Role of Developmental Signaling Pathways in Maintenance of Spinal Discs

项目总结/摘要 衰老是几种退行性疾病发病的重要危险因素，包括脊柱或 椎间盘（IVD）变性和相关的慢性背痛。IVD变性和慢性背部 疼痛是最重要的神经系统疾病和巨大的经济负担，但没有治疗或治愈。每个IVD都有 髓核（NP）的中心核心，由纤维环（AF）的正交层包围， 夹在将IVD连接到椎体的一对终板之间。仍有许多工作要 了解了IVD生长、成熟和维持的关键调节因子，以及它们的丢失是否与 年龄导致IVD病理。我们将使用条件遗传小鼠模型，谱系追踪，异时 IVD器官培养、人类椎间盘样本分析和高通量无偏倚方法 转录组学，以确定关键的发育调节剂，包括音刺猬（SHH），在IVD 以填补这些空白。我们的中心假设是NP细胞的Shh-表达对于 IVD的生长和成熟，以及其年龄相关的损失导致IVD病理学。的表达 脊索的SHH信号配体对于胚胎发生至关重要。以前，我们表明，产后NP 细胞继续表达SHH，SHH信号调节NP细胞增殖和NP细胞分泌ECM。 虽然所有的NP细胞都是表达Shh的脊索细胞的后代，但我们的初步数据显示， 他们中的大多数人在出生后关闭了嘘的表达。此外，与年龄相关的Shh表达下降， 与NP细胞终末分化为多核合胞体和随后的沿着丢失有关 对IVD功能重要的ECM蛋白表达下降。我们的初步数据还 显示成年小鼠中Shh的条件性靶向加速IVD老化，沿着NP细胞的损失， 为这个新项目提供了逻辑前提。这些数据表明SHH信号传导是至关重要的;然而， 我们不知道它在生长和成熟过程中的确切功能，也不知道它是否对老化的IVD至关重要。目的 1将测试假设SHH是一个关键的信号通路，其下游调节剂发挥不同的作用。 它在婴儿期和成熟期发挥重要作用，其丧失导致IVD病理。目标2将检验假设 表达Shh的NP细胞是祖细胞，Shh的随机表达调节所有NP 细胞的分子异质性目的3研究SHH信号通路对延缓衰老的有益作用。 我们希望这项研究的完成将提供对SHH作为一种关键调节剂的作用的见解。 的生长和成熟，并确定靶向这些分子的途径，以逆转或延迟 加快老龄化进程，提高老龄人口的生活质量。

PROJECT SUMMARY/ ABSTRACT Aging is a significant risk factor for the onset of several degenerative diseases, including spinal or intervertebral disc (IVD) degeneration and associated chronic back pain. IVD degeneration and chronic back pain are top neurological disorders and substantial financial burden, but with no therapy or cure. Each IVD has a central core of nucleus pulposus (NP), surrounded by orthogonal layers of annulus fibrosus (AF), together sandwiched between a pair of endplates that connect the IVD to the vertebral bodies. Much remains to be learned about the critical regulators of IVD growth, maturation, and maintenance, and whether their loss with age results in IVD pathologies. We will use conditional genetic mouse models, lineage tracing, heterochronic IVD organ culture, analysis of human disc samples, and unbiased approaches of high throughput transcriptomics to identify crucial developmental regulators', including sonic hedgehog (SHH), in IVD maintenance to fill in these gaps. Our central hypothesis is that Shh-expression by the NP cells is essential for growth and maturation of the IVD, and its age-related loss leads to the IVD pathologies. The expression of SHH signaling ligand by the notochord is crucial for embryogenesis. Previously, we showed that postnatal NP cells continue to express SHH, and SHH signaling regulates NP cell proliferation and ECM production by NP and AF. Though all NP cells are descendants of Shh-expressing notochord cells, our preliminary data reveals that most of them turn-off Shh expression after birth. Besides, age-related decline in Shh expression is associated with terminal differentiation of NP cells into multinucleated syncytium and subsequent loss along with the declined expression of ECM proteins that are important for IVD function. Our preliminary data also show that conditional targeting of Shh in adult mice accelerates IVD aging, along with the loss of NP cells, providing the logical premise for this new project. These data indicate that SHH signaling is crucial; however, we do not know its precise function during growth and maturation and whether it is critical for aging IVDs. Aim 1 will test the hypothesis that SHH is a critical signaling pathway and its downstream regulators play a distinct role during infancy and maturation, and its loss causes IVD pathologies. Aim 2 will test the hypothesis that Shh-expressing NP cells are the progenitor cells, and the stochastic expression of Shh regulates all NP cells' molecular heterogeneity. Aim 3 will investigate the beneficial effects of SHH signaling for delaying aging. We expect that the completion of this study will provide insights into the role of SHH as a critical regulator of growth and maturation of the IVD and identify avenues for targeting such molecules to reverse or delay the aging process and improve the quality of life of the aging population.