Bioabsorbable stents: only bad news?

Applying Principles of Regenerative Medicine to Vascular Stent Development

Stents are a widely-used device to treat a variety of cardiovascular diseases. The purpose of this review is to explore the application of regenerative medicine principles into current and future stent designs. This review will cover regeneration-relevant approaches emerging in the current research landscape of stent technology. Regenerative stent technologies include surface engineering of stents with cell secretomes, cell-capture coatings, mimics of endothelial products, surface topography, endothelial growth factors or cell-adhesive peptides, as well as design of bioresorable materials for temporary stent support. These technologies are comparatively analyzed in terms of their regenerative effects, therapeutic effects and challenges faced; their benefits and risks are weighed up for suggestions about future stent developments. This review highlights two unique regenerative features of stent technologies: selective regeneration, which is to selectively grow endothelial cells on a stent but inhibit the proliferation and migration of smooth muscle cells, and stent-assisted regeneration of ischemic tissue injury.

Bioresorbable polymer and durable polymer metallic stents in coronary artery disease: a meta-analysis

BACKGROUND

Literature on bioresorbable-polymer-stents (BPS) and second-generation durable-polymer-stents (DPS) in percutaneous coronary intervention (PCI) for all comer CAD is conflicting.

METHODS

Randomized controlled studies comparing PCI among BPS and second-generation DPS were identified up until May-2020 from online databases.  Primary outcomes included are all-cause myocardial infarction (MI), cardiac-death, target-vessel-revascularization (TVR), target-vessel MI (TVMI), and stent-thrombosis (ST). Random effect method of risk ratio and confidence interval of 95% was used.

RESULTS

25 prospective randomized controlled trials with 31,822 patients (BPS n = 17,065 and DPS n = 14,757) were included in the study. Follow-up ranged between a minimum of 6 months to more than 5 years. Cardiac death (RR 1.02, 95% CI 0.89-1.45, p = 0.16) was comparable in BPS and second-generation DPS. Risk of all-cause MI was similar between BPS and DPS (RR 0.97, 95% CI 0.84-1.11, p = 0.73). TVMI (RR 0.88, 95% CI 0.69-1.11, p = 0.33) and ST rates were also comparable in BPS and DPS groups (RR 1.06, 95% CI 0.80-1.40, p = 1.00). Overall TVR had comparable outcomes between BPS and DPS (RR 0.95, 95% CI 0.79-1.14, p < 0.001); however, higher TVR was seen among BPS group at follow-up of ≥5 years (RR 1.39, 95% CI 1.12-1.14, p = 0.02). Bias was low and heterogeneity was moderate.

CONCLUSION

Patients undergoing PCI treated with BPS had comparable outcomes in terms of cardiac death, TVR, ST, TVMI, and all-cause MI to patients treated with second-generation DPS; however, BPS had higher rates of TVR for follow-up of ≥5-years.

Advancing Toward 3D Printing of Bioresorbable Shape Memory Polymer Stents

Stents have evolved significantly since their introduction to the medical field in the early 1980s, becoming widely used in percutaneous coronary interventions and following nephrological procedures. However, the current commercially available stents do not degrade and remain in the body forever, leading to problems like restenosis in cardiovascular applications or requiring removal procedures in ureteral applications. Efforts to replace metal with resorbable materials have largely been halted after the commercial failure of and safety concerns elicited by Abbott's Absorb stent in 2017. Industry continues to use common polymers such as poly(l-lactide) (PLLA) and polycaprolactone (PCL) for biomedical products, but due to the weak mechanical properties of these bioresorbable materials in comparison to metals, these devices have struggled to accomplish the goals set, increasing risk of thrombosis. 3D printing stents using bioresorbable and shape memory materials could provide a method of patient-personalized production, remove the need for balloon expansion, and limit stent migration, thus bringing a new age of stent technology. The investigation of a range of 3D-printable and bioresorbable shape-memory polymers can provide solutions to the shortcomings of previously explored bioresorbable stents and revitalize the medical device industry efforts into advancing stent technology.