Hierarchical collagen fibers are the primary source of strength in musculoskeletal tendons, ligaments, and menisci. It has remained a challenge to develop these large fibers in engineered replacements or in vivo after injury. The objective of this study was to investigate the ability of restrained cell-seeded high density collagen gels to drive hierarchical fiber formation for multiple musculoskeletal tissues. We found boundary conditions applied to high density collagen gels were capable of driving tenocytes, ligament fibroblasts, and meniscal fibrochondrocytes to develop native-sized hierarchical collagen fibers 20-40 μm in diameter. The fibers organize similar to bovine juvenile collagen with native fibril banding patterns and hierarchical fiber bundles 50-350 μm in diameter by 6 weeks. Mirroring fiber organization, tensile properties of restrained samples improved significantly with time, reaching ∼1 MPa. Additionally, tendon, ligament, and meniscal cells produced significantly different sized fibers, different degrees of crimp, and different GAG concentrations, which corresponded with respective juvenile tissue. To our knowledge, these are some of the largest, most organized fibers produced to date in vitro. Further, cells produced tissue specific hierarchical fibers, suggesting this system is a promising tool to better understand cellular regulation of fiber formation to better stimulate it in vivo after injury.

分层胶原纤维是肌肉骨骼肌腱、韧带和半月板强度的主要来源。在工程替代品或体内开发这些大纤维仍然是一个挑战受伤后。本研究的目的是研究受约束的细胞种子高密度胶原凝胶驱动多个肌肉骨骼组织的分层纤维形成的能力。我们发现应用于高密度胶原凝胶的边界条件能够驱动肌腱细胞、韧带成纤维细胞和半月板纤维软骨细胞形成直径为 20-40 μm 的天然大小的分级胶原纤维。纤维组织类似于牛幼年胶原蛋白，具有天然原纤维带模式和分级纤维束，6 周时直径为 50-350 μm。镜像纤维组织，受限样品的拉伸性能随时间显着改善，达到~1 MPa。此外，肌腱、韧带和半月板细胞产生明显不同大小的纤维，不同程度的卷曲，和不同的GAG浓度，对应于各自的幼年组织。据我们所知，这些是迄今为止生产的一些最大、最有组织的纤维体外。此外，细胞产生组织特异性分层纤维，表明该系统是一种有前途的工具，可以更好地了解纤维形成的细胞调节，从而在损伤后更好地在体内刺激它。