Neointimal hyperplasia (NH) is a main source of failures in arteriovenous fistulas and vascular grafts. Several studies have demonstrated the promise of perivascular wraps to reduce NH via promotion of adventitial neovascularization and providing mechanical support. Limited clinical success thus far may be due to inappropriate material selection (e.g., nondegradable, too stiff) and geometric design (e.g., pore size and spacing, diameter). The influence of pore size and spacing on implant neovascularization is investigated here for a new biodegradable, thermoresponsive shape memory polymer (SMP) perivascular wrap. Following an initial pilot, 21 mice were each implanted with six scaffolds: four candidate SMP macroporous designs (a–d), a nonporous SMP control (e), and microporous GORETEX (f). Mice were sacrificed after 4 (N = 5), 14 (N = 8), and 28 (N = 8) days. There was a statistically significant increase in neovascularization score between all macroporous groups compared to nonporous SMP (p < .023) and microporous GORETEX (p < .007) controls at Day 28. Wider‐spaced, smaller‐sized pore designs (223 μm‐spaced, 640 μm‐diameter Design c) induced the most robust angiogenic response, with greater microvessel number (p < .0114) and area (p < .0055) than nonporous SMPs and GORETEX at Day 28. This design also produced significantly greater microvessel density than nonporous SMPs (p = 0.0028) and a smaller‐spaced, larger‐sized pore (155 μm‐spaced, 1,180 μm‐sized Design b) design (p = .0013). Strong neovascularization is expected to reduce NH, motivating further investigation of this SMP wrap with controlled pore spacing and size in more advanced arteriovenous models.

中文翻译：

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孔径和间距对可生物降解形状记忆聚合物血管周围包裹物新生血管的影响。


新内膜增生（NH）是动静脉瘘和血管移植失败的主要原因。多项研究表明，血管周围包裹物有望通过促进外膜新生血管形成和提供机械支撑来减少 NH。迄今为止有限的临床成功可能是由于材料选择不当（例如不可降解、太硬）和几何设计（例如孔径和间距、直径）。本文研究了新型可生物降解、热响应形状记忆聚合物 (SMP) 血管周围包裹物的孔径和间距对植入物新生血管形成的影响。经过初步试验，21 只小鼠每只植入了 6 个支架：四种候选 SMP 大孔设计 (a-d)、无孔 SMP 对照 (e) 和微孔 GORETEX (f)。 4 ( N = 5)、14 ( N = 8) 和 28 ( N = 8) 天后处死小鼠。第 28 天时，与无孔 SMP ( p < .023) 和微孔 GORETEX ( p < .007) 对照相比，所有大孔组的新生血管评分均有统计学显着增加。更宽间距、更小尺寸的孔设计 (223 μm-间隔、直径 640 μm 的设计 c) 在第 28 天诱导了最强烈的血管生成反应，与无孔 SMP 和 GORETEX 相比，微血管数量 ( p < .0114) 和面积 ( p < .0055) 更大。该设计还产生了显着更大的微血管密度高于无孔 SMP ( p = 0.0028) 和更小间距、更大尺寸的孔隙（155 μm 间距，1,180 μm 大小的设计 b）设计 ( p = .0013)。 强烈的新生血管形成预计会减少 NH，从而推动在更先进的动静脉模型中进一步研究这种具有受控孔隙间距和大小的 SMP 包裹物。