Hedgehog pathway in periosteum-mediated repair and regeneration

描述(由申请人提供)：本申请将再生医学(11)作为广泛的挑战领域。具体地说，这一应用寻求进一步了解在皮质骨移植愈合和结合过程中控制骨膜间充质干细胞(MSCs)扩张和分化的分子途径。该提案符合以下挑战主题：11-AR-101*：肌肉骨骼和皮肤组织再生。骨膜在修复和再生中起着关键作用。自体移植优于人造或同种异体移植，很大程度上是由于间充质干细胞(MSCs)存在于骨膜中。目前，调控骨膜间充质干细胞在愈合部位的增殖和分化的分子途径还知之甚少。针对美国国立卫生研究院提出的挑战主题，我们提出了一系列新的方法来定义骨膜介导的骨移植修复和整合中的关键途径，即Hedgehog途径。HH途径已被证明在胚胎肢体发育中起关键作用。然而，它在成人骨修复中的作用仍然难以捉摸。我们的初步数据表明，HH通路在成人骨膜修复中仍然起作用。HH途径的激活可显著促进自体骨膜来源的MSCs的分化，并在体内诱导成骨。因此，我们推测HH途径的激活通过刺激骨膜间充质干细胞的成骨分化在皮质骨移植的骨整合中起关键作用。将HH活化的骨膜间充质干细胞植入受损骨膜部位，可促进皮质骨的愈合和融合。在Aim1中，我们将通过靶向缺失Smoothens受体来确定HH功能丧失在骨膜依赖的皮质骨移植中的作用。Smoothens是骨膜间充质干细胞中传递所有HH信号的受体。在AIM2中，我们将通过将HH激活的骨膜间充质干细胞植入受损的骨膜部位来确定HH功能增强在同种异体皮质骨移植中的作用。这项拟议的研究将为理解骨膜启动的骨移植整合的分子控制带来新的见解，进一步为促进骨膜受损部位的愈合提供一种潜在的靶向治疗途径。我们项目的长期目标是确定骨修复和重建的关键途径和机制。具体地说，在这个项目中，我们建议研究HH途径在修复和再生中的作用。

DESCRIPTION (provided by applicant): This current application addresses Regenerative Medicine (11) as the broad challenge area. Specifically, this application seeks further understanding of molecular pathways that control expansion and differentiation of periosteal mesenchymal stem cells (MSCs) during cortical bone graft healing and incorporation. The proposal fits into the following challenge topics: 11-AR-101*: Musculoskeletal and Skin Tissue Regeneration. Periosteum plays key role in repair and regeneration. Autograft is superior to synthetics or allograft in reconstruction largely due to the presence of mesenchymal stem cells (MSCs) residing in periosteum. Currently the molecular pathways that regulate proliferation and differentiation of periosteal MSCs at the site of healing are poorly understood. In response to the challenge topics identified by NIH, we propose a series of novel approaches to define a critical pathway, namely the Hedgehog pathway, in periosteum-mediated bone graft repair and incorporation. Hh pathway has been shown to be critically involved in embryonic limb development. However, its role in adult bone repair remains elusive. Our preliminary data demonstrates that Hh pathway still operates in adult periosteal repair. Activation of Hh pathway markedly enhances the differentiation of MSCs isolated from autograft periosteum and induces bone formation in vivo. We therefore hypothesize that activation of Hh pathway plays key roles in osseointegration of cortical bone grafts via stimulating osteogenic differentiation of periosteal MSCs. Engraftment of Hh activated periosteal MSCs at the site of compromised periosteum will enhance cortical bone graft healing and incorporation. In Aim1, we will define the role of Hh-loss-of function in periosteum-dependent cortical bone graft incorporation by targeted deletion of Smoothened, the receptor that tranduces all Hh signaling in periosteal MSCs. In Aim2, we will define the role of Hh-gain-of function in cortical bone allograft incorporation by engraftment of Hh-activated periosteal MSCs at the site of compromised periosteum. The proposed study will bring new insights into the understanding of molecular control of periosteum-initiated bone graft incorporation, further offering a potential pathway-targeted therapy for improved healing at the site of compromised periosteum. The long-term goal of our project is to identify critical pathways and mechanisms for bone repair and reconstruction. Specifically in this project we propose to examine the role of Hh pathway in repair and regeneration.