The effect of parathyroid hormone on modeling-based bone formation

 描述(申请人提供)：应聘者：我获得了生物医学工程博士学位。我的博士后培训侧重于骨微结构变化的临床研究，这些变化会影响骨量减少、骨质疏松症和其他代谢性骨骼疾病的骨强度和骨折风险。我的长期目标是发展成为一名独立的研究调查员，能够将骨成像和生物力学领域与骨细胞和分子生物学相结合。因此，我在这里的具体目标是获得细胞和分子生物学以及活体动物模型方面的培训，以揭示和阐明甲状旁腺激素诱导的、基于模型的骨形成的整体机制。通过将我在创新成像和图像分析方面的专业知识与细胞、分子和活体动物方法相结合，拟议的研究项目有望成为理解甲状旁腺素合成代谢作用的直接建模部分的重大新尝试。导师和咨询委员会：主要导师Louis Soslowsky博士是肌肉骨骼组织机械适应方面的国际领导者，他将担任我的职业发展和科学内容方面的导师。共同导师莫里齐奥·帕西菲博士是世界著名的骨骼发育和生长科学家，他将担任科学导师。咨询委员会的成员包括约翰·霍普金斯大学的曹旭博士，他将为骨骼建模和重塑提供建议；保拉·迪维埃蒂·帕耶维奇博士，他将为哈佛医学院的甲状旁腺素受体和骨细胞信号转导提供建议；以及凌勤博士，他将提供细胞和分子实验技能方面的实践培训。环境：宾夕法尼亚大学的研究/培训环境包括McKay整形外科研究实验室15,500平方英尺的共享实验室空间；多个共享实验设施，包括一台活体和一台标本微型计算机断层扫描(µCT)扫描仪、组织学核心设施、细胞和分子生物学设备以及机械测试核心设施；为研究人员提供的大量隔膜设施，用于传统和屏障住房选择；众多研讨会和讲师以及职业发展课程。培训计划：培训计划包括在导师和顾问的实验室进行利用转基因小鼠模型的技术的研究培训，以及使用组织学、生化分析和免疫组织化学进行细胞和分子测量。培训计划还包括关于衰老的分子生物学、补助金撰写、职业发展和负责任的研究行为的课程；出席与候选人研究培训有关的几个研讨会系列；期刊俱乐部；以及每年至少两次全国会议上的陈述。研究：目前的骨质疏松症治疗旨在引起抗分解代谢或合成代谢的骨反应。然而，由于骨形成-吸收耦合机制，抑制骨吸收的药物往往会抑制骨形成，而促进骨吸收的药物也会增加骨吸收，从而限制了其潜在的益处。相反，一些研究，包括我们最近进行的研究，表明用双膦酸预处理后间歇性重组人甲状旁腺激素1-34(IPTH)治疗可能导致基于模型的骨形成，即骨形成与最小的吸收激活。通过这一机制，iPTH和抗分解代谢药物的联合治疗可以在最小限度伴随骨吸收的情况下激活骨形成，从而产生比目前单一治疗更强的整体有益效果。然而，临床试验的结果变化很大。争议仍然存在，部分原因是甲状旁腺素在控制基于模型的骨形成中的作用机制不清楚。最近的研究表明，甲状旁腺激素通过调节骨细胞中的Sost/skerostin、RANKL和OPG而作用于骨细胞，控制骨吸收和形成之间的平衡。有趣的是，最近发现用硬化素中和抗体治疗可以诱导强烈的基于模型的骨形成。IPTH已被证明下调硬化素的产生，这导致了我们的中心假设，iPTH调节基于模型的骨形成，部分是通过作用于骨细胞并影响其信号活性来实现的。根据这项研究，目的1是在幼年和老年小鼠模型中，研究iPTH对骨小梁和皮质骨表面骨形成的影响。我们将利用我们基于微CT的新型3D活体骨动态成像方法，结合2D组织学方法，以无与伦比的灵敏度和准确性对单个部位基于建模和重塑的骨形成进行表征。目标2是勾勒出 骨细胞和成骨细胞中甲状旁腺素受体(PPR)在iPTH诱导的、基于模型的骨形成中的表达。在这里，我们将确定这种合成代谢反应是否需要在骨细胞或成骨细胞中表达PPR。Dmp1-Creer、PPRfl/fl和Ocn-Creer；PPRf1/fl小鼠将分别用他莫昔芬诱导骨细胞和成骨细胞PPR缺陷。将评估他们对iPTH以及iPTH和阿伦磷酸钠联合治疗的反应。我们预计，这项研究将阐明更有效的治疗骨质疏松症的策略，这些策略有利于骨质疏松症的形成而不是吸收。对候选人的机构承诺：候选人在宾夕法尼亚大学担任终身教职，该校为研究生和博士后提供实验室空间、创业资金和支持。

 DESCRIPTION (provided by applicant): Candidate: I obtained my Ph.D in Biomedical Engineering. My post-doc training focused on clinical investigations of changes in bone microstructure that affect bone strength and fracture risk in osteopenia, osteoporosis, and other metabolic bone diseases. My long-term goal is to develop as an independent research investigator able to combine the fields of bone imaging and biomechanics with bone cell and molecular biology. Thus, my specific objective here is to obtain training in cell and molecular biology and in vivo animal models in order to uncover and clarify the overall mechanisms behind PTH-induced, modeling-based bone formation. By combining my expertise in innovative imaging and image analyses with cellular, molecular and in vivo animal approaches, the proposed research project promises to represent a major new first attempt to understand the direct modeling component of PTH's anabolic action at the local level. Mentor and Advisory Committee: The primary Mentor Dr. Louis Soslowsky, an international leader in mechanical adaptation of musculoskeletal tissue, will serve as my mentor for both career development and scientific content. The co-Mentor Dr. Maurizio Pacifici, a world-renowned scientist in skeletal development and growth, will serve as scientific mentor. The advisory committee consists of Dr. Xu Cao at the Johns Hopkins University, who will advise on bone modeling and remodeling; Dr. Paola Divieti Pajevic at the Harvard Medical School, who will advise on PTH receptor and osteocyte signaling; and Dr. Ling Qin at my local institution, who will provide hands-on training in cellular and molecular experiment skills. Environment: The research/training environment at Penn includes 15,500 ft2 of shared lab space in the McKay Orthopaedic Research Laboratory; multiple shared experimental facilities, including an in vivo and a specimen micro computed tomography (µCT) scanner, histology core facilities, equipment for cellular and molecular biology, and mechanical testing core facilities; numerous vivarium facilities available to investigators for both conventional and barrier housing options; numerous seminars and lecturers, and career development courses. Training Plan: The training plan includes research training in the Mentors' and advisors' laboratories in techniques utilizing genetically-modified mouse models, and cell and molecular measurements using histology, biochemical assays, and immunohistochemistry. The training plan also includes courses in the molecular biology of aging, grant writing, career development, and responsible conduct of research; attendance at several seminar series pertinent to candidate's research training; journal clubs; and presentations at a minimum of 2 national conferences per year. Research: Current osteoporosis treatments aim to elicit an anti-catabolic or anabolic bone response. However, due to bone formation-resorption coupling mechanisms, drugs inhibiting bone resorption often inhibit formation, and those increasing formation also increase resorption, thereby limiting their potential benefits. In contrast, several studies including those we recently performed, suggest that pre-treatment with bisphosphonates followed by intermittent recombinant human parathyroid hormone 1-34 (iPTH) treatment may result in modeling-based bone formation, i.e., bone formation with minimal activation of resorption. Through this mechanism, a combination therapy of iPTH and anti-catabolic agents could activate bone formation with minimal concomitant bone resorption, thus eliciting an overall beneficial effect stronger than current mono- therapies. However, results from clinical trials have been highly variable. Controversies remain, due in part to unclear mechanisms of PTH's role in controlling modeling-based bone formation. Recent studies suggested that PTH acts on osteocytes to control the balance between resorption and formation through the regulation of Sost/sclerostin, RANKL and OPG in osteocytes. Interestingly, treatment with a sclerostin-neutralizing antibody was recently found to induce strong modeling-based bone formation. iPTH has been shown to down-regulate sclerostin production, leading to our central hypothesis that iPTH regulates modeling-based bone formation and does so partially by acting on osteocytes and influencing their signaling activity. According, Aim 1 is to characterize modeling-based bone formation on trabecular and cortical bone surfaces in response to iPTH in a young and old mouse model. We will exploit our novel 3D, µCT-based, in vivo bone dynamic imaging approaches, combined with 2D histological methods, to allow characterization of modeling- and remodeling- based bone formation at individual sites with unparalleled sensitivity and accuracy. Aim 2 is to delineate the roles of the PTH receptor (PPR) in osteocytes and osteoblasts in iPTH-induced, modeling-based bone formation. Here we will determine whether this anabolic response requires expression of PPR in osteocytes or osteoblasts. Dmp1-CreER; PPRfl/fl and OCN-CreER; PPRfl/fl mice will be treated with tamoxifen to induce PPR deficiency in osteocytes and osteoblasts, respectively. Their responses to iPTH and combined iPTH and alendronate treatment will be evaluated. We anticipate that this investigation will shed light on more efficient therapeutic strategies for osteoporosis that favor formation over resorption. Institutional Commitment to the Candidate: The candidate holds a tenure-track faculty position at Penn, which has provided laboratory space, start-up funding, and support for graduate students and post-docs.