The Use of Coacervate Technology as a New Drug Delivery System for Musculoskeleta

描述（由申请人提供）：关键尺寸骨缺损（包括颅面骨骼缺损）的不完全愈合很常见。成骨蛋白，包括骨形态发生蛋白2和4（BMP 2，BMP 4），促进骨愈合，但蛋白质具有短的半衰期，并迅速被血液清除，这限制了它们的效用。我们以前的工作的目标是开发基因治疗和组织工程方法，以有效地提供成骨蛋白和促进骨愈合使用肌源性干细胞（MDSC）。我们已经表明，基因工程改造表达BMP 2或4的鼠和人MDSC（hMDSC）可以向成骨谱系分化，并改善颅骨和长骨缺损的骨愈合。我们还发现，血管内皮生长因子（VEGF）的伴随基因递送改善了表达BMP 2或4的MDSC植入后的骨愈合。类似地，我们已经报道了从小鼠和人骨骼肌中分离的MDSC也能够软骨分化，并且可以用于促进急性损伤（骨软骨缺损）和疾病（骨关节炎[OA]）后的关节软骨修复，特别是当经遗传修饰以表达骨形态发生蛋白4（BMP 4-MDSC）时。然而，与骨相反，我们的研究结果还表明，MDSC的遗传修饰以表达BMP 4和血管生成拮抗剂sFlt-1，可以加速细胞的AC修复能力，支持阻断血管生成有利于AC修复的事实。 尽管在过去的几年里，我们在基于肌肉干细胞的骨和AC愈合治疗方面取得了实质性进展，但我们以前的大部分工作都涉及移植前干细胞的遗传修饰，这一步骤限制了工作的临床转化。因此，我们提出了一组新的实验，其旨在通过使用新型肝素-聚阳离子凝聚层递送系统来规避使用病毒转导的必要性，所述肝素-聚阳离子凝聚层递送系统能够缓慢释放所需的治疗性蛋白质，包括BMP 2、VEGF和/或sFlt-1，以与未转导的MDSC结合促进骨和AC修复。在第一组实验中，我们将利用肝素-聚阳离子凝聚层递送系统来递送BMP 2和VEGF以增强hMDSC介导的骨修复。第二组实验旨在利用肝素-聚阳离子凝聚层递送系统缓慢释放BMP 2和sFlt-1，与hMDSC组合，在诱导OA后促进AC修复，以增强AC修复。将使用凝聚物-hMDSC技术的骨和AC修复效率与基于hMDSC的基因疗法和基于hMDSC的游离蛋白质疗法（即不使用肝素-聚阳离子凝聚物）进行比较。该申请概述了一个新的研究领域，旨在提供基于新的生物工程概念的有价值的临床相关方法，用于治疗肌肉骨骼组织损伤和疾病。

DESCRIPTION (provided by applicant): Incomplete healing of critical size bone defects, including defects of the craniofacial skeleton, are common. Osteogenic proteins, including bone morphogenetic protein 2 and 4 (BMP2, BMP4), promote bone healing, but the proteins have short half-lives and are rapidly cleared by the bloodstream, which limits their utility. The goals f our previous work were to develop gene therapy and tissue engineering approaches to efficiently deliver osteogenic proteins and improve bone healing using muscle-derived stem cells (MDSCs). We have shown that murine and human MDSCs (hMDSCs) genetically engineered to express BMP2 or 4 could differentiate toward an osteogenic lineage and improve bone healing in calvarial and long bone defects. We also found that concomitant gene delivery of vascular endothelial growth factor (VEGF) improves bone healing after the implantation of BMP2 or 4 expressing MDSCs. Similarly, we have reported that MDSCs isolated from mouse and human skeletal muscle were also capable of chondrogenic differentiation and could be used to promote articular cartilage repair after acute injury (osteochondral defects) and disease (osteoarthritis [OA]), especially when genetically modified to express bone morphogenetic protein 4 (BMP4-MDSC). However, in contrast to bone, our findings also suggested that genetic modification of MDSCs to express both BMP4 and the angiogenic antagonist sFlt-1, could accelerate the AC repair capacity of the cells supporting the fact that blocking angiogenesis is beneficial for AC repair. Although we have made substantial progress in muscle stem cell based therapy for bone and AC healing over the past number of years, most of our previous work involved genetic modification of the stem cells prior to transplantation, a step that limits te clinical translation of the work. We therefore propose a new set of experiments which will aim to circumvent the necessity of using viral transduction via the use of a novel heparin-polycation coacervate delivery system capable of slowly releasing the required therapeutic proteins including BMP2, VEGF and/or sFlt-1 to promote bone and AC repair in conjunction with non- transduced MDSCs. In the first set of experiments we will utilize the heparin-polycation coacervate delivery system to deliver BMP2 and VEGF to enhance hMDSC mediated bone repair. The second set of experiment will aim to promote AC repair after the induction of OA utilizing the heparin-polycation coacervate delivery system to slowly release BMP2 and sFlt-1, in combination with hMDSCs, to enhance AC repair. The efficiency of bone and AC repair with the coacervate-hMDSCs technology will be compared to both hMDSC based gene therapy and hMDSC based free protein therapy (i.e. without the use of the heparin-polycation coacervate). This application outlines a new area of research designed to offer valuable clinically relevant approaches based on novel bioengineering concepts for the treatment of musculoskeletal tissues following injury and disease.