Department of Chemical & Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
J Mech Behav Biomed Mater. 2012 Jul;11:27-40. doi: 10.1016/j.jmbbm.2011.12.004. Epub 2011 Dec 24.
Biomaterials for orthopedic tissue engineering must balance mechanical and bioactivity concerns. This work describes the fabrication of a homologous series of anisotropic collagen-GAG (CG) scaffolds with aligned tracks of ellipsoidal pores but increasing relative densities (ρ(∗)/ρ(s)), and we report the role scaffold relative density plays in directing tenocyte bioactivity. Scaffold permeability and mechanical properties, both in tension and compression, were significantly influenced by relative density in a manner predicted by cellular solids models. Equine tenocytes showed greater levels of attachment, metabolic activity, soluble collagen synthesis, and alignment as well as less cell-mediated scaffold contraction in anisotropic CG scaffolds of increasing relative density. Notably, the lowest density scaffolds experienced significant cell-mediated contraction with associated decreases in tenocyte number as well as loss of microstructural integrity, aligned contact guidance cues, and preferential tenocyte orientation over a 14 day culture period. Gene expression analyses suggested tenocyte de-differentiation in the lowest density scaffold while indicating that the highest density scaffold supported significant increases in COMP (4-fold), tenascin-C (3-fold), and scleraxis (15-fold) expression as well as significant decreases in MMP-1 (9-fold) and MMP-13 (13-fold) expression on day 14. These results suggest that anisotropic scaffold relative density can help to modulate the maintenance of a more tendon-like microenvironment and aid long-term tenocyte transcriptomic stability. Overall, this work demonstrates that relative density is a critical scaffold parameter, not only for insuring mechanical competence, but also for directing cell transcriptomic stability and behavior.
用于骨科组织工程的生物材料必须平衡力学和生物活性的问题。本工作描述了一系列各向异性的胶原 - GAG（CG）支架的制造，这些支架具有排列的椭圆形孔的轨迹，但具有增加的相对密度（ρ（∗）/ ρ（s）），并报告了支架相对密度在指导肌腱细胞生物活性方面的作用。支架的渗透性和机械性能，无论是在拉伸还是压缩时，都受到相对密度的显著影响，这与多孔固体模型的预测一致。随着相对密度的增加，马肌腱细胞在各向异性 CG 支架中的附着、代谢活性、可溶性胶原合成和排列以及细胞介导的支架收缩程度都表现出更高的水平。值得注意的是，最低密度的支架经历了显著的细胞介导收缩，伴随着肌腱细胞数量的减少以及微结构完整性、排列的接触引导线索以及在 14 天培养期间优先的肌腱细胞取向的丧失。基因表达分析表明，在最低密度支架中，肌腱细胞发生去分化，而最高密度支架则支持 COMP（4 倍）、腱生蛋白-C（3 倍）和 Scleraxis（15 倍）表达的显著增加，以及 MMP-1（9 倍）和 MMP-13（13 倍）表达的显著减少在第 14 天。这些结果表明，各向异性支架的相对密度可以帮助调节更类似于肌腱的微环境的维持，并有助于长期肌腱细胞转录组稳定性。总的来说，这项工作表明，相对密度不仅是确保机械性能的关键支架参数，也是指导细胞转录组稳定性和行为的关键参数。
