Abstract：
Compromised osteogenesis and angiogenesis is the character of stem cell senescence, which brought difficulties for bone defects repairing in senescent microenvironment. As the most abundant bone-related miRNA, miRNA-21-5p plays a crucial role in inducing osteogenic and angiogenic differentiation. However, highly efficient miR-21-5p delivery still confronts challenges including poor cellular uptake and easy degradation. Herein, TDN-miR-21-5p nanocomplex is constructed based on DNA tetrahedral (TDN) and has great potential in promoting osteogenesis and alleviating senescence of senescent bone marrow stem cells (O-BMSCs), simultaneously enhancing angiogenic capacity of senescent endothelial progenitor cells (O-EPCs). Of note, the activation of AKT and Erk signaling pathway may direct regulatory mechanism of TDN-miR-21-5p mediated osteogenesis and senescence of O-BMSCs. Also, TDN-miR-21-5p can indirectly mediate osteogenesis and senescence of O-BMSCs through pro-angiogenic growth factors secreted from O-EPCs. In addition, gelatin methacryloyl (GelMA) hydrogels are mixed with TDN and TDN-miR-21-5p to fabricate delivery scaffolds. TDN-miR-21-5p@GelMA scaffold exhibits greater bone repair with increased expression of osteogenic- and angiogenic-related markers in senescent critical-size cranial defects in vivo. Collectively, TDN-miR-21-5p can alleviate senescence and induce osteogenesis and angiogenesis in senescent microenvironment, which provides a novel candidate strategy for senescent bone repair and widen clinical application of TDNs-based gene therapy.
摘要：
受损的成骨和血管生成是干细胞衰老的特征，这给衰老微环境下的骨缺损修复带来了困难。作为最丰富的骨相关miRNA,miRNA-21-5p在诱导成骨和血管生成分化中起关键作用。然而,高效的miR-21-5p递送仍然面临挑战,包括细胞摄取差和容易降解.在这里，TDN-miR-21-5p纳米复合物是基于DNA四面体（TDN）构建的，在促进成骨和缓解衰老骨髓干细胞（O-BMSCs）衰老方面具有巨大潜力，同时增强衰老内皮祖细胞（O-EPCs）的血管生成能力。值得注意的是，AKT和Erk信号通路的激活可能是TDN-miR-21-5p介导O-BMSCs成骨和衰老的调控机制。此外，TDN-miR-21-5p可通过O-EPCs分泌的促血管生成生长因子间接介导O-BMSCs的成骨和衰老。此外,将明胶甲基丙烯酰(GelMA)水凝胶与TDN和TDN-miR-21-5p混合以制造递送支架。TDN-miR-21-5p@GelMA支架在体内衰老临界尺寸颅骨缺损中表现出更大的骨修复，成骨细胞和血管生成相关标志物的表达增加。总的来说，TDN-miR-21-5p可以缓解衰老，诱导衰老微环境中的成骨和血管生成，这为衰老骨修复提供了新的候选策略，并拓宽了基于TDNs的基因治疗的临床应用。
