Mesenchymal Regulation of Osteogenesis

 描述(由申请人提供)：为了努力设计新的治疗颅面部出生缺陷、疾病和损伤的方法，需要进行更多的研究，以了解控制颌骨长度的发育机制。颌骨通常表现出一系列与大小相关的异常，包括下颌发育不全、下颌后突、不对称和唇裂。我们的研究将通过重点研究颌骨前体细胞的分配、增殖、分化和生长过程中颌骨长度是如何调节的，从而为解决这一未得到满足的需求提供关键信息。我们采用了一种独特的体内策略来操纵颌骨前体，这些前体是从神经脊间充质(NCM)胚胎发育而来的。我们公布的初步数据表明，NCM自主执行分子和组织学程序，确定颌骨骨骼的大小和形状。NCM如何完成如此复杂的任务，以及哪些特定的机制作为颌骨长度的决定因素，仍然是未知的。许多遗传学和胚胎学研究表明，Sonic Hedgehog(SHH)、成纤维细胞生长因子(成纤维细胞生长因子)、骨形态发生蛋白(BMP)和转化生长因子-β(转化生长因子-β)通路是决定颌骨长度的关键因素。我们假设，NCM以物种特异性的方式对SHH、FGF、BMP和TGF？信号进行差异调节和响应，从而调节颌骨祖细胞的增殖、分化和生长，并产生颌骨长度的变化。为了验证我们的假设，我们在一个新的嵌合系统中结合了鹌鹑和鸭子特定物种的发育程序。鹌鹑的下巴较短，而鸭子的下巴相对较长，并且鹌鹑胚胎的发育速度比鸭子快得多。在鹌鹑和鸭子之间交换NCM提供了一种独特的方式来操纵供体NCM和邻近宿主组织之间的信号传递，并允许发现NCM依赖的过程。我们提出三个相辅相成的具体目标。在目标1中，我们将确定调节颌骨前体种群大小的机制，并评估它们控制物种特定颌骨长度的程度。我们将专注于NCM介导的细胞周期长度，并进行功能增减实验，以确定祖细胞数量和细胞周期长度的变化何时何地会影响颌骨长度。在目标2中，我们将确定整合NCM介导的SHH和成纤维细胞生长因子信号、增殖动力学和颌骨长度的机制。我们将进行控制上皮-NCM相互作用的功能获得和功能丧失实验，并确定SHH和成纤维细胞生长因子信号的变化何时何地可以解释颌骨长度的变化。在目标3中，我们将确定NCM介导的BMP和转化生长因子？信号、分化和骨生长之间的联系机制。我们将使用获得和丧失功能的策略来了解骨沉积和骨吸收的变化如何影响颌骨长度。每个特定的目的都与临床相关，并可以作为分子疗法可以用于操纵颌骨长度的原则的证明。我们相信，我们的研究将为以生物学为基础的非手术方法治疗人类颌骨疾病奠定基础，而目前侵入性手术是唯一的选择。

 DESCRIPTION (provided by applicant): In an effort to devise novel treatments for craniofacial birth defects, disease, and injuries, more research needs to be done to understand developmental mechanisms that control jaw length. The jaws often display a range of size-related anomalies including mandibular hypoplasia, retrognathia, asymmetry, and clefting. Our study will provide critical information to address this unmet need by focusing on how jaw length gets regulated during the allocation, proliferation, differentiation, and growth of jaw precursor cells. We employ a unique in vivo strategy to manipulate jaw precursors, which arise embryonically from neural crest mesenchyme (NCM). Our published and preliminary data demonstrate that NCM autonomously executes molecular and histological programs that establish the size and shape of the jaw skeleton. How NCM accomplishes such a complex task, and what specific mechanisms function as determinants of jaw length, remain unknown. Many genetic and embryological studies point to the Sonic Hedgehog (SHH), Fibroblast Growth Factor (FGF), Bone Morphogenetic Protein (BMP), and Transforming Growth Factor-Beta (TGFß) pathways as crucial players in establishing jaw length. We hypothesize that NCM differentially regulates and responds to SHH, FGF, BMP, and TGFß signaling, in a species-specific manner, which modulates the proliferation, differentiation, and growth of jaw progenitors, and generates variation in jaw length. To test our hypothesis, we combine the species-specific developmental programs of quail and duck in a novel chimeric system. Quail have short jaws whereas those of duck are relatively long, and quail embryos develop much faster than do duck. Exchanging NCM between quail and duck provides a unique way to manipulate signaling between donor NCM and adjacent host tissues, and allows discovery of NCM-dependent processes. We propose three complementary Specific Aims. In Aim 1 we will identify mechanisms that regulate the size of the jaw progenitor population and assess the extent to which they govern species-specific jaw length. We will focus on NCM-mediated cell cycle length, and perform gain- and loss-of-function experiments to resolve when and where changes to progenitor numbers and cell cycle length can affect jaw length. In Aim 2 we will ascertain mechanisms that integrate NCM-mediated SHH and FGF signaling, proliferation dynamics, and jaw length. We will perform gain- and loss-of-function experiments that manipulate epithelial-NCM interactions, and determine when and where changes to SHH and FGF signaling can account for variation in jaw length. In Aim 3 we will determine mechanisms that link NCM- mediated BMP and TGFß signaling, differentiation, and bone growth. We will employ gain- and loss-of-function strategies to understand how changes in bone deposition and resorption can affect jaw length. Each Specific Aim is clinically relevant and can serve as a proof-of-principle that molecular therapies can be used to manipulate jaw length. We are confident that our research will provide a foundation for biologically-based, non- surgical methods to treat disorders of the human jaw, whereas currently invasive surgery is the only option.