The Nmp4 Anti-Anabolic Bone Axis R01AR070144-01A1

骨质疏松症治疗的圣杯仍然是…的恢复骨量…“1和随之而来的骨折 还原。目前的骨质疏松症治疗方法有很大的局限性2，NIAMS的目标包括 解决“为什么一些治疗剂在长期使用和探索过程中变得不那么有效” 发现新发现的新药治疗分子靶点的机会“3.携带有 编码转录因子Nmp4的基因功能丧失突变是健康、长寿和 表现出不起眼的骨骼表型，直到受到包括几个合成代谢刺激的挑战 骨质疏松症治疗类别，可促进骨形成4-8。没有基线 表型与改善的治疗反应相结合，为发展Nmp4提供了独特的优势。 (或其上游/下游成分之一)作为安全靶点，以提高现有疗法的疗效 确定新疗法的分子靶点。我们的目标是确定禁用Nmp4如何提高 对药物治疗的骨合成代谢反应，以区分可翻译的靶向分子 对病人来说。我们已发表的和初步的-omic5，生化5-7，11和骨机械数据告诉我们 假设Nmp4限制骨祖细胞的数量，并调节其成分、生产和 输出基质，并最终输出骨骼的机械性能。此外，Nmp4在成骨细胞中的丢失 大大提高了整体mRNA的翻译，与诱导部分展开的一致 蛋白质反应(UPR)，这有助于扩大内质网的处理能力，促进蛋白质 分泌，将成骨细胞转化为超级分泌细胞11。我们建议这些超级秘书 释放不成比例高水平的骨钙素和骨桥蛋白5，7，这两种物质有助于形成骨桥 抗骨折骨87。三个独立的目标将揭示Nmp4行动的机制。 目的#1：确定驱动NMP4-/-对合成代谢药物反应的特定细胞类型(S)。去卵巢小鼠 含有来自MSPC、成骨细胞或破骨细胞的Nmp4选择性基因组缺失(FLOX)的患者将得到治疗 骨质疏松症的单一疗法和联合疗法。以NMP4通路为靶点进行药理学研究 干预确定驱动有益效果的细胞类型是至关重要的。目标2：确定NMP4如何 调节成骨细胞核糖体的生物发生，基质蛋白的全局和基因特异性的mRNA翻译率， 普遍定期审议的战略部分符合对ER扩张的控制。普遍定期审议途径是一种潜在的 多种疾病的治疗目标，包括骨质疏松21-27。目标3：确定矩阵和 NMP4-/-骨的矿物组成在能量耗散机制的背景下 疲劳和断裂韧性试验28-33。完成这一目标将为两国关系提供视角 成骨细胞分泌体和骨材料特性之间的关系。我们有一个强大的方法来放大 本研究旨在评估现有骨质疏松症治疗方法的有效性，为新的治疗方法提供新的分子靶点。

“The holy grail of osteoporosis therapy remains the restoration of … bone mass…”1, and consequent fracture reduction. Current osteoporosis therapies have significant limitations2 and NIAMS objectives include addressing “why some therapeutic agents become less effective with long-term use and “exploring opportunities for discovery of newly identified molecular targets for new drug treatments”3. Mice harboring a loss-of-function mutation in the gene encoding the transcription factor Nmp4 are healthy, long-lived, and exhibit an unremarkable skeletal phenotype until challenged with an anabolic stimulus including several classes of osteoporosis therapies, which elicits enhanced bone formation4-8. The absence of a baseline phenotype, combined with the improved response to therapy, affords a unique advantage for developing Nmp4 (or one of its upstream/downstream components) as a safe target to enhance efficacy of existing therapies and identify molecular targets for new therapies. Our goal is to determine how disabling Nmp4 improves the osteoanabolic response to drug treatments, in order to distinguish targetable molecules that can be translated to patients. Our published and preliminary –omic5, biochemical5-7,11, and bone mechanical data inform our hypothesis that Nmp4 limits the number of osteoprogenitors and regulates the composition, production, and export of the matrix and ultimately bone mechanical properties. Furthermore, loss of Nmp4 in osteogenic cells sharply enhances global mRNA translation, coincident with induction of select portions of the unfolded protein response (UPR), which serve to expand the processing capacity of the ER and facilitate protein secretion, converting the osteoblast into a super-secretory cell11. We propose that these super-secretors release a disproportionately high level of osteocalcin and osteopontin5,7 that contribute to the formation of fracture resistant bone87. Three independent aims will reveal the mechanisms underlying Nmp4 action. Aim #1: identify the specific cell type(s) driving the Nmp4-/- response to anabolic agents. Ovariectomized mice harboring selective genomic deletion (flox) of Nmp4 from MSPCs, osteoblasts, or osteoclasts will be treated with mono- and combination osteoporosis therapies. To target the Nmp4 pathways for pharmacological intervention it is crucial to identify the cell type driving the beneficial effects. Aim #2: determine how Nmp4 regulates osteoblast ribosome biogenesis, global and gene-specific mRNA translation rates of matrix proteins, and strategic portions of the UPR coincident with control of ER expansion. The UPR pathway is a potential therapeutic target for numerous disorders including osteoporosis21-27. Aim #3: determine the matrix and mineral composition of the Nmp4-/- bone in the context of energy dissipation mechanisms subsequent to fatigue and fracture toughness tests28-33. Completion of this aim will provide perspectives into the relationship between the osteoblast secretome and bone material properties. We have a powerful way to magnify the effectiveness of existing osteoporosis therapies and provide novel molecular targets for new therapies.