Department of Emergency Medicine, Shengjing Hospital of China Medical University, Shenyang, China.
Department of Oncology, Shengjing Hospital of China Medical University, Shenyang, China.
Lab Invest. 2023 Jul;103(7):100121. doi: 10.1016/j.labinv.2023.100121. Epub 2023 Mar 17.
Fracture healing is a complex physiological process in which angiogenesis plays an essential role. Microfibril-associated glycoprotein-2 (MAGP2) has been reported to possess a proangiogenic activity via integrin αvβ3, yet its role in bone repair is unexplored. In this study, a critical-sized femoral defect (2 mm) was created in mice, followed by the delivery of an adenovirus-based MAGP2 overexpression vector or its negative control at the fracture site. At days 7, 14, 21, and 28 postfracture, bone fracture healing was evaluated by radiography, micro-computed tomography, and histopathologic analysis. Adenovirus-based MAGP2 overexpression vector-treated mice exhibited increased bone mineral density and bone volume fraction. MAGP2 overexpression contributed to an advanced stage of endochondral ossification and induced cartilage callus into the bony callus. Further analysis indicated that MAGP2 was associated with enhanced angiogenesis, as evidenced by marked MAGP2 and integrin αvβ3 costaining and increased endothelial cell markers such as endomucin and CD31 levls, as well as elevated phosphorylation of protein tyrosine kinase 2 (PTK2) and AKT serine/threonine kinase 1 (AKT) in the callus. In vitro, recombinant human MAGP2 treatment enhanced the viability, migration, and tube formation ability of human microvascular endothelial cells, which was partially reversed by integrin αvβ3 inhibition or MK-2206, a specific AKT inhibitor. Inhibition of integrin αvβ3 abolished MAGP2-induced PTK2 and AKT activation. Taken together, our data provide the first evidence that MAGP2 promotes angiogenesis and bone formation by activating the integrin αvβ3/PTK2/AKT signaling pathway.
骨折愈合是一个复杂的生理过程，其中血管生成起着至关重要的作用。已有研究报道，微纤维相关糖蛋白-2（MAGP2）通过整合素 αvβ3 具有促血管生成活性，但它在骨修复中的作用尚未被探索。在本研究中，在小鼠股骨造成 2mm 的临界尺寸骨缺损，然后在骨折部位递送基于腺病毒的 MAGP2 过表达载体或其阴性对照。在骨折后第 7、14、21 和 28 天，通过 X 射线、微计算机断层扫描和组织病理学分析评估骨骨折愈合。基于腺病毒的 MAGP2 过表达载体处理的小鼠表现出增加的骨密度和骨体积分数。MAGP2 过表达有助于软骨内骨化的晚期阶段，并诱导软骨愈伤组织进入骨愈伤组织。进一步分析表明，MAGP2 与增强的血管生成有关，这表现在 MAGP2 和整合素 αvβ3 的明显共染色以及内皮细胞标志物如内粘蛋白和 CD31 水平的增加，以及在愈伤组织中蛋白酪氨酸激酶 2（PTK2）和丝氨酸/苏氨酸激酶 1（AKT）的磷酸化水平升高。在体外，重组人 MAGP2 处理增强了人微血管内皮细胞的活力、迁移和管形成能力，而整合素 αvβ3 抑制或特定的 AKT 抑制剂 MK-2206 部分逆转了这一过程。整合素 αvβ3 抑制消除了 MAGP2 诱导的 PTK2 和 AKT 激活。总之，我们的数据首次提供了证据，证明 MAGP2 通过激活整合素 αvβ3/PTK2/AKT 信号通路促进血管生成和骨形成。
