Adult Multipotent Mesenchymal Stromal Cells for Fracture Repair

描述（由申请人提供）：骨折损伤是一个重要的临床负担，仅在美国每年就有多达620万例骨折发生，其中10%伴有骨不连。目前骨移植物治疗骨不连的方法有很多缺点，导致对替代方法的迫切和未满足的需求。成人骨髓（BM）含有多能间充质基质细胞（MSC），具有治疗骨不连的新方法。MSC通过其多谱系、终末期间充质细胞类型分化潜能（自分泌效应）和通过分泌调节损伤组织再生微环境的生物活性分子（自分泌效应）具有充足的再生能力。在该资助的第一个周期，我们的实验室在几项已发表的研究中报道了移植后MSC的体内动态，它们在特定骨折痂骨内皮生态位中植入，在那里它们表达骨形态发生蛋白-2 (BMP-2)，以及它们对骨折组织愈合和强度的有益影响。我们还发现，移植的表达胰岛素样生长因子- i （IGF-I）的间充质干细胞在骨折痂内分化为骨细胞，并通过诱导比单独的间充质干细胞更多的新骨形成来促进骨折愈合。该建议的中心假设是MSC通过自分泌和旁分泌作用促进再生微环境，从而改善骨折修复过程。具体而言，我们提出以下建议：特异性目的1，确定MSC是否通过诱导BMP-2表达改善骨折修复过程；具体目的2，确定MSC编程表达IGF-I是否通过自分泌和旁分泌机制促进骨形成，从而改善骨折愈合。我们的研究结果将为充分认识MSC的再生能力开辟新的视角，从而为再生医学领域设定新的研究方向。一种综合的方法，结合体内和体外研究的基因工程小鼠，小鼠模型的不愈合和新的方法来评估骨折愈合将被应用于实现提出的目标。研究将具有重要的生物医学相关性和意义，因为它们可以更好地理解MSC促进骨折修复的机制，这将为开发新的基于MSC的治疗方法来促进骨不连患者的骨折愈合奠定基础。

DESCRIPTION (provided by applicant): Fracture injuries represent a significant clinical burden, with up to 6.2 million fractures occurring annually in the United States alone, of which 10% are complicated by non-unions. Current methods for treatment of non- unions with bone grafts have been fraught with multiple shortcomings, leading to an urgent and unmet need for alternative approaches. Adult bone marrow (BM) contains multipotent mesenchymal stromal cells (MSC) that have all the properties to become a novel therapeutic approach to treat non-unions. MSC have ample regenerative abilities via their multilineage, end-stage mesenchymal cell type differentiation potential (autocrine effect) and through secretion of bioactive molecules that regulate the regenerative microenvironment of an injured tissue (autocrine effect). During the first cycle of this grant, our laboratory has reported in several published investigations the in vivo dynamics of MSC after transplant, their engraftment within a specific fracture callus endosteal niche where they express bone morphogenic protein-2 (BMP-2) and their beneficial effects on fracture tissue healing and strength. We have also found that transplanted MSC expressing insulin- like growth factor-I (IGF-I) differentiate into bone cells within the fracture callus and promote fracture healing by inducing more new bone formation than MSC alone. The central hypothesis of this proposal is that MSC improve the fracture repair process by promoting a regenerative microenvironment through autocrine and paracrine actions. Specifically, we propose the following: Specific Aims1, to determine whether MSC improve the fracture repair process through induction of BMP-2 expression; Specific Aim 2, to determine whether MSC programmed to express IGF-I improve fracture healing by promoting bone formation through autocrine and paracrine mechanisms. Our results will open novel perspectives that will allow the full appreciation of the regenerative capacities of MSC and therefore set new research directions in the field of regenerative medicine. A comprehensive approach that combines in vivo and in vitro studies on genetically engineered mice, mouse models for non-unions and novel methods to assess fracture healing will be applied to accomplish the proposed aims. Studies would have major biomedical relevance and implications, as they lead to a better understanding of the mechanisms through which MSC promote fracture repair that will set the foundation for the development of novel MSC-based therapies to promote fracture healing in patients with non-unions. PUBLIC HEALTH RELEVANCE: Non-union fractures remain a challenging clinical problem that affect approximately 600,000 people every year in the United States. Because our elderly population is becoming larger, an increased incidence of non- unions as consequence of poor healing and age-related worsening of osteoporosis is expected. Adult bone marrow contains multipotent mesenchymal stromal cells (MSC) that have all the properties to become a novel therapeutic approach to treat non-unions. The overall goal of this proposal is to understand the mechanisms through which MSC exert their beneficial effects in fracture repair. Unraveling how MSC are capable to respond to the fracture regenerative clue and to provide the adequate environment for tissue regeneration will provide critical insights to develop novel MSC-based therapies to treat patients with non-unions