The rising incidence of cardiovascular disease has increased the demand for small diameter (<6 mm) synthetic vascular grafts for use in bypass surgery. Clinically available synthetic grafts (polyethylene terephthalate and expanded polytetrafluorethylene) are incredibly strong, but also highly hydrophobic and inelastic, leading to high rates of failure when used for small diameter bypass. The poor clinical outcomes of commercial synthetic grafts in this setting have driven significant research in search of new materials that retain favourable mechanical properties but offer improved biocompatibility. Over the last several decades, silk fibroin derived from Bombyx mori silkworms has emerged as a promising biomaterial for use in vascular applications. Progress has been driven by advances in silk manufacturing practices which have allowed unprecedented control over silk strength, architecture, and the ensuing biological response. Silk can now be manufactured to mimic the mechanical properties of native arteries, rapidly recover the native endothelial cell layer lining vessels, and direct positive vascular remodelling through the regulation of local inflammatory responses. This review summarises the advances in silk purification, processing and functionalisation which have allowed the production of robust vascular grafts with promise for future clinical application.
Long Terminal Repeat (LTR) retrotransposons replicate through “copy and paste” mechanisms mediated by reverse transcription in virus-like particles (VLPs) and integration in the nucleus (see article from Lee and Martienssen, pp. 2241–2251). VLP DNA-sequencing reveals complementary DNA (cDNA) replication intermediates from active retrotransposons. Instead of functional linear intermediates that integrate in the nucleus, the Arabidopsis retroelement SISYPHUS lacks features important for nuclear import, and instead accumulates circular cDNA from futile autointegration within the VLP. In Greek mythology, Sisyphus was condemned to the futile task of rolling a huge boulder uphill eternally. Image created and provided Seung Cho Lee, Evan Ernst, and Robert A. Martienssen.
Bioengineering silk into blood vessels
Yuen Ting Lam, Richard P. Tan, Praveesuda L. Michael, Kieran Lau, Nianji Yang, Jelena Rnjak-Kovacina, Steven G. Wise; Bioengineering silk into blood vessels. Biochem Soc Trans 1 November 2021; 49 (5): 2271–2286. doi: https://doi.org/10.1042/BST20210359
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