Circadian rhythms in the ageing spine: implications in intervertebral disc degeneration and stem-cell based regeneration

下背痛是最普遍的脊柱疾病之一，导致严重的疼痛和丧失活动能力。椎间盘（IVD）组织的进行性变性是一个主要原因，衰老是一个主要的风险因素。基于干细胞的治疗为IVD的组织再生和功能恢复提供了希望。Hoyland和Meng实验室首次显示了小鼠IVD组织外植体和人IVD细胞中的自主昼夜（24小时）节律（Dudek et al. Annals Rheum Dis 2016）。我们已经产生了选择性地破坏IVD中的昼夜节律的条件性BMAL 1（核心时钟因子）敲除小鼠模型，以及使用CRISPR-CAS技术的BMAL 1-Venus敲入小鼠模型（Yang et al.，PLoS Gen 2020）。这些令人兴奋的新发现和动物模型使我们在国际上处于独特的地位，并为我们进一步了解IVD变性和腰痛的发病机制提供了前所未有的新机会。因此，我们假设生物钟的破坏（例如，在衰老过程中）可能是人类椎间盘退变的关键风险因素。因此，增强昼夜节律可以减缓组织变性并促进基于干细胞的再生疗法。在这个博士项目中，我们将利用最先进的“组学”技术（RNAseq深度测序），生物信息学，高端成像，生物化学和时钟基因活动的监测，以阐明昼夜节律在人类椎间盘退变和基于细胞的治疗椎间盘退变的作用。该项目将为核心生物钟因子BMAL 1在IVD生理学和发病机制中的功能提供新的见解，并建立衰老和IVD昼夜节律破坏之间的机制联系。更重要的是，该项目将直接证明生物钟在人类退行性椎间盘和间充质干细胞分化方案中的相关性，这些方案目前正在开发用于治疗椎间盘退行性变和腰痛的细胞再生策略。

Low back pain is amongst the most prevalent spinal diseases, causing severe pain and loss of mobility. Progressive degeneration of the intervertebral disc (IVD) tissue is a major cause, with ageing as a major risk factor. Stem cell-based therapies provide hope for tissue regeneration of the IVD and restoration of function. The Hoyland and Meng labs have r shown, for the first time, an autonomous circadian (24 hourly) rhythm in mouse IVD tissue explants and human IVD cells (Dudek et al., Annals Rheum Dis 2016). We have generated a conditional BMAL1 (a core clock factor) knockout mouse model that selectively disrupts circadian rhythm in the IVD, and a BMAL1-Venus knock-in mouse model using CRISPR-CAS technique (Yang et al., PLoS Gen 2020). These exciting novel discoveries and animal models place us in a unique position internationally and provide an unprecedented new opportunity to further our understanding of the pathogenesis of IVD degeneration and low back pain. We therefore hypothesize that disruption to the circadian clock (for example, during ageing) may be a critical risk factor in human disc degeneration. Consequently, enhancing circadian rhythms may slow down tissue degeneration and promote stem-cell based regenerative therapies. In this PhD project, we will utilize state of the art "-omics" techniques (RNAseq deep sequencing), bio-informatics, high-end imaging, biochemistry and monitoring of clock gene activities, to elucidate roles of circadian rhythm in human disc degeneration and cell-based therapy for treatment of disc degeneration. This project will provide fresh new insights into the function of a core circadian clock factor BMAL1 in IVD physiology and pathogenesis and establish a mechanistic link between ageing and IVD circadian rhythm disruption. More importantly, the project will directly demonstrate the relevance of circadian clocks in human degenerative discs and mesenchymal stem-cell differentiation protocols being currently developed for cell based regenerative strategies for the treatment of disc degeneration and low back pain.