Department of Materials Science & Engineering, Iowa State University, Ames, IA 50011, United States of America.
Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, United States of America.
Mater Sci Eng C Mater Biol Appl. 2021 Oct;129:112370. doi: 10.1016/j.msec.2021.112370. Epub 2021 Aug 13.
Fabricating hydrogel scaffolds that are both bioreactive toward fibroblasts while still mechanically compatible with surrounding tissue is a major challenge in tissue engineering. This is because the outcome of scaffold implantation is largely determined by fibroblasts differentiating toward myofibroblasts, which is characterized by the expression of α-smooth muscle actin (α-SMA). Previous studies promoted fibroblasts differentiation by increasing scaffold substrate stiffness. However, the stiffness of scaffold has to be compatible with surrounding tissue, as mismatched stiffness may cause initial hyperplasia and inappropriate endothelial layer development. Therefore, we adjusted the hydrogel chemical component, and thus viscoelasticity to affect the mechano-signaling of fibroblasts and promote fibroblasts differentiation. Elastic gellan gum and viscoelastic gelatin were hybridized at different ratios to fabricate hydrogel scaffold with varied stress-relaxation. Vitronectin (VN) was used to further regulate the interaction between fibroblasts and the substrate. Fibroblast differentiation, characterized by α-SMA area per cell, increased from~3000-4000 μm/cell on less viscoelastic gels to ~5000 μm/cell on the most viscoelastic gel. Fibroblasts seeded on hydrogels had a slower migration rate on more viscoelastic hydrogels (slowest at 38 ± 14 μm/h) compared to the migration speed on less viscoelastic hydrogels (74 ± 20 μm/h). VN slowed the migration speed on all hydrogels. The organization of collagen deposited by fibroblasts cultured on the hydrogels was characterized by second harmonic generation (SHG), which showed that collagen was more organized (parallel) on more viscoelastic hydrogels. In summary, we provided a novel strategy to fabricate hydrogel scaffolds that can promote fibroblasts differentiation while keeping the stiffness compatible with blood vessels. The most viscoelastic hydrogel studied here meets these requirements best.
制造对成纤维细胞具有生物反应性且与周围组织机械兼容的水凝胶支架是组织工程中的一个主要挑战。这是因为支架植入的结果在很大程度上取决于成纤维细胞向肌成纤维细胞分化，其特征是表达α-平滑肌肌动蛋白（α-SMA）。以前的研究通过增加支架基质的刚度来促进成纤维细胞分化。然而，支架的刚度必须与周围组织相匹配，因为不匹配的刚度可能导致最初的过度增生和不适当的内皮层发育。因此，我们调整了水凝胶的化学组成和粘弹性，以影响成纤维细胞的机械信号转导并促进成纤维细胞分化。弹性的结冷胶和粘弹性明胶以不同的比例杂交，以制造具有不同应力松弛的水凝胶支架。纤连蛋白（VN）用于进一步调节成纤维细胞与基底之间的相互作用。以α-SMA 面积/细胞计，细胞的成纤维细胞分化从较不粘弹性凝胶上的3000-4000 μm/cell 增加到最粘弹性凝胶上的5000 μm/cell。与较不粘弹性水凝胶（74 ± 20 μm/h）相比，在粘弹性较高的水凝胶上，接种在水凝胶上的成纤维细胞的迁移速度较慢（最慢为 38 ± 14 μm/h）。VN 减慢了所有水凝胶上的迁移速度。在水凝胶上培养的成纤维细胞沉积的胶原蛋白的组织通过二次谐波产生（SHG）进行表征，其显示胶原蛋白在更粘弹性的水凝胶上更有组织（平行）。总之，我们提供了一种制造水凝胶支架的新策略，该策略可以在保持与血管的刚度相匹配的同时促进成纤维细胞分化。这里研究的最粘弹性水凝胶最能满足这些要求。
