Role of glucocorticoid-suppression of preosteoclast PDGF-BB in skeletal angiogenesis

项目摘要 糖皮质激素的骨毒性副作用，如骨质疏松和骨坏死，限制了临床应用。儿童 是一个特别脆弱的人群，因为慢性服用糖皮质激素的儿童中有30%-50%会发展成骨毒性 副作用，而且没有FDA批准的儿童治疗方法。尽管已经有广泛的研究 关于糖皮质激素对成熟骨骼中骨骼的影响，主要集中在破骨细胞和成骨细胞， 知识差距仍然存在，这些差距存在于不断增长的骨架中。骨骼，特别是正在生长的骨骼，是高度血管化的。 骨质疏松、骨坏死和骨骼生长受损的统一组织学特征是骨质减少。 脉管系统。糖皮质激素损害骨骼血管生成与动物骨骼脆性相关 模特们。这项研究的目的是阐明受影响的关键细胞和细胞内信号机制。 参与糖皮质激素抑制血管生成及其与骨毒性副作用的关系。我们有 建立幼龄糖皮质激素-骨毒性小鼠模型。我们发现糖皮质激素对人体健康有很大影响 减少H型血管，这是与成骨相关的一种特定的血管亚型。建立在我们之前的基础上 研究表明Trap+破骨前细胞分泌血小板衍生生长因子BB(PDGF-BB)，这是一种 我们招募内皮前体细胞(EPC)形成H型血管，发现糖皮质激素抑制 Pdgfb转录通过干扰核因子kappaβ(NF-κB)与pdgfb启动子的结合来实现。 PDGF-BB降低与H型血管数量、成熟血管数量减少相关 成骨细胞减少，骨体积减少。我们推测糖皮质激素对破骨前细胞的抑制 血小板衍生生长因子-BB通过使核因子-κB失活而导致糖皮质激素对骨骼血管生成的损害。在这 建议，我们将剖析糖皮质激素抑制血管生成的关键细胞机制。 具体地说，我们将1)证明破骨前细胞是糖皮质激素抑制的主要细胞类型。 骨骼血管生成。2)确定核因子-κB介导的糖皮质激素抑制机制 破骨前细胞Pdgfb转录。3)检测增加破骨前细胞PDGF-BB的预防效果 糖皮质激素抑制骨骼血管生成。调节骨特异性因子的测定 血管生成对骨骼的生长至关重要，它将允许有针对性的药物治疗来治疗和/或预防 糖皮质激素在儿童中的骨毒性副作用。此外，对其作用机制的识别也是必要的 糖皮质激素抑制血管生成将推进我们的基础知识，拓展未来的研究 特别是关于骨坏死，帮助治疗干预的药物开发，并提供洞察力 慢性使用糖皮质激素后观察到的其他非靶组织副作用的机制。

Project Summary Osteotoxic side effects of glucocorticoids, such as osteoporosis and osteonecrosis, limit clinical use. Children are a particularly vulnerable population as 30-50% of children on chronic glucocorticoids develop an osteotoxic side effect and there are no-FDA approved treatments for children. Although there have been extensive studies about glucocorticoid effects on the bone in the mature skeleton focusing largely on osteoclasts and osteoblasts, knowledge gaps still exist which in the growing skeleton. Bone, particularly growing bone, is highly vascularized. A unifying histological feature of osteoporosis, osteonecrosis, and impaired skeletal growth, is reduced bone vasculature. Glucocorticoids impair skeletal angiogenesis, which correlates with skeletal fragility in animal models. The purpose of this study is to elucidate the key affected cell and intracellular signaling mechanism involved in glucocorticoid suppression of angiogenesis and its relation to osteotoxic side effects. We have established a young glucocorticoid-osteotoxic mouse model. We have found that glucocorticoids drastically reduce type H vessels, a specific subtype of blood vessels associated with osteogenesis. Building on our prior work demonstrating that Trap+ preosteoclasts secrete platelet-derived growth factor type BB (PDGF-BB), which recruits endothelial precursor cells (EPCs) to form type H blood vessels, we found that glucocorticoids suppress Pdgfb transcription by interfering with binding of nuclear factor kappa beta (NF-κB) to the Pdgfb promoter. Decreased PDGF-BB was associated with a decreased number of type H vessels, number of mature osteoblasts, and decreased bone volume. We hypothesize that glucocorticoid suppression of preosteoclast PDGF-BB via inactivation of NF-κB is the cause of glucocorticoid impairment of skeletal angiogenesis. In this proposal, we will dissect the key cellular mechanism involved in glucocorticoid suppression of angiogenesis. Specifically, we will 1) Demonstrate preosteoclasts are the major cell type in glucocorticoid-suppression of skeletal angiogenesis. 2) Determine the mechanism of glucocorticoid-suppression of NF-κB-mediated preosteoclast Pdgfb transcription. 3) Examine efficacy of increasing preosteoclast PDGF-BB for preventing glucocorticoid-suppression of skeletal angiogenesis. Determination of bone-specific factors that regulate angiogenesis, which is critical to the growing skeleton, will allow targeted drug therapy to treat and/or prevent osteotoxic side effects of glucocorticoids in children. Furthermore, identification of the mechanism of glucocorticoid-suppression of angiogenesis will advance our fundamental knowledge and expand future studies specifically on osteonecrosis, aid in drug-development for therapeutic interventions, and provide insight into mechanisms of other off-target tissue side effects observed with chronic glucocorticoid usage.