COLLABORATIVE RESEARCH: Enhancing bone regeneration by mimicking the osteogenic niche

1264848/1264832考纳斯/格雷戈里在美国每年发生的1300万例骨折中，约10%无法修复，在极端情况下会导致无法动弹或截肢。虽然自体骨移植是修复复杂缺损的最有效方法，但可用的移植材料有限，而且该过程涉及额外的手术，已知的手术会导致许多患者供区的慢性疼痛。人们对人骨髓间充质干细胞(HMSCs)促进骨愈合的能力进行了深入的研究，但结果是多种多样的，令人失望。这至少部分是由于hMSCs在损伤部位没有保持足够的时间来实现植入和促进修复。为了解决这些问题，hMSCs被小分子PPARã抑制剂GW9662处理以产生成骨增强型hMSCs(OEhMSCs)。这些OEhMSCs产生细胞外基质(HMatrix)，显著增加hMSC在颅骨缺损中的保留率和骨对。该项目的中心假设是，联合应用GW9662、hMatrix和hMSCs的可注射微球载体将通过延长hMSC保留、营养因子分泌和宿主基质旁分泌激活的机制来促进骨修复。为了测试这一点，将构建和评估复合微球，用于GW9662递送和hMatrix呈现给培养中的hMSCs，以及它们促进修复小鼠颅骨模型中临界大小的缺陷的能力。最后，将确定hMSCs分泌的促进骨再生的可溶性因子。这些研究将为将这种基于hMSC的新型骨修复方法转化为临床奠定基础。该项目的成功完成可能会带来一种革命性的骨修复新方法，可以有效地消除再生骨科中自体骨移植的需要。这些研究是基于这样一个概念，即提供一个类似活体的微环境可以刺激hMSCs在正常组织生成期间的行为。这一概念一般适用于hMSC介导的修复，因此，从拟议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。用于构建和评估微球复合材料的方法和概念将在期刊和会议上广泛传播，并被纳入德克萨斯A&M大学教授的课程。PI有在他的实验室成功指导来自代表性不足人群的本科生研究人员的记录；拟议的项目将为实验室中的本科生研究提供更多机会。作为该项目的一部分，将支持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的外联活动中，并开发在德克萨斯州学校系统中广泛使用的媒体。

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.