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Elastin

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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 vertebrates and used in places where mechanical energy is required to be stored. In humans, elastin is encoded by the ELN gene.[1]

Function

This gene encodes a protein that is one of the two components of elastic fibers. The encoded protein is rich in hydrophobic amino acids such as glycine and proline, which form mobile hydrophobic regions bounded by crosslinks between lysine residues.[2] Multiple transcript variants encoding different isoforms have been found for this gene.[2] The other name for elastin is tropoelastin.[3] The characterization of disorder is consistent with an entropy-driven mechanism of elastic recoil. It is concluded that conformational disorder is a constitutive feature of elastin structure and function.[4]

Clinical significance

Deletions and mutations in this gene are associated with supravalvular aortic stenosis (SVAS) and autosomal dominant cutis laxa.[2] Other associated defects in elastin include Marfan's Syndrome and emphysema caused by α1-antitrypsin deficiency.

Composition

Elastic fiber is composed of the protein fibrillin and elastin made of simple amino acids such as glycine, valine, alanine, and proline.[5] The total elastin ranges from 58 to 75% of the weight of the dry defatted artery in normal canine arteries.[6] Comparison between fresh and digested tissues shows that, at 35% strain, a minimum of 48% of the arterial load is carried by elastin, and a minimum of 43% of the change in stiffness of arterial tissue is due to the change in elastin stiffness.[7] Elastin is made by linking many soluble tropoelastin protein molecules, in a reaction catalyzed by lysyl hydroxylase, to make a massive insoluble, durable cross-linked array. The amino acid responsible for these cross-links is lysine. Tropoelastin is a specialized protein with a molecular weight of 64 to 66 kDa, and an irregular or random coil conformation made up of 830 amino acids.

Desmosine and isodesmosine are types of links for the tropoelastin molecules.

Tissue distribution

Elastin serves an important function in arteries as a medium for pressure wave propagation to help blood flow and is particularly abundant in large elastic blood vessels such as the aorta. Elastin is also very important in the lungs, elastic ligaments, the skin, and the bladder, elastic cartilage. It is present in all vertebrates above the jawless fish.[8]

Use in biomedical engineering research

The University of Pittsburgh Marketing Center and the Office of Public Affairs put a story by Morgan E. Kelly online (found at the university's home page) on Monday, January 31, 2011, stating that researchers have grown arteries (in a remarkably simple process that is easier than previous methods- using either virally-induced gene alteration, or transforming growth factor, or rolling cell sheets into tubes) that exhibit the elasticity of natural blood vessels at the highest levels reported. This is a development that could overcome a major barrier to creating living-tissue replacements for damaged arteries, according to the team's report in the Proceedings of the National Academy of Sciences. The team, including postdoctoral researcher Kee-Won Lee and Pitt School of Medicine professor Donna Stolz, was led by lead author Yadong Wang, a professor of bioengineering in Pitt's Swanson School of Engineering. They used smooth muscle cells from 4-year-old adult baboons (equivalent in age to 20-year-old humans) that were transferred to degradable honey comb-like rubber tube. The tubes were then transferred to a bioreactor for culturing, where a nutrient-rich solution was pumped through the tubes under conditions mimicking the human circulatory system- the pump produced a regular pulse, and the fluid was kept at 98.6 degrees Fahrenheit . As the muscle cells grew, they produced proteins that fused to form the vessel. Mechanical tests revealed that the cultured artery could withstand a burst pressure between 200 and 300 millimeters of mercury (mmHg). Healthy human blood pressure is between 120 and 80 mmHg. However, native arteries can withstand pressures ten times that of their constructs and contain up to 15 times more elastin. To quantify the elastin present in the engineered vessel, the researchers used two methods: a Fastin Elastin assay (Biocolor, UK), which quantifies elastin by binding the protein with a dye, and a desmosine ELISA, which quantifies the amount of elastin cross-linking present and is indicative or mature elastin, unlike the Fastin Elastin assay. The desmosine ELISA revealed that the engineered tissues produced 19% of the mature elastin present in native arteries positive controls (common carotid arteries from 3-year-old male baboons and 3.5-year-old female wild type pigs. The arteries contained only 10% collagen, which is much lower than native arteries or even tissue engineered arteries made by other groups.[9]
Thus elastin is a natural biomedical material of great potential. Being endowed with the special crosslinking and hydrophobic structure, elastin retains many good properties such as good elasticity, ductibility, biocompatibility, biodegradability and so on. Nowadays, elastin as a material, which is gradually attracting people' s attention in the biomedical materials field, has been used as tissue engineering scaffolds, derma substitutes and other biomedical materials.[10]

See also

References

  1. ^ Curran ME, Atkinson DL, Ewart AK, Morris CA, Leppert MF, Keating MT (1993). "The elastin gene is disrupted by a translocation associated with supravalvular aortic stenosis". Cell. 73 (1): 159–68. doi:10.1016/0092-8674(93)90168-P. PMID 8096434. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  2. ^ a b c "Entrez Gene: elastin".
  3. ^ "Elastin (ELN)". Retrieved 31 October 2011.
  4. ^ Lisa D Muiznieks, Anthony S Weiss and Fred W Keeley (2010). "Structural disorder and dynamics of elastin". Biochem Cell Biol. 88 (2): 239–50. doi:10.1139/o09-161. PMID 20453927. {{cite journal}}: Cite has empty unknown parameter: |1= (help)
  5. ^ Kielty CM, Sherratt MJ, Shuttleworth CA (2002). "Elastic fibres". J. Cell. Sci. 115 (Pt 14): 2817–28. PMID 12082143. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  6. ^ Grace M. Fischer M.D. Josep G. Llaurado M.D. (1966). "Collagen and Elastin Content in Canine Arteries Selected from Functionally Different Vascular Beds". Circulation Research. 19 (2): 394–399. PMID 5914851. {{cite journal}}: Unknown parameter |month= ignored (help)
  7. ^ Lammers SR, Kao PH, Qi HJ, Hunter K, Lanning C, Albietz J, Hofmeister S, Mecham R, Stenmark KR, Shandas R. (2008). "Changes in the structure-function relationship of elastin and its impact on the proximal pulmonary arterial mechanics of hypertensive calves". Am J Physiol Heart Circ Physiol. 295 (4): H1451-9. doi:10.1152/ajpheart.00127.2008. PMID 18660454. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  8. ^ Sage EH, Gray WR (1977). "Evolution of elastin structure". Adv. Exp. Med. Biol. 79: 291–312. PMID 868643.
  9. ^ Lee, KW, Stolz, DB, Wang, Y. (2011). "Substantial expression of mature elastin in arterial constructs". Proc Natl Acad Sci USA. 108 (7): 2705–10. doi:10.1073/pnas.1017834108. PMC 3041142. PMID 21282618. {{cite journal}}: Cite has empty unknown parameter: |1= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  10. ^ Decai Chang, Xiaoli Wang, Xin Hou, Kangde Yao (2008). "Application of elastin in biomedical materials". Sheng Wu Yi Xue Gong Cheng Xue Za Zhi. 25 (6): 1454–7. PMID 19166230. {{cite journal}}: Cite has empty unknown parameter: |1= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)

Further reading

External links

This article incorporates text from the United States National Library of Medicine, which is in the public domain.

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