Layer-by-Layer Nano Matrix for Growth Plate Regeneration

摘要 儿童生长板骨折是临床上的一个重大问题。尽管只有15%-30%的人 儿童骨折是生长板骨折，因为生长板决定了骨折的长度和形状。 成熟骨，这种类型的骨折可能会导致患者严重的生长异常。据了解，~1.4% 生长板骨折会导致某种类型的生长停滞，这可能是由 当中心部位的病变发生时，周围干扰或纵向缩短。生长板骨折 延伸到骨痂的血液供应，使骨髓和间充质干细胞得以运输 细胞(MSCs)进入干骺端生长板，导致骨桥的形成和生长停滞。 因此，修复生长板损伤的关键挑战是如何在空间上调节MSC的分化。 损伤部位并恢复与周围未受伤者暂时匹配的生长和发育 软骨生长板。目前，还没有临床批准的组织工程疗法来治疗生长。 钢板骨折。手术是唯一可用的治疗方法，只有在骨桥形成后才能提供。它 包括移除骨桥并将自体脂肪或软骨组织插入空隙中以 阻止骨桥改革。然而，这种外科手术是非常有侵入性的，而且有 成功率不尽如人意。 为了克服这些限制，这项提议的目标是开发一种可注射的纳米基质，以 将软骨再生因子直接植入骨折内，具有多个功能层来控制时机 药物递送。我们的中心假设是，我们可以开发一种逐层纳米基质(LBL-NM)来 实现空间和时间可控的SDF1和转化生长因子-β1的输送，以促进生长板的再生。这个 该提议背后的理论基础是，一旦这种可注射的LBL-NM被开发成空间和 暂时介导小鼠骨髓间充质干细胞分化，可进一步发展为微创、高分化的 在较大动物模型中治疗生长板骨折的有效组织工程学方法。我们将测试我们的 中心假设通过追求两个具体目标：1)开发LBL-NM以空间控制递送 转化生长因子-β-1和SDF1的体外实验，并评价其对体内生长板再生的治疗效果； 控制转化生长因子-β-1在体外培养中持续供应的LBLNM的建立及其治疗效果评价 体内生长板再生的结果。随着这项研究的完成，我们预计将实现LBL- NM实现时空可控的转化生长因子-β-1和SDF1介导骨髓间充质干细胞分化 一个受伤的生长板。这一结果将对开发第一个组织产生重要的积极影响 生长板愈合的工程方法。

Abstract Growth plate fracture in children represents a significant problem in clinics. Although only 15-30% of all childhood fractures are growth plate fractures, because a growth plate determines the length and shape of a mature bone, this type of fracture may result in severe growth abnormalities in patients. It is known that ~1.4% of growth plate fractures result in some type of growth arrest, which can be angular deformities caused by peripheral disturbances or longitudinal shortening when centrally located lesions occur. Growth plate fractures that extend into the blood supply of the epiphysis enable the transport of bone marrow and mesenchymal stem cells (MSCs) into the metaphyseal growth plate leading to the formation of a bony bridge and growth arrest. Therefore, the key challenge to repairing a growth plate injury is how to mediate MSC differentiation spatially at the injury site and restoring a growth and development that temporally matches the surrounding uninjured cartilaginous growth plate. Currently, there is no clinically-approved tissue engineering therapy to treat growth plate fractures. Surgery is the only available treatment, and is only offered after a bony bridge has formed. It includes removing the bony bridge and inserting autologous fat or cartilage tissue into the empty space to discourage bony bridge reformation. However, this surgical procedure is very invasive and has an unsatisfactory success rate. To overcome these limitations, the objective of this proposal is to develop an injectable nano-matrix to place cartilage-regenerating factors directly into the fracture, with multiple functional layers to control the timing of drug delivery. Our central hypothesis is that we can develop a layer-by-layer nano-matrix (LbL-NM) to achieve spatially and temporally controlled SDF1 and TGF-β1 delivery for growth plate regeneration. The rationale that underlies the proposal is that once this injectable LbL-NM is developed to spatially and temporally mediate MSC differentiation in mice, it can be further developed as a minimally invasive and highly effective tissue engineering approach to treat growth plate fracture in a larger animal model. We will test our central hypothesis by pursuing two specific aims: 1) Develop an LbL-NM to spatially control the delivery of TGF-β1 and SDF1 in vitro and evaluate its treatment outcomes for growth plate regeneration in vivo, and 2) Develop an LbL-NM to control the duration of TGF-β1 supply in the LbL-NM in vitro and evaluate its treatment outcomes for growth plate regeneration in vivo. With the completion of this study, we expect to realize an LbL- NM to achieve spatially and temporally controlled TGF-β1 and SDF1 delivery to mediate MSC differentiation in an injured growth plate. This outcome would have an important positive impact on developing the first tissue engineering approach to growth plate healing.