Growth Plate Cartilage Repair via Novel Matrilin3/Rosette Nanotube Hybrid Matrix

 描述(申请人提供)：大约15%到30%的儿童骨折是生长板骨折。因为生长板决定了成熟骨骼的长度和形状，这种类型的骨折可能会导致儿童严重的生长异常。病理上，生长异常是由于在受损的生长板软骨中形成骨桥所致。目前，生长板骨折的临床治疗包括手术切除骨桥，并在空隙中植入自体脂肪或软骨组织以阻止骨桥重建。这种外科手术是侵入性的，结果并不令人满意。此外，这种治疗只有在骨桥后才有用 已经形成了。我们的长期目标是了解如何在细胞和分子水平上预防骨桥形成和促进生长板软骨再生，并开发第一种生长板骨折的预防和治疗方法。具体地说，这项建议的主要目标是评估由matrlin-3(MATN3)和玫瑰花结纳米管(RNT)组装的纳米基质在临床前生长板骨折模型中的治疗效果。我们的中心假设是，MATN3/RNT纳米基质特异性地促进软骨细胞的生长，促进间充质干细胞(MSCs)的软骨生成，同时它也抑制骨折部位的血管形成和成骨。这是这种纳米基质促进生长板软骨再生、防止骨桥形成的细胞基础。我们将验证我们的中心假设，并通过追求两个具体目标来实现该提案的目标：1)确定MATN3/RNT阻止骨桥形成的能力；以及2)确定MATN3/RNT运送生长因子的能力，以进一步促进软骨形成和生长板软骨再生。为了实现这两个目标，我们的总体研究策略包括：1)优化MATN3/RNT的比例和剂量及其体外负载生长因子的能力和生物活性；2)确定纳米基质在我们建立的大鼠生长板骨折模型中的长期治疗效果。建议的研究具有创新性：1)在生物学上，它同时促进软骨再生和抑制骨桥的形成；2)在治疗上，MATN3和RNT可以作为液体以微创的方式注射，并在骨折处形成纳米基质；3)结构上，纳米基质在骨折局部聚集生物活性的MATN3，并结合转化生长因子-β-1和胰岛素样生长因子-1实现多功能输送。有了这两个特定目标的结果，我们希望1)实现一种协同策略，在抑制成骨和血管形成的同时特别促进软骨生成；以及2)开发一种局部注射软骨生长因子的方法。这些结果对开发新的，也许是第一个预防和治疗生长板软骨修复的方法具有重要的积极影响。

 DESCRIPTION (provided by applicant): Approximately 15% to 30% of all childhood fractures are growth plate fractures. Because the growth plate determines the length and shape of a mature bone, this type of fracture may result in severe growth abnormalities in children. Pathologically, the growth abnormality is caused by the formation of a bony bridge in the injured growth plate cartilage. Currently, the clinical treatment of growth plate fractures includes the surgical removal of the bony bridge and insertion of autologous fat or cartilage tissue into the empty space to discourage bony bridge reformation. Such surgical procedures are invasive and result in unsatisfactory outcomes. In addition, this treatment is only useful after the bony bridge has formed. Our long-term goal is to understand how to prevent bony bridge formation and improve growth plate cartilage regeneration at cellular and molecular levels and develop the first preventive and therapeutic approach for growth plate fracture. Specifically, the primary objective of this proposal is to evaluate the therapeutic effects of a nano-matrix assembled from matrilin-3 (MATN3) and rosette nanotube (RNT) in a preclinical growth plate fracture model. Our central hypothesis is that the MATN3/RNT nano-matrix specifically promotes chondrocyte growth and enhances chondrogenesis of mesenchymal stem cells (MSCs), while it also inhibits vascularization and osteogenesis at the fracture site. This is the cellular basis for such nano-matrix to improve growth plate cartilage regeneration and prevent bony bridge formation. We will test our central hypothesis and achieve the objective of the proposal by pursuing two specific aims: 1) to determine the ability of MATN3/RNT to prevent bony bridge formation; and 2) to determine the ability of MATN3/RNT to deliver growth factors for further improvement of chondrogenesis and growth plate cartilage regeneration. To achieve the two aims, our overall research strategy includes: 1) optimization of the ratio and dose of MATN3/RNT and its ability and bioactivity for loading growth factors in vitro; and 2) determination of the therapeutic efficay of the nano-matrix in our established growth plate fracture model in rats in long term. The proposed research is innovative: 1) biologically, it simultaneously promotes cartilage regeneration and inhibits bony bridge formation; 2) therapeutically, MATN3 and RNT can be injected as a liquid in a minimally invasive manner, and form a nano- matrix at the fracture site; 3) structurally, the nano-matrix concentrates bioactive MATN3 locally at the fracture site as well as binds TGF-β1 and IGF-1 to achieve multi-functional delivery. With the results of the two specific aims, we expect to 1) realize a synergistic strategy to specifically promote chondrogenesis while inhibiting osteogenesis and vascularization; and 2) develop an injectable approach for the localized delivery of cartilage growth factors. These outcomes have an important positive impact in developing novel, perhaps the first, preventive and therapeutic approach for growth plate cartilage repair.