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A hepatic stellate cell is generally located in the liver and is usually spindle-shaped. The nucleus is typically elongated or has an oval shape, while researchers believe a spine-like projection may detect chemical signals and relay them to the interior of the cell. Also called perisinusoidal cells, hepatic stellate cells are typically located between the liver’s sinusoids and hepatocytes. They normally store vitamin A and may help to transport various proteins, including immune messengers called cytokines. There is often a strong response to liver damage as these cells can help form scar tissue within the liver.
Usually there are fat droplets in the hepatic stellate cell that store vitamin A. The cell may also present lipid antigens within the liver which can help to stimulate the immune system. In addition to being fat storing cells and regulating some immune functions, hepatic stellate cells sometimes release proteins that can stimulate liver regeneration after a transplant. Research studies have shown that cellular signaling by these cells helps repair the liver after an injury as well.
While being vital to the function of the liver, a hepatic stellate cell is usually in a dormant or quiescent state until it is activated in response to liver damage. When the liver is injured or diseased, the cell tends to multiply; its ability to contract becomes more prevalent as well. Other changes typically include a decreased ability to store vitamin A, greater sensitivity and response to certain chemicals, and secretion of collagen as a scar tissue, which is often the cause of cirrhosis.
The variety found in the liver is similar to the pancreatic stellate cell, except the hepatic type is usually less prone to damage from a lack of oxygen if blood flow from arteries decreases. Most of the liver’s blood supply comes from veins, and this characteristic of the cells, along with other processes, may contribute to how the liver can regenerate. A hepatic stellate cell can also trigger inflammatory responses, and it often includes receptors for common proteins that can influence these.
Even after being damaged, the liver cells can revert to a quiescent state or the damaged ones can die off, which often occurs in the regression of diseases such as liver fibrosis. Stellate cells in the liver are sometimes called Ito cells, after a Japanese physician who studied them in the 20th century. Similar cells that store vitamin A and resemble the hepatic stellate cell can also be found in the kidneys, lungs, and intestines.