Abstract：
We present a transcriptomic analysis that provides a better understanding of regulatory mechanisms within the healthy and injured periosteum. The focus of this work is on characterizing early events controlling bone healing during formation of periosteal callus on day 3 after fracture. Building on our previous findings showing that induced Notch1 signaling in osteoprogenitors leads to better healing, we compared samples in which the Notch 1 intracellular domain is overexpressed by periosteal stem/progenitor cells, with control intact and fractured periosteum. Molecular mechanisms and changes in skeletal stem/progenitor cells (SSPCs) and other cell populations within the callus, including hematopoietic lineages, were determined. Notably, Notch ligands were differentially expressed in endothelial and mesenchymal populations, with Dll4 restricted to endothelial cells, whereas Jag1 was expressed by mesenchymal populations. Targeted deletion of Dll4 in endothelial cells using Cdh5CreER resulted in negative effects on early fracture healing, while deletion in SSPCs using α-smooth muscle actin-CreER did not impact bone healing. Translating these observations into a clinically relevant model of bone healing revealed the beneficial effects of delivering Notch ligands alongside the osteogenic inducer, BMP2. These findings provide insights into the regulatory mechanisms within the healthy and injured periosteum, paving the way for novel translational approaches to bone healing.
摘要：
我们提出了一个转录组学分析，可以更好地了解健康和受损骨膜内的调节机制。这项工作的重点是表征骨折后第3天骨膜骨痂形成过程中控制骨愈合的早期事件。基于我们之前的发现表明，骨祖细胞中诱导的Notch1信号传导导致更好的愈合，我们比较了Notch1胞内结构域被骨膜干/祖细胞过表达的样本与对照完整和骨折的骨膜。愈伤组织中骨骼干/祖细胞（SSPC）和其他细胞群体的分子机制和变化，包括造血谱系的测定。值得注意的是,Notch配体在内皮细胞和间质细胞中差异表达，Dll4只限于内皮细胞，而Jag1由间充质群体表达。使用Cdh5CreER在内皮细胞中靶向删除Dll4会对骨折早期愈合产生负面影响，而使用α-平滑肌肌动蛋白-CreER在SSPC中的缺失不影响骨愈合。将这些观察结果转化为临床相关的骨愈合模型，揭示了与成骨诱导剂一起递送Notch配体的有益作用。BMP2.这些发现为健康和受伤的骨膜内的调节机制提供了见解，为骨愈合的新转化方法铺平了道路。
