The Role of MEK5 in Melatonin-induced Osteoblast and Osteoclast Differentiation

 描述(申请人提供)：我们的长期目标是开发新的疗法，以改善骨形成和增加骨密度的女性和男性骨量减少或骨质疏松。褪黑素是当前治疗方法的一种新的替代品，因为它通过刺激成骨细胞、抑制破骨细胞以及可能通过其清除自由基的特性来保护骨细胞免受过度的骨吸收，从而具有多种骨保护作用。人们预计长期使用褪黑素将通过对成骨细胞和破骨细胞的作用来预防骨量减少和骨质疏松，并减少骨折。采用人骨髓间充质干细胞(HMSCs)与人外周血单核细胞(HPBMCs)共培养体系，探讨褪黑素对啮齿类动物成骨细胞和破骨细胞的作用机制(S)。该项目的目标是使用更接近体内发生的模型来确定MEK5和MEK1/2在调节褪黑素介导的成骨细胞生成和破骨细胞生成中的作用。我们的中心假设是褪黑素通过MEK1/2和5，分别通过调节成骨细胞特异性标志物RUNX2、Osteocalin和FRA-1，以及通过调节护骨素和RANKL的比例来抑制破骨细胞生成，从而刺激成骨细胞的生成和抑制破骨细胞的生成。我们计划通过追求以下两个特定目标来客观验证我们的假设：(1)评估MEK5对褪黑素介导的成骨细胞和破骨细胞分化和信号的影响；(2)评估褪黑素和MEK1/2和5在体内褪黑素介导的成骨细胞和破骨细胞功能、骨形成和密度变化中的作用。这些研究不仅将阐明褪黑素对成骨细胞、破骨细胞和骨骼的作用机制，还将为未来的骨形成疗法的开发确定一个新的靶点(MEK5)，以降低易感人群的骨折风险。

 DESCRIPTION (provided by applicant): Our long-term goal is to develop novel therapies to improve bone formation and increase bone density in women and men with osteopenia or osteoporosis. Melatonin is a novel alternative to current treatments because it possesses multiple bone-protective actions by working through a stimulation of osteoblasts, an inhibition of osteoclasts and possibly through its free-radical scavenging properties to protect bone cells against excessive bone resorption. It is expected that long-term use of melatonin in people will prevent osteopenia and osteoporosis and reduce bone fractures through its effects on both osteoblasts and osteoclasts. The objective is to clarify the mechanism(s) underlying melatonin's effects on osteoblasts and osteoclasts in rodent bone and in vitro using a novel co-culture system consisting of human mesenchymal stem cells (hMSCs) and human peripheral blood monocytes (hPBMCs). The project goal is to identify the role of MEK5 and MEK1/2 on regulating melatonin-mediated osteoblastogenesis and osteoclastogenesis using models that more closely mimics what occurs in vivo. Our central hypothesis is that melatonin, through MEK1/2 and 5, will stimulate osteoblastogenesis and inhibit osteoclastogenesis by modulating osteoblast-specific markers, RUNX2, osteocalcin and FRA-1 and by regulating the ratios of osteoprotegerin and RANKL to inhibit osteoclastogenesis, respectively. We plan to objectively test our hypothesis by pursuing the following two specific aims: (1) Assess the effects of MEK5 on melatonin-mediated osteoblast and osteoclast differentiation and signaling in hMSC-hPBMC co-cultures; (2) Assess the role of melatonin and MEK1/2 and 5 on melatonin-mediated changes in osteoblast and osteoclast function, bone formation and density in vivo. These studies will not only clarify the mechanisms underlying melatonin's actions on osteoblasts, osteoclasts and bone but will also identify a novel target (MEK5) for the development of future bone-forming therapies to reduce fracture risk in susceptible populations.