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Clinical Outcomes of Elastin Fibre Defects

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Clinical Outcomes of Elastin Fibre Defects ytology & f C H i o s l t a o n l o r g u y o Hassan et al., J Cytol Histol 2013, 4:1 J Journal of Cytology & Histology DOI: 10.4172/2157-7099.1000166 ISSN: 2157-7099 CommentaryResearch Article OpenOpen Access Access Clinical Outcomes of Elastin Fibre Defects Ashfaq Ul Hassan1*, Ghulam Hassan2, Zahida Rasool3 and Shabinul Hassan3 1Anatomy Department, SKIMS Medical College, Bemina, Srinagar, Kashmir, India 2Department of Anatomy, Al Qassim University, Saudi Arabia 3Islamic University of Science and Technology, Kashmir, India Abstract Elastic fibres are a major class of extracellular matrix fibres that are abundant in dynamic connective tissues such as arteries, lungs, skin and ligaments. Their structural role is to endow tissues with elastic recoil and resilience. They also act as an important adhesion template for cells, and they regulate growth factor availability. Mutations in major structural components of elastic fibres, especially elastin, fibrillins and fibulin-5, cause severe, often life-threatening, heritable connective tissue diseases such as Marfan syndrome, Menkes Syndrome, Cutis laxa. Elastic-fibre function is also frequently compromised in damaged or aged elastic tissues. The ability to regenerate or engineer elastic fibres and tissues remains a significant challenge, requiring improved understanding of the molecular and cellular basis of elastic-fibre biology and pathology. The aim of the article is to present in brief the structural details of elastin fibres, the defects and pleiotrophic effects as a result of damage and various clinical conditions associated with defects in elastin fibres ranging from rare pediatric syndromes to common entities like hypertension. Keywords: Marfans syndrome (MFS); Menkes disease; Cutis laxa group of diseases due to mutations in several of the genes encoding (CL); Fibrillin; Lysyl oxidase (LO); Homocystenemia microfibrillar proteins. Introduction Elastinopathies are diseases due to mutations in the elastin gene. Together, both fibrillinopathies and elastinopathies can be considered Elastic fibers or yellow fibers are bundles of proteins (elastin) found as primary disorders of elastic fibers and as due to mutations in genes in connective tissue and produced by fibroblasts and smooth muscle encoding proteins that are an integral part of elastic fibers. cells in arteries. Elastic fibers include elastin, elaunin and oxytalan. Elastic fibers stain well with aldehyde fuchsin, orcein, and Weigert’s Discussion elastic stain in histological sections. Marfan Syndrome (MFS) is a spectrum disorder caused by a The permanganate-bisulfite-toluidine blue reaction is a highly heritable genetic defect of connective tissue that has an autosomal selective and sensitive method for demonstrating elastic fibers under dominant mode of transmission. First described by the French polarizing optics. Resilience and elastic recoil are properties conferred physician Bernard JA Marfan in 1896, the defect has been isolated to on all vertebrate elastic tissues by elastic fibers [1,2]. The amorphous the FBN1 gene on chromosome 15, which codes for the connective component is made up of insoluble elastin, a highly cross-linked tissue protein fibrillin.1, Abnormalities in fibrillin protein cause a and hydrophobic protein assembled from soluble precursor proteins myriad of distinct clinical problems, of which the musculoskeletal, called “tropoelastins.” The microfibrillar component of elastic fibers cardiac, and ocular system problems predominate. Connective tissue is composed of several glycoproteins, of which the best known are provides substance and support to tendons, ligaments, blood vessel the fibrillins (fibrillin-1 and fibrillin-2). Once synthesized in early walls, cartilage, heart valves and many other structures. In the Marfan development, elastic fibers undergo very little turnover in normal syndrome, the chemical makeup of the connective tissue isn’t normal. adult tissues, with the notable exception of the uterus. The elastic fibers As a result, many of these structures aren’t as stiff as they should be. deposited in one’s aorta as a young child, for example, are the same Marfan syndrome is caused by a fault in a gene on chromosome elastic fibers that one usually will die with. In a variety of elastic-tissue 15, which codes for the glycoprotein fibrillin. This is known as the diseases, however, new elastic-fiber synthesis in adult tissue results in fibrillin-1 gene or FBN1 for short. Fibrillin-1 is encoded by FBN1 the aberrant accumulation of dysfunctional elastic fibers. Examples on human chromosome 15q21 and fibrillin-2 is encoded by FBN2 of such common disorders involving aberrant elastic-fiber assembly on 5q23. Fibrillin is a major building-block of microfibrils, which include emphysema, hypertension and aortic aneurysms. The various defects in the Expression, Structure, Assembly, Degradation of the constituent structural glycoprotein (or glycoproteins) of micro fibrils *Corresponding author: Dr. Ashfaq Ul Hassan, MBBS, MS, Lecturer, Anatomy may be implicated in the causation of diseases associated with elastic Department, SKIMS Medical College, Bemina, Srinagar, Kashmir, India, E-mail: fibres. It has been seen that a protein called fibulin-5, or DANCE [email protected] (Developing Arteries and Neural Crest EGF-like) plays a substantial Received December 03, 2012; Accepted January 30, 2013; Published February role in the generation and organization of elastic fibers in mice. 01, 2013 The mutations in fibrillin genes result in disorders affecting Citation: Hassan AU, Hassan G, Rasool Z, Hassan S (2013) Clinical Outcomes microfibril assembly are referred to as “fibrillinopathies.” Although no of Elastin Fibre Defects. J Cytol Histol 4: 166. doi:10.4172/2157-7099.1000166 mutations have yet been found in genes encoding other microfibrillar Copyright: © 2013 Hassan AU, et al. This is an open-access article distributed proteins such as MFAPs (Microfibril-Associated Proteins), it’s entirely under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the possible and indeed very likely that the fibrillinopathies will define a original author and source are credited. J Cytol Histol ISSN: 2157-7099 JCH, an open access journal Volume 4 • Issue 1 • 1000166 Citation: Hassan AU, Hassan G, Rasool Z, Hassan S (2013) Clinical Outcomes of Elastin Fibre Defects. J Cytol Histol 4: 166. doi:10.4172/2157- 7099.1000166 Page 2 of 3 constitute the structural components of the suspensory ligament Ocular findings include myopia, cataracts, retinal detachment, and of the lens and serve as substrates for elastin in the aorta and other superior dislocation of the lens. connective tissues throughout the body. Classical Marfan syndrome is The skeleton of patients with MFS typically displays multiple associated with mutation in fibrillin-1, an important component of the deformities including arachnodactyly (i.e, abnormally long and thin elastic microfibril. Fibrillin-1 is a 350 kD glycoprotein, synthesized as digits), dolichostenomelia (i.e, long limbs relative to trunk length), a 375 kD precursor that is processed and secreted into the extracellular pectus deformities (i.e, pectus excavatum and pectus carinatum), and matrix (ECM). It polymerises to form microfibrils and helps to stabilize thoracolumbar scoliosis. latent transforming growth factor -binding proteins (LTBPs) in the ECM. LTBPs hold Transforming Growth Factor-(TGF) in an inactive Cutis Laxa (CL) comprises a rare and heterogeneous group of state. A failure of the interaction between fibrillin-1 and LTBPs may disorders characterized by lax inelastic skin with or without internal result in excess TGF signaling. Most fibrillin-1 mutations are missense, manifestations. The skin of CL patients tends to hang in loose folds, suggesting a dominant-negative effect on microfibrillar assembly. The giving an appearance of premature ageing. In contrast to Ehlers–Danlos defect renders the tissue compliant than it would be in a non-Marfan syndrome, the skin in CL is neither hyperelastic nor fragile; wound person. Since there is less tension at either end of the long bones, healing is normal and there is no joint hypermobility. they keep growing while the individual does, becoming abnormally Gastrointestinal tract: Diverticula of the small and large bowels elongated. Weak connective tissue also explains the ‘hypermobility of may be present; rectal prolapse may occur. joints. Seen in Marfans syndrome is Synthesis of decreased amount of fibrillin Pulmonary: Bronchiectasis, emphysema, and cor pulmonale may be present. In acquired CL, pulmonary involvement typically manifests Synthesis and secretion of a normal amount of fibrillin but protein as emphysema due to the loss of the elastin support network and is the functions less efficiently than control cells. most common cause of death in these patients. Synthesis and secretion of normal amounts of fibrillin but the Cardiovascular: Cardiomegaly, congestive heart failure, murmurs, protein is poorly incorporated into extracellular matrix. cor pulmonale, and aortic aneurysms may occur. Severe aortic disease The most conspicuous ultrastructural defects were the may be present as a result of aortic vessel medial degeneration and extracellular elastin deposits lacking microfibrillar elements. Formation of abrupt transverse tears in thick and compact elastic lamellae the local breaking up of smooth muscle cell–elastic lamella Skeletal: Dislocation
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