COLLABORATIVE RESEARCH: Enhancing bone regeneration by mimicking the osteogenic niche

在美国每年发生的1300万例骨折中，约有10%无法修复，在极端情况下导致行动不便或截肢。自体骨移植是治疗复杂缺损最有效的方法，但可用的移植物材料有限，而且该过程涉及额外的手术，已知会导致许多患者的慢性供体部位疼痛。人间充质干细胞（hMSCs）促进骨愈合的能力已被广泛研究，但结果不一且令人失望。这至少部分是由于hMSCs在损伤部位的保留时间不足，不足以实现植入和促进修复。为了解决这些问题，研究人员利用小分子PPARã抑制剂GW9662对hMSCs进行处理，生成成骨增强型hMSCs （OEhMSCs）。这些OEhMSCs产生细胞外基质（hMatrix），显著增加hMSC的保留和颅骨缺损的骨修复。该项目的中心假设是，一种可注射的微球载体联合给药GW9662、hMatrix和hMSCs，将通过延长hMSC保留、营养因子分泌和宿主基质旁分泌激活的机制促进骨修复。为了验证这一点，将构建复合微球，并评估GW9662的递送和hMatrix在培养的hMSCs中的呈现，以及它们在小鼠颅骨模型中促进临界尺寸缺陷修复的能力。最后，确定由造血干细胞分泌的促进骨再生的可溶性因子。这些研究将为这种基于hmsc的骨修复新方法的临床应用奠定基础。该项目的成功完成可能会导致一种革命性的骨修复新方法，可以有效地消除再生骨科对自体骨移植的需求。这些研究是基于提供体内样微环境的概念，刺激hMSCs表现出正常组织生成时的行为。这一概念一般适用于hmsc介导的愈合，因此从所提出的研究中获得的知识最终可能应用于其他组织靶点的再生。用于构建和评价微球复合材料的方法和概念将在期刊和会议上广泛传播，并纳入德克萨斯农工大学的课程。PI在他的实验室里成功地指导了来自弱势群体的本科生研究人员；拟议的项目将为本科生在实验室进行研究提供额外的机会。作为该项目的一部分，将资助两名研究生攻读博士学位。PI和研究生将各自参与到大休斯顿地区的高中外展活动，并开发媒体，以便在德克萨斯州的学校系统中广泛使用。

1264848/1264832Kaunas/GregoryOf the 13 million yearly fractures that occur in the United States, about 10% fail to repair and in extreme cases result in immobility or amputation. While autologous bone grafts are the most effective method to heal complex defects, the available graft material is limited, and the procedure involves additional surgery known to cause chronic donor-site pain in many patients. Human mesenchymal stem cells (hMSCs) have been intensely investigated for their ability to promote bone healing, but results have been variable and disappointing. This is at least partly due insufficient retention of hMSCs at the site of injury for sufficient time to achieve engraftment and promote repair. In an attempt to solve these problems, hMSCs have been treated with the small molecule PPARã inhibitor GW9662 to produce osteogenically-enhanced hMSCs (OEhMSCs). These OEhMSCs produce extracellular matrix (hMatrix) that dramatically increases hMSC retention and osteorepair in calvarial defects. The central hypothesis for this project is that an injectable microsphere vehicle co-administering GW9662, hMatrix and hMSCs will promote osteo-repair through a mechanism that involves extended hMSC retention, trophic factor secretion and paracrine activation of the host stroma. To test this, composite microspheres will be constructed and assessed for GW9662 delivery and hMatrix presentation to hMSCs in culture, as well as for their ability to promote repair of critical-sized defects in a mouse calvarial model. Finally, soluble factors secreted by hMSCs responsible for promoting osteoregeneration will be identified. These studies will lay the groundwork for translating this novel hMSC-based method for osteo-repair to the clinic. Successful completion of this project could lead to a revolutionary new method for bone repair that could effectively dismiss the need for autologus bone graft in regenerative orthopedics. These studies are based on the concept that providing an in vivo-like microenvironment stimulates hMSCs to behave as they do during normal tissue generation. This concept applies to hMSC-mediated healing in general, thus the knowledge gained from the proposed studies may eventally be applied to the regeneration of other tissue targets. The methods and concepts used to construct and evaluate the microsphere composites will be broadly disseminated in journals and conferences and incorporated into courses taught at Texas A&M. The PI has a record of successfully mentoring undergraduate researchers from underrepresented populations in his lab; the proposed project will provide additional opportunities for undergraduate research in the laboratory. As part of the project, two graduate students will be supported for their doctoral studies. The PI and the graduate students will each participate in outreach to high schools in the greater Houston area and develop media for broad use in the Texas school system.