MicroRNA regulation of osteoblast physiology and glucocorticoid signaling

内源性糖皮质激素对正常的骨生理至关重要。然而，糖皮质激素过量，由于 全身用药或症状，如库欣病，会导致骨量减少和代谢 无序。总体而言，糖皮质激素受体信号必须受到严格控制，才能获得最佳的骨骼健康。我们 发现在成骨细胞系中，microRNA-433(miR-433)是糖皮质激素信号的负调节因子。 在体外，抑制miR-433活性使间充质细胞对糖皮质激素和 糖皮质激素受体在细胞核内滞留增加，提示miR-433可能有靶向机制 旨在限制细胞对糖皮质激素信号的反应。 除了对糖皮质激素信号转导的影响外，miR-433还是成骨细胞的负性调节因子 差异化。MiR-433随着成骨细胞分化的进展而降低，并抑制miR-433的活性 增加成骨细胞标志物基因的表达。为了更好地了解miR-433在骨骼中的功能，我们 产生在成骨细胞中表达miR-433竞争抑制物(坚韧诱饵)的转基因小鼠。 MiR-433诱饵小鼠的头盖骨增加了骨钙素和直接miR-433的mRNA 目标运行2。此外，miR-433诱饵小鼠表现出骨小梁和皮质厚度增加，这是由于 增加骨形成，尽管分子机制仍有待确定。 我们建议检验miR-433靶向成骨细胞形成关键基因和途径的假设。 以及限制糖皮质激素受体信号。 在目标1中，我们将全面描述男性和女性miR-433的骨骼表型 成熟和衰老中的诱饵小鼠。我们还将使用无偏见的方法识别miR-433目标，以更好地 了解miR-433如何调节成骨细胞生物学。在目标2中，我们将确定通过哪些机制 MIR-433在分子水平限制糖皮质激素的反应性，以及确定miR-4的影响。 433关于骨骼对外源性糖皮质激素过量的反应。 总体影响：MIR-433是一种新的糖皮质激素反应性和成骨细胞的负性药物 差异化。糖皮质激素过量是骨量减少的最常见的次要原因，组织 对糖皮质激素的敏感性受多种机制调节。了解两国之间的互动 成骨细胞生成和糖皮质激素信号转导对于设计限制不良反应的新策略至关重要。 糖皮质激素过量对骨骼的影响。

Endogenous glucocorticoids are critical for normal bone physiology. However, glucocorticoid excess, due to systemic administration or syndromes such as Cushing’s disease, causes osteopenia and metabolic disorder. Overall, glucocorticoid receptor signaling must be tightly controlled for optimal bone health. We identified microRNA-433 (miR-433) as negative regulator of glucocorticoid signaling in the osteoblast lineage. In vitro, inhibition of miR-433 activity made mesenchymal cells more responsive to glucocorticoids and increased glucocorticoid receptor residence in the nucleus, suggesting that miR-433 may target mechanisms designed to limit the responsiveness of cells to glucocorticoid signaling. In addition to effects on glucocorticoid signaling, miR-433 is a negative regulator of osteoblastic differentiation. miR-433 decreases as osteoblast differentiation progresses, and inhibition of miR-433 activity increases osteoblastic maker gene expression. To better understand the function of miR-433 in bone, we generated transgenic mice expressing a miR-433 competitive inhibitor (tough decoy) in osteoblastic cells. Calvarial bone from the miR-433 decoy mice has increased mRNA for osteocalcin and the direct miR-433 target Runx2. Further, miR-433 decoy mice display increased trabecular and cortical bone thickness due to increased bone formation, although molecular mechanisms remain to be identified. We propose to test the hypothesis that miR-433 targets genes and pathways critical for osteoblastogenesis and for limiting glucocorticoid receptor signaling. In Aim 1, we will comprehensively characterize the skeletal phenotype of both male and female miR-433 decoy mice in maturity and aging. We will also identify miR-433 targets using a non-biased approach, to better understand how miR-433 regulates osteoblast biology. In Aim 2, we will determine the mechanisms by which miR-433 limits glucocorticoid responsiveness at a molecular level, as well as determining the impact of miR- 433 on the response of bone to exogenous glucocorticoids excess. Overall Impact: miR-433 is a novel negative of both glucocorticoid responsiveness and osteoblast differentiation. Glucocorticoid excess is the most common secondary cause of osteopenia, and tissue sensitivity to glucocorticoids is regulated by multiple mechanisms. Understanding the interaction between osteoblastogenesis and glucocorticoid signaling is critical for the design of novel strategies to limit the adverse effects of glucocorticoid excess on the skeleton.