Abstract
Silk fibroin (SF) is an eligible biomaterial for the development of small caliber vascular grafts for substitution, repair, and regeneration of blood vessels. This study presents the properties of a newly designed multi-layered SF tubular scaffold for vascular grafting (SilkGraf). The wall architecture consists of two electrospun layers (inner and outer) and an intermediate textile layer. The latter was designed to confer high mechanical performance and resistance on the device, while electrospun layers allow enhancing its biomimicry properties and host's tissues integration. In vitro cell interaction studies performed with adult Human Coronary Artery Endothelial Cells (HCAECs), Human Aortic Smooth Muscle Cells (HASMCs), and Human Aortic Adventitial Fibroblasts (HAAFs) demonstrated that the electrospun layers favor cell adhesion, survival, and growth. Once cultured in vitro on the SF scaffold the three cell types showed an active metabolism (consumption of glucose and glutamine, release of lactate), and proliferation for up to 20 days. HAAF cells grown on SF showed a significantly lower synthesis of type I procollagen than on polystyrene, meaning a lower fibrotic effect of the SF substrate. The cytokine and chemokine expression patterns were investigated to evaluate the cells' proliferative and pro-inflammatory attitude. Interestingly, no significant amounts of truly pro-inflammatory cytokines were secreted by any of the three cell types which exhibited a clearly proliferative profile. Good hemocompatibility was observed by complement activation, hemolysis, and hematology assays. Finally, the results of an in vivo preliminary pilot trial on minipig and sheep to assess the functional behavior of implanted SF-based vascular graft identified the sheep as the more apt animal model for next medium-to-long term preclinical trials.
Highlights
Cardiovascular pathologies are the leading cause of death worldwide (World Health Organization, 2012), with very high overall incidence on health expenditures
The results demonstrated that there were no differences in the amino acid composition, indicating that neither processing conditions nor sterilization with ethylene oxide (EtO) (Zhao et al, 2011) altered the intrinsic properties of Silk fibroin (SF) materials (Table S1)
SilkGraft is a small caliber vascular graft entirely made of pure silk fibroin
Summary
Cardiovascular pathologies are the leading cause of death worldwide (World Health Organization, 2012), with very high overall incidence on health expenditures. As the vascular diseases progress with age, the related burden is likely to increase with the global rise in life expectancy. The availability of grafts for the treatment of vascular diseases becomes a real and urgent need. In the vascular surgery field of either coronary or peripheral bypass procedures, there is a crucial necessity of novel viable solutions, which might complement or even replace current surgical approaches, based on autografts, or synthetic grafts (Catto et al, 2014; Hiob et al, 2017; Sugiura et al, 2017). There are some factors which may strongly curb the use of autografts: absence of a usable graft, significative atherosclerosis of the arteries, previous usage of an autograft for surgical procedures, or angiographic approaches (Catto et al, 2014)
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