Elastic fiber

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Elastic fiber
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Subcutaneous tissue from a young rabbit. Highly magnified. (Elastic fibers labeled at right)
Identifiers
FMA 63868
Anatomical terminology

Elastic fibers (or yellow fibers) are an essential component of the extracellular matrix composed of bundles of proteins (elastin) which are produced by a number of different cell types including fibroblasts, endothelial, smooth muscle, and airway epithelial cells. [1] These fibers are able to stretch many times their length, and snap back to their original length when relaxed without loss of energy. Elastic fibers include elastin, elaunin and oxytalan.

Contents

Elastic fibers are formed via elastogenesis, [2] [3] a highly complex process involving several key proteins including fibulin-4, fibulin-5, latent transforming growth factor β binding protein 4, and microfibril associated protein 4. [4] [5] [6] [7] In this process tropoelastin, the soluble monomeric precursor to elastic fibers is produced by elastogenic cells and chaperoned to the cell surface. Following excretion from the cell, tropoelastin self associates into ~200 nm particles by coacervation, an entropically driven process involving interactions between tropoelastin's hydrophobic domains, which is mediated by glycosaminoglycans, heparan, and other molecules. [8] [9] [10] These particles then fuse to give rise to 1-2 micron spherules which continue to grow as they move down from the cells surface before being deposited onto fibrillin microfibrillar scaffolds. [1]

Following deposition onto microfibrils tropoelastin is insolubilized via extensive crosslinking by members of the lysyl oxidase and lysyl oxidase like family of copper-dependent amine oxidases into amorphous elastin, a highly resilient, insoluble polymer that is metabolically stable over a human lifespan. [1] These two families of enzymes react with the many lysine residues present in tropoelastin to form reactive aldehydes and allysine via oxidative deamination. [11]

These reactive aldehydes and allysines can react with other lysine and allysine residues to form desmosine, isodesmosine, and a number of other polyfunctional crosslinks that join surrounding molecules of tropoelastin into an extensively crosslinked elastin matrix. This process creates a diverse array of intramolecular and intermolecular crosslinks [12] These unique crosslinks are responsible for elastin's durability and persistence. Maintenance of crosslinked elastin is carried out by a number of proteins including lysyl oxidase-like 1 protein. [13]

Mature elastic fibers consist of an amorphous elastin core surrounded by a glycosaminoglycans, heparan sulphate, [14] and number of other proteins such as microfibrillar-associated glycoproteins, fibrillin, fibullin, and the elastin receptor.

Distribution

Thick elastic fibers from the visceral pleura (outer lining) of the human lung STD 190219 SWITCH Tissue 2 93x CMLE 20SNR 50IT Elastin.png
Thick elastic fibers from the visceral pleura (outer lining) of the human lung

Elastic fibers are found in the skin, lungs, arteries, veins, connective tissue proper, elastic cartilage, periodontal ligament, fetal tissue and other tissues which must undergo mechanical stretching. [1] In the lung there are thick and thin elastic fibers. [3]

Elastic fibers are absent from scarring, keloids and dermatofibromas and they are decreased greatly, or are absent in anetodermas. [15]

Histology

Elastic fibers stain well with aldehyde fuchsin, orcein, [16] and Weigert's elastic stain in histological sections.

The permanganate-bisulfite-toluidine blue reaction is a highly selective and sensitive method for demonstrating elastic fibers under polarizing optics. The induced birefringence demonstrates the highly ordered molecular structure of the elastin molecules in the elastic fiber. This is not readily apparent under normal optics.

Defects and disease

There is evidence to believe that certain defects of any components of the elastic matrix may impair and alter the structural appearance of elastic and collagen fibers.

Cutis laxa and Williams syndrome have elastic matrix defects that have been directly associated with alterations in the elastin gene.

Alpha-1 antitrypsin deficiency is a genetic disorder where elastin is excessively degraded by elastase, a degrading protein released by neutrophils during the inflammatory response. This leads most often to emphysema and liver disease in affected individuals.

Buschke-Ollendorff syndrome, Menkes disease, pseudoxanthoma elasticum, and Marfan's syndrome have been associated with defects in copper metabolism and lysyl oxidase or defects in the microfibril (defects in fibrillin, or fibullin for example).

Hurler disease, a lysosomal storage disease, is associated with an altered elastic matrix.

Hypertension and some congenital heart defects are associated with alterations in the great arteries, arteries, and arterioles with alterations in the elastic matrix.

Elastosis

Elastosis is the buildup of elastic fibers in tissues, and is a form of degenerative disease. [17] There are a multitude of causes, but the most commons cause is actinic elastosis of the skin, also known as solar elastosis, which is caused by prolonged and excessive sun exposure, a process known as photoaging. Uncommon causes of skin elastosis include elastosis perforans serpiginosa, perforating calcific elastosis and linear focal elastosis. [17]

Skin elastosis causes
ConditionDistinctive featuresHistopathology
Actinic elastosis
(most common, also called solar elastosis)		Elastin replacing collagen fibers of the papillary dermis and reticular dermis Micrograph of solar elastosis.jpg
Elastosis perforans serpiginosa Degenerated elastic fibers and transepidermal perforating canals (arrow in image points at one of them) [18] Histopathology of elastosis perforans serpiginosa.jpg
Perforating calcific elastosis Clumping of short elastic fibers in the dermis. [18] Histopathology of perforating calcific elastosis.jpg
Linear focal elastosis Accumulation of fragmented elastotic material within the papillary dermis and transcutaneous elimination of elastotic fibers. [18] Histopathology of linear focal elastosis.jpg

See also

Related Research Articles

Collagen is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole-body protein content. Collagen consists of amino acids bound together to form a triple helix of elongated fibril known as a collagen helix. It is mostly found in connective tissue such as cartilage, bones, tendons, ligaments, and skin. Collagen makes up 30% of the protein found in the human body. Vitamin E improves the production of collagen.

<span class="mw-page-title-main">Elastin</span> Protein allowing tissue in the body to resume shape after stretching

Elastin is a protein that in humans is encoded by the ELN gene. Elastin is a key component of the extracellular matrix in gnathostomes. It is highly elastic and present in connective tissue allowing many tissues in the body to resume their shape after stretching or contracting. Elastin helps skin to return to its original position when it is poked or pinched. Elastin is also an important load-bearing tissue in the bodies of vertebrates and used in places where mechanical energy is required to be stored.

<span class="mw-page-title-main">Elastic cartilage</span>

Elastic cartilage, fibroelastic cartilage or yellow fibrocartilage is a type of cartilage present in the pinnae (auricles) of the ear giving it shape, provides shape for the lateral region of the external auditory meatus, medial part of the auditory canal Eustachian tube, corniculate and cuneiform laryneal cartilages, and the epiglottis. It contains elastic fiber networks and collagen type II fibers. The principal protein is elastin.

<span class="mw-page-title-main">Basement membrane</span> Thin fibrous layer between the cells and the adjacent connective tissue in animals

The basement membrane, also known as base membrane is a thin, pliable sheet-like type of extracellular matrix that provides cell and tissue support and acts as a platform for complex signalling. The basement membrane sits between epithelial tissues including mesothelium and endothelium, and the underlying connective tissue.

<span class="mw-page-title-main">Fibrillin</span> Protein family

Fibrillin is a glycoprotein, which is essential for the formation of elastic fibers found in connective tissue. Fibrillin is secreted into the extracellular matrix by fibroblasts and becomes incorporated into the insoluble microfibrils, which appear to provide a scaffold for deposition of elastin.

<span class="mw-page-title-main">Fibril</span> Thin Fibre

Fibrils are structural biological materials found in nearly all living organisms. Not to be confused with fibers or filaments, fibrils tend to have diameters ranging from 10–100 nanometers. Fibrils are not usually found alone but rather are parts of greater hierarchical structures commonly found in biological systems. Due to the prevalence of fibrils in biological systems, their study is of great importance in the fields of microbiology, biomechanics, and materials science.

A microfibril is a very fine fibril, or fiber-like strand, consisting of glycoproteins and cellulose. It is usually, but not always, used as a general term in describing the structure of protein fiber, e.g. hair and sperm tail. Its most frequently observed structural pattern is the 9+2 pattern in which two central protofibrils are surrounded by nine other pairs. Cellulose inside plants is one of the examples of non-protein compounds that are using this term with the same purpose. Cellulose microfibrils are laid down in the inner surface of the primary cell wall. As the cell absorbs water, its volume increases and the existing microfibrils separate and new ones are formed to help increase cell strength.

Ground substance is an amorphous gel-like substance in the extracellular space of animals that contains all components of the extracellular matrix (ECM) except for fibrous materials such as collagen and elastin. Ground substance is active in the development, movement, and proliferation of tissues, as well as their metabolism. Additionally, cells use it for support, water storage, binding, and a medium for intercellular exchange. Ground substance provides lubrication for collagen fibers.

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

Lysyl oxidase (LOX), also known as protein-lysine 6-oxidase, is an enzyme that, in humans, is encoded by the LOX gene. It catalyzes the conversion of lysine residues into its aldehyde derivative allysine. Allysine form cross-links in extracellular matrix proteins. Inhibition of lysyl oxidase can cause osteolathyrism, but, at the same time, its upregulation by tumor cells may promote metastasis of the existing tumor, causing it to become malignant and cancerous.

<span class="mw-page-title-main">Isodesmosine</span> Chemical compound

Isodesmosine is a lysine derivative found in elastin. Isodesmosine is an isomeric pyridinium-based amino acid resulting from the condensation of four lysine residues between elastin proteins by lysyl-oxidase. These represent ideal biomarkers for monitoring elastin turnover because these special cross-links are only found in mature elastin in mammals.

<span class="mw-page-title-main">Fibrillin-1</span> Protein-coding gene in the species Homo sapiens

Fibrillin-1 is a protein that in humans is encoded by the FBN1 gene, located on chromosome 15. It is a large, extracellular matrix glycoprotein that serves as a structural component of 10-12 nm calcium-binding microfibrils. These microfibrils provide force bearing structural support in elastic and nonelastic connective tissue throughout the body. Mutations altering the protein can result in a variety of phenotypic effects differing widely in their severity, including fetal death, developmental problems, Marfan syndrome or in some cases Weill-Marchesani syndrome.

<span class="mw-page-title-main">FBLN5</span> Protein-coding gene in the species Homo sapiens

Fibulin-5 is a protein that in humans is encoded by the FBLN5 gene.

<span class="mw-page-title-main">FBLN2</span> Protein-coding gene in the species Homo sapiens

Fibulin-2 is a protein that in humans is encoded by the FBLN2 gene.

<span class="mw-page-title-main">MFAP2</span> Protein-coding gene in the species Homo sapiens

Microfibrillar-associated protein 2 is a protein that in humans is encoded by the MFAP2 gene.

<span class="mw-page-title-main">LOXL1</span> Protein-coding gene in the species Homo sapiens

Lysyl oxidase homolog 1, also known as LOXL1, is an enzyme which in humans is encoded by the LOXL1 gene.

<span class="mw-page-title-main">LOXL4</span> Protein-coding gene in the species Homo sapiens

Lysyl oxidase homolog 4 is an enzyme that in humans is encoded by the LOXL4 gene.

<span class="mw-page-title-main">LOXL3</span> Protein-coding gene in the species Homo sapiens

Lysyl oxidase homolog 3 is an enzyme that in humans is encoded by the LOXL3 gene.

Histology is the study of the minute structure, composition, and function of tissues. Mature human vocal cords are composed of layered structures which are quite different at the histological level.

Wrinkly skin syndrome(WSS) is a rare genetic condition characterized by sagging, wrinkled skin, low skin elasticity, and delayed fontanelle (soft spot) closure, along with a range of other symptoms. The disorder exhibits an autosomal recessive inheritance pattern with mutations in the ATP6V0A2 gene, leading to abnormal glycosylation events. There are only about 30 known cases of WSS as of 2010. Given its rarity and symptom overlap with other dermatological conditions, reaching an accurate diagnosis is difficult and requires specialized dermatological testing. Limited treatment options are available but long-term prognosis is variable from patient to patient, based on individual case studies. Some skin symptoms recede with increasing age, while progressive neurological advancement of the disorder causes seizures and mental deterioration later in life for some patients.

MFAP4 is an extracellular matrix protein encoded by the MFAP4 gene. It is part of the MFAP family of proteoglycans, which are involved in cell adhesion, intercellular interactions and the assembly and/or maintenance of elastic fibres.

References

  1. 1 2 3 4 Vindin H, Mithieux SM, Weiss AS (November 2019). "Elastin architecture". Matrix Biology. 84: 4–16. doi:10.1016/j.matbio.2019.07.005. PMID   31301399. S2CID   196458819.
  2. ↑ Mithieux SM, Weiss AS (2005). "Elastin". Advances in Protein Chemistry. Elsevier. 70: 437–61. doi:10.1016/s0065-3233(05)70013-9. ISBN   978-0-12-034270-9. PMID   15837523.
  3. 1 2 Thunnissen E, Motoi N, Minami Y, Matsubara D, Timens W, Nakatani Y, Ishikawa Y, Baez-Navarro X, Radonic T, Blaauwgeers H, Borczuk AC, Noguchi M (August 2021). "Elastin in pulmonary pathology: relevance in tumours with a lepidic or papillary appearance. A comprehensive understanding from a morphological viewpoint". Histopathology. 80 (3): 457–467. doi: 10.1111/his.14537 . PMC   9293161 . PMID   34355407.
  4. ↑ Robertson IB, Horiguchi M, Zilberberg L, Dabovic B, Hadjiolova K, Rifkin DB (September 2015). "Latent TGF-β-binding proteins". Matrix Biology. 47: 44–53. doi:10.1016/j.matbio.2015.05.005. PMC   4844006 . PMID   25960419.
  5. ↑ Pilecki B, Holm AT, Schlosser A, Moeller JB, Wohl AP, Zuk AV, et al. (January 2016). "Characterization of Microfibrillar-associated Protein 4 (MFAP4) as a Tropoelastin- and Fibrillin-binding Protein Involved in Elastic Fiber Formation". The Journal of Biological Chemistry. 291 (3): 1103–14. doi: 10.1074/jbc.M115.681775 . PMC   4714194 . PMID   26601954.
  6. ↑ Dabovic B, Chen Y, Choi J, Vassallo M, Dietz HC, Ramirez F, et al. (April 2009). "Dual functions for LTBP in lung development: LTBP-4 independently modulates elastogenesis and TGF-beta activity". Journal of Cellular Physiology. 219 (1): 14–22. doi:10.1002/jcp.21643. PMC   2719250 . PMID   19016471.
  7. ↑ Nakamura T, Lozano PR, Ikeda Y, Iwanaga Y, Hinek A, Minamisawa S, et al. (January 2002). "Fibulin-5/DANCE is essential for elastogenesis in vivo". Nature. 415 (6868): 171–5. doi:10.1038/415171a. PMID   11805835. S2CID   4343659.
  8. ↑ Yeo GC, Keeley FW, Weiss AS (September 2011). "Coacervation of tropoelastin". Advances in Colloid and Interface Science. 167 (1–2): 94–103. doi:10.1016/j.cis.2010.10.003. PMID   21081222.
  9. ↑ Wu WJ, Vrhovski B, Weiss AS (July 1999). "Glycosaminoglycans mediate the coacervation of human tropoelastin through dominant charge interactions involving lysine side chains". The Journal of Biological Chemistry. 274 (31): 21719–24. doi: 10.1074/jbc.274.31.21719 . PMID   10419484.
  10. ↑ Tu Y, Weiss AS (July 2008). "Glycosaminoglycan-mediated coacervation of tropoelastin abolishes the critical concentration, accelerates coacervate formation, and facilitates spherule fusion: implications for tropoelastin microassembly". Biomacromolecules. 9 (7): 1739–44. doi:10.1021/bm7013153. PMID   18547105.
  11. ↑ Lucero HA, Kagan HM (October 2006). "Lysyl oxidase: an oxidative enzyme and effector of cell function". Cellular and Molecular Life Sciences. 63 (19–20): 2304–16. doi:10.1007/s00018-006-6149-9. PMID   16909208. S2CID   31863161.
  12. ↑ Schräder CU, Heinz A, Majovsky P, Karaman Mayack B, Brinckmann J, Sippl W, Schmelzer CE (September 2018). "Elastin is heterogeneously cross-linked". The Journal of Biological Chemistry. 293 (39): 15107–15119. doi: 10.1074/jbc.RA118.004322 . PMC   6166741 . PMID   30108173.
  13. ↑ Liu X, Zhao Y, Gao J, Pawlyk B, Starcher B, Spencer JA, et al. (February 2004). "Elastic fiber homeostasis requires lysyl oxidase-like 1 protein". Nature Genetics. 36 (2): 178–82. doi: 10.1038/ng1297 . PMID   14745449.
  14. ↑ Gheduzzi D, Guerra D, Bochicchio B, Pepe A, Tamburro AM, Quaglino D, et al. (February 2005). "Heparan sulphate interacts with tropoelastin, with some tropoelastin peptides and is present in human dermis elastic fibers". Matrix Biology. 24 (1): 15–25. doi:10.1016/j.matbio.2004.12.001. PMID   15748998.
  15. ↑ Ackerman AB, Böer A, Bennin B, Gottlieb GJ (January 2005). Histologic Diagnosis of Inflammatory Skin Diseases An Algorithmic Method Based on Pattern Analysis: Embryologic, Histologic, and Anatomic Aspects: Elastic Fibers (Third ed.). Ardor Scribendi. p. 522. ISBN   9781893357259. Archived from the original on June 20, 2018. Retrieved December 28, 2016. Elastic fibers are absent from scarring processes such as scars, keloids, and dermatofibromas
  16. ↑ "Connective Tissue". Archived from the original on November 7, 2008.
  17. 1 2 Wright B. "Elastosis". DermNet NZ.
  18. 1 2 3 Hosen MJ, Lamoen A, De Paepe A, Vanakker OM (2012). "Histopathology of pseudoxanthoma elasticum and related disorders: histological hallmarks and diagnostic clues". Scientifica. 2012: 598262. doi: 10.6064/2012/598262 . PMC   3820553 . PMID   24278718.
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