Abstract
Elastic fibres play a key role in bodily functions where fatigue resistance and elastic recovery are necessary while regulating phenotype, proliferation and migration in cells. While in vivo elastic fibres are created at a late foetal stage, a major obstacle in the development of engineered tissue is that human vascular smooth muscle cells (hVSMCs), one of the principal elastogenic cells, are unable to spontaneously promote elastogenesis in vitro. Therefore, the overall aim of this study was to activate elastogenesis in vitro by hVSMCs seeded in fibrin, collagen, glycosaminoglycan (FCG) scaffolds, following the addition of recombinant human tropoelastin. This combination of scaffold, tropoelastin and cells induced the deposition of elastin and formation of lamellar maturing elastic fibres, similar to those found in skin, blood vessels and heart valves. Furthermore, higher numbers of maturing branched elastic fibres were synthesised when a higher cell density was used and by drop-loading tropoelastin onto cell-seeded FCG scaffolds prior to adding growth medium. The addition of tropoelastin showed no effect on cell proliferation or mechanical properties of the scaffold which remained dimensionally stable throughout. With these results, we have established a natural biomaterial scaffold that can undergo controlled elastogenesis on demand, suitable for tissue engineering applications.
Highlights
Fatigue resistance and elastic recovery are critically important me chanical properties for the correct functioning of the heart, skin, lungs and other dynamic connective tissues within the human body
We have proven that a mature extracellular matrix (ECM) increased significantly the deposi tion of elastin and maturing elastic fibres in human vascular smooth muscle cells (hVSMCs) seeded on glass slides
As there is no significant production of elastin or associated proteins by cells, we have demonstrated that elastogenesis was induced solely by adding tropoelastin on hVSMCs
Summary
Fatigue resistance and elastic recovery are critically important me chanical properties for the correct functioning of the heart, skin, lungs and other dynamic connective tissues within the human body. Elastin is one of the most abundant proteins found in vertebrates, providing resistance to permanent tissue deformation [2] and delivering biochemical cues that regulate cell migration, preventing proliferative diseases in heart and blood vessels [3,4]. In a mature elastic fibre, approximately 90% of the volume is composed of elastin that is surrounded by a fibrillin-rich microfibrillar mesh [5]. The content, alignment and morphology of these mature elastic fibres is dictated by functional demands and the cells that deposit and orientate the fibrillin-rich microfibrils. Blood vessels have a 30% elastin content, and the elastic fibres can be observed as concentric fenestrated lamellae required for stress propa gation during each cardiac cycle. Skin, which contains approximately 2% of elastin [9], has elastic fibres that are thick and horizontally arranged in the dermis, whereas in the papillary
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