The application of trabecular bone organoids to investigate mineral-sensing in skeletal physiology and disease

应用小梁骨类器官研究骨骼生理学和疾病中的矿物质感应

• 批准号: NC/X000907/1
• 负责人: Alexandra Iordachescu
• 金额: $ 9.22万
• 依托单位: University of Birmingham
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NC%2FX000907%2F1
• 关键词: application; trabecular; bone; organoids; investigate

Bone is an endocrine organ which fulfils a whole range of vital functions. One of these is the process of calcium and phosphate homeostasis, two elements which, in bone tissue, are associated to form the mature mineral, hydroxyapatite, and within the circulation are essential for numerous cell processes, including clotting, signalling and even muscle contraction. The bone mineral content is maintained by resident cells in this tissue; and is continuously adjusted with ageing, mechanical stress, as well as the physiological demands. The key controller of calcium and phosphate regulation is the calcium sensing receptor (CaSR), located in several organs, including the kidneys. Importantly, within the parathyroid glands, it controls the secretion of the parathyroid hormone (PTH) in response to fluctuating levels of calcium in the circulation. As such, bone uses this signalling path to release these ions from its mineralised tissue, as required. Because these processes are very inter-related, when these signalling paths are dysregulated, they lead to abnormal levels of mineral in the tissue itself or within the circulation, as well as triggering further pathologies. Abnormal changes can take place when one or more of these organ functions is dysregulated. For example, in chronic kidney disease (CKD), inadequate removal of phosphate leads to excessive circulating levels of this ion and an exacerbated increase in PTH secretion, which can result in complications such as osteoporosis, due to excessive removal of mineral. It is therefore essential to better understand the molecular interaction with bone in order to develop novel therapeutics and better interventions for bone loss and other metabolic dysfunctions. Currently, rodent models (rats and mice) are used in laboratories around the world to study these mechanisms and to test compounds. Many models require detrimental procedures such as surgical interventions, immobilisation or genetic alterations to remove components that are involved in the bone formation process. Secondly, some of these models are too complex to allow isolation of individual organ effects. This represents a bottleneck in the search for promising therapeutics. Previous NC3Rs funded work conducted by Dr Alexandra Iordachescu (Uni. Birmingham), allowed the development of a model of mature bone in vitro for the first time, where mineral and cells could be monitored over extended periods of time (up to one year and beyond). Subsequently, through further NC3Rs funding, Dr Iordachescu miniaturised this model into an organoid system which contained a complete spectrum of cells found in bone and was suitable for studying early events, including bone loss, mineral deposition; as well as for conducting larger-scale pharmacological testing. At the same time, recent work from Dr Donald Ward's lab (Uni. Manchester) identified that phosphate also binds at sites on the CaSR, acting as a phosphate sensor, explaining how excessive circulating phosphate worsens secondary hyperparathyroidism (the resulting increase in PTH secretion) in CKD. Because this receptor has been shown in mice models to be present in bone, where it responds to and controls fracture repair and callus maturation, it is important to understand how the fluctuating levels of phosphate affect the receptor in this tissue. This is of importance also because major clinical trials where clinical compounds were targeting this receptor did not necessarily cause beneficial increases in bone mass. Therefore, these bone organoids will be applied to test several pathological conditions in order to detect novel information, particularly as they allow the monitoring of mineral and recapitulate many of the fracture repair events. This project will therefore translate and transfer the knowledge and skills into a molecular endocrinology lab, reducing the need for genetically-altered mouse models to test these hypotheses, which would require a large number of rodents.

骨是一个内分泌器官，可实现各种重要功能。其中之一是钙和磷酸盐稳态的过程，这两个元素在骨组织中与成熟的矿物质，羟基磷灰石相关，而在循环中，对于许多细胞过程至关重要，包括凝结，信号传导甚至肌肉收缩。居民细胞在该组织中维持骨矿物质含量。并通过衰老，机械应力以及生理需求进行连续调整。钙和磷酸盐调节的关键控制器是位于包括肾脏在内的多个器官中的钙传感受体（CASR）。重要的是，在甲状旁腺内，它控制着甲状旁腺激素（PTH）的分泌，以响应循环中钙的波动水平。因此，骨骼使用此信号通路将这些离子从其矿化组织中释放出来。由于这些过程非常相关，因此当这些信号通路失调时，它们会导致组织本身或循环中矿物质的异常水平，并触发进一步的病理。当这些器官一个或多个功能失调时，可能会发生异常的变化。例如，在慢性肾脏疾病（CKD）中，磷酸盐的去除不足会导致该离子的过度循环水平和PTH分泌的加剧增加，这会导致诸如骨质疏松症的并发症，例如骨质疏松症，由于过度去除矿物质。因此，必须更好地了解与骨骼的分子相互作用，以开发新的治疗疗法，并更好地干预骨质流失和其他代谢功能障碍。当前，啮齿动物模型（大鼠和小鼠）用于世界各地的实验室中，以研究这些机制并测试化合物。许多模型需要有害程序，例如手术干预，固定或遗传改变，以去除骨骼形成过程中涉及的组件。其次，其中一些模型太复杂了，无法隔离单个器官效应。这代表着寻找有希望的治疗剂的瓶颈。以前的NC3RS资助了Alexandra Iordachescu博士（Uni。Birmingham）进行的工作，允许在体外开发成熟的骨骼模型，在该模型中，可以在长时间（最多一年及以后）内对矿物和细胞进行监测。随后，通过进一步的NC3RS资金，Iordachescu博士将该模型小型化为一个类器官系统，该模型包含骨骼中发现的完整细胞，适合研究早期事件，包括骨质流失，矿物质沉积；以及进行大规模的药理测试。同时，唐纳德·沃德（Donald Ward）博士（Uni。Manchester）的最新工作确定，磷酸盐在CASR上的位点也结合起来，充当磷酸盐传感器，解释了CKD中的磷酸循环过多会使继发性甲状旁腺功能降临（PTH分泌的增加）如何恶化。由于该受体已在小鼠模型中显示在骨骼中，在骨骼中反应并控制骨折修复和愈伤组织的成熟，因此了解磷酸盐的波动水平如何影响该组织中的受体很重要。这也很重要，因为临床化合物靶向该受体的主要临床试验并不一定会导致骨骼量的有益增加。因此，这些骨骼类器官将用于测试几种病理条件以检测新信息，特别是因为它们允许监测矿物质并概括许多断裂修复事件。因此，该项目将把知识和技能转化为分子内分泌学实验室，从而减少了对遗传变化的小鼠模型测试这些假设的需求，这将需要大量的啮齿动物。