In vivo role of FLT3-CD45 signalling for bone remodelling

在上一个项目期间，使用疾病特异性小鼠模型研究了致癌受体酪氨酸激酶（RTK）FLT3-ITD和蛋白酪氨酸磷酸酶CD45在骨生成调节中的作用。为此，详细表征了FLT3-ITD表达小鼠的骨表型，并描述了FLT3-ITD和CD45失活对骨细胞活性的影响以及相关细胞类型的信号传导特征。因此，该项目阐明了FLT3-ITD在骨代谢调节中的先前未知作用。这些结果提供了对正常和病理性骨生理学的进一步了解。它为骨疾病的靶向影响提供了潜力，以建立改进的治疗方法。除了正在进行的项目特定工作外，我们还开始使用FLT3敲除小鼠（可在FLI Jena获得）和已建立的实验库进行研究，以解决野生型FLT3对骨形成的作用，用于分析骨生成。我们的初步工作清楚地显示了FLT3-WT在骨造血生态位形成中的先前未被注意的功能。此外，我们表征了FLT3-ITD阳性与FLT3-WT AML患者的基因表达谱。在这里，我们能够证明致癌FLT3-ITD的合成显著改变了参与成骨的许多组分的表达，并且它们的合成改变显著控制了FLT3-ITD-AML患者的生存。此外，我们的初步工作表明，产生FTL 3-ITD的AML患者会出现骨骼异常。计划的项目扩展的目标是从这项初步工作中招募的：i）FLT3灭活小鼠骨表型的详细表征。具体技术可在骨生物学专业的申请人2和3的实验室中获得。ii）来源于FLT3-ITD与FLT3-WT-AML患者的原代骨和细胞材料在骨微结构、骨转换和参与骨转换的细胞类型的比活性方面的比较。因此，该项目扩展将阐明FLT3介导的信号通路如何控制骨形成和重塑的机制。所涉及的骨细胞类型的分子特征、其干细胞生物学和再增殖能力将描述FLT3在骨代谢中的作用。FLT3-ITD AML患者样本的表征将提供对该癌基因如何控制骨重建、干细胞生态位以及两者在人体中相互作用的了解。解开这一机制对于理解正常和病理性造血和骨生理学至关重要，并提供了针对血液和骨骼疾病的潜力，以建立改进的治疗方法。

In the previous project period, the role of the oncogenic receptor tyrosine kinase (RTK) FLT3-ITD and protein tyrosine phosphatase CD45 in the regulation of osteogenesis was investigated using disease-specific mouse models. For this purpose, the bone phenotype of FLT3-ITD-expressing mice was characterized in detail, and the influence of FLT3-ITD and the inactivation of CD45 on bone cell activity and the signaling characteristics of the involved cell types was described. Thus, the project elucidated the previously unknown role of FLT3-ITD in the regulation of bone metabolism. These results provide further insight into normal and pathological bone physiology. It provides the potential for the targeted influencing of bone diseases to establish improved therapeutic approaches. In addition to the ongoing project-specific work, we started investigations that address the role of wild-type FLT3 on bone formation using FLT3 knock out mice (available at the FLI Jena) and the established experimental repertoire for the analysis of osteogenesis. Our preliminary work clearly shows a previously unnoticed function of FLT3-WT in the formation of the osteo-hematopoietic niche. Besides, we characterized the gene expression profiles of FLT3-ITD-positive versus FLT3-WT AML patients. Here we were able to show that the synthesis of oncogenic FLT3-ITD significantly alters the expression of a number of components involved in osteogenesis and their altered synthesis significantly controls the survival of FLT3-ITD-AML patients. In addition, our preliminary work has shown bone abnormalities occuring in AML patients that produce FTL3-ITD. The aims of the planned project extension are recruited from this preliminary work: i) The detailed characterization of the bone phenotype of mice inactivated for FLT3. The specific techniques are available in the laboratory of Applicants 2 and 3 specialized in bone biology. ii) Comparison of primary bone and cell material derived from FLT3-ITD with FLT3-WT-AML patients regarding bone microstructure, bone turnover and specific activity of cell types involved in bone turnover. Thus, this project extension will elucidate the mechanisms, how FLT3-mediated signaling pathways control bone formation and remodeling. The molecular characterization of the bone cell types involved, their stem cell biology, and repopulation capacity will describe the role of FLT3 in bone metabolism. Characterization of FLT3-ITD AML patient samples will provide insight, how this oncogene controls bone remodeling, the stem cell niche and the interaction of both in humans. Unraveling this mechanism is critical to understanding normal and pathological hematopoiesis and bone physiology, and provides the potential to target hematological and bone diseases to establish improved therapeutic approaches.