Regulation Effects of Biomimetic Hybrid Scaffolds on Vascular Endothelium Remodeling

The formation of complete and well-functioning endothelium is critical for the success of tissue-engineered vascular grafts yet remaining a fundamental challenge. Endothelium remodeling onto the lumen of tissue-engineered vascular grafts is affected by their topographical, mechanical, and biochemical characteristics. For meeting multiple requirements, composite strategies have recently emerged for fabricating hybrid scaffolds, where the integrated properties are tuned by varying their compositions. However, the underlying principle how the integrated properties of hybrid scaffolds regulate vascular endothelium remodeling remains unclear. To uncover the regulation effects of hybrid scaffolds on vascular endothelium remodeling, we prepared different biomimetic hybrid scaffolds using gelatin methacrylamide (GelMA) and poly-ε-caprolactone (PCL) and then investigated vascular endothelial cell responses on them. GelMA and PCL, respectively, conferred the resulting scaffolds with biomimetic bioactivity and mechanical properties, which were tuned by varying GelMA/PCL mass ratios (3:1, 1:1, or 1:3). On different GelMA/PCL hybrid scaffolds, distinct vascular endothelial cell responses were observed. Firm cell-scaffold/cell-cell interactions were rapidly established on the hybrid scaffolds with the highest mass ratio of bioactive GelMA. However, they were mechanically insufficient as vascular grafts. On the contrary, the scaffolds with the highest mass ratio of PCL showed significantly reinforced mechanical properties but poor biological performance. Between the two extremes, the scaffolds with the same GelMA/PCL mass ratio balanced the pros and cons of two materials. Therefore, they could meet the mechanical requirements of vascular grafts and support the early-stage vascular endothelial cell remodeling by appropriate biological signaling and mechanotransduction. This investigation experimentally proves that scaffold bioactivity is the dominant factor affecting vascular endothelial cell adhesion and remodeling, whereas mechanical properties are crucial factors for the integrity of endothelium. This work offers a universal design strategy for desirable vascular grafts for improved endothelium remodeling.