Repressing Retrotransposon LINE-1: New Concepts for Osteoarthritis Treatment

摘要 骨关节炎(OA)是一种退行性关节疾病，涉及关节软骨退化，慢性 炎症和骨骼重塑。虽然它是老年人残疾的主要原因，但没有FDA 目前批准的治疗骨关节炎的疾病药物(DMOADs)。科学上的挑战是 对衰老或退变过程中关节炎症和退变的触发机制认识不完全 在受伤后，这阻碍了可以针对这些过程的DMOAD的发展。科学目标 这个项目的目的是确定反转录转座子长散布的核元件-1(Line-1，或L1)， 它在正常体细胞中被抑制，但在衰老或创伤后的衰老细胞中被解除抑制 损伤，会导致衰老相关或创伤后骨性关节炎(PTOA)。我们发现L1水平显著地 人骨关节炎软骨损伤及衰老相关骨关节炎和PTOA小鼠关节软骨中的升高 模特们。创新的假设是，在衰老和/或损伤相关的骨性关节炎期间，L1的细胞内容物 反转录转座子是1)关节中显著增加，2)负责刺激SASP和 导致关节破坏的炎症。如果是这样的话，可以通过使用FDA抑制L1来抑制OA的发病。 批准的抗病毒药物核苷逆转录酶抑制剂(NRTI)。这一假设将得到检验。 通过R61阶段的两个目标。第一个目标是表征衰老和损伤引起的L1抑制 在Col2a1-CreERT2；miR-365小鼠中，能够诱导早发性骨性关节炎和/或PTOA。它将建立 无论是衰老、损伤，还是两者兼而有之，都会导致小鼠关节中L1水平在骨关节炎过程中受到抑制。这个 第二个目的是确定NRTIs是否通过抑制OA动物的L1水平来抑制OA的发病 活体模型。NRTI核苷胞苷类似物拉米夫定将被测试其抑制能力 CreERT2；miR-365小鼠的OA/PTOA。它将确立NRTI的疗效和干预窗口 改善骨性关节炎软骨退变、骨重塑、SASP基因表达和运动缺陷 活体动物模型。如果R61阶段的实验明确支持这一假设，它将 通过R33阶段的机制目标进一步探索，通过以下方式确定分子途径 其中L1激活了OA小鼠模型和人OA组织中的OA发病机制。它将建立 L1去阻抑的分子途径诱导了OA标记基因和SASP在细胞水平的表达。 该项目代表了该领域的一个新的和独特的方向，因为它解决了 反转录转座子在骨性关节炎发病机制中的首次应用。如果成功，NRTI是安全和容易的 可用于人类骨性关节炎的治疗。它不仅将改变推动办公自动化的概念 研究领域，也极大地影响了我们临床实践中如何治疗骨性关节炎患者。

Abstract Osteoarthritis (OA) is a degenerative joint disease involving articular cartilage degradation, chronic inflammation, and bone remodeling. Although it is a leading cause of disability in the elderly, there is no FDA approved disease modifying osteoarthritis drugs (DMOADs) currently. The scientific challenge is the incomplete understanding of mechanisms triggering inflammation and degeneration in the joint during aging or after injury, which hampers the development of DMOADs that can target these processes. The scientific goal of this project is to determine whether retrotransposon Long Interspersed Nuclear Element-1 (LINE-1, or L1), which is repressed in normal somatic cells but de-repressed in senescent cells during aging or after traumatic injury, contribute to aging-associated or post-traumatic OA (PTOA). We found that L1 levels are significantly elevated in human OA cartilage lesions and in cartilage joint of both aging-associated OA and PTOA mouse models. The innovative hypothesis is that, during aging and/or injury-associated OA, the cellular content of L1 retrotransposons is 1) significantly increased in the joint and 2) responsible for stimulation of SASP and inflammation that lead to joint destruction. If so, OA pathogenesis can be inhibited by repressing L1 using FDA- approved anti-viral drug nucleoside reverse transcriptase inhibitors (NRTIs). This hypothesis will be tested through two aims in the R61 Phase. The first aim is to characterize aging and injury induced L1 de-repression in the Col2a1-CreERT2; miR-365 mice capable of inducing early onset-OA and/or PTOA. It will establish whether aging, injury, or both would result in de-repression of the L1 levels in mouse joint during OA. The second aim is to determine whether NRTIs inhibit OA pathogenesis by repressing L1 levels in OA animal models in vivo. NRTI nucleoside cytidine analogue Lamivudine will be tested for its ability of inhibiting OA/PTOA in CreERT2; miR-365 mice. It will establish the efficacy and the window of intervention for NRTI to modify cartilage degeneration, bone remodeling, SASP gene expression, and movement deficiency in OA animal models in vivo. If the hypothesis is unambiguously supported by the experiments in R61 Phase, it will be further explored, through a mechanistic aim in the R33 Phase, to determine the molecular pathways by which L1 activates OA pathogenesis in OA mouse models and human OA tissues. It will establish the molecular pathways of L1 de-repression induced OA marker genes and SASP expression at the cellular level. This project represents a new and distinct direction for the field because it addresses the role of retrotransposons in OA pathogenesis for the very first time. If successful, NRTIs, which are safe and readily available, can be re-purposed for OA treatment in human. It will not only change the concepts that drive the OA research field, but also greatly impact the clinical practice of how we treat OA patients.