In vivo two-photon imaging of vascular invasion and stem cell translocation in calvarial bone

项目总结 颅骨缺损通常是由于创伤、先天畸形和医源性条件造成的。 骨缺损的修复有赖于颅骨的再生能力来替代受损的骨。 组织和骨骼干细胞的可获得性是产生新骨的关键因素之一 恢复结构和功能的完整性。表达标记基因Gli1、Axin2或PrX1的颅骨SSCs 驻留在缝合干细胞的缝隙中，有助于颅骨的动态平衡和损伤后的愈合。它 目前尚不清楚颅骨SSCs如何从缝隙转移到头盖骨的远端区域 用于缝合远端部位损伤后的骨修复。我们通过双光子成像的初步分析 表明表达Gli1的颅骨SSCs不仅存在于缝隙中，而且排列在血壁中。 血管广泛分布于出生后的颅骨。在这个项目中，我们将检验这一假设 缝合区的颅骨SSCs可能在出生后随着血管的侵袭而移位 缝合，并可驻留在颅骨内，有助于损伤后的骨再生。我们建议两个 本项目的具体目标：1)确定缝合处血管侵入是否会导致骨髓腔 出生后颅骨的形成，以及2)确定缝隙中的颅骨干细胞是否随着 血管侵入以建立出生后颅骨骨髓腔中的SSC生态位。这 研究计划利用两个调查实验室的独特专业知识来解决我们 颅骨愈合方面的知识。这项探索性研究的成功完成将为进一步 机制研究，如分子调控的头盖骨SSC易位，可能会促进 发展创伤后快速骨再生的新治疗方法。

PROJECT SUMMARY Calvarial bone defects commonly occur as a result of trauma, congenital anomalies and iatrogenic conditions. The healing of bone defects relies on the regenerative capability of calvarial bones to replace damaged bone tissues and the availability of skeletal stem cells (SSCs) is one of the key factors for generating new bones to restore both structural and functional integrity. Calvarial SSCs that express marker gene Gli1, Axin2 or Prx1 reside in the sutural stem cell niche and contribute to calvarial bone homeostasis and healing after injury. It remains unclear how calvarial SSCs translocate from the sutural niche to distant regions of the calvarial bones for bone repair after injury of sites remote to the suture. Our preliminary analysis through 2-photon imaging indicates that Gli1-expressing calvarial SSCs not only reside in the sutural niche but also line the walls of blood vessels distributed widely throughout the postnatal calvarial bones. In this project, we will test the hypothesis that calvarial SSCs in the sutural niche could translocate with vascular invasion that initiates at the postnatal suture, and could reside within calvarial bones to contribute to bone regeneration after injury. We propose two specific aims for this project: 1) Determine if vascular invasion from the suture results in bone marrow cavity formation in postnatal calvarial bones, and 2) Determine if calvarial SSCs in the sutural niche translocate with vascular invasion to establish the SSC niche in bone marrow cavities of postnatal calvarial bones. This research proposal leverages the unique expertise of two investigative labs to address a key gap in our knowledge of calvarial healing. Successful completion of this exploratory research will set the stage for further mechanistic studies such as molecular regulation of calvarial SSC translocation, which could facilitate the development of new therapeutic approaches for rapid bone regeneration after injury.