Skeletal Fragility

项目 2：细胞衰老在骨骼衰老中的作用 – 摘要 Khosla/Farr 项目 2，“细胞衰老在骨骼衰老中的作用”，测试了针对衰老的假设 使用治疗化合物的细胞可以延缓、预防或减轻与年龄相关的骨脆性。虽然我们的 已发表的和额外的初步数据强烈支持这一假设，更好地理解 需要负责与年龄相关的骨骼功能障碍的机制来指导发育和转化 骨质疏松症的治疗药物。在这个项目中，我们解决了几个关键的、未解决的问题： 细胞衰老在介导与年龄相关的骨质流失中的作用：（1）p16Ink4a- vs 的机制是什么 p21Cip1 驱动的衰老以及骨微环境中特定衰老细胞类型的衰老 导致与年龄相关的骨质流失？； (2) 清除衰老细胞是否会增强骨骼对衰老细胞的反应？ 合成代谢刺激？； (3) 衰老细胞是否会调节骨折愈合？除了这些项目特定的 问题，我们将从核心C（健康跨度表型）中的常见动物模型中获得骨骼组织 测试核心 B（药物发现与开发）中的新型治疗药物的骨骼功效并延长 使用新型转基因大鼠模型（INK-ATTAC 大鼠）对小鼠和大鼠进行了研究。我们将在 我们的 3 个具体目标的背景： 目标 1. 定义衰老细胞导致衰老的机制 相关的骨质流失和骨髓肥胖。使用新开发的 p21-ATTAC 小鼠和新型转基因 小鼠，LOX-ATTAC，能够清除细胞和时间特异性的衰老细胞，我们将测试 （目标 1a）p16Ink4a 与 p21Cip1 驱动的衰老和（目标 1b）特定细胞类型的相对贡献 骨（骨髓细胞、骨祖细胞、骨细胞）介导与年龄相关的骨骼脆性和骨髓脂肪 积累。在目标 1c 中，我们将定义 SASP 如何同时抑制骨形成并刺激骨形成 骨髓脂肪生成；然后，我们将使用中和来确定最重要的 SASP 因素 抗体和药理学方法。目标 2. 评估衰老细胞清除对 合成代谢骨骼疗法和骨折愈合。在目标 2a 中，我们将确定是否清除衰老细胞 细胞增强骨骼对合成代谢刺激的反应[间歇性 PTH (1-34) 和硬化蛋白抗体 疗法]。在目标 2b 中，我们将测试衰老细胞的清除是否会损害年轻小鼠的骨折愈合 但可以增强老年小鼠的骨折愈合。目标 3. 确定并优化缓解措施 两个物种与衰老相关的骨骼脆弱性。在目标 3a 中，我们将评估治疗方法 使用核心 C 中描述的常见小鼠模型在核心 B 中开发用于骨骼功效的化合物。 目标3b，我们将使用所有项目通用的INK-ATTAC大鼠模型来测试是否清除衰老细胞 还可以预防大鼠中与年龄相关的骨质流失和骨髓肥胖，从而评估细胞的作用 衰老介导第二个物种的骨骼衰老，因此更接近人类翻译。

PROJECT 2: The Role of Cellular Senescence in Skeletal Aging – SUMMARY Khosla/Farr Project 2, “The Role of Cellular Senescence in Skeletal Aging,” tests the hypothesis that targeting senescent cells using senotherapeutic compounds can delay, prevent, or alleviate age-related bone fragility. Although our published and additional preliminary data strongly support this hypothesis, a better understanding of the mechanisms responsible for age-related skeletal dysfunction is needed to guide development and translation of senotherapeutics for osteoporosis. In this Project, we address several key, unresolved questions regarding the role of cellular senescence in mediating age-related bone loss: (1) What are the mechanisms of p16Ink4a- vs p21Cip1-driven senescence as well as that of specific senescent cell types in the bone microenvironment in causing age-related bone loss?; (2) Does clearance of senescent cells enhance the skeletal response to an anabolic stimulus?; and (3) Do senescent cells modulate fracture healing? In addition to these Project-specific questions, we will derive skeletal tissues from the common animal models in Core C (Healthspan Phenotyping) to test novel senotherapeutics from Core B (Drug Discovery & Development) for skeletal efficacy and to extend findings in mice to rats using a novel transgenic rat model (INK-ATTAC rat). We will address these questions in the context of our 3 Specific Aims: Aim 1. Define the mechanisms by which senescent cells cause age- related bone loss and marrow adiposity. Using a newly developed p21-ATTAC mouse and novel transgenic mouse, LOX-ATTAC, capable of cellular- and temporal-specific senescent cell clearance, we will test the relative contributions of (Aim 1a) p16Ink4a- vs p21Cip1-driven senescence and (Aim 1b) specific cell types in bone (myeloid cells, osteoprogenitors, osteocytes) in mediating age-related skeletal fragility and marrow fat accumulation. In Aim 1c, we will define how the SASP simultaneously inhibits bone formation and stimulates marrow adipogenesis; then, we will identify the most important SASP factors responsible using neutralizing antibodies and pharmacological approaches. Aim 2. Evaluate the impact of senescent cell clearance on anabolic skeletal therapies and fracture healing. In Aim 2a, we will determine whether clearance of senescent cells enhances the skeletal response to anabolic stimuli [intermittent PTH (1-34) and sclerostin antibody therapy]. In Aim 2b, we will test whether clearance of senescent cells impairs fracture healing in young mice but enhances fracture healing in aged mice. Aim 3. Identify and optimize interventions that alleviate senescence-related skeletal fragility in two species. In Aim 3a, we will evaluate the senotherapeutic compounds developed in Core B for skeletal efficacy using the common mouse models described in Core C. In Aim 3b, we will use the INK-ATTAC rat model common to all Projects to test whether clearing senescent cells also prevents age-related bone loss and marrow adiposity in rats, thereby evaluating the role of cellular senescence in mediating skeletal aging in a second species, therefore moving closer to human translation.