Tissue Engineering Strategies to Revitalize Allografts

由于先天畸形，创伤， 感染和肿瘤切除。全世界每年进行的骨移植手术超过200万例， 临床‘黄金标准’是使用自体移植物。自体移植完全愈合和融合，由 骨膜，一层薄薄的组织和骨周围的骨膜细胞(PC)。然而，自体移植是有限的。 由于组织可获得性和供体部位发病率。因此，脱细胞同种异体移植物被普遍采用。 然而，缺乏骨膜的同种异体移植物重建和与宿主组织整合的能力有限。 在植入后2年和10年内，直接导致约35%和60%的失败率。骨膜介导的 修复是由各种上下文线索协调的，包括基质重塑和粘连以及时间上的 明确释放旁分泌因子。我们的主要假设是同种异体移植物的愈合将会戏剧性地 通过捕捉组织工程骨膜(TEP)中的关键愈合线索进行了改进。在第一个资金周期中， 我们率先开发了TEP，它将间充质干细胞(MSCs)和OPs整合到 可降解的聚乙二醇基水凝胶，形成于同种异体移植物周围， 类似于天然骨膜。TEP显示出促进小鼠同种异体移植物愈合的突出前景，导致 植入后9周，最大骨折扭矩比未改良的同种异体骨增加300%。 然而，愈合受到纤维组织的困扰，这导致同种异体移植物仅占自体移植物的50%。 最大扭矩。纤维化与宿主血管/组织对TEP的低支持渗透是一致的，a 大量水解性TEP降解造成的限制，导致支撑的结构性不足 完全的宿主组织渗透。因此，此次更新的重点是蜂窝改装的TEP，它能够 局部的、细胞要求的降解，同时保持大量水凝胶的性质以支持宿主组织 渗透。概述了三个具体目标：具体目标1：调整TEP矩阵线索(粘附肽和 基质金属蛋白酶可降解的交联物)，以协调组织渗透和促进同种异体移植物愈合。具体目标2： TEP介导的宿主组织募集的特征。具体目标3：利用优化的TEP矩阵交付 模拟骨膜旁分泌提示的多肽是可翻译的、无细胞的TEP。成功完成这些任务 AIMS将大大提高我们对骨膜如何协调同种异体移植物愈合和修复的理解 设计工程化骨膜来促进这些骨再生过程。开发出的材料 平台和一般方法也很容易应用于其他组织工程应用。

There are limited options for reconstruction of bone defects resulting from congenital anomalies, trauma, infection, and oncologic resection. Over 2 million bone graft procedures are performed annually worldwide, with the clinical ‘gold standard’ being the use of autografts. Autografts fully heal and integrate, mediated by the periosteum, a thin layer of tissue and periosteal cells (PCs) surrounding bone. However, autografts are limited due to tissue availability and donor site morbidity. Thus, decellularized allografts are commonly employed. However, the limited ability of allografts, which lack periosteum, to remodel and integrate with the host tissue directly contributes to ~35% and 60% failure rates within 2 and 10 years of implantation. Periosteal-mediated healing is coordinated by a variety of contextual cues including matrix remodeling and adhesion and temporally defined release of paracrine factors. Our overarching hypothesis is that allograft healing will be dramatically improved by capturing critical healing cues in a tissue engineered periosteum (TEP). In the first funding cycle, we pioneered development of the TEP, which incorporates mesenchymal stem cells (MSCs) and OPs within hydrolytically degradable poly(ethylene glycol)(PEG)-based hydrogels, which are formed around allografts, similar to native periosteum. TEP shows outstanding promise to enhance murine allograft healing, resulting in a 300% increase in maximum fracture torque versus unmodified allografts at 9 weeks post-implantation. However, healing was plagued by fibrotic tissue, which results in the allograft limited to ~50% of autograft maximum torque. Fibrosis is consistent with poorly supported infiltration of TEP by host vessel/tissue, a limitation resulting from bulk hydrolytic TEP degradation which results in structural insufficiencies to support complete host-tissue infiltration. Thus, the focus of this renewal is a cellularly remodeled TEP, which enables localized, cell-demanded degradation while maintaining bulk hydrogel properties to support host-tissue infiltration. Three specific aims are outlined: Specific Aim 1: Tune TEP matrix cues (adhesive peptides and MMP-degradable crosslinks) to coordinate tissue infiltration and improve allograft healing. Specific Aim 2: Characterize TEP-mediated host-tissue recruitment. Specific Aim 3: Exploit the optimized TEP matrix to deliver peptides emulating periosteal paracrine cues as a translatable, acellular TEP. Successful completion of these Aims will significantly advance our understanding of how the periosteum coordinates allograft healing and the design of engineered periosteum to promote these bone regeneration processes. The developed material platforms and general approach are also readily applicable in other tissue engineering applications.