Tendon Tissue Engineering by Electrochemically Aligned Collagen Bioscaffolds

描述(申请人提供)：仅在美国，每年就有数以万计的肌腱损伤修复，以恢复受累关节的活动范围。自体移植是主要的选择；然而，供区发病率和供区限制是重要的问题。异体/异种移植物可能会引起免疫反应。对合成聚合物的异物反应是一个重大缺陷。再生解决方案可以加速肌腱修复，实现更早的活动，并通过降低治疗成本来降低失败率，这将是非常重要的。肌腱重建面临着多重挑战，因为缺乏一种生物支架，它结合了机械稳定性、肌腱诱导性和一种能够通过手术整合到修复部位的形式。在R21项目的部分支持下，我们开发了一种新的方法来制备电化学排列的胶原(ELAC)线，其织物取向、堆积密度和机械性能与天然肌腱相匹配。ELAC在局部条件下诱导间充质干细胞(MSC)向肌腱分化，在编织支架中MSCs合成一种I型胶原和肌腱特异性肌腱调节蛋白分子阳性的基质。ELAC在体内具有生物相容性，可分解为肌腱样纤维组织。ELAC的降解率与肌腱的缓慢修复速度相匹配。因此，ELAC是一种独特的生物活性和机械性能良好的平台，可以在不添加生长因子的情况下修复肌腱。建议的研究将检验这样一种假设，即以ELAC为基础的再生策略修复的肌腱缺损区的生物力学性能将达到或超过自体移植的水平。第一个目标是优化ELAC的形貌和体外调节过程，以最大限度地促进骨髓间充质干细胞在编织ELAC支架中的腱形成。具体地说，子目标1.1将研究衬底紧实度、对准和硬度在引发观察到的 张性反应。骨髓来源的MSCs将被种植在随机与排列、电致密与凝胶形式的纹理上，并在六个数量级(1 kPa至1000兆帕)范围内调制基质刚性值，这是ELAC独有的范围。次目标1.2研究将优化细胞种植密度，并调用机械刺激来评估应变幅度和应变率对进一步促进体外肌腱形成的影响。第二个目标是通过使用编织ELAC支架来改善严重肌腱缺损的修复效果。将采用兔冈下肌腱缺损模型。治疗组包括自体移植修复、ELAC支架(带细胞和不带细胞)和空白对照。结果指标包括修复生物力学、从头开始基质分子的类型、炎症反应和愈合形态。阐明基于材料和体外条件作用的肌腱发生线索，并使用兔模型深入验证其优点，将为在大型动物模型中对这种新型生物材料进行临床前评估铺平道路。如果ELAC的性能至少与自体移植物一样好，那么与自体移植物相关的成本和发病率将被消除。ELAC将通过恢复关节活动范围和通过 取消翻修手术。

DESCRIPTION (provided by applicant): Repair of massive tendon defects occur in tens of thousands annually in the U.S. alone to restore the range of motion of involved joints. Autografts are the primary choice; however, donor site morbidity and limits in supply are significant issues. Allografts/xenografts may elicit immune response. Foreign body reaction to synthetic polymers is a significant drawback. Regenerative solutions expediting tendon repair, enabling earlier mobilization and reducing failure rates would be highly significant by reducing treatment costs. Tendon reconstruction faces multiple challenges due to the absence of a bioscaffold which unifies mechanical robustness, tenoinductivity and a form that enables integration to the repair site surgically. Supported in part by a R21 project, we developed a novel method to fabricate electrochemically aligned collagen (ELAC) threads whose fabric orientation, packing density and mechanical properties match those of the native tendon. ELAC induces tenogenic differentiation of mesenchymal stem cell (MSC) topographically and MSCs in woven scaffolds synthesize a matrix that is positive of collagen I and the tendon-specific tenomodulin molecule. ELAC is biocompatible in vivo and resolves into a tendon-like fibrous tissue. The degradation rate of ELAC matches the slow repair-rate of tendon. Therefore, ELAC is a unique bioactive and mechanically competent platform with the potential to repair tendon without the addition of growth factors. The proposed studies will test the hypothesis that the biomechanics of the tendon gap defects repaired by ELAC-based regenerative strategies will match or exceed that is attained by autografts. The first aim will optimize ELAC topography and in vitro conditioning processes to maximize tenogenesis of MSCs in woven ELAC scaffolds. Specifically, Sub-Aim 1.1 will study the roles of substrate compaction, alignment and stiffness in eliciting the observed tenogenic response. Marrow- derived MSCs will be seeded on textures of random vs. aligned, electrocompacted vs. gel form, and matrix stiffness values modulated over six orders of magnitude (1 kPa to 1000 MPa), a range coverage that is unique to ELAC. Sub Aim 1.2 studies will optimize cell seeding density and invoke mechanostimulation to assess effects of strain amplitude and strain rate towards further enhancement of tenogenesis in vitro. The second aim will improve the repair outcome on critical sized tendon defects by using woven ELAC scaffolds. A rabbit infraspinatus tendon defect model will be employed. The treatment groups will include autograft repair, ELAC scaffolds (with and without cells) and gap-defect as the negative control. Outcome measures will include repair biomechanics, types of de novo matrix molecules, inflammatory response and healing morphology. Elucidation of material-based and in vitro conditioning based cues in tenogenesis and in depth validation of its merits using the rabbit model will pave the way for a preclinical assessment of this novel biomaterial in large animal models. If ELAC performs at least as good as autografts the costs and morbidity associated with autografts will be eliminated. ELAC will benefit patients by restoring joint range of motion and by eliminating revision surgeries.