Liver is a vital organ, which has regenerative property. Liver functions include metabolism, digestion, storage, synthesis and release of vitamins, carbohydrates, proteins and lipids. It also detoxifies and inactivates endogenous and exogenous substances including toxins and metals.

Liver Cirrhosis and liver circulation

Liver cirrhosis is one of the diseases of liver, which is caused by different reasons like alcohol excess, chronic viral hepatitis, drugs and chemicals etc. Cirrhosis is a condition of severe damage to the liver that impairs its ability to function normally. It causes formation of scar tissue. This scarring distorts the normal structure, functions and re-growth of liver cells.

Circulation in Normal Liver

Hepatic circulation is a portal system. First blood has to pass through splanchnic and then hepatic capillary. Blood enter liver through portal vein and hepatic artery but the out flow is only by hepatic vein. Portal vein carries blood from the spleen and other digestive organs whereas hepatic artery carries oxygenated blood from heart. Central vein carries the detoxified blood from the liver to the heart.

Circulation in Cirrhotic Liver

In cirrhotic liver blood vessels inside the liver lobule are partially blocked due the formation of excess collagen fiber in the liver. Blood coming from the spleen cannot able to enter liver which increases intrahepatic resistance to blood flows resulting in hepatic insufficiency and portal hypertension.

Portal hypertension

Portal pressure is described mathematically as a function of flow and resistance across the hepatic vasculature. In cirrhosis, increased intrahepatic resistance results from both intrahepatic vasoconstriction and surrounding mechanical factors including collagen deposition and regenerative nodules. Within the splanchnic and systemic circulation there is increased cardiac output and hyperdynamic circulation that contributes to increased flow into the portal circulation thereby perpetuating portal hypertension.

Hepatic Stellate Cells (HSCs) and Liver Cirrhosis

HSC Physiology

Hepatic Stellate Cells (HSCs) are vitamin A storing perisinusoidal pericytes that undergo phenotypic changes characterized as “myfibroblastic activation” during liver cirrhosis. Activated HSCs produce fibrosis factors such as collagen, which leads to the formation of scar tissue in liver and therefore increases intra hepatic resistance to blood flow. This is how stressed liver ultimately slips into hepatic insufficiency and portal hypertension.

The left lobe of the liver gets blood from the spleen and the right lobe of the liver get it from the superior mesenteric vein. The portal vein and the hepatic artery have anastomotic connection with the sinusoid. Sinusoid is a smooth-walled cylindrical tube and is lined by phagocytic cells (Kupffer).
Sinusoid consists of endothelial cell lining having large pores, through which substances in the plasma move freely into the space of disse. Hepatic stellate cells exist just beneath the endothelial cell lineage of the blood vessel.

HSC Pathology

Hepatic Stellate cells number increases from normal 3% to 15% during liver cirrhosis. HSCs and sinusoidal endothelial cells exist in close proximity to each other in hepatic sinusoid. The hepatic stellate cells (HSC) are now well established as the key cellular element involved in the development of hepatic fibrosis.

Hepatic stellate cell percentage increases from 3% to 15% during cirrhotic condition which can lead to cross talk between hepatic stellate cells and endothelial cells in different way than in normal sinusoid.

During liver cirrhosis cross talk between activated HSCs and sinusoidal endothelial cells may lead to remodeling of hepatic sinusoid.

Group’s objectives

Hepatic stellate cells and endothelial cells: Do they cross talk?

If yes in what language do they talk – dissection of pathways.

Modalities of nitric oxide-use as a therapeutic mean to rectify erroneous cross talk between HSC and EC?

Possible Experimental Approaches

1. Nitric Oxide Donors

Different nitric oxide donors are used as therapeutic entities for liver cirrhosis. These are non-specific donors like SNP used for the treatment of liver cirrhosis (Webb DJ etal. Gut, 2003)

2. Targeted NO delivery

There are different liver specific NO donors such as NCX1000 and V-PYRRO-NO which specifically donate NO to the liver. NCX-1000 is a NO releasing derivative of ursodeoxycholic acid. Treatment with NCX-1000 resulted in decreased hepatic vasculature resistance; vasoconstrictor responses without affecting systemic homodynamic and increased cyclic GMP levels (Stefano Fiorucci etal, PNAS, 2001 and Shah etal. Journal of Hepatology, 2006).

3. NOS gene therapy

Delivering NOS gene using viral vector in cirrhotic rat (Shah etal. AJPGI, 2006)

Our working models

Cell based model of HSC-EC cross talk in liver cirrhosis

Conditional media

Here the hepatic pericytes (here pericyte model is hepatic stellate cells) grown media is used in order to check the effect of the components released by pericytes on endothelial cells.

Co-culture model

This model mimics the situation of liver sinusoid where hepatic stellate cells and endothelial cell lineage exist very close to each other and can able to affect each other’s activity. We are using this model in order to find out the effect of hepatic stellate cells on endothelial cells.

Figure 1 showing the parts of the co-culture chamber (membrane and internal parts.) Figure 2 Membrane is placed inside the chamber in order to grow cells upon the membrane. Figure 3 and 4 Membrane supporting part of the co-culture chamber is placed inside to hold the membrane in place. Figure 5 Upper part of the co-culture chamber is tightened in order to hold the membrane along with the membrane holder. Figure 6 the whole set up is placed in the 12-well tissue culture plate already plated with cells. In this set up, it is possible to grow two cell layers simultaneously as depicted in the upper right cartoon.

Our observations

1) Activated hepatic stellate cells remodel endothelial monolayer.

2) Cirrhotic stress alters topography of endothelial cells.

3) Cirrhotic stress attenuates nitric oxide production by endothelial cells.

4) Nitric oxide rectifies cirrhosis induced erroneous remodeling of endothelial monolayer.

Major groups working in this area:

1. Vijay H. Shah, Gastroenterology Research Unit, Mayo Clinic, Rochester, MN 55905, USA

2. Don C. Rockey, Gastroenterology Division, Duke University Medical Center, Durham, North Carolina, USA

3. H. Senoo, Department of Anatomy, Akita University, School of Medicine, Akita, Japan.

4. Scott L. Friedman, Icahn Medical Institute, Mount Sinai School of Medicine, New York

5. Pinzani M, Dipartimento di Farmacologia Preclinica e Clinica, Italy

Webpage creator:
Syamantak Majumdar



For further discussions, collaborations and comments contact suvro@au-kbc.org