Short-term safety and efficacy of the biodegradable iron stent in mini-swine coronary arteries

Background To overcome the drawbacks of permanent stents, biodegradable stents have been studied in recent years. The bioabsorbable polymer vascular scaffold (BVS) was the first bioabsorbable stent to undergo clinical trials, demonstrating safety and feasibility in the ABSORB studies. Iron can potentially serve as the biomaterial for biodegradable stents. This study aimed to assess the short-term safety and efficacy of a biodegradable iron stent in mini-swine coronary arteries.

Methods Eight iron stents and eight cobalt chromium alloy (VISION) control stents were randomly implanted into the LAD and RCA of eight healthy mini-swine, respectively. Two stents of the same metal base were implanted into one animal. At 28 days the animals were sacrificed after coronary angiography, and histopathological examinations were performed.

Results Histomorphometric measurements showed that mean neointimal thickness ((0.46±0.17) mm vs. (0.45±0.18) mm, P=0.878), neointimal area ((2.55±0.91) mm2 vs. (3.04±1.15) mm2, P=0.360) and percentage of area stenosis ((44.50±11.40)% vs. (46.00±17.95)%, P=0.845) were not significantly different between the iron stents and VISION stents. There was no inflammation, thrombosis or necrosis in either group. The scanning electron microscopy (SEM) intimal injury scores (0.75±1.04 vs. 0.88±0.99, P=0.809) and number of proliferating cell nuclear antigen (PCNA) positive staining cells were not significantly different between the two groups. The percentage of neointimal coverage by SEM examination was numerically higher in iron stents than in VISION stents ((84.38±14.50)% vs. (65.00±22.04)%, P=0.057), but the difference was not statistically significant. Iron staining in the tissue surrounding the iron stents at 28 days was positive and the vascular wall adjacent to the iron stent had a brownish tinge, consistent with iron degradation. No abnormal histopathological changes were detected in coronary arteries or major organs.

Conclusions The biodegradable iron stent has good biocompatibility and short-term safety and efficacy in the mini-swine coronary artery. Corrosion of iron stents is observed at four weeks and no signs of organ toxicity related to iron degradation were noted.