Hepatic stellate cell
Encyclopedia
Hepatic stellate cells (here HSC), also known as perisinusoidal cells or Ito cells (earlier lipocytes or fat-storing cells), are pericyte
s found in the perisinusoidal space
(a small area between the sinusoid
s and hepatocyte
s) of the liver
also known as the space of Disse
. The stellate cell
is the major cell type involved in liver fibrosis
, which is the formation of scar tissue in response to liver damage.
, but their distinguishing feature in routine histological preparations is the presence of multiple lipid droplets in their cytoplasm
. Reelin
expressed by Ito cells has been shown to be a reliable marker in discerning them from other myofibroblast
s. The expression of reelin is increased after liver injury.
droplets in the cell body store vitamin A
. The function and role of quiescent hepatic stellate cells is unclear. Recent evidence suggests a role as a liver-resident antigen-presenting cell presenting lipid antigens to and stimulating proliferation of NKT cells
.
When the liver is damaged, stellate cells can change into an activated state. The activated stellate cell is characterized by proliferation, contractility, and chemotaxis
. The amount of stored vitamin A decreases progressively in liver injury. The activated stellate cell is also responsible for secreting collagen
scar tissue, which can lead to cirrhosis
. More recent studies have also shown that in vivo activation of hepatic stellate cells by agents causing liver fibrosis can eventually lead to senescence of these cells, marked by increased SA-beta-galactosidase staining, as well as p53 accumulation and activation of Rb–hallmarks of cellular senescence. The senescent hepatic stellate cells have been demonstrated to limit liver fibrosis by activating the immune system by activating interactions with the NK cells
.
Pericyte
A pericyte is a type of cell found in the central nervous system. These cells play an integral role in the maintenance of the blood brain barrier as well as several other homeostatic and hemostatic functions of the brain. Pericytes are also a key component of the neurovascular unit, which also...
s found in the perisinusoidal space
Space of Disse
The space of Disse is a location in the liver between a hepatocyte and a sinusoid. It contains the blood plasma. Microvilli of hepatocytes extend into this space, allowing proteins and other plasma components from the sinusoids to be absorbed by the hepatocytes. Fenestration and discontinuity of...
(a small area between the sinusoid
Liver sinusoid
A liver sinusoid is a type of sinusoidal blood vessel that serves as a location for the oxygen-rich blood from the hepatic artery and the nutrient-rich blood from the portal vein....
s and hepatocyte
Hepatocyte
A hepatocyte is a cell of the main tissue of the liver. Hepatocytes make up 70-80% of the liver's cytoplasmic mass.These cells are involved in:* Protein synthesis* Protein storage* Transformation of carbohydrates...
s) of the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
also known as the space of Disse
Space of Disse
The space of Disse is a location in the liver between a hepatocyte and a sinusoid. It contains the blood plasma. Microvilli of hepatocytes extend into this space, allowing proteins and other plasma components from the sinusoids to be absorbed by the hepatocytes. Fenestration and discontinuity of...
. The stellate cell
Stellate cell
In neuroscience, stellate cells are neurons with several dendrites radiating from the cell body giving them a star shaped appearance. The three most common stellate cells are the inhibitory interneurons found within the molecular layer of the cerebellum, excitatory spiny stellate interneurons and...
is the major cell type involved in liver fibrosis
Fibrosis
Fibrosis is the formation of excess fibrous connective tissue in an organ or tissue in a reparative or reactive process. This is as opposed to formation of fibrous tissue as a normal constituent of an organ or tissue...
, which is the formation of scar tissue in response to liver damage.
Staining
Ito cells can be selectively stained with gold chlorideGold chloride
Gold chloride can refer to:* Gold chloride , AuCl* Gold chloride , AuCl2* Gold chloride , AuCl3* Chloroauric acid, HAuCl4...
, but their distinguishing feature in routine histological preparations is the presence of multiple lipid droplets in their cytoplasm
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
. Reelin
Reelin
Reelin is a large secreted extracellular matrix protein that helps regulate processes of neuronal migration and positioning in the developing brain by controlling cell–cell interactions. Besides this important role in early development, reelin continues to work in the adult brain. It modulates the...
expressed by Ito cells has been shown to be a reliable marker in discerning them from other myofibroblast
Myofibroblast
A Myofibroblast is a cell that is in between a fibroblast and a smooth muscle cell in differentiation.-Developmental origin:There are many possible ways of myofibroblast development:#Partial smooth muscle differentiation of a fibroblastic cell...
s. The expression of reelin is increased after liver injury.
Function
In normal liver, stellate cells are described as being in a quiescent state. Quiescent stellate cells represent 5-8% of the total number of liver cells. Each cell has several long protrusions that extend from the cell body and wrap around the sinusoids. The lipidLipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
droplets in the cell body store vitamin A
Retinol
Retinol is one of the animal forms of vitamin A. It is a diterpenoid and an alcohol. It is convertible to other forms of vitamin A, and the retinyl ester derivative of the alcohol serves as the storage form of the vitamin in animals....
. The function and role of quiescent hepatic stellate cells is unclear. Recent evidence suggests a role as a liver-resident antigen-presenting cell presenting lipid antigens to and stimulating proliferation of NKT cells
Natural Killer T cell
Natural killer T cells are a heterogeneous group of T cells that share properties of both T cells and natural killer cells. Many of these cells recognize the non-polymorphic CD1d molecule, an antigen-presenting molecule that binds self- and foreign lipids and glycolipids...
.
When the liver is damaged, stellate cells can change into an activated state. The activated stellate cell is characterized by proliferation, contractility, and chemotaxis
Chemotaxis
Chemotaxis is the phenomenon in which somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. This is important for bacteria to find food by swimming towards the highest concentration of food molecules,...
. The amount of stored vitamin A decreases progressively in liver injury. The activated stellate cell is also responsible for secreting collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
scar tissue, which can lead to cirrhosis
Cirrhosis
Cirrhosis is a consequence of chronic liver disease characterized by replacement of liver tissue by fibrosis, scar tissue and regenerative nodules , leading to loss of liver function...
. More recent studies have also shown that in vivo activation of hepatic stellate cells by agents causing liver fibrosis can eventually lead to senescence of these cells, marked by increased SA-beta-galactosidase staining, as well as p53 accumulation and activation of Rb–hallmarks of cellular senescence. The senescent hepatic stellate cells have been demonstrated to limit liver fibrosis by activating the immune system by activating interactions with the NK cells
Natural killer cell
Natural killer cells are a type of cytotoxic lymphocyte that constitute a major component of the innate immune system. NK cells play a major role in the rejection of tumors and cells infected by viruses...
.
External links
- Liver Research at AU-KBC Stellate cell biology