are probably most effective in early disease, while drugs that antagonize BS toxicity, such as ursodeoxycholic acid and nor-ursodeoxycholic acid, may be effective at all disease stages. Endoscopic stenting in PSC should be reserved for situations of intercurrent cholestasis and cholangitis, not for cholestasis in end-stage disease. These are arguments to consider a step-wise pathophysiology for these diseases, with therapy adjusted to disease stage. An obstacle in such an approach is that disease stage-defining biomarkers are still lacking. This review is meant to serve as a call to prioritize the development of biomarkers that help to obtain a better stratification of these diseases. (Hepatology 2017;65:722-738).

Authors: P. L. Jansen, A. Ghallab, N. Vartak, R. Reif, F. G. Schaap, J. Hampe, J. G. Hengstler

Date Published: 17th Feb 2017

Publication Type: Not specified

The ascending pathophysiology of cholestatic liver disease

Abstract (Expand)

In this review we develop the argument that cholestatic liver diseases, particularly primary biliary cholangitis and primary sclerosing cholangitis (PSC), evolve over time with anatomically an ascending … course of the disease process. The first and early lesions are in "downstream" bile ducts. This eventually leads to cholestasis, and this causes bile salt (BS)-mediated toxic injury of the "upstream" liver parenchyma. BS are toxic in high concentration. These concentrations are present in the canalicular network, bile ducts, and gallbladder. Leakage of bile from this network and ducts could be an important driver of toxicity. The liver has a great capacity to adapt to cholestasis, and this may contribute to a variable symptom-poor interval that is often observed. Current trials with drugs that target BS toxicity are effective in only about 50%-60% of primary biliary cholangitis patients, with no effective therapy in PSC. This motivated us to develop and propose a new view on the pathophysiology of primary biliary cholangitis and PSC in the hope that these new drugs can be used more effectively. These views may lead to better stratification of these diseases and to recommendations on a more "tailored" use of the new therapeutic agents that are currently tested in clinical trials. Apical sodium-dependent BS transporter inhibitors that reduce intestinal BS absorption lower the BS load and are best used in cholestatic patients. The effectiveness of BS synthesis-suppressing drugs, such as farnesoid X receptor agonists, is greatest when optimal adaptation is not yet established. By the time cytochrome P450 7A1 expression is reduced these drugs may be less effective. Anti-inflammatory agents are probably most effective in early disease, while drugs that antagonize BS toxicity, such as ursodeoxycholic acid and nor-ursodeoxycholic acid, may be effective at all disease stages. Endoscopic stenting in PSC should be reserved for situations of intercurrent cholestasis and cholangitis, not for cholestasis in end-stage disease. These are arguments to consider a step-wise pathophysiology for these diseases, with therapy adjusted to disease stage. An obstacle in such an approach is that disease stage-defining biomarkers are still lacking. This review is meant to serve as a call to prioritize the development of biomarkers that help to obtain a better stratification of these diseases. (Hepatology 2017;65:722-738).

Authors: Peter L.M. Jansen, Ahmed Ghallab, Nachiket Vartak, Raymond Reif, Frank G. Schaap, Jochen Hampe, Jan G. Hengstler

Date Published: 1st Feb 2017

Publication Type: Not specified

Cholestasis-induced adaptive remodeling of interlobular bile ducts.

Abstract (Expand)

UNLABELLED: Cholestasis is a common complication in liver diseases that triggers a proliferative response of the biliary tree. Bile duct ligation (BDL) is a frequently used model of cholestasis in … rodents. To determine which changes occur in the three-dimensional (3D) architecture of the interlobular bile duct during cholestasis, we used 3D confocal imaging, surface reconstructions, and automated image quantification covering a period up to 28 days after BDL. We show a highly reproducible sequence of interlobular duct remodeling, where cholangiocyte proliferation initially causes corrugation of the luminal duct surface, leading to an approximately five-fold increase in surface area. This is analogous to the function of villi in the intestine or sulci in the brain, where an expansion of area is achieved within a restricted volume. The increase in surface area is further enhanced by duct branching, branch elongation, and loop formation through self-joining, whereby an initially relatively sparse mesh surrounding the portal vein becomes five-fold denser through elongation, corrugation, and ramification. The number of connections between the bile duct and the lobular bile canalicular network by the canals of Hering decreases proportionally to the increase in bile duct length, suggesting that no novel connections are established. The diameter of the interlobular bile duct remains constant after BDL, a response that is qualitatively distinct from that of large bile ducts, which tend to enlarge their diameters. Therefore, volume enhancement is only due to net elongation of the ducts. Because curvature and tortuosity of the bile duct are unaltered, this enlargement of the biliary tree is caused by branching and not by convolution. CONCLUSION: BDL causes adaptive remodeling that aims at optimizing the intraluminal surface area by way of corrugation and branching.

Authors: N. Vartak, A. Damle-Vartak, B. Richter, O. Dirsch, U. Dahmen, S. Hammad, J. G. Hengstler

Date Published: 27th Nov 2015

Publication Type: Not specified

Powered by
 (v.1.15.2)
About FAIRDOM | About LiSyM | Funding and Programmes | Credits | Terms & Conditions | Imprint
Copyright © 2008 - 2024 The University of Manchester and HITS gGmbH