Adult Multipotent Mesenchymal Stromal Cells for Fracture Repair

描述(由申请人提供)：骨折损伤是一项重大的临床负担，仅在美国每年就有多达620万例骨折发生，其中10%的骨折合并为骨不连。目前骨移植治疗骨不连的方法存在多种缺陷，导致对替代方法的迫切和未得到满足的需求。成人骨髓(BM)含有多能间充质基质细胞(MSC)，具有成为治疗骨不连的新方法的所有特性。间充质干细胞通过其多谱系、终末期间充质细胞类型的分化潜能(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)而具有丰富的再生能力。在这笔赠款的第一个周期中，我们的实验室在几个已发表的研究中报道了MSC在移植后的体内动力学，它们在表达骨形态发生蛋白-2(BMP-2)的特定骨折骨痂内的植入，以及它们对骨折组织愈合和强度的有益影响。我们还发现，表达胰岛素样生长因子-I(IGF-I)的移植MSC在骨折骨痂中分化为骨细胞，通过诱导比单独使用MSC更多的新骨形成来促进骨折愈合。这一建议的中心假设是，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。具体地说，我们提出如下建议：特异性目的1，确定MSC是否通过诱导BMP-2表达来改善骨折修复过程；特异性目的2，确定编程表达IGF-I的MSC是否通过自分泌和旁分泌机制促进骨形成，从而促进骨折愈合。我们的结果将开辟新的视角，使人们能够充分了解MSC的再生能力，从而在再生医学领域设定新的研究方向。将采用一种综合的方法，结合对基因工程小鼠的体内和体外研究、小鼠骨不连模型和评估骨折愈合的新方法来实现拟议的目标。这些研究将具有重大的生物医学意义和意义，因为它们有助于更好地了解MSC促进骨折修复的机制，这将为基于MSC的新疗法的开发奠定基础，以促进骨不连患者的骨折愈合。 公共卫生相关性：骨不连骨折仍然是一个具有挑战性的临床问题，每年在美国影响大约60万人。由于我们的老年人口越来越多，由于骨质疏松症的愈合不良和年龄相关的恶化，预计骨不连的发生率会增加。成人骨髓含有多能间充质基质细胞(MSC)，具有成为治疗骨不连的新方法的所有特性。这项建议的总体目标是了解MSC在骨折修复中发挥其有益作用的机制。揭示MSC如何对骨折再生线索作出反应并为组织再生提供足够的环境，将为开发基于MSC的治疗骨不连患者的新疗法提供关键的见解

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