Bioresorbable vascular scaffolds technology: current use and future developments

Design and comprehensive assessment of a biomimetic tri-layer tubular scaffold via biodegradable polymers for vascular tissue engineering applications

Considering the structural complexity of the native artery wall and the limitations of current treatment strategies, developing a biomimetic tri-layer tissue-engineered vascular graft is a major developmental direction of vascular tissue regeneration. Biodegradable polymers exhibit adequate mechanical characteristics and feasible operability, showing potential prospects in the construction of tissue engineering scaffold. Herein, we present a bio-inspired tri-layer tubular graft using biodegradable polymers to simulate natural vascular architecture. The inner layer made of polycaprolactone (PCL) nanofiber possesses high tensile strength and contributed to endothelial cell adhesion and proliferation. The middle layer consisted of poly(lactic-co-glycolide) (PLGA) with a three-dimensional porous structure is appropriate for vascular smooth muscle cells (SMCs) penetration. The polyurethane (PU) was selected to be the outer layer, aiming to hold the entire tubular structure, suggesting superior mechanical properties and ideal biocompatibility. Adhesion between independent layers is achieved by thermal crosslinking. The compliance, burst pressure and suture retention force of the tubular scaffold were 2.50 ± 1.60%, 2737.73 ± 583.41 mmHg and 13.06 ± 1.89 N, respectively. The in vivo study of subcutaneous implantation for 8 weeks demonstrated the biomimetic tri-layer vascular graft could maintain intimal integrity, cell infiltration, collagen deposition and scaffold biodegradation. Overall, the biomimetic tri-layer vascular graft promises to be a potential candidate for vascular replacement and regeneration.

Bioresorbable Vascular Scaffolds-Dead End or Still a Rough Diamond?

Percutaneous coronary interventions with stent-based restorations of vessel patency have become the gold standard in the treatment of acute coronary states. Bioresorbable vascular scaffolds (BVS) have been designed to combine the efficiency of drug-eluting stents (DES) at the time of implantation and the advantages of a lack of foreign body afterwards. Complete resolution of the scaffold was intended to enable the restoration of vasomotor function and reduce the risk of device thrombosis. While early reports demonstrated superiority of BVS over DES, larger-scale application and longer observation exposed major concerns about their use, including lower radial strength and higher risk of thrombosis resulting in higher rate of major adverse cardiac events. Further focus on procedural details and research on the second generation of BVS with novel properties did not allow to unequivocally challenge position of DES. Nevertheless, BVS still have a chance to present superiority in distinctive indications. This review presents an outlook on the available first and second generation BVS and a summary of results of clinical trials on their use. It discusses explanations for unfavorable outcomes, proposed enhancement techniques and a potential niche for the use of BVS.

Improvement of Mechanical Performance of Bioresorbable Magnesium Alloy Coronary Artery Stents through Stent Pattern Redesign

Optimized stent pattern design can effectively enhance the mechanical performance of magnesium alloy stents by adjusting strain distribution and evolution during stent deformation, thereby overcoming the limitations imposed by the intrinsic mechanical properties of magnesium alloys. In the present study, a new stent design pattern for magnesium alloys was proposed and compared to two existing stent design patterns. Measures of the mechanical performance of these three stents, including crimping and expanding deformability, radial scaffolding capacity, radial recoil and bending flexibility, were determined. Three-dimensional finite element (FE) models were built to predict the mechanical performance of the stents with the three design patterns and to assist in understanding the experimental results. The results showed that, overall, the stent with the new design pattern was superior to the stents based on the existing designs, though the expanding capacity of the newly designed stent still needed to be improved.

Impact of PSP Technique on Clinical Outcomes Following Bioresorbable Scaffolds Implantation

Bioresorbable scaffolds (BRS) were introduced in clinical practice to overcome the long-term limitations of newer-generation drug-eluting stents. Despite some initial promising results of the Absorb BRS, safety concerns have led to the discontinuation of the commercialization of this device. Several retrospective studies have assessed the impact of the so-called Pre-dilation, Sizing and Post-dilation (PSP) technique concluding that an optimal PSP technique can improve clinical outcomes following BRS implantation. In this article, the definition of the PSP technique, and the current evidence of its impact on clinical outcomes are put in perspective. Additionality, the relationship between the PSP technique and the dual-antiplatelet therapy to prevent scaffold thrombosis is addressed. Finally, the future perspectives of BRS technology in clinical practice are commented.