Analysis of the molecular and physiological influence of Wnt1 on the skeleton

Wnt1对骨骼的分子和生理影响分析

• 批准号: 504019650
• 负责人: Dr. Timur Yorgan
• 金额: --
• 依托单位: Institut für Osteologie und Biomechanik (IOBM)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/504019650?language=en
• 关键词: Analysis; molecular; physiological; influence; Wnt1

The Wnt signaling pathway is emerging as one of the most important regulatory mechanisms controlling bone remodeling. Especially the ligand Wnt1 turned out to play a major role in this context as demonstrated by several studies including our own previous investigations. Mutations of WNT1 in patients cause low bone mass pathologies and deterioration of bone matrix quality that were recapitulated in our respective murine disease models. Furthermore, conditional Wnt1 loss-of-function mouse lines displayed similar phenotypes with increased skeletal fragility. Most importantly, we were able to demonstrate the tremendous osteoanabolic potential of Wnt1 in an inducible mouse model (Wnt1-Tg).Despite these advances, several important questions regarding the influence of Wnt1 on the skeleton remain or have even been raised by the previous investigations: 1) A molecular influence of Wnt1 on cultured osteoblast progenitor cells was only observed in complex with Sfrp1. Recent data indicates that Sfrp1, generally considered to be a Wnt-signaling inhibitor, is required to solubilize Wnt1. Therefore we plan to investigate the necessity of Sfrp1 for the osteoanabolic effect of Wnt1 by cell culture experiments with recombinant proteins and cross breeding Wnt1-Tg with Sfrp1-deficient mice. 2) The main receptor for Wnt1 in the skeleton remains elusive. Importantly, our previous investigations indicate Fzd4 as a potential candidate. We plan to prove or refute this hypothesis by extensive cell culture experiments and cross breeding of Wnt1-Tg with Fzd4-deficient mice. These experiments are set up to be extended to other receptor candidates if necessary. 3) Although Wnt1 has been demonstrated to influence bone material quality in addition to bone mass, the underlying molecular mechanism has not been established. Results from our previous studies demonstrate that Osteomodulin is a downstream target of Wnt1 and that Osteomodulin may be a major effector facilitating the impact of Wnt1 signaling on bone quality. Published in vitro data from other groups show that Osteomodulin can regulate collagen fiber thickness, but no in vivo analyses have been performed to date. Therefore we plan to thoroughly investigate the skeletal phenotype of Osteomodulin-deficient mice and elucidate the connection between Wnt1 and Osteomodulin by cross breeding experiments with Wnt1-Tg mice. Overall, the investigations planned in this grant proposal have a high potential to generate novel and also clinically relevant insights into the molecular mechanisms explaining the influence of Wnt1 on the skeleton. While an understanding of the downstream effectors of Wnt1 may improve treatment of patients suffering from Wnt1-related skeletal pathologies, the identification of the receptor and crucial supportive molecules of the signal transduction pathway may highlight novel targets that can potentially be modulated to treat common skeletal disorders such as osteoporosis.

Wnt信号通路是骨重塑最重要的调控机制之一。特别是配体Wnt1在这种情况下发挥了重要作用，包括我们自己之前的研究在内的几项研究都证明了这一点。患者中WNT1的突变导致骨量低的病理和骨基质质量的恶化，这在我们各自的小鼠疾病模型中得到了概括。此外，条件Wnt1功能丧失小鼠系显示出与骨骼脆性增加相似的表型。最重要的是，我们能够在诱导小鼠模型（Wnt1- tg）中证明Wnt1具有巨大的骨合成代谢潜力。尽管有这些进展，关于Wnt1对骨骼影响的几个重要问题仍然存在，甚至在以前的研究中提出：1)Wnt1对培养的成骨祖细胞的分子影响仅在与strp1的复合物中观察到。最近的数据表明，通常被认为是wnt信号抑制剂的strp1是溶解Wnt1所必需的。因此，我们计划通过重组蛋白的细胞培养实验，以及Wnt1- tg与缺乏Sfrp1的小鼠杂交，来探讨Sfrp1对Wnt1骨代谢作用的必要性。2)骨架中Wnt1的主要受体尚不明确。重要的是，我们之前的研究表明Fzd4是潜在的候选者。我们计划通过广泛的细胞培养实验和Wnt1-Tg与fzd4缺陷小鼠的杂交来证明或反驳这一假设。如果有必要，这些实验将扩展到其他受体候选物。3)虽然Wnt1已被证明除了影响骨量外还影响骨材料质量，但其潜在的分子机制尚未建立。我们之前的研究结果表明骨调节素是Wnt1的下游靶点，骨调节素可能是促进Wnt1信号传导对骨质量影响的主要效应因子。其他研究小组发表的体外数据表明，骨调节蛋白可以调节胶原纤维的厚度，但迄今为止还没有进行体内分析。因此，我们计划通过与Wnt1- tg小鼠的杂交实验，深入研究骨调节蛋白缺失小鼠的骨骼表型，并阐明Wnt1与骨调节蛋白之间的联系。总的来说，本资助计划中的研究在解释Wnt1对骨骼影响的分子机制方面具有很高的潜力，并且具有临床相关性。虽然了解Wnt1的下游效应物可能会改善患有Wnt1相关骨骼疾病的患者的治疗，但识别信号转导途径的受体和关键支持分子可能会突出可能被调节治疗骨质疏松症等常见骨骼疾病的新靶点。