Bone marrow stromal/stem cell-derived extracellular vesicles regulate osteoblast activity and differentiation in vitro and promote bone regeneration in vivo.

Emerging evidence suggests that extracellular vesicles (EVs) are secreted by diverse tissues and play important roles in cell-cell communication, organ interactions and tissue homeostasis. Studies have reported the use of EVs to stimulate tissue regeneration, such as hepatic cell regeneration, and to treat diseases, such as pulmonary hypertension. However, little is known about the osteogenic effect of EVs. In this study, we explore the role of bone marrow stromal cell-derived EVs in the regulation of osteoblast activity and bone regeneration. We isolated bone marrow stromal/stem cell (BMSC)-derived EVs through gradient ultracentrifugation and ultrafiltration, and tested the influence of the EVs on osteogenesis both in vivo and in vitro. The results indicated that EVs positively regulated osteogenic genes and osteoblastic differentiation but did not inhibit proliferation in vitro. Furthermore, we constructed an EVs delivery system to stimulate bone formation in Sprague Dawley (SD) rats with calvarial defects. We found that BMSC-derived EVs led to more bone formation in the critical-size calvarial bone defects. Moreover, we found that miR-196a plays an essential role in the regulation of osteoblastic differentiation and the expression of osteogenic genes. We anticipate that our assay using bone marrow stromal cell-derived EVs will become a valuable tool for promoting bone regeneration.

新出现的证据表明，细胞外囊泡（EVs）由多种组织分泌，在细胞间通讯、器官相互作用和组织内稳态中发挥重要作用。研究报道了利用细胞外囊泡刺激组织再生，如肝细胞再生，以及治疗疾病，如肺动脉高压。然而，对于细胞外囊泡的成骨作用知之甚少。在本研究中，我们探讨了骨髓基质细胞衍生的细胞外囊泡在调节成骨细胞活性和骨再生中的作用。我们通过梯度超速离心和超滤分离出骨髓基质/干细胞（BMSC）衍生的细胞外囊泡，并在体内和体外测试了这些细胞外囊泡对成骨的影响。结果表明，细胞外囊泡在体外正向调节成骨基因和成骨细胞分化，但不抑制增殖。此外，我们构建了一个细胞外囊泡递送系统，以刺激颅骨缺损的Sprague Dawley（SD）大鼠的骨形成。我们发现，骨髓基质细胞衍生的细胞外囊泡导致临界尺寸颅骨缺损处更多的骨形成。而且，我们发现miR - 196a在调节成骨细胞分化和成骨基因表达中起关键作用。我们预期，我们使用骨髓基质细胞衍生的细胞外囊泡的检测方法将成为促进骨再生的有价值的工具。