The role of the osteocyte in responses to osteoporosis anabolic treatment in humans and mice

骨质疏松症和其他骨脆性疾病可以用两类药物治疗：抗吸收药 (双磷酸盐，RANKL抗体)或合成代谢物，及其连续或联合使用。合成代谢药物包括 甲状旁腺素类似物(Teriparatide和Abaloparatide)和硬化素抗体(scl-Ab，Romosozumab)和增加 BMD和降低骨折风险，但它们有局限性，随着时间的推移，它们的活性会减弱。了解 它们的合成代谢作用和药效随时间的下降的潜在机制可能有助于识别新的 治疗靶点，并导致更好的骨合成代谢药物。本应用程序重点介绍了 骨细胞是骨骼中含量最丰富的细胞，也是骨骼建模和重塑的“协调者”，在 PTH1-34和Scl-Ab在人和小鼠体内的作用重要的是，骨细胞是骨移植的靶细胞。 PTH/PTHrP和硬化素的来源。在小鼠中，甲状旁腺素受体或WNT的骨细胞特异性缺失 受体(LRP5/6)分别阻止对PTH1-34或scl-Ab治疗的合成代谢反应，建立 坚定地认为，骨细胞在对合成代谢治疗的反应中发挥着主要作用。他们如何为 对人类合成代谢活动下降的反应和反应尚不清楚。在这里，我们建议确定 人和小鼠骨细胞对合成代谢治疗的反应，比较早期和晚期时间 点数回应。为此，绝经后骨质疏松症(PMOP)患者的活体组织标本 对女性进行组织形态计量学、超高分辨率µ-CT和背向散射电子显微镜(BSEM)分析。 从这些样本中提取的富含骨细胞的制剂将通过RNA测序进行分析。平行的，相似的 方法将应用于OVX小鼠，一种PMOP模型，用同样的药物治疗。 我们的具体目标是：1)具体目标。测定和比较人骨细胞的变化 甲状旁腺素(1-34)(Teriparatide)早期反应和硬化素抗体早期和晚期反应的网络 (Romosozumab)在PMOP中。2)特定目的2.测定和比较小鼠骨细胞的变化 相同合成代谢药物(PTH1-34和scl-Ab)在小鼠模型中早期和晚期反应中的网络 并将这些变化与目标1中对PMOP妇女的观察结果进行比较。 该项目有助于CORT的翻译主题，并解决由 CORT来推进翻译的总体目标。它可能揭示新的治疗机制和靶点。 这可能会显著提高合成代谢疗法的疗效，甚至可能是安全的。此外，这个项目 与项目1有关，因为骨细胞影响骨稳态和骨髓微环境，以及 生物信息学研究核心，在转录组分析中至关重要。该项目的成果将 通过将骨细胞的变化与骨的调节联系起来，通知CORT中提出的其他项目 建模/重塑和骨骼干细胞行为。这些研究将有助于产生新的假说 骨脆性疾病的合成代谢反应的治疗诱导。

Osteoporosis and other diseases of bone fragility are treated with two classes of drugs: Anti-resorptives (bisphosphonates, antibodies to RANKL) or anabolics, and their sequential or combined use. Anabolics include PTH analogs (Teriparatide and Abaloparatide) and sclerostin antibody (Scl-Ab, Romosozumab) and increase BMD and reduce fracture risk, but they have limitations and their activity wanes over time. Understanding the mechanisms underlying their anabolic action and their decrease in efficacy over time could help identify novel therapeutic targets and lead to better osteo-anabolic drugs. This application focuses on the role of osteocytes, the most abundant cells in bone and “orchestrator” of bone modeling and remodeling, in mediating the effects of PTH1-34 and Scl-Ab in humans and in mice. Importantly, osteocytes are target cells of PTH/PTHrP and the source of sclerostin. In mice, osteocyte specific deletion of the PTH receptor or the WNT receptors (LRP5/6) prevents the anabolic response to PTH1-34 or Scl-Ab treatment, respectively, establishing firmly that osteocytes play a major role in the responses to anabolic treatments. How they contribute to the responses and to the decline in anabolic activity in humans is not known. Here, we propose to determine the response of osteocyte to anabolic treatments, in humans and in mice, comparing early and late time points responses. For this purpose, human biopsy samples from post-menopausal osteoporotic (PMOP) women will be analyzed by histomorphometry, ultra-high resolution µ-CT and back-scattered EM (BSEM). Osteocyte-enriched preparations from these samples will be analyzed by RNA sequencing. In parallel, similar methods will be applied to OVX mice, a PMOP model, treated with the same agents. Our specific aims are: 1) Specific Aim1. Determine and compare the changes in the human osteocyte network in early responses to PTH(1-34) (Teriparatide) and early and late responses to sclerostin antibody (romosozumab) in PMOP. 2) Specific Aim 2. Determine and compare the changes in the mouse osteocyte network in early and late responses to the same anabolic drugs (PTH 1-34 and Scl-Ab) in a mouse model of PMOP and compare these changes to the observations made in Aim 1 in PMOP women. This project contributes to the translational theme of the CORT and addresses critical questions identified by the CORT to advance the overall translational objectives. It may reveal novel therapeutic mechanisms and targets that could significantly improve the efficacy, and possibly safety, of anabolic therapies. Further, this project relates to Project 1, since osteocytes influence bone homeostasis and the bone marrow micro-environment, and to the Bioinformatics Research Core, essential in the transcriptome analysis. The outcomes of this project will inform the other projects proposed in the CORT by linking changes in osteocytes to the regulation of bone modeling/remodeling and skeletal stem cells behavior. These studies will help generate novel hypothesis for the therapeutic induction of an anabolic response in diseases of bone fragility.