Mechanistic and Therapeutic Studies of Initiation and Expansion for Genetic and Acquired Heterotopic Ossification

项目总结/摘要 异位骨化（HO）是指骨外病理性骨形成， 损伤后的并发症或作为特定遗传疾病的表现。然而，由于贫困 由于缺乏对潜在细胞和分子机制的理解，目前没有有效的治疗方法， 手术切除常常导致复发。该项目的总体目标是研究细胞和分子 HO启动和扩增的潜在机制，并确定遗传和 收购HO。我们的初步数据表明，在进行性骨异型增生（POH）的小鼠模型中， 一种由编码Gαs的GNAS无效突变引起的人类疾病，异位骨进行性扩张 是由于周围野生型细胞的募集。从机制上讲，Gnas-/-间充质细胞分化 并通过激活雅普来招募野生型细胞形成骨，YAP是一种调节 Sonic hedgehog（Shh）的表达，其编码Hh家族中的分泌配体。进一步分泌SHH 诱导雅普激活，从而导致额外的Shh表达和成骨细胞分化。 野生型细胞周围。在具有获得性HO的人类样本中，上调的雅普和HH信号传导也被抑制。 发现，表明我们的研究结果的临床重要性。在我们未发表的初步研究中，我们发现 在体外的Gnas-/- SMPs中和在体内的POH小鼠模型的HO损伤中上调Wnt 5a表达。Wnt5a 不仅调节干细胞增殖和增强再生，而且在长骨中起着重要作用。 和软骨的发育。重要的是，我们发现Wnt 5a的表达也是 由雅普激活控制，并且是遗传性和获得性HO中HO所需的。这些发现导致 一个中心假设，即雅普和WNT 5a在正反馈回路中被激活，以募集祖细胞， 软组织中的成骨细胞分化，从而促进遗传性和获得性HO小鼠中的HO形成 模型我们将在三个目标中检验这些假设。第一个目的是澄清雅普和 Wnt 5a在POH异位骨形成中的表达，并测试雅普和WNT 5a是否以阳性表达相互作用。 反馈回路第二个目的是阐明在细胞中应答雅普和WNT 5a的分子机制。 异位骨形成第三个目的是研究WNT 5a对异位骨形成的贡献， 进行性骨化性纤维发育不良（FOP）和创伤诱导的HO模型。综合起来，这些建议 研究将产生新的见解，一个共同的细胞和分子机制的基础启动和 不同HO形式的扩展，并强调罕见遗传病研究在确定一种遗传病中的重要性。 一类疾病的共同核心病理机制。

Project Summary/Abstract Heterotopic ossification (HO) refers to extraskeletal pathological bone formation that occurs as a common complication after injury or as a manifestation of particular genetic disorders. However, limited by poor understanding of the underlying cellular and molecular mechanisms, there is currently no effective treatment and surgical eviction often results in recurrence. The overall goal of the project is to investigate cellular and molecular mechanisms underlying HO initiation and expansion and identify potential treatment targets for genetic and acquired HO. Our preliminary data suggests that in mouse models of progressive osseous heteroplasia (POH), a human disease caused by null mutations in GNAS that encodes Gαs, progressive expansion of ectopic bone was due to recruitment of surrounding wild-type cells. Mechanistically, Gnas-/- mesenchymal cells differentiate into osteoblasts and recruit wild-type cells to form bone by activating YAP, a transcription factor that regulates expression of Sonic hedgehog (Shh), which encodes a secreted ligand in the Hh family. Secreted SHH further induces YAP activation, thereby resulting in additional Shh expression and osteoblast differentiation in surrounding wild type cells. In human samples with acquired HO, upregulated YAP and HH signaling were also found, indicating the clinical importance of our findings. In our unpublished preliminary studies, we found upregulated Wnt5a expression in Gnas-/- SMPs in vitro and in HO lesions of POH mouse models in vivo. WNT5a not only regulates stem cell proliferation and enhances repopulation, but also plays an essential role in long bone and cartilage development during embryogenesis. Importantly, we found that Wnt5a expression was also controlled by YAP activation and was required for HO in both genetic and acquired HO. These findings lead to a central hypothesis that YAP and WNT5a are activated in a positive feedback loop to recruit progenitor cells for osteoblast differentiation in soft tissues, thereby promoting HO formation in both genetic and acquired HO mouse models. We will test these hypotheses in three aims. The first aim is to clarify the relationship between YAP and Wnt5a expression in ectopic bone formation in POH and test whether YAP and WNT5a interact in a positive feedback loop. The second aim is to illuminate the molecular mechanism in response to YAP and WNT5a in ectopic bone formation. The third aim is to investigate the contribution of WNT5a to ectopic bone formation in fibrodysplasia ossificans progressiva (FOP) and trauma-induced HO models. Taken together, these proposed studies will yield novel insights into a common cellular and molecular mechanism underlying initiation and expansion of distinct HO forms and highlight the importance of rare genetic disease studies in identifying a shared core pathological mechanism underlying a class of diseases.