Epigenetic Regulation of Orofacial Bone Homeostasis and Aging by KDM4B

项目概要/摘要 本申请的目标是了解控制基因表达的表观遗传和分子机制。 口面骨老化和骨质疏松症与长骨平行，并探讨在多大程度上， 表观遗传因子可防止口面骨老化，促进牙、口腔和颅面组织的生长 再生衰老导致骨骼发生显著变化，其特征是成体干细胞减少。 池，自我更新和骨小梁形成，并增加骨髓脂肪组织积累。 口面骨，尤其是牙槽骨/松质骨，是一种动态的、自我更新的高更新组织 这一比率往往随着年龄的增长而急剧下降。间充质干细胞/基质细胞（MSC）是成体干细胞， 长和口面骨中的细胞，负责持续的组织更新、再生和修复。 口腔颌面部骨组织来源的间充质干细胞（OMSCs）是颅面骨再生的良好来源 因为它们的胚胎起源离受伤部位更近。在过去十年中， 在理解骨骼老化和骨质疏松症的分子机制方面取得了进展。不过小 已知表观遗传因素如何控制骨骼稳态和衰老，特别是口面骨 衰老利用siRNA筛选，我们发现组蛋白去甲基化酶KDM 4 B在细胞凋亡中起关键作用。 通过在赖氨酸9处擦除三甲基化组蛋白H3（H3 K9 me 3），BMSC的成骨分化。的 与对照组相比，从衰老小鼠分离的BMSCs中Kdm 4 b的表达显著下调。 年轻的老鼠为了探讨KDM 4 B在口面骨稳态和衰老中的功能作用，我们利用 Prx 1Cre小鼠在肢体和颅间充质中缺失Kdm 4 b。我们发现KDM 4 B的缺失 通过减少骨形成和增加脂肪生成加速口面骨老化和骨质疏松症。 重要的是，我们还确定了甲状旁腺激素（PTH），它已被证明可以调节MSC 干细胞和命运决定，诱导OMSCs中的Kdm 4 b。基于这些令人兴奋的研究，我们假设 KDM 4 B是控制口面骨老化和OMSC干性的关键表观遗传因子， 诱导KDM 4 B促进OMSC介导的颅面骨再生。为了验证我们的假设，我们 提出以下三个具体目标：1）确定KDM 4 B是否在监管中发挥关键作用 OMSCs与BMSCs并行的命运决定、成骨和自我更新; 2）为了确定OMSCs是否 KDM 4 B的诱导在体内防止口面骨老化并促进口面骨再生， 探讨KDM 4 B调控口面骨的表观遗传机制 OMSC的老化和自我更新与BMSC平行。我们研究的新发现将具有重要意义 在开发预防口面骨老化的创新治疗策略方面的意义， 促进颅面骨再生。

Project Summary/Abstract The goals of this application are to understand the epigenetic and molecular mechanisms that control orofacial bone aging and osteoporosis in parallel with long bones and explore the extent to which targeting epigenetic factor could prevent orofacial bone aging and promote dental, oral and craniofacial tissue regeneration. Aging causes significant changes to bone, characterized by a decrease in the adult stem cell pool, self-renewal and trabecular bone formation, and an increase in marrow adipose tissue accumulation. Orofacial bone, especially alveolar/trabecular bone, is a dynamic and self-renewing tissue with high turnover rate which often dramatically decreases with aging. Mesenchymal stem/stromal cells (MSCs) are adult stem cells in long and orofacial bones and are responsible for continuous tissue renewal, regeneration, and repair. MSCs derived from orofacial bone tissues (OMSCs) are excellent sources for craniofacial bone regeneration due to their closer embryonic origins to the injured sites. Over the past decade, significant progress has been made in understanding the molecular mechanisms governing skeletal aging and osteoporosis. However, little is known about how epigenetic factors control skeletal homeostasis and aging, specifically orofacial bone aging. Using siRNA screening, we discovered that the histone demethylase KDM4B played a critical role in osteogenic differentiation of BMSCs by erasing trimethylated histone H3 at lysine 9 (H3K9me3). The expression of Kdm4b was significantly downregulated in BMSCs isolated from aging mice compared to young mice. To explore the functional role of KDM4B in orofacial bone homeostasis and aging, we utilized Prx1Cre mice to delete Kdm4b in limb and cranial mesenchyme. We found that the deletion of KDM4B accelerated orofacial bone aging and osteoporosis by reducing bone formation and increasing adipogenesis. Importantly, we also identified that parathyroid hormone (PTH), which has been showed to regulate MSC stemness and fate decision, induced Kdm4b in OMSCs. Based on these exciting studies, we hypothesize that KDM4B is a critical epigenetic factor which controls orofacial bone aging and OMSC stemness, and induction of KDM4B promotes OMSC-mediated craniofacial bone regeneration. To test our hypothesis, we propose the following three specific aims: 1) To determine whether KDM4B plays a critical role in regulation of fate decision, osteogenesis and self-renewal of OMSCs in parallel with BMSCs; 2) To determine whether induction of KDM4B prevents orofacial bone aging and promotes orofacial bone regeneration in vivo in parallel with long bones; and 3) To explore epigenetic mechanisms by which KDM4B controls orofacial bone aging and self-renewal of OMSCs in parallel with BMSCs. New findings from our studies will have important implications in developing innovative therapeutic strategies for preventing orofacial bone aging and promoting craniofacial bone regeneration.