Development of Osteogenic Oxysterols for Local Bone Formation

用于局部骨形成的成骨氧甾醇的开发

• 批准号: 8501384
• 负责人: FARHAD PARHAMI
• 金额: $ 32.92万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-11 至 2016-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8501384
• 关键词: Address; Adverse effects; Animal Model; Animals; BMP2 gene; Blood Circulation; Bone Marrow; Bone Matrix; Bone Morphogenetic Proteins; Bone Transplantation; Calvaria; Cholesterol Homeostasis; Collagen; Defect; Development; Effectiveness; Embryo; Erinaceidae; Family; Fibroblasts; Fracture; Future; Gene Targeting; Goals; Healed; Human; In Vitro; Investigation; Ligands; Liver; Mediating; Mediator of activation protein; Mesenchymal; Mesenchymal Stem Cells; Modeling; Molecular; Molecular Mechanisms of Action; Mus; Neonatal; Nuclear; Organ Culture Techniques; Osteogenesis; Parents; Pathway interactions; Play; Property; Proteins; Rat-1; Rattus; Receptor Activation; Receptor Signaling; Recombinants; Relative (related person); Reporting; Role; Signal Pathway; Signal Transduction; Speed; Spinal Fusion; Stromal Cells; Structure-Activity Relationship; Testing; Tissues; analog; bone; bone cell; bone healing; clinically relevant; comparative efficacy; cost; healing; immunogenic; improved; in vitro activity; in vivo; in vivo Model; lipid biosynthesis; notch protein; novel; osteogenic; osteoprogenitor cell; receptor; response; scaffold; small molecule; smoothened signaling pathway; transcription factor

DESCRIPTION (provided by applicant): We have previously reported that specific endogenously produced small molecule oxysterols, formed in vivo as intermediaries of cholesterol metabolism, have potent osteogenic effects on multipotent mesenchymal stem cells (MSC) in vitro. We have shown that these effects are mediated through activation of the Hedgehog (Hh) signaling pathway, independent of Hh proteins. In addition, we have demonstrated that these oxysterols induce bone formation in neonatal mouse calvaria organ cultures, and bone healing in both a rat calvarial critical-sized defect model and a rat spinal fusion model in vivo. Thus, these oxysterols could potentially replace currently used expensive recombinant bone morphogenetic proteins (BMPs) and autogenous bone grafts for stimulation of local bone formation in non-healing fractures and critical bone defects. In addition, we have shown that when used in combination with BMPs, osteogenic oxysterols greatly reduce the concentration of BMPs required to induce effective osteogenesis in vitro. Accordingly, we have recently performed oxysterol structure activity relationship (SAR) studies that have resulted in the synthesis of a novel family of potent oxysterol analogues that possess osteogenic and anti-adipogenic activity equal or superior to the parent oxysterols. However, in addition to activating the Hh pathway, osteogenic oxysterols also activate liver X receptor (LXR) signaling whose role in osteogenesis is unclear and may promote oxysterol-induced osteogenesis by regulating targets of Notch signaling. Therefore, we hypothesize that osteogenic oxysterol analogues activate Hh and LXR signaling in osteoprogenitor cells and that both signaling pathways play an important role in osteogenic responses to oxysterols. To examine this hypothesis, we will pursue the following specific aims: 1) Elucidate the molecular signaling profile of osteogenic oxysterol analogues to determine the role and relative activation levels of Hh and LXR signaling in oxysterol-induced osteogenesis in vitro; 2) Examine the osteogenic activity of oxysterols and their mechanism of action in vivo for local administration using the rat spinal fusion and femoral defect models, while defining the optimal scaffold for local delivery and elucidating the role of Hh signaling in oxysterol effects in vivo; and 3) Examine the role of baseline and oxysterol-induced Hh pathway activity in BMP2-induced osteogenesis by determining whether Hh signaling through Gli transcription factors mediates the synergy between oxysterols and BMPs in stimulating osteogenesis in vitro and in vivo, and whether oxysterols may potentially improve the quality of the newly formed bone by inhibiting BMP2 stimulation of adipogenesis. These studies will provide important new information regarding the basic mechanisms regulating osteogenesis and the effects of oxysterols, as well as guidance for future investigations of oxysterols as a potential new class of osteoinductive agents for localized and perhaps systemic osteoregeneration.

描述（由申请人提供）：我们之前曾报道过，体内形成的特定内源性小分子氧甾醇作为胆固醇代谢的中介物，在体外对多能间充质干细胞（MSC）具有有效的成骨作用。我们已经证明，这些效应是通过激活 Hedgehog (Hh) 信号通路介导的，与 Hh 蛋白无关。此外，我们还证明这些氧甾醇在新生小鼠颅盖器官培养物中诱导骨形成，并在大鼠颅骨临界尺寸缺损模型和体内大鼠脊柱融合模型中诱导骨愈合。因此，这些氧甾醇有可能取代目前使用的昂贵的重组骨形态发生蛋白（BMP）和自体骨移植物，以刺激不愈合骨折和严重骨缺损的局部骨形成。此外，我们还发现，当与 BMP 结合使用时，成骨氧甾醇可大大降低体外诱导有效成骨所需的 BMP 浓度。因此，我们最近进行了氧甾醇结构活性关系（SAR）研究，合成了一个新的强效氧甾醇类似物家族，其具有等于或优于母体氧甾醇的成骨和抗脂肪形成活性。然而，除了激活Hh通路外，成骨氧甾醇还激活肝X受体（LXR）信号，其在成骨中的作用尚不清楚，并且可能通过调节Notch信号的靶点来促进氧甾醇诱导的成骨。因此，我们假设成骨氧甾醇类似物激活骨祖细胞中的Hh和LXR信号传导，并且这两种信号通路在氧甾醇的成骨反应中发挥重要作用。为了检验这一假设，我们将追求以下具体目标：1）阐明成骨氧甾醇类似物的分子信号传导谱，以确定Hh和LXR信号在体外氧甾醇诱导成骨中的作用和相对激活水平； 2）利用大鼠脊柱融合和股骨缺损模型，研究氧甾醇的成骨活性及其体内局部给药的作用机制，同时确定局部递送的最佳支架，并阐明Hh信号在氧甾醇体内作用中的作用； 3) 通过确定通过 Gli 转录因子的 Hh 信号传导是否介导氧甾醇和 BMP 之间在体外和体内刺激成骨方面的协同作用，以及氧甾醇是否可能潜在地发挥作用，检查基线和氧甾醇诱导的 Hh 通路活性在 BMP2 诱导的成骨中的作用通过抑制 BMP2 对脂肪生成的刺激来提高新形成骨的质量。这些研究将为调节骨生成的基本机制和氧甾醇的作用提供重要的新信息，并为氧甾醇作为潜在的新型骨诱导剂用于局部甚至全身骨再生的未来研究提供指导。