Pharmacologic modulation of innate immune dysfunction in heterotopic ossification

项目摘要/摘要 异位骨化是一种罕见但破坏性的不适当骨形成情况。虽然免疫 系统活动是异位骨化的关键因素，我们缺乏明确的了解 免疫系统驱动骨形成。进行性骨化性纤维发育不良(FOP)是一种遗传性疾病。 大量异位骨化，与损伤后可能发生的炎性“红斑”有关。我们 最近发现FOP患者的血清在基线水平上增加了促炎细胞因子的水平。 此外，原代FOP单核细胞对内毒素的反应性增强，内毒素是一种刺激血管内皮细胞生长的配体。 TLR4途径，而不是激活其他TLR受体的其他配体。这些初步结果导致了我们的 FOP是一种自身免疫性疾病的中心假设是由于先天不适当的激活引起的 免疫系统。尽管目前还没有有效的治疗方法，但维甲酸受体-γ(RAR-γ) 激动剂可以抑制小鼠模型的异位成骨。加州大学旧金山分校是正在进行的多中心II/III阶段的一部分 由铁线莲制药公司赞助的研究RAR-γ激动剂帕罗罗汀在 阻断FOP的骨形成。完成的随机研究的初步结果(NCT02190747)和 正在进行的开放标签随访研究(NCT02279095)表明，帕洛胡萝卜素可以减少 FOP受试者的异位骨形成。正在进行的开放标签PVO-1A-202(NCT02279095)和阶段 III PVO-1A-301(NCT03312634)介入试验将是提议的独一无二的亲代研究 和时间敏感的机会来阐明FOP的免疫机制。在目标1中，我们将阐明 FOP原代单核细胞对内源性TLR4激活的反应。我们将化验FOP血清以确定 创伤后可表达的内源性TLR4激活物，并检测FOP单核细胞是否表现为增加 对HMGB1等TLR4激活剂的反应性。在目标2中，我们将测试FOP原代单核细胞是否致敏 内皮细胞对炎症反应。我们将使用共培养来检测FOP单核细胞是否表现出更强的趋化性 对FOP内皮细胞的作用，如果这种作用被软脂素抑制的话。我们还将测试FOP内皮细胞 在FOP单核细胞存在的情况下，显示促炎症细胞因子的表达增强。这些评估 还将显示棕榈酸是否会影响免疫细胞功能。在目标3中，我们将确定ACVR1和 棕榈胡萝卜素改变先天免疫细胞的激活。我们将使用单细胞RNAseq来阐明ACVR1是如何 R206H突变改变了外周免疫细胞的组成，如果帕罗瓦罗汀能使这一图谱正常化， 如果细胞因子产生的变化可以与炎症和FOP临床异位骨形成联系起来。 我们的结果将揭示关键的炎症机制，可能提供第一个机制和 FOP中疾病活动性的诊断生物标志物。这一结果也可能改善我们的治疗策略。 通过识别可能与异位其他情况相关的新的炎症靶点 骨化。

PROJECT SUMMARY/ABSTRACT Heterotopic ossification is a rare but devastating condition of inappropriate bone formation. Although immune system activity is a critical contributor to heterotopic ossification, we lack a clear understanding of how the immune system drives bone formation. Fibrodysplasia ossificans progressiva (FOP) is a genetic disease of massive heterotopic ossification that is associated with inflammatory “flares” that can occur after injury. We recently found that sera from FOP patients have increased levels of pro-inflammatory cytokines at baseline. Furthermore, primary FOP monocytes showed increased responsiveness to LPS, a ligand that stimulates the TLR4 pathway, but not to other ligands that activate other TLR receptors. These preliminary results lead to our central hypothesis that FOP is an autoimmune disease caused by inappropriate activation of the innate immune system. Although there are currently no effective treatments for FOP, retinoic acid receptor-γ (RAR-γ) agonists can inhibit heterotopic ossification in mouse models. UCSF is part of an ongoing multicenter Phase II/III program sponsored by Clementia Pharmaceuticals to study the efficacy of the RAR-γ agonist palovarotene in blocking bone formation in FOP. Preliminary results from a completed randomized study (NCT02190747) and ongoing open label followup study (NCT02279095) indicate that palovarotene can decrease the amount of heterotopic bone formation in FOP subjects. The ongoing open label PVO-1A-202 (NCT02279095) and Phase III PVO-1A-301 (NCT03312634) interventional trials will be the parent studies for the proposed unique and time-sensitive opportunity to elucidate the immune mechanisms in FOP. In Aim 1, we will elucidate how FOP primary monocytes respond to endogenous TLR4 activation. We will assay FOP sera for known endogenous TLR4 activators that can be expressed after trauma, and test if FOP monocytes show increased responsiveness to the TLR4 activators such as HMGB1. In Aim 2, we will test if FOP primary monocytes sensitize endothelial cells to inflammation. We will use co-cultures to assay if FOP monocytes show increased chemotaxis towards FOP endothelial cells and if this is dampened by palovarotene. We will also test if FOP endothelial cells show enhanced pro-inflammatory cytokine expression in the presence of FOP monocytes. These assessments will also show if palovarotene affects immune cell function. In Aim 3, we will determine how ACVR1 and palovarotene change innate immune cell activation. We will use single cell RNAseq to elucidate how the ACVR1 R206H mutation changes the composition of peripheral immune cells, if palovarotene can normalize this profile, and if changes in cytokine production can be linked to inflammation and FOP clinical heterotopic bone formation. Our results will reveal critical inflammatory mechanisms that may provide the first mechanistic and diagnostic biomarkers for disease activity in FOP. The results may also improve our treatment strategies by identifying novel inflammatory targets that may be relevant to other conditions of heterotopic ossification.