Role of Developmental Signaling Pathways in Maintenance of Spinal Discs

项目摘要/摘要 衰老是几种退行性疾病发病的重要风险因素，包括脊柱或 腰间盘(IVD)退变和伴随的慢性背痛。IVD变性与慢性背部 疼痛是最常见的神经疾病，也是巨大的经济负担，但没有治疗或治愈的方法。每个IVD都有 髓核(NP)的中央核心，周围环绕着纤维环(AF)的正交层 夹在连接IVD和椎体的一对终板之间。还有很多事情要做 了解了IVD生长、成熟和维持的关键调控因素，以及它们的损失是否与 年龄导致IVD病理。我们将使用条件遗传小鼠模型、血统追踪、异时 IVD器官培养、人盘样本分析和无偏见的高通量方法 识别IVD中关键发育调节因子的转录组学，包括Sonic Hedgehog(SHH) 维护以填补这些空白。我们的中心假设是NP细胞Shh的表达对 IVD的生长和成熟，以及与年龄相关的丧失导致了IVD的病理。的表达方式 脊索上的Shh信号配体对胚胎发育起着至关重要的作用。之前，我们证明了出生后的NP 细胞持续表达SHH，SHH信号调节NP细胞的增殖和细胞外基质的产生 和房颤。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都会关闭嘘的表达。此外，Shh表达的年龄相关性下降是 与NP细胞向多核合胞体的末端分化和随后的丢失有关 对IVD功能起重要作用的ECM蛋白表达下降。我们的初步数据也 结果表明，在成年小鼠中有条件地靶向Shh会加速IVD衰老，同时伴随着NP细胞的损失， 为这个新项目提供了合乎逻辑的前提。这些数据表明SHH信号是至关重要的；然而， 我们不知道它在生长和成熟过程中的确切功能，也不知道它是否对衰老的IVD至关重要。目标 1将检验SHH是一个关键信号通路的假设，它的下游调节因子发挥着不同的 在婴儿期和成熟期起作用，它的缺失会导致IVD病理。目标2将检验这一假设 Shh表达的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将研究SHH信号在延缓衰老方面的有益作用。 我们期望这项研究的完成将为卫生和卫生局作为关键的监管机构的作用提供深入的见解。 IVD的生长和成熟，并确定靶向这类分子的途径，以逆转或延缓 推进老龄化进程，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.