Dynamic Fibrous Scaffolds for Repairing Dense Connective Tissues

描述（由申请人提供）：肌肉骨骼系统的纤维组织受到其固有愈合能力差的困扰。在上一个资助周期中，我们开发了生产新型复合电纺支架的技术，并使用这些支架开发具有天然组织特性和组织的基于细胞的组织工程构建体。在这次竞争性更新中，我们将重点转移到使用这些使能技术来增强内源性组织修复。我们的重点是膝关节半月板，一个纤维组织的关键适当的负荷转移和目前的修复策略不能恢复功能。这次更新的总体目标是利用这些脚手架 以在不同的时间尺度上递送多种药剂，从而专门解决内源性半月板修复的固有局限性。成人中的这些局限性包括滑膜炎症、低内源性细胞构成和细胞向伤口界面的移动受阻。这项建议将采用复合支架（在第一个供资周期期间开发），提供稳定的纤维比例（聚己内酯（PCL），以提供指导图案和机械稳定性），牺牲纤维部分（聚环氧乙烷（PEO），以确定初始支架孔隙率），和MMP-可裂解的透明质酸（HA）纤维部分（其响应于半月板损伤患者滑液中蛋白水解活性的升高而降解）。HA纤维部分的降解将增强细胞浸润（通过增加支架孔隙率），同时减少新生修复组织的降解（通过竞争性抑制滑膜MMP）。这些复合支架还将通过快速和局部降低内源性半月板细胞中的核硬度（通过递送降低异染色质含量和/或核纤层蛋白A/C加工的试剂）来解决通过致密周围ECM的有限细胞移动性。最后，这些支架将选择性地向伤口界面招募内源性半月板细胞，以加速和维持修复过程，通过递送基质衍生因子-1 β（SDF-1 β），一种增加半月板细胞迁移的强效细胞因子。这些不同修复佐剂的协同相互作用将通过体外支架和骨外植研究进行验证，然后在我们的大型动物（绵羊）半月板缺损模型中进行测试。如果成功，这些研究和技术将通过克服内源性半月板修复的固有局限性，为人类半月板损伤的临床转化和治疗奠定基础。

DESCRIPTION (provided by applicant): Fibrous tissues of the musculoskeletal system are plagued by their poor intrinsic healing capacity. In the previous funding cycle, we developed enabling technologies towards the production of a novel class of composite electrospun scaffolds, and used these scaffolds to develop cell-based tissue engineered constructs with native-like tissue properties and organization. In this competitive renewal, we shift our focus to using these enabling technologies to enhance endogenous tissue repair. Our focus is on the knee meniscus, a fibrous tissue critical for proper load transfer and for which current repair strategies do not restore function. The overall objective of this renewal is to use these scaffolds to deliver multiple agents over different temporal scales to specifically address the inherent limitations to endogenous meniscus repair. These limitations in the adult include synovial inflammation, low endogenous cellularity, and hindered cell mobility to the wound interface. This proposal will employ composite scaffolds (developed during the first funding cycle) that provide a stable fiber fraction (polycaprolactone (PCL), to provide an instructional pattern and mechanical stability), a sacrificial fiber fraction (polyethylene oxide (PEO), to define initial scaffold porosity), and an MMP-cleavable hyaluronic acid (HA) fiber fraction (that degrades in response to elevated proteolytic activity in synovial fluid of patients with meniscus damage). Degradation of the HA fiber fraction will both enhance cellular infiltration (by increasing scaffol porosity) and at the same time reduce degradation of nascent repair tissue (via competitive inhibition of synovial MMPs). These composite scaffolds will also address limited cellular mobility through the dense surrounding ECM by rapidly and locally decreasing nuclear stiffness (via the delivery of agents that reduce heterochromatin content and/or Lamin A/C processing) in endogenous meniscus cells. Finally, these scaffolds will selectively recruit endogenous meniscus cells towards the wound interface, to accelerate and sustain the repair process, via the delivery of stromal derived factor-1� (SDF-1�), a potent cytokine that increases meniscal cell migration. The synergistic interactions of these different repair adjuvants will be validated through in vitro scaffold and meniscal explant studies, and then tested in our large animal (ovine) meniscus defect model. If successful, these studies and technologies will set the stage for clinical translation and treatment of human meniscal injury by overcoming the inherent limitations to endogenous meniscus repair.