How is elastin obtained?

Before the advent of biotechnologies, the only way to obtain elastin for scientific or cosmetic purposes was to extract it directly from animal tissues rich in elastic fibres. These tissues, such as the aorta or the skin of cattle and pigs, constitute significant natural sources of tropoelastin – the soluble, immature form of elastin secreted before its cross-linking in the extracellular matrix – and elastin. The most commonly used tissues are from foetuses or newborn animals, periods during which elastin synthesis is at its highest. In adult animals, production is low.

Mature elastin, being a highly cross-linked and virtually insoluble protein, its direct extraction is challenging yet feasible. Once tissues are harvested—often obtained from abattoirs—they are finely minced and then incubated in a culture medium containing enzyme inhibitors and antibiotics. After washing and homogenising in an acidic solution, the soluble fractions are isolated by acid extraction followed by separation with organic solvents (propanol and butanol). The elastin-containing phase is subsequently concentrated, precipitated with acetone, centrifuged, dried and finally lyophilised to yield a pure powder. The purity of the elastin is typically verified by SDS-PAGE electrophoresis and by amino acid analysis.

Besides conventional mammalian sources, some studies have shown that elastin can also be extracted from fish. In this case, the tissues are first analysed to confirm the presence of elastin and to determine the composition of specific amino acids (desmosine and isodesmosine). For commercial production, the tissues are thawed, defatted, boiled to remove collagen, and then hydrolysed by proteolytic enzymes. The mixture is filtered and spray-dried to obtain soluble elastin peptides. The marine elastin is particularly used in the development of dietary supplements.

These techniques currently pose ethical and environmental constraints. This is why the cosmetic and biomedical industries are now moving towards more sustainable biotechnological approaches, enabling the production of recombinant elastin without resorting to animal tissues.

Faced with the ethical and technical constraints of extracting elastin from animal tissues, research has turned towards more sustainable alternatives: recombinant elastin in the form of peptides. These biopolymers are produced by genetic engineering, most often in bacteria such as Escherichia coli. The objective is to reproduce the repetitive sequence of human elastin while avoiding the use of animal tissues. Synthesis begins with designing a gene encoding elastin that reproduces its sequence. Once the gene is synthesised and inserted into a plasmid—a circular DNA molecule serving as a vector—it is introduced into bacteria E. coli to produce the protein via recombinant overexpression.

After induction with IPTG (isopropyl-β-D-thiogalactopyranoside), a lactose metabolite utilised in molecular biology, the bacteria begin producing elastin peptides, which are then extracted from the cells. The purification step relies on the thermosensitive properties of these peptides: above a threshold temperature, they become insoluble and precipitate. The purification is carried out as follows:

• Cell lysis and removal of insoluble debris at a temperature below the threshold temperature.

• Heating the supernatant above the threshold temperature, causing the selective precipitation of elastin peptides.

• Cooling and redissolution of the precipitate in a cold buffer, followed by a further centrifugation to remove impurities.

This method, requiring neither organic solvents nor animal tissue, allows the production of proteins that replicate the mechanical and hydrating properties of natural elastin, while minimising environmental impact.

Note : This section, which describes the natural synthesis of elastin in the skin, is provided for informational purposes only. It is not a method used by the cosmetics industry to produce elastin.

Elastin fibres form a complex network in the dermis, the intermediate layer of the skin. The synthesis of elastic fibres, or elastogenesis, is a highly organised process, depending on the availability, the assembly and cross-linking of tropoelastin, the precursor of elastin. Fibroblasts, which are also responsible for the synthesis of collagen and hyaluronic acid, are the cells that secrete tropoelastin. This is then oxidised by enzymes of the lysyl oxidase family, before being cross-linked to form stable bundles. With the aid of the glycoprotein fibulin-5, these tropoelastin bundles are deposited onto microfibrils, which serve as support, ultimately forming a functional elastin fibre.

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• NAKABA N. & al. Properties of soluble elastin peptide from bulbus arteriosus in fish species. Fisheries Science (2006).

• MECHAM R. P. & al. Methods in elastic tissue biology: Elastin isolation and purification. Methods (2008).

• CHILKOTI A. & al. Elastin-like polypeptides for biomedical applications. Annual Review of Biomedical Engineering (2020).

• CHOLI-PAPADOPOULOU T. & al. De novo synthesis of elastin-like polypeptides (ELPs): An applied overview on the current experimental techniques. ACS Biomaterials Science & Engineering (2021).

• DANIELS R. & al. Clinical relevance of elastin in the structure and function of skin. Aesthetic Surgery Journal Open Forum (2021).