Center for Engineering in Medicine, Harvard Medical School, Massachusetts General Hospital, Boston, MA 02114, USA.
Acta Biomater. 2011 Jun;7(6):2437-47. doi: 10.1016/j.actbio.2011.02.038. Epub 2011 Mar 21.
Load-bearing tissues owe their mechanical strength to their highly anisotropic collagenous structure. To date attempts to engineer mechanically strong connective tissue have failed, mainly due to a lack of ability to reproduce the native collagen organization in constructs synthesized by cultured cells in vitro. The ability to influence the orientation of self-assembling collagen molecules to produce highly anisotropic structures has applications ranging from de novo engineering of complex tissues to the production of organized scaffolds for cell culture contact guidance. In this investigation we have used the simple technique of spin-coating to produce highly aligned arrays of collagen fibrils. By a simple modification of the method we have also successfully produced orthogonal collagen lamellae. Alternating collagen lamellae are frequently seen in load-bearing tissues such as cornea, annulus fibrosus, and cortical bone. Culturing of corneal fibroblasts on aligned collagen shows that the cells adopt the organization of fibrils. In this investigation we observed the reversal of fibrillar growth direction or "hook" formation similar to that seen previously in a microfluidic shear flow chamber. Although the results of this investigation clearly show that it is possible to produce small areas (1cm(2)) of collagen fibrils with enough alignment to guide fibroblasts, there is evidence that thin film instabilities are likely to be a significant barrier to producing organized collagen fibrils over larger areas. Successful application of this method to produce highly controlled and organized collagenous structures will require the development of techniques to control thin film instability and will be the subject of future work.
承重组织的机械强度归功于其各向异性的胶原结构。迄今为止，试图设计机械强度高的结缔组织的尝试都失败了，主要是因为缺乏在体外培养细胞合成的构建体中重现天然胶原组织的能力。影响自组装胶原分子取向以产生各向异性结构的能力，其应用范围从复杂组织的从头工程设计到用于细胞培养接触引导的有组织支架的生产。在这项研究中，我们使用简单的旋涂技术来生产高度排列的胶原原纤维阵列。通过对该方法的简单修改，我们还成功地生产了正交胶原薄片。在诸如角膜、纤维环和皮质骨等承重组织中经常看到交替的胶原薄片。在排列的胶原上培养角膜成纤维细胞表明细胞采用纤维的组织。在这项研究中，我们观察到纤维生长方向的反转或“钩”形成，类似于以前在微流控剪切流室中观察到的情况。尽管这项研究的结果清楚地表明，有可能生产出具有足够取向以引导成纤维细胞的小面积（1cm²）胶原纤维，但有证据表明，薄膜不稳定性可能是在更大面积上产生有组织的胶原纤维的一个重大障碍。成功应用该方法生产高度可控和有组织的胶原结构将需要开发控制薄膜不稳定性的技术，这将是未来工作的主题。
