Lu Helen H, Cooper James A, Manuel Sharron, Freeman Joseph W, Attawia Mohammed A, Ko Frank K, Laurencin Cato T
Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA.
Biomaterials. 2005 Aug;26(23):4805-16. doi: 10.1016/j.biomaterials.2004.11.050. Epub 2005 Jan 13.
The anterior cruciate ligament (ACL) is the most commonly injured intra-articular ligament of the knee, and limitations in existing reconstruction grafts have prompted an interest in tissue engineered solutions. Previously, we reported on a tissue-engineered ACL scaffold fabricated using a novel, three-dimensional braiding technology. A critical factor in determining cellular response to such a graft is material selection. The objective of this in vitro study was to optimize the braided scaffold, focusing on material composition and the identification of an appropriate polymer. The selection criteria are based on cellular response, construct degradation, and the associated mechanical properties. Three compositions of poly-alpha-hydroxyester fibers, namely polyglycolic acid (PGA), poly-L-lactic acid (PLLA), and polylactic-co-glycolic acid 82:18 (PLAGA) were examined. The effects of polymer composition on scaffold mechanical properties and degradation were evaluated in physiologically relevant solutions. Prior to culturing with primary rabbit ACL cells, scaffolds were pre-coated with fibronectin (Fn, PGA-Fn, PLAGA-Fn, PLLA-Fn), an important protein which is upregulated during ligament healing. Cell attachment and growth were examined as a function of time and polymer composition. While PGA scaffolds measured the highest tensile strength followed by PLLA and PLAGA, its rapid degradation in vitro resulted in matrix disruption and cell death over time. PLLA-based scaffolds maintained their structural integrity and exhibited superior mechanical properties over time. The response of ACL cells was found to be dependent on polymer composition, with the highest cell number measured on PLLA-Fn scaffolds. Surface modification of polymer scaffolds with Fn improved cell attachment efficiency and effected the long-term matrix production by ACL cells on PLLA and PLAGA scaffolds. Therefore based on the overall cellular response and its temporal mechanical and degradation properties in vitro, the PLLA braided scaffold pre-coated with Fn was found to be the most suitable substrate for ACL tissue engineering.
前交叉韧带（ACL）是膝关节最常受损的关节内韧带，现有重建移植物的局限性促使人们对组织工程解决方案产生了兴趣。此前，我们报道了一种采用新型三维编织技术制造的组织工程ACL支架。决定细胞对这种移植物反应的一个关键因素是材料选择。这项体外研究的目的是优化编织支架，重点是材料组成和合适聚合物的鉴定。选择标准基于细胞反应、构建体降解及相关力学性能。研究了三种聚α-羟基酯纤维组成，即聚乙醇酸（PGA）、聚-L-乳酸（PLLA）和82:18聚乳酸-乙醇酸共聚物（PLAGA）。在生理相关溶液中评估了聚合物组成对支架力学性能和降解的影响。在用原代兔ACL细胞培养之前，支架预先用纤连蛋白（Fn，PGA-Fn、PLAGA-Fn、PLLA-Fn）包被，纤连蛋白是韧带愈合过程中上调的一种重要蛋白质。研究了细胞附着和生长随时间及聚合物组成的变化。虽然PGA支架的拉伸强度最高，其次是PLLA和PLAGA，但它在体外的快速降解导致基质破坏和细胞随时间死亡。基于PLLA的支架保持了其结构完整性，并随着时间推移表现出优异的力学性能。发现ACL细胞的反应取决于聚合物组成，在PLLA-Fn支架上测得的细胞数量最多。用Fn对聚合物支架进行表面修饰提高了细胞附着效率，并影响了ACL细胞在PLLA和PLAGA支架上的长期基质生成。因此，基于体外整体细胞反应及其随时间的力学和降解特性，发现预先用Fn包被的PLLA编织支架是ACL组织工程最合适的基质。
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