Mesenchymal Regulation of Osteogenesis

 描述（由申请人提供）：为了设计颅面出生缺陷、疾病和损伤的新治疗方法，需要进行更多的研究以了解控制颌骨长度的发育机制。颌骨通常显示一系列与大小相关的异常，包括下颌发育不全、下颌后缩、不对称和裂。我们的研究将提供关键信息，以解决这一未满足的需求，重点是如何在颌骨前体细胞的分配，增殖，分化和生长过程中调节颌骨长度。我们采用了一种独特的在体内的策略来操纵颌骨前体，这产生胚胎从神经嵴间充质（NCM）。我们发表的和初步的数据表明，NCM自主执行分子和组织学程序，建立颌骨的大小和形状。NCM如何完成这样一个复杂的任务，以及什么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指出，Sonic Hedgehog（SHH），成纤维细胞生长因子（FGF），骨形态发生蛋白（BMP）和转化生长因子-β（TGF β）途径是建立颌骨长度的关键因素。我们假设NCM以物种特异性方式差异调节和响应SHH、FGF、BMP和TGF β信号传导，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，我们联合收割机结合鹌鹑和鸭的物种特异性发育程序在一个新的嵌合系统。鹌鹑的下颚短，而鸭子的下颚相对较长，鹌鹑的胚胎发育比鸭子快得多。鹌鹑和鸭之间的NCM交换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导，并允许发现NCM依赖性过程。我们提出了三个互补的具体目标。在目标1中，我们将确定机制，调节颌骨祖先人口的大小，并评估在何种程度上，他们管理物种特异性颌骨长度。我们将专注于NCM介导的细胞周期长度，并进行增益和功能丧失实验，以解决何时何地祖细胞数量和细胞周期长度的变化会影响颌骨长度。在目标2中，我们将确定整合NM介导的SHH和FGF信号传导，增殖动力学和颌骨长度的机制。我们将进行增益和功能丧失的实验，操纵上皮细胞NCM的相互作用，并确定何时何地SHH和FGF信号的变化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TGF β信号传导、分化和骨生长之间的联系机制。我们将采用获得和丧失功能的策略来了解骨沉积和吸收的变化如何影响颌骨长度。每个特定目标都具有临床相关性，可以作为分子疗法可用于控制钳口长度的原理证明。我们相信，我们的研究将为基于生物学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.