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要问题。虽然只有15-30%的人 儿童骨折是生长板骨折，因为生长板决定了儿童骨折的长度和形状。 成熟骨，这种类型的骨折可能导致患者严重的生长异常。据了解，约1.4% 生长板骨折导致某种类型的生长停滞，这可能是由于 当发生位于中心的病变时，外周紊乱或纵向缩短。生长板骨折 延伸到骨骺的血液供应中，使骨髓和间充质干细胞能够运输， 细胞（MSC）进入干骺端生长板，导致骨桥形成和生长停滞。 因此，修复生长板损伤的关键挑战是如何在空间上介导MSC分化， 损伤部位，并恢复与周围未受伤部位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 接骨板断裂。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的空间中， 不鼓励骨桥重建。然而，这种外科手术是非常侵入性的， 不满意的成功率。 为了克服这些局限性，本提案的目标是开发可注射的纳米基质， 将软骨再生因子直接置入骨折处，多个功能层控制时机 药物输送。我们的中心假设是，我们可以开发一种逐层纳米基质（LbL-NM）， 实现用于生长板再生的空间和时间受控的SDF 1和TGF-β1递送。的 该提议的基本原理是，一旦这种可注射的LbL-NM被开发成在空间上和 在小鼠中暂时介导的MSC分化，其可以进一步发展为微创和高度分化的细胞因子。 有效的组织工程方法来治疗生长板骨折在更大的动物模型。我们将测试我们的 通过追求两个具体目标来实现中心假设：1）开发LbL-NM以空间控制 体外TGF-β1和SDF 1，并评估其在体内生长板再生的治疗结果，以及2） 开发LbL-NM以控制体外LbL-NM中TGF-β1供应的持续时间并评估其治疗 体内生长板再生的结果。随着这项研究的完成，我们预计将实现一个LBL- NM实现空间和时间控制的TGF-β1和SDF 1递送以介导MSC分化， 受伤的生长板这一结果将对第一个组织的发育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.