Mechanisms of Tfr1-mediated iron uptake in bone and effects of iron on bone cell bioenergetics

成骨细胞依赖于铁的微妙平衡来进行适当的分化和功能。虽然铁是各种细胞过程所必需的，包括DNA复制，增殖和细胞呼吸，但高水平的铁抑制成骨细胞功能。尽管有这些知识，我们对铁对成骨细胞的影响的基本理解仍然非常有限。到目前为止，还不清楚铁如何影响成骨细胞的细胞功能，哪些代谢途径参与调节细胞功能，以及铁是否具有相同的影响，这取决于成骨细胞的分化状态。甚至不知道铁是如何进入成骨细胞的。在这个项目中，我们将破译这些未解决的方面。我们假设转铁蛋白受体1（Tfr1）是成骨细胞中主要的铁摄取受体。此外，我们的初步数据使我们假设，高浓度的铁促进成骨细胞增殖的分化为代价，从而限制骨形成。这些假设将通过研究成骨细胞特异性Tfr1基因敲除小鼠在稳态和骨缺损条件下的骨表型进行检验。由于破骨细胞在骨吸收中起主要作用，Tfr 1的作用也没有在体内得到解决，我们还将表征破骨细胞特异性Tfr 1敲除小鼠。为了解决特定成骨细胞亚群如何利用铁，我们将使用单细胞RNA测序，非靶向代谢组学和体外功能测试将代谢谱与特定成骨细胞亚群及其功能（例如增殖与基质生产与基质矿化）联系起来。该项目将揭示Tfr1对骨骼铁吸收的重要性，并将提供铁在成骨细胞功能和生物能量学中的作用的详细见解。

Osteoblasts rely on a delicate balance of iron for proper differentiation and function. While iron is necessary for various cellular processes including DNA replication, proliferation, and cellular respiration, high levels of iron suppress osteoblast function. Despite this knowledge, our basic understanding on the impact of iron on osteoblasts remains very limited. To date, it is unclear how iron affects cellular functions in osteoblasts, what metabolic pathways are involved in regulating cell function, and if iron has the same impact depending on the differentiation state of the osteoblasts. It is even unknown how iron enters into osteoblasts. In this project, we will decipher these unresolved aspects. We hypothesize that transferrin receptor 1 (Tfr1) is the main iron-uptake receptor in osteoblasts. Moreover, our preliminary data lead us to hypothesize that high concentrations of iron promote osteoblast proliferation at the expense of differentiation, thereby limiting bone formation. These hypotheses will be tested by investigating the bone phenotype of osteoblast-specific Tfr1 knockout mice under homeostatic and hormone-deficiency conditions. As osteoclasts play a major role in bone resorption and the role of Tfr1 has also not been addressed in vivo, we will also characterize osteoclast-specific Tfr1 knock-out mice. To address how iron is utilized by specific osteoblast subsets, we will use single-cell RNA sequencing, untargeted metabolomics, and functional tests in vitro to link metabolic profiles to specific osteoblast subsets and their function (e.g. proliferation vs. matrix production vs. matrix mineralization). This project will unravel the importance of Tfr1 for iron uptake in the skeleton and will provide detailed insights into the role of iron in osteoblast function and bioenergetics.