Elastic fibers
Encyclopedia
Elastic fibres are bundles of protein
s (elastin
) found in extracellular matrix
of connective tissue
and produced by fibroblast
s and smooth muscle
cells in arteries
. These fibers can stretch up to 1.5 times their length, and snap back to their original length when relaxed. Elastic fibers include elastin, elaunin
and oxytalan
.
Elastic tissue is classified as "connective tissue proper".
The elastic fibre is formed from the elastic microfibril
(consisting of numerous proteins such as microfibrillar-associated glycoproteins, fibrillin
, fibullin, and the elastin receptor) and amorphous elastin
.
The microfibril scaffolds and organizes the deposition of amorphous elastin. Amorphous elastin forms from monomer
s of soluble tropoelastin
which is insolubilized and crosslinked into amorphous elastin by lysyl oxidase
. Lysyl oxidase reacts with specific lysine
residues and by oxidative deamination
generates reactive aldehyde
s and allysine
.
These reactive aldehydes and allysines can react with lysine and other allysine residues to crosslink and form desmosine
, isodesmosine
, and a number of other polyfunctional crosslinks that join surrounding elastin molecules to build an elastin matrix and elastic fiber. These unique crosslinks are responsible for elastin's elasticity.
, veins, connective tissue proper, elastic cartilage
, periodontal ligament
, fetal tissue and other structures.
, 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.
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 defect
s are associated with alterations in the great arteries
, arteries, and arterioles with alterations in the elastic matrix.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s (elastin
Elastin
Elastin is a protein in connective tissue that is elastic and allows 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...
) found in extracellular matrix
Extracellular matrix
In biology, the extracellular matrix is the extracellular part of animal tissue that usually provides structural support to the animal cells in addition to performing various other important functions. The extracellular matrix is the defining feature of connective tissue in animals.Extracellular...
of connective tissue
Connective tissue
"Connective tissue" is a fibrous tissue. It is one of the four traditional classes of tissues . Connective Tissue is found throughout the body.In fact the whole framework of the skeleton and the different specialized connective tissues from the crown of the head to the toes determine the form of...
and produced by fibroblast
Fibroblast
A fibroblast is a type of cell that synthesizes the extracellular matrix and collagen, the structural framework for animal tissues, and plays a critical role in wound healing...
s and smooth muscle
Smooth muscle
Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...
cells in arteries
Artery
Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....
. These fibers can stretch up to 1.5 times their length, and snap back to their original length when relaxed. Elastic fibers include elastin, elaunin
Elaunin
Elaunin is a component of elastic fibers formed from a deposition of elastin between oxytalan fibers. It is found in the periodontal ligament and in the connective tissue of the dermis, particularly in association with sweat glands...
and oxytalan
Oxytalan
Oxytalan fibres are a component of the extracellular matrix. They were first described by Fullmer & Lillie in periodontal membranes. On light microscope examination, these fibres may be distinguished from mature elastic fibers by their failure to stain with aldehyde fuchsin solutions, unless they...
.
Elastic tissue is classified as "connective tissue proper".
The elastic fibre is formed from the elastic microfibril
Microfibril
The 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, examples are hair and sperm tail. Its most frequently observed structural pattern is 9+2...
(consisting of numerous proteins such as microfibrillar-associated glycoproteins, fibrillin
Fibrillin
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 scaffoldfor deposition of elastin.It...
, fibullin, and the elastin receptor) and amorphous elastin
Elastin
Elastin is a protein in connective tissue that is elastic and allows 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...
.
The microfibril scaffolds and organizes the deposition of amorphous elastin. Amorphous elastin forms from monomer
Monomer
A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...
s of soluble tropoelastin
Tropoelastin
Tropoelastin is a water-soluble molecule with a molecular weight of approximately 72,000 daltons. Multiple tropoelastin molecules covalently bind together with crosslinks to form the protein elastin that is very prevalent in the body. There is only one gene for this molecule and so only one protein...
which is insolubilized and crosslinked into amorphous elastin by lysyl oxidase
Lysyl oxidase
Lysyl oxidase also known as protein-lysine 6-oxidase is a protein that, in humans, is encoded by the LOX gene. Its inhibition can cause lathyrism, but, at the same time, its upregulation by tumor cells may promote metastasis of the existing tumor, causing it to become malignant and cancerous.-...
. Lysyl oxidase reacts with specific lysine
Lysine
Lysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....
residues and by oxidative deamination
Oxidative deamination
Oxidative deamination is a form of deamination that generates oxoacids in the liver.The presence of nitrous acid can cause transition mutations, by converting cytosine to uracil. Primarily occurs in the liver and kidneys.-In Urea cycle:...
generates reactive aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
s and allysine
Allysine
Allysine is a derivative of Lysine, used in the production of elastin and collagen. It is produced by the actions of the enzyme lysyl oxidase in the extracellular matrix and is essential in the crosslink formation that stabilizes collagen and elastin....
.
These reactive aldehydes and allysines can react with lysine and other allysine residues to crosslink and form desmosine
Desmosine
A desmosine cross-link is formed from three allysyl side chains plus one unaltered lysyl side chain from the same or neighbouring polypeptides.It is found in elastin. Desmosine causes a yellow color....
, isodesmosine
Isodesmosine
Isodesmosine is a lysine derivative found in elastin....
, and a number of other polyfunctional crosslinks that join surrounding elastin molecules to build an elastin matrix and elastic fiber. These unique crosslinks are responsible for elastin's elasticity.
Distribution
Elastic fibers are found in the skin, lungs, arteriesArtery
Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....
, veins, connective tissue proper, elastic cartilage
Elastic cartilage
Elastic cartilage or yellow cartilage is a type of cartilage present in the outer ear, larynx, and epiglottis. It contains elastic fiber networks and collagen fibers. The principal protein is elastin....
, periodontal ligament
Periodontal ligament
The periodontal fiber or periodontal ligament, commonly abbreviated as the PDL, is a group of specialized connective tissue fibers that essentially attach a tooth to the alveolar bone within which it sits...
, fetal tissue and other structures.
Histology
Elastic fibers stain well with aldehyde fuchsin, orceinOrcein
Orcein, also archil, orchil, lacmus, Citrus Red 2, and C.I. Natural Red 28, are names for dyes extracted from several species of lichen, commonly known as "orchella weeds", found in various parts of the world. A major source is the archil lichen, Roccella tinctoria. Orcinol is extracted from such...
, and Weigert's elastic stain
Weigert's elastic stain
Weigert's elastic stain is a combination of stains used in histology which is useful in identifying elastic fibers. Often orcein or a combination of resorcinol and fuchsine are used for staining. For counterstaining cell nuclei nuclear fast red or hematoxylin is also used. After applying elastic...
in histological
Histology
Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...
sections.
The permanganate-bisulfite-toluidine blue reaction is a highly selective and sensitive method for demonstrating elastic fibers under polarizing optics. The induced birefringence
Birefringence
Birefringence, or double refraction, is the decomposition of a ray of light into two rays when it passes through certain anisotropic materials, such as crystals of calcite or boron nitride. The effect was first described by the Danish scientist Rasmus Bartholin in 1669, who saw it in calcite...
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 collagenCollagen
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...
fibers.
Cutis laxa
Cutis laxa
Cutis laxa is a group of rare connective tissue disorders in which the skin becomes inelastic and hangs loosely in folds.-Causes:In most cases, cutis laxa is inherited...
and Williams syndrome
Williams syndrome
Williams syndrome is a rare neurodevelopmental disorder characterized by a distinctive, "elfin" facial appearance, along with a low nasal bridge; an unusually cheerful demeanor and ease with strangers; developmental delay coupled with strong language skills; and cardiovascular problems, such as...
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
Elastase
In molecular biology, elastase is an enzyme from the class of proteases that break down proteins.- Forms and classification:There exist eight human genes for elastase:Bacterial forms: Organisms such as P...
, a degrading protein released by neutrophils during the inflammatory response. This leads most often to emphysema
Emphysema
Emphysema is a long-term, progressive disease of the lungs that primarily causes shortness of breath. In people with emphysema, the tissues necessary to support the physical shape and function of the lungs are destroyed. It is included in a group of diseases called chronic obstructive pulmonary...
and liver disease in affected individuals.
Buschke-Ollendorff syndrome
Buschke-Ollendorff syndrome
Buschke–Ollendorff syndrome, also known as Dermatofibrosis lenticularis disseminata, is a rare genetic disorder associated with LEMD3. It is believed to be inherited in an autosomal dominant manner....
, Menkes disease
Menkes disease
Menkes disease , also called Menkes syndrome, copper transport disease, steely hair disease, kinky hair disease, or Menkes kinky hair syndrome, is a disorder that affects copper levels in the body, leading to copper deficiency...
, pseudoxanthoma elasticum
Pseudoxanthoma elasticum
Pseudoxanthoma elasticum , also known as Grönblad–Strandberg syndrome, is a genetic disease that causes fragmentation and mineralization of elastic fibers in some tissues. The most common problems arise in the skin and eyes, and later in blood vessels in the form of premature atherosclerosis...
, and Marfan's syndrome have been associated with defects in copper metabolism and lysyl oxidase or defects in the microfibril (defects in fibrillin
Fibrillin
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 scaffoldfor deposition of elastin.It...
, or fibullin for example).
Hurler disease, a lysosomal storage disease, is associated with an altered elastic matrix.
Hypertension
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
and some congenital heart defect
Congenital heart defect
A congenital heart defect is a defect in the structure of the heart and great vessels which is present at birth. Many types of heart defects exist, most of which either obstruct blood flow in the heart or vessels near it, or cause blood to flow through the heart in an abnormal pattern. Other...
s are associated with alterations in the great arteries
Great arteries
Great arteries is a term used to refer collectively to the primary arteries of the heart, which include:* Pulmonary artery: the vessel that carries oxygen-depleted blood from the right ventricle to the lungs....
, arteries, and arterioles with alterations in the elastic matrix.