Geometrical Microfeature Cues for Directing Tubulogenesis of Endothelial Cells

Angiogenesis, the formation of new blood vessels by sprouting from pre-existing ones, is critical for the establishment and maintenance of complex tissues. Angiogenesis is usually triggered by soluble growth factors such as VEGF. However, geometrical cues also play an important role in this process. Here we report the induction of angiogenesis solely by SVVYGLR peptide micropatterning on polymer surfaces. SVVYGLR peptide stripes were micropatterned onto polymer surfaces by photolithography to study their effects on endothelial cell (EC) behavior. Our results showed that the EC behaviors (cell spreading, orientation and migration) were significantly more guided and regulated on narrower SVVYGLR micropatterns (10 and 50 µm) than on larger stripes (100 µm). Also, EC morphogenesis into tube formation was switched on onto the smaller patterns. We illustrated that the central lumen of tubular structures can be formed by only one-to-four cells due to geometrical constraints on the micropatterns which mediated cell-substrate adhesion and generated a correct maturation of adherens junctions. In addition, sprouting of ECs and vascular networks were also induced by geometrical cues on surfaces micropatterned with SVVYGLR peptides. These micropatterned surfaces provide opportunities for mimicking angiogenesis by peptide modification instead of exogenous growth factors. The organization of ECs into tubular structures and the induction of sprouting angiogenesis are important towards the fabrication of vascularized tissues, and this work has great potential applications in tissue engineering and tissue regeneration.

血管生成（Angiogenesis）指由已存在的血管出芽形成新生血管的过程，对复杂组织的建立与维持具有关键作用。血管生成通常由血管内皮生长因子（VEGF）等可溶性生长因子触发，但几何信号（geometrical cues）在该过程中也发挥着重要作用。本研究报道，仅通过在聚合物表面制备SVVYGLR肽微图案即可诱导血管生成。研究人员通过光刻技术将SVVYGLR肽条纹微图案化于聚合物表面，以探究其对内皮细胞（endothelial cell, EC）行为的影响。结果显示，相较于宽度为100 μm的较宽条纹，内皮细胞在10 μm与50 μm的窄幅SVVYGLR微图案上的行为（细胞铺展、取向与迁移）受到更为显著的引导与调控。此外，在尺寸更小的微图案上可诱导内皮细胞发生管腔形成的形态发生过程。本研究证实，由于微图案带来的几何约束介导了细胞-基质黏附并促使黏着连接正确成熟，管状结构的中央管腔仅需1至4个细胞即可形成。此外，在修饰有SVVYGLR肽的微图案化表面上，几何信号同样可诱导内皮细胞出芽与血管网络形成。这类微图案化表面为通过肽修饰而非外源性生长因子模拟血管生成提供了可行途径。内皮细胞有序组装为管状结构以及诱导出芽型血管生成，对于血管化组织的构建具有重要意义，本研究在组织工程与组织再生领域具备巨大的应用潜力。