A Biological Basis for Repair of the ACL

描述（由申请人提供）：每年有超过100，000例患者发生前交叉韧带（ACL）断裂。它不能自行愈合。由于手术修复和非手术治疗均不能提供可靠满意的临床结局，ACL断裂仍然是一个紧迫的骨科问题。本提案中描述的研究旨在通过应用新的生物学方法改善ACL的修复。这些是基于最近的数据表明，与所接受的观点相反，当加强的胶原水凝胶插入韧带的切断端之间时，断裂的ACL产生愈合反应。这种反应的关键是细胞从受损韧带迁移到水凝胶中。初步数据表明，这些并不代表ACL细胞作为一个整体，但构成了一个独特的群体，其中共享的许多性质的间充质干细胞（MSC）。为了实现临床上有用的修复，这些细胞必须分裂、分化成韧带细胞并形成具有足够机械强度的基质。本提案中描述的实验使用体外和体内猪模型解决了这些基本问题。在特定目标1中，从受损ACL迁移的细胞将从水凝胶中回收，并通过生物学和免疫学标准进行研究，以确定它们在多大程度上共享MSC的特性。它们在ACL内的位置将通过免疫组织化学确定。在具体目标2中，将确定这些细胞对选定的生长因子子集的反应。这些因子是：FGF-2、BMP-12、BMP-13和TGF-β 1。将在单层培养物和ACL损伤和修复的体外“间隙”模型中评价腺病毒介导的基因转移和重组蛋白（如可能）。在特定目标3中，猪的全层ACL断裂模型将用于确定当使用基因负载的增强水凝胶修复临床相关缺损时可实现的机械强度。MRI、组织学和免疫组织化学也将用于评价愈合的韧带。这些研究将推进我们对受伤ACL生物学的了解，并提出新的基于生物学的愈合方法。

DESCRIPTION (provided by applicant): Rupture of the anterior cruciate ligament (ACL) occurs in over 100,000 patients each year. It cannot heal spontaneously. As neither surgical repair nor non-surgical treatments provide a reliably satisfactory clinical outcome, ACL ruptures remain a pressing orthopaedic problem. The research described in this proposal is directed towards improving the repair of the ACL through the application of novel biological approaches. These are based upon recent data suggesting that, contrary to the received view, the ruptured ACL mounts a healing response when a reinforced collagenous hydrogel is interposed between the severed ends of the ligament. Critical to this response is the migration of cells from the damaged ligament into the hydrogel. Preliminary data suggest that these are not representative of ACL cells as a whole, but constitute a distinct population which shares many of the properties of mesenchymal stem cells (MSCs). To achieve a clinically useful repair, these cells must divide, differentiate into ligament cells and lay down a matrix of sufficient mechanical strength. The experiments described in this proposal address these fundamental issues using in vitro and in vivo porcine models. In Specific Aim 1, the cells that migrate from the damaged ACL will be recovered from the hydrogel and investigated by biological and immunological criteria to determine to what degree they share the properties of MSCs. Their location within the ACL will be determined by immunohistochemistry. In Specific Aim 2, the responses of therse cells to a selected sub-set of growth factors will be determined. These factors are: FGF-2, BMP-12, BMP-13 and TGF-beta1. Both adenovirus- mediated gene transfer and, where possible, recombinant proteins will be evaluated in monolayer culture and in an in vitro "gap" model of ACL injury and repair. In Specific Aim 3, a full thickness, ACL rupture model in the pig will be used to determine the mechanical strength that is achievable when a gene-laden, reinforced hydrogel is used to repair a clinically-relevant defect. MRI, histology and immunohistochemistry will also be used to evaluate the healed ligament. These studies will advance our knowledge of the biology of the injured ACL and suggest novel, biologically-based approaches to healing.