Repair of Focal Defects in the Annulus Fibrosus Using Injectable High-Density Col

描述(申请人提供)：脊柱内的间盘(IVD)由髓内核(NP)和纤维外环(AF)组成。下腰痛是一种常见的问题，通常通过手术切除突出的椎间盘组织来治疗，在 自动对焦。为了恢复椎间盘的某些功能，已经开发了几种关闭缺陷的方法，如缝合术和障碍物，它们为缺陷提供机械支持，但不能促进生物愈合。目前正在开发各种组织工程化方法，使用生物材料作为模拟房颤构造的支架。这些进展是有希望的，但它们在房颤缺陷中的表现尚未见报道。我们的方法使用体外和体内的房颤缺损模型来从机械和生物学的角度评估用于房颤修复的生物材料。AF主要由I型胶原和胶原水凝胶组成，胶原水凝胶已被用于许多组织工程应用。作为一种凝胶，胶原蛋白是可注射的，可以很容易地输送到不规则的缺陷；然而，它通常表现出低硬度。我们实验室在全盘置换中使用了胶原凝胶，显示出与周围房颤组织良好的整合(Bowles等人，2011年)。因此，我们选择I型胶原水凝胶作为房颤修复的平台。我们将通过三个目标来评估胶原水凝胶用于房颤修复的性能，包括体外和体内研究。第一个目标是评估凝胶密度和交联度对胶原凝胶在体外植入房颤缺损处的力学贡献的影响。已有研究表明，胶原水凝胶的硬度随胶原密度的增加而增加(Ibus uki等人，2007年)。同样，用核黄素等无毒物质进行交联会增加凝胶硬度。我们将筛选具有不同胶原凝胶密度和核黄素浓度的配方，以找到产生僵硬凝胶的组合，然后在房颤缺陷中对该凝胶进行机械测试。目标2和目标3专注于长期房颤修复和在体内缺陷模型中评估胶原凝胶的整合。更具体地说，目标2的目标是评估从目标1结果中提取的非种子胶原凝胶保持椎间盘高度和NP含量的能力。用于全盘置换的胶原凝胶在与绵羊房颤细胞一起种植时显示出更高的集成度(Bowles等人，2011年；Bowles等人，2010年)。因此，目标3将重点评估不同细胞密度对凝胶结合的影响 环绕着天然的房颤组织。当这些研究完成后，将建立评估可注射生物材料的新方法，并将表征用于房颤修复的高密度胶原的性能。

DESCRIPTION (provided by applicant): Intervertebral discs (IVDs) in the spine consist of an inner nucleus pulposus (NP) and an outer annulus fibrosus (AF). Low back pain is a common problem that is often treated by surgically removing herniated disc tissue, leaving a defect in the AF. In order to return some function to the disc, several defect closure methods have been developed, such as sutures and barriers, which provide mechanical support for the defect but do not promote biological healing. Various tissue engineered approaches are currently being developed that employ biomaterials as scaffolds for AF-mimicking constructs. These advances are promising but their performance in an AF defect has not been reported. Our approach uses both in vitro and in vivo AF defect models to mechanically and biologically evaluate a biomaterial for AF repair. The AF is comprised of primarily type I collagen and collagen hydrogels have been used for many tissue engineering applications. As a gel, collagen is injectable and can be delivered easily to irregular defects; however, it typically exhibits low stiffness. Our lab has used collagen gels in a total disc replacement that exhibited good integration with surrounding AF tissue (Bowles et al., 2011). Therefore we chose type I collagen hydrogels as our platform for AF repair. We will assess the performance of collagen hydrogels for AF repair through three aims encompassing both in vitro and in vivo studies. The first aim will be to evaluate the effects of gel density and crosslinking on the mechanical contribution of collagen gels delivered to AF defects in vitro. It has been shown that the stiffness of collagen hydrogels increases with collagen density (Ibusuki et al., 2007). Likewise, crosslinking with a nontoxic agent like riboflavin increases gel stiffness. We will screen formulations with different collagen gel densities and riboflavin concentrations to find the combination that yields the stiffet gel, then mechanically test that gel in an AF defect. Aims 2 and 3 focus on long term AF repair and assessing collagen gel integration in an in vivo defect model. More specifically, the goal of Aim 2 is to evaluate the ability of unseeded collagen gels taken from Aim 1 outcomes to preserve disc height and NP content. Collagen gels for total disc replacement have shown increased integration when seeded with ovine AF cells (Bowles et al, 2011; Bowles et al., 2010). Therefore Aim 3 will focus on assessing the effect different cell densities on gel integration with surrounding native AF tissue. When these studies are complete, new methods for the assessment of injectable biomaterials will be established and the performance of high-density collagen for AF repair will be characterized.