Single-cell RNA-seq analysis reveals two specific endothelial cells promote fracture healing

Recent studies have identified a bone vessel subtype of CD31hi endomucinhi (CD31hiEMCNhi) endothelium that positively promotes bone formation. However, it remains unknown how CD31hiEMCNhi endothelium participate in the healing of fractures. Here we find that CD31hiEMCNhi endothelial cells increase significantly during fracture healing by single-cell profiling. Furthermore, CD31hiEMCNhi endothelial cells can balance membrane and cartilage osteogenesis in this progress. Moreover, two different types of CD31hiEMCNhi endothelial cells were found in this progress, One of these endothelial cells tends to deliver molecules that induce mesenchymal stem cells differentiate into osteoblast. The other one tends to deliver inflammatory factors associated with osteoclasts. Thus, our study indicates that two specific endothelial cells promote fracture healing and may represent a potential treatment for promoting fracture healing. Overall design: scRNA profiles of fracture at different stage(control group, third day, 7th day, 14th day)

已有研究鉴定出一种CD31高表达、内膜黏蛋白高表达（CD31hiEMCNhi）的骨血管亚型内皮细胞，其可正向促进骨形成。然而，CD31hiEMCNhi内皮细胞如何参与骨折愈合过程，目前仍不明确。本研究通过单细胞测序分析发现，骨折愈合过程中CD31hiEMCNhi内皮细胞的数量显著升高。进一步研究表明，该过程中CD31hiEMCNhi内皮细胞可平衡膜内成骨与软骨内成骨。此外，本研究在该过程中发现两种不同亚型的CD31hiEMCNhi内皮细胞：其中一类亚型倾向于分泌可诱导间充质干细胞分化为成骨细胞的分子，另一类亚型则倾向于分泌与破骨细胞相关的炎症因子。综上，本研究证实两种特异性内皮细胞可促进骨折愈合，或可成为促进骨折愈合的潜在治疗靶点。实验整体设计：不同时间阶段（对照组、术后第3天、第7天、第14天）骨折组织的单细胞RNA测序（scRNA）谱分析。