Experimental obstructive cholestasis: the wound-like inflammatory liver response

Abstract

Obstructive cholestasis causes hepatic cirrhosis and portal hypertension. The pathophysiological mechanisms involved in the development of liver disease are multiple and linked. We propose grouping these mechanisms according to the three phenotypes mainly expressed in the interstitial space in order to integrate them.Experimental extrahepatic cholestasis is the model most frequently used to study obstructive cholestasis. The early liver interstitial alterations described in these experimental models would produce an ischemia/reperfusion phenotype with oxidative and nitrosative stress. Then, the hyperexpression of a leukocytic phenotype, in which Kupffer cells and neutrophils participate, would induce enzymatic stress. And finally, an angiogenic phenotype, responsible for peribiliary plexus development with sinusoidal arterialization, occurs. In addition, an intense cholangiocyte proliferation, which acquires neuroendocrine abilities, stands out. This histopathological finding is also associated with fibrosis.It is proposed that the sequence of these inflammatory phenotypes, perhaps with a trophic meaning, ultimately produces a benign tumoral biliary process - although it poses severe hepatocytic insufficiency. Moreover, the persistence of this benign tumor disease would induce a higher degree of dedifferentiation and autonomy and, therefore, its malign degeneration.

Figure 1

Schematic 3D representation of a complex acinus according to Rappaport. Three portal tracts diverge from one axis, made up of the bile duct, the hepatic arterial and portal venous branches. At the same time, several trabeculae or laminae hepatis that are two cells thick arise from these three portal spaces and are oriented towards the efferent veins (central veins). In the lower part of the drawing, the liver plates are covered by the sinusoidal endothelium and the space of Disse located between both structures contains tissue fluid, which flows outwards into the lymphatics of the portal zones. The space of Disse continues with the portal space, and they both make up the interstitial space of the acinus.

Figure 2

Representation of the rat's liver made up of four lobes: median (ML), left lateral (LLL), right lateral (RLL) and caudate (CL). In the hilum, the relation between the portal, arterial and biliary branches is appreciated, as well as the inexistence of the gall bladder. CBD, common bile duct; HA, hepatic artery; PV, portal vein.

Figure 3

Microsurgical technique of extrahepatic cholestasis in the rat. The common bile duct and the lobular bile ducts are sectioned between ligations. The dissection, ligation and sectioning of the lobular bile ducts must be performed without damaging either the portal or arterial vascularization of these lobes. CL, caudate lobe; LLL, left lateral lobe; ML, middle lobe; RLL, right lateral lobe.

Figure 4

Microsurgical technique for producing extrahepatic cholestasis in mice. CBD, common bile duct with a long ligature to facilitate handling; CL, caudate lobe; D, duodenum; G, gall bladder; LLL, left lateral lobe; LM, medial lobe; RLL, right lateral lobe.

Figure 5

Cholecystectomy during the production of extrahepatic cholestasis in mice. The gall bladder is grasped with forceps near the fundus. The cystic artery is divided by caught and then the mesentery is cut with scissors (on top). The gall bladder is held in the left hand and the cystic duct is cleared of soft tissue by gentle blunt dissection. Then, the lobular bile ducts of the median and left lateral lobes (on bottom) are sectioned between ligations.

Figure 6

Ischemia-revascularization and leukocytic phenotypes during the evolution of obstructive cholestasis. Predominance of oxidative stress with edema and enzymatic stress with infiltration by leukocytes and Kupffer cell activation. AC: arterial capillar; B: bacteria; C: cholangiocyte; ECM: extracellular matrix; HSC: hepatic stellate cell; KC: Kupffer cell; LPS: lipopolysaccharide; MC: mast cell; N: Neutrophyl; PM: portal myofibroblast; PP: peribiliary arterial plexus; RBC: red blood cells; SC: stem cells; SS: sinusoidal space; Th₁: T cell h₁; Thi: intraepithelial lymphocyte.

Figure 7

Angiogenic phenotype during the evolution of obstructive cholestasis. Increase in the proliferation of cholangiocytes with an important development of the peribiliar plexus and sinusoidal arterializations with hepatocytary aplasia. AC: arterial capillar; C: cholangiocyte; ECM: extracellular matrix;H: hepatocyte; M: myofibroblast; PP: peribiliary arterial plexus; SS: sinusoidal space; ; Th₂: T cell h₂; Treg: regulatory T cell.

Figure 8

Periportal biliary proliferation that invades Rappaport spaces I and II. Peribiliary fibrosis is observed (hematoxylin and eosin (H&E) stain, 50 × magnification).

Figure 9

Significant inhibition of liver cytochrome oxidase activity after microsurgical extrahepatic cholestasis in the rat.