Rspondin-Lgr Axis in Bone Regeneration

我们的资助项目R01DE030716，“响应素-LGR轴在骨再生中的作用”，专注于研究这种作用。 Rspo2-Lgr6信号在颅骨再生中的作用。虽然在治愈过程中有一些相似之处， 长骨和头盖骨之间存在着重要的区别。作为一个例子， 头盖骨仅通过膜内突愈合，而长骨则通过两者愈合。 膜内和软骨内成骨。另一个重要的区别是 颅骨和长骨愈合是促进骨愈合的祖细胞的来源和类型。在……里面 长骨，骨愈合过程中的一个关键方面，始于间充质的扩张。 祖细胞来自骨髓和骨膜，在受伤后立即发生。然后这些细胞变成 成骨细胞和软骨细胞。然而，控制长骨骨骼的机制 祖细胞/干细胞在损伤后的激活、扩增和分化反应很少被描述。这 补充内容将研究R-响应蛋白(配体)-LGR(受体)信号轴在调节长骨中的作用 祖细胞和骨骼再生。R-Spinins(屋顶板特异性Spinins)是一个四口之家分泌的。 与富含亮氨酸重复序列的G蛋白偶联受体4/5/6结合的基质细胞蛋白(Rspo1-4) (LGRS)。RSPO-LGR相互作用通过阻止Wnt FrizzledWnt翻转增强典型Wnt途径 受体，并因此决定典型的Wnt信号水平。虽然已知规范的WNT信令 在骨再生中发挥重要作用，但很少有研究探索WNT的正向调节因素 发信号。特别是，在长骨骨折愈合的背景下，RSPO-LGR的要求从未 由于缺乏适当的模型，对其进行了审查。我们的主要目标是定义以下要求 Rsp2/3和Lgr6在骨髓间充质祖细胞对股骨骨折反应中的作用。我们已经定义了两个具体的 旨在解决这一目标。在Aim1中，我们将使用Rspo2和Rspo3杂交的单个和复合小鼠 用αSMACreERT2小鼠干扰长骨间充质祖细胞的Rspo2/3基因 骨折时间。我们将评估体内祖细胞的增殖、Wnt信号和成骨作用，以及 通过使用µCT、组织学和机械测试分析愈合情况。在AIM 2中，Lgr6基因敲除小鼠将被 使用类似于目标1的参数来研究它们的骨愈合特性。该项目的完成将 确定Rspo2/3-Lgr6相互作用在长骨骨折愈合中的要求，并将提供新的 对cWnt信号在骨愈合中作用的机械论见解，可以直接与类似的 在父母赠款中进行的颅骨愈合实验。

Our funded grant, R01DE030716, ”Rspondin-Lgr Axis in Bone Regeneration”, is focused on examining the role of Rspo2-Lgr6 signaling in calvarial regeneration. While there are some similarities in healing processes that exist between long bones and bones of the skull, there are also important differences. As an example, the calvaria heals exclusively through an intramembranous process while long bones heal through both intramembranous and endochondral bone formation. An additional important difference that exists between calvarial and long bone healing is the source and type of progenitor cell that contributes to bone healing. In long bones, a critical aspect of the bone healing process begins with the expansion of mesenchymal progenitors from the marrow and periosteum, which occurs immediately after injury. These cells then become bone forming osteoblasts and chondrocytes. However, mechanisms that control long-bone skeletal progenitor/stem cell activation, expansion, and differentiation in response to injury are poorly described. This supplement will study the role of the R-spondin (ligand) – Lgr (receptor) signaling axis in regulating long bone progenitors and bone regeneration. R-spondins (roof plate specific spondin) are a family of four secreted matricellular proteins (Rspo1-4) that bind to Leucine-rich repeat-containing G-protein coupled receptors 4/5/6 (Lgrs). Rspo-Lgr interaction potentiate canonical Wnt pathway by preventing the turnover of Wnt Frizzled receptors, and hence determines canonical Wnt signaling levels. While canonical Wnt signaling is known to play an important role in bone regeneration, very little research has explored positive modulators of Wnt signaling. In particular, the requirement of Rspo-Lgr in the context of long-bone fracture healing has never been examined, due to the lack of appropriate models. Our primary goal is to define the requirement of Rspo2/3 and Lgr6 in mesenchymal progenitors in response to femoral fracture. We have defined two specific aims to address this goal. In Aim1, we will use single and compound Rspo2 and Rspo3 floxed mice crossed with an alphaSMACreERT2 mouse to disrupt the Rspo2/3 genes in long-bone mesenchymal progenitors at the time of fracture. We will assess in vivo proliferation, Wnt signaling, and osteogenesis of progenitors, and analyze healing by using µCT, histology, and mechanical testing. In Aim 2, Lgr6 knockout mice will be investigated for their bone healing properties using parameters similarly to Aim 1. Completion of this project will identify the requirement of Rspo2/3-Lgr6 interaction in long-bone fracture healing and will provide new mechanistic insights into the action of cWnt signaling in bone healing that can be directly compared to similar experiments conducted with calvarial healing in the parent grant.