Hepatocyte

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Hepatocyte
Sinusoid.jpeg
Hepatocyte and sinusoid (venule) in a section of rat liver
Human liver.jpg
Details
Location Liver
Identifiers
MeSH D022781
TH H3.04.05.0.00006
FMA 14515
Anatomical terms of microanatomy

A hepatocyte is a cell of the main parenchymal tissue of the liver. Hepatocytes make up 80% of the liver's mass. These cells are involved in:

Contents

Structure

The typical hepatocyte is cubical with sides of 20-30  μm, (in comparison, a human hair has a diameter of 17 to 180 μm). [1] The typical volume of a hepatocyte is 3.4 x 10−9 cm3. [2] Smooth endoplasmic reticulum is abundant in hepatocytes, in contrast to most other cell types. [3]

Microanatomy

Hepatocytes display an eosinophilic cytoplasm, reflecting numerous mitochondria, and basophilic stippling due to large amounts of rough endoplasmic reticulum and free ribosomes. Brown lipofuscin granules are also observed (with increasing age) together with irregular unstained areas of cytoplasm; these correspond to cytoplasmic glycogen and lipid stores removed during histological preparation. The average life span of the hepatocyte is 5 months; they are able to regenerate.

Hepatocyte nuclei are round with dispersed chromatin and prominent nucleoli. Anisokaryosis (or variation in the size of the nuclei) is common and often reflects tetraploidy and other degrees of polyploidy, a normal feature of 30-40% of hepatocytes in the adult human liver. [4] Binucleate cells are also common.

Hepatocytes are organised into plates separated by vascular channels (sinusoids), an arrangement supported by a reticulin (collagen type III) network. The hepatocyte plates are one cell thick in mammals and two cells thick in the chicken. Sinusoids display a discontinuous, fenestrated endothelial cell lining. The endothelial cells have no basement membrane and are separated from the hepatocytes by the space of Disse, which drains lymph into the portal tract lymphatics.

Kupffer cells are scattered between endothelial cells; they are part of the reticuloendothelial system and phagocytose spent erythrocytes. Stellate (Ito) cells store vitamin A and produce extracellular matrix and collagen; they are also distributed amongst endothelial cells but are difficult to visualise by light microscopy.

Function

Protein synthesis

The hepatocyte is a cell in the body that manufactures serum albumin, fibrinogen, and the prothrombin group of clotting factors (except for Factors 3 and 4).

It is the main site for the synthesis of lipoproteins, ceruloplasmin, transferrin, complement, and glycoproteins. Hepatocytes manufacture their own structural proteins and intracellular enzymes.

Synthesis of proteins is by the rough endoplasmic reticulum (RER), and both the rough and smooth endoplasmic reticulum (SER) are involved in secretion of the proteins formed.

The endoplasmic reticulum (ER) is involved in conjugation of proteins to lipid and carbohydrate moieties synthesized by, or modified within, the hepatocytes.

Proteins produced by hepatocytes that function as hormones are known as hepatokines.

Carbohydrate metabolism

The liver forms fatty acids from carbohydrates and synthesizes triglycerides from fatty acids and glycerol. [5] Hepatocytes also synthesize apoproteins with which they then assemble and export lipoproteins (VLDL, HDL).

The liver is also the main site in the body for gluconeogenesis, the formation of carbohydrates from precursors such as alanine, glycerol, and oxaloacetate.

Lipid metabolism

The liver receives many lipids from the systemic circulation and metabolizes chylomicron remnants. It also synthesizes cholesterol from acetate and further synthesizes bile salts. The liver is the sole site of bile salts formation.

Detoxification

Hepatocytes have the ability to metabolize, detoxify, and inactivate exogenous compounds such as drugs (see drug metabolism), insecticides, and endogenous compounds such as steroids.

The drainage of the intestinal venous blood into the liver requires efficient detoxification of miscellaneous absorbed substances to maintain homeostasis and protect the body against ingested toxins.

One of the detoxifying functions of hepatocytes is to modify ammonia into urea for excretion.

The most abundant organelle in liver cells is the smooth endoplasmic reticulum.

Aging

As mammalian liver cells age, damages in their DNA increase in prevalence. A review of the literature indicated that in mouse liver cells DNA damages (single-strand breaks, oxidized bases and 7-methylguanine) increase with age. [6] Also, in rat liver, DNA single- and double-strand breaks, oxidized bases, and methylated bases increase with age; and in rabbit liver, cross-linked bases increase with age. [6] Liver cells depend on DNA repair pathways that specifically protect the transcribed compartment of the genome to promote sustained functionality and cell preservation with age. [7]

Society and culture

Use in research

Primary hepatocytes are commonly used in cell biological and biopharmaceutical research. In vitro model systems based on hepatocytes have been of great help to better understand the role of hepatocytes in (patho)physiological processes of the liver. In addition, pharmaceutical industry has heavily relied on the use of hepatocytes in suspension or culture to explore mechanisms of drug metabolism and even predict in vivo drug metabolism. For these purposes, hepatocytes are usually isolated from animal or human [8] whole liver or liver tissue by collagenase digestion, which is a two-step process. In the first step, the liver is placed in an isotonic solution, in which calcium is removed to disrupt cell-cell tight junctions by the use of a calcium chelating agent. Next, a solution containing collagenase is added to separate the hepatocytes from the liver stroma. This process creates a suspension of hepatocytes, which can be seeded in multi-well plates and cultured for many days or even weeks. For optimal results, culture plates should first be coated with an extracellular matrix (e.g. collagen, Matrigel) to promote hepatocyte attachment (typically within 1-3 hr after seeding) and maintenance of the hepatic phenotype. In addition, and overlay with an additional layer of extracellular matrix is often performed to establish a sandwich culture of hepatocytes. The application of a sandwich configuration supports prolonged maintenance of hepatocytes in culture. [9] [10] Freshly-isolated hepatocytes that are not used immediately can be cryopreserved and stored. [11] They do not proliferate in culture. Hepatocytes are intensely sensitive to damage during the cycles of cryopreservation including freezing and thawing. Even after the addition of classical cryoprotectants there is still damage done while being cryopreserved. [12] Nevertheless, recent cryopreservation and resuscitation protocols support application of cryopreserved hepatocytes for most biopharmaceutical applications. [13]

Additional images

See also

Related Research Articles

<span class="mw-page-title-main">Endoplasmic reticulum</span> Cell organelle that synthesizes, folds and processes proteins

The endoplasmic reticulum (ER) is a part of a transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum (RER), and smooth endoplasmic reticulum (SER). The endoplasmic reticulum is found in most eukaryotic cells and forms an interconnected network of flattened, membrane-enclosed sacs known as cisternae, and tubular structures in the SER. The membranes of the ER are continuous with the outer nuclear membrane. The endoplasmic reticulum is not found in red blood cells, or spermatozoa.

<span class="mw-page-title-main">Endomembrane system</span> Membranes in the cytoplasm of a eukaryotic cell

The endomembrane system is composed of the different membranes (endomembranes) that are suspended in the cytoplasm within a eukaryotic cell. These membranes divide the cell into functional and structural compartments, or organelles. In eukaryotes the organelles of the endomembrane system include: the nuclear membrane, the endoplasmic reticulum, the Golgi apparatus, lysosomes, vesicles, endosomes, and plasma (cell) membrane among others. The system is defined more accurately as the set of membranes that forms a single functional and developmental unit, either being connected directly, or exchanging material through vesicle transport. Importantly, the endomembrane system does not include the membranes of plastids or mitochondria, but might have evolved partially from the actions of the latter.

<span class="mw-page-title-main">Fibroblast</span> Animal connective tissue cell

A fibroblast is a type of biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework (stroma) for animal tissues, and plays a critical role in wound healing. Fibroblasts are the most common cells of connective tissue in animals.

<span class="mw-page-title-main">Fibronectin</span> Protein involved in cell adhesion, cell growth, cell migration and differentiation

Fibronectin is a high-molecular weight glycoprotein of the extracellular matrix that binds to membrane-spanning receptor proteins called integrins. Fibronectin also binds to other extracellular matrix proteins such as collagen, fibrin, and heparan sulfate proteoglycans.

<span class="mw-page-title-main">Extracellular matrix</span> Network of proteins and molecules outside cells that provides structural support for cells

In biology, the extracellular matrix (ECM), also called intercellular matrix (ICM), is a network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide structural and biochemical support to surrounding cells. Because multicellularity evolved independently in different multicellular lineages, the composition of ECM varies between multicellular structures; however, cell adhesion, cell-to-cell communication and differentiation are common functions of the ECM.

<span class="mw-page-title-main">Proteoglycan</span> Class of compounds

Proteoglycans are proteins that are heavily glycosylated. The basic proteoglycan unit consists of a "core protein" with one or more covalently attached glycosaminoglycan (GAG) chain(s). The point of attachment is a serine (Ser) residue to which the glycosaminoglycan is joined through a tetrasaccharide bridge. The Ser residue is generally in the sequence -Ser-Gly-X-Gly-, although not every protein with this sequence has an attached glycosaminoglycan. The chains are long, linear carbohydrate polymers that are negatively charged under physiological conditions due to the occurrence of sulfate and uronic acid groups. Proteoglycans occur in connective tissue.

In cell biology, microsomes are heterogeneous vesicle-like artifacts re-formed from pieces of the endoplasmic reticulum (ER) when eukaryotic cells are broken-up in the laboratory; microsomes are not present in healthy, living cells.

<span class="mw-page-title-main">Kupffer cell</span> Macrophages located in the liver

Kupffer cells, also known as stellate macrophages and Kupffer–Browicz cells, are specialized cells localized in the liver within the lumen of the liver sinusoids and are adhesive to their endothelial cells which make up the blood vessel walls. Kupffer cells comprise the largest population of tissue-resident macrophages in the body. Gut bacteria, bacterial endotoxins, and microbial debris transported to the liver from the gastrointestinal tract via the portal vein will first come in contact with Kupffer cells, the first immune cells in the liver. It is because of this that any change to Kupffer cell functions can be connected to various liver diseases such as alcoholic liver disease, viral hepatitis, intrahepatic cholestasis, steatohepatitis, activation or rejection of the liver during liver transplantation and liver fibrosis. They form part of the mononuclear phagocyte system.

<span class="mw-page-title-main">Osteonectin</span> Mammalian protein found in Homo sapiens

Osteonectin (ON) also known as secreted protein acidic and rich in cysteine (SPARC) or basement-membrane protein 40 (BM-40) is a protein that in humans is encoded by the SPARC gene.

<span class="mw-page-title-main">Perisinusoidal space</span> Location in liver between hepatocyte and sinusoid

The perisinusoidal space 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 endothelium facilitates this transport. This space may be obliterated in liver disease, leading to decreased uptake by hepatocytes of nutrients and wastes such as bilirubin.

<span class="mw-page-title-main">Liver sinusoid</span> Hepatic sinusoidal blood vessel

A liver sinusoid is a type of capillary known as a sinusoidal capillary, discontinuous capillary or sinusoid, that is similar to a fenestrated capillary, having discontinuous endothelium that serves as a location for mixing of the oxygen-rich blood from the hepatic artery and the nutrient-rich blood from the portal vein.

<span class="mw-page-title-main">Heat shock protein 47</span> Protein-coding gene in the species Homo sapiens

Heat shock protein 47, also known as SERPINH1 is a serpin which serves as a human chaperone protein for collagen.

<span class="mw-page-title-main">PDIA3</span> Protein-coding gene in the species Homo sapiens

Protein disulfide-isomerase A3 (PDIA3), also known as glucose-regulated protein, 58-kD (GRP58), is an isomerase enzyme encoded by the autosomal gene PDIA3 in humans. This protein localizes to the endoplasmic reticulum (ER) and interacts with lectin chaperones calreticulin and calnexin (CNX) to modulate folding of newly synthesized glycoproteins. It is thought that complexes of lectins and this protein mediate protein folding by promoting formation of disulfide bonds in their glycoprotein substrates.

In cellular biology, inclusions are diverse intracellular non-living substances that are not bound by membranes. Inclusions are stored nutrients/deutoplasmic substances, secretory products, and pigment granules. Examples of inclusions are glycogen granules in the liver and muscle cells, lipid droplets in fat cells, pigment granules in certain cells of skin and hair, and crystals of various types. Cytoplasmic inclusions are an example of a biomolecular condensate arising by liquid-solid, liquid-gel or liquid-liquid phase separation.

<span class="mw-page-title-main">Binding immunoglobulin protein</span> Protein-coding gene in the species Homo sapiens

Binding immunoglobulin protein (BiPS) also known as 78 kDa glucose-regulated protein (GRP-78) or heat shock 70 kDa protein 5 (HSPA5) is a protein that in humans is encoded by the HSPA5 gene.

<span class="mw-page-title-main">PLOD3</span> Protein-coding gene in the species Homo sapiens

Procollagen-lysine,2-oxoglutarate 5-dioxygenase 3 is an enzyme that in humans is encoded by the PLOD3 gene.

<span class="mw-page-title-main">FKBP10</span> Protein-coding gene in the species Homo sapiens

FK506-binding protein 10 is a protein that in humans is encoded by the FKBP10 gene.

<span class="mw-page-title-main">Liver</span> Vertebrate organ involved in metabolism

The liver is a major metabolic organ only found in vertebrate animals, which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it is located in the right upper quadrant of the abdomen, below the diaphragm and mostly shielded by the lower right rib cage. Its other metabolic roles include carbohydrate metabolism, the production of hormones, conversion and storage of nutrients such as glucose and glycogen, and the decomposition of red blood cells.

Liver cytology is the branch of cytology that studies the liver cells and its functions. The liver is a vital organ, in charge of almost all the body’s metabolism. Main liver cells are hepatocytes, Kupffer cells, and hepatic stellate cells; each one with a specific function.

Liver sinusoidal endothelial cells (LSECs) form the lining of the smallest blood vessels in the liver, also called the hepatic sinusoids. LSECs are highly specialized endothelial cells with characteristic morphology and function. They constitute an important part of the reticuloendothelial system (RES).

References

  1. ↑ The diameter of human hair ranges from 17 to 181 μm. Ley, Brian (1999). Elert, Glenn (ed.). "Diameter of a human hair". The Physics Factbook. Retrieved 2018-12-08.
  2. ↑ Lodish, H., Berk, A., Zipursky, S. L., Matsudaira, P., Baltimore, D., Darnell, J. E. Molecular Cell Biology (Fifth Edition). W. H. Freeman and Company. New York, 2000, pp 10.
  3. ↑ Pavelka, Margit; Roth, J. (Cell and molecular pathologist) (2010). Functional ultrastructure : Atlas of tissue biology and pathology. Wien: SpringerWeinNewYork. ISBN   978-3-211-99390-3. OCLC   663096046.
  4. ↑ Celton-Morizur, S; Merlen, G; Couton, D; Desdouets, C (1 February 2010). "Polyploidy and liver proliferation: central role of insulin signaling" (PDF). Cell Cycle. 9 (3): 460–6. doi: 10.4161/cc.9.3.10542 . PMID   20090410. S2CID   22708555. Archived from the original (PDF) on 2012-04-25.
  5. ↑ Ali ES, Hua J, Wilson CH, Tallis GA, Zhou FH, Rychkov GY, Barritt GJ (2016). "The glucagon-like peptide-1 analogue exendin-4 reverses impaired intracellular Ca2+ signalling in steatotic hepatocytes". Biochimica et Biophysica Acta (BBA) - Molecular Cell Research. 1863 (9): 2135–46. doi: 10.1016/j.bbamcr.2016.05.006 . PMID   27178543.
  6. 1 2 Holmes GE, Bernstein C, Bernstein H. Oxidative and other DNA damages as the basis of aging: a review. Mutat Res. 1992 Sep;275(3-6):305-15. doi: 10.1016/0921-8734(92)90034-m. PMID: 1383772
  7. ↑ Vougioukalaki M, Demmers J, Vermeij WP, Baar M, Bruens S, Magaraki A, Kuijk E, Jager M, Merzouk S, Brandt RMC, Kouwenberg J, van Boxtel R, Cuppen E, Pothof J, Hoeijmakers JHJ. Different responses to DNA damage determine ageing differences between organs. Aging Cell. 2022 Apr;21(4):e13562. doi: 10.1111/acel.13562. Epub 2022 Mar 4. PMID: 35246937; PMCID: PMC9009128
  8. ↑ Lecluyse EL, Alexandre E (2010). "Isolation and culture of primary hepatocytes from resected human liver tissue". Hepatocytes. Methods Mol. Biol. Vol. 640. pp. 57–82. doi:10.1007/978-1-60761-688-7_3. ISBN   978-1-60761-687-0. PMID   20645046.
  9. ↑ Dunn JC, Yarmush ML, Koebe HG, Tompkins RG (Feb 1989). "Hepatocyte function and extracellular matrix geometry: long-term culture in a sandwich configuration". FASEB J. 3 (2): 174–7. doi: 10.1096/fasebj.3.2.2914628 . PMID   2914628. S2CID   449420. Erratum in: FASEB J 1989 May;3(7):1873.
  10. ↑ De Bruyn T, Chatterjee S, Fattah S, Keemink J, Nicolaï J, Augustijns P, Annaert P (May 2013). "Sandwich-cultured hepatocytes: utility for in vitro exploration of hepatobiliary drug disposition and drug-induced hepatotoxicity". Expert Opin Drug Metab Toxicol. 9 (5): 589–616. doi:10.1517/17425255.2013.773973. PMID   23452081. S2CID   27593521.
  11. ↑ Li Albert P (2001). "Screening for human ADME/Tox drug properties in Drug Discovery". Drug Discovery Today. 6 (7): 357–366. doi:10.1016/s1359-6446(01)01712-3. PMID   11267922.
  12. ↑ Hamel, F.; Grondin, M. L.; Denizeau, F.; Averill-Bates, D. A.; Sarhan, F. (2006). "Wheat extracts as an efficient cryoprotective agent for primary cultures of rat hepatocytes". Biotechnology and Bioengineering. 95 (4): 661–670. doi:10.1002/bit.20953. PMID   16927246. S2CID   4981423.
  13. ↑ De Bruyn T, Ye ZW, Peeters A, Sahi J, Baes M, Augustijns PF, Annaert PP (Jul 2011). "Determination of OATP-, NTCP- and OCT-mediated substrate uptake activities in individual and pooled batches of cryopreserved human hepatocytes". Eur J Pharm Sci. 43 (4): 297–307. doi:10.1016/j.ejps.2011.05.002. PMID   21605667.
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