Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, 200233, PR China.
Stem Cell Res Ther. 2021 Jul 22;12(1):415. doi: 10.1186/s13287-021-02487-3.
Osteogenesis is tightly coupled with angiogenesis during bone repair and regeneration. However, the underlying mechanisms linking these processes remain largely undefined. The present study aimed to test the hypothesis that epidermal growth factor-like domain-containing protein 6 (EGFL6), an angiogenic factor, also functions in bone marrow mesenchymal stem cells (BMSCs), playing a key role in the interaction between osteogenesis and angiogenesis.
We evaluated how EGFL6 affects angiogenic activity of human umbilical cord vein endothelial cells (HUVECs) via proliferation, transwell migration, wound healing, and tube-formation assays. Alkaline phosphatase (ALP) and Alizarin Red S (AR-S) were used to assay the osteogenic potential of BMSCs. qRT-PCR, western blotting, and immunocytochemistry were used to evaluate angio- and osteo-specific markers and pathway-related genes and proteins. In order to determine how EGFL6 affects angiogenesis and osteogenesis in vivo, EGFL6 was injected into fracture gaps in a rat tibia distraction osteogenesis (DO) model. Radiography, histology, and histomorphometry were used to quantitatively evaluate angiogenesis and osteogenesis.
EGFL6 stimulated both angiogenesis and osteogenic differentiation through Wnt/β-catenin signaling in vitro. Administration of EGFL6 in the rat DO model promoted CD31EMCN type H-positive capillary formation associated with enhanced bone formation. Type H vessels were the referred subtype involved during DO stimulated by EGFL6.
EGFL6 enhanced the osteogenic differentiation potential of BMSCs and accelerated bone regeneration by stimulating angiogenesis. Thus, increasing EGFL6 secretion appeared to underpin the therapeutic benefit by promoting angiogenesis-coupled bone formation. These results imply that boosting local concentrations of EGFL6 may represent a new strategy for the treatment of compromised fracture healing and bone defect restoration.
在骨修复和再生过程中，成骨与血管生成紧密偶联。然而，将这些过程联系起来的潜在机制在很大程度上仍未得到明确。本研究旨在验证这样一个假设，即血管生成因子表皮生长因子样结构域蛋白 6（EGFL6）也在骨髓间充质干细胞（BMSCs）中发挥作用，在成骨与血管生成的相互作用中发挥关键作用。
我们通过增殖、Transwell 迁移、划痕愈合和管形成实验评估 EGFL6 如何影响人脐静脉内皮细胞（HUVECs）的血管生成活性。碱性磷酸酶（ALP）和茜素红 S（AR-S）用于检测 BMSCs 的成骨潜能。qRT-PCR、western blot 和免疫细胞化学用于评估血管生成和骨特异性标记物以及与通路相关的基因和蛋白。为了确定 EGFL6 如何在体内影响血管生成和成骨，将 EGFL6 注射到大鼠胫骨牵张成骨（DO）模型的骨折间隙中。使用放射学、组织学和组织形态计量学定量评估血管生成和成骨。
EGFL6 通过 Wnt/β-catenin 信号通路在体外同时刺激血管生成和成骨分化。在大鼠 DO 模型中给予 EGFL6 可促进与增强骨形成相关的 CD31EMCN 阳性 H 型血管形成。H 型血管是 EGFL6 刺激 DO 时涉及的特化亚型。
EGFL6 通过刺激血管生成增强了 BMSCs 的成骨分化潜能，并加速了骨再生。因此，增加 EGFL6 的分泌似乎通过促进血管生成耦联的骨形成来支持治疗益处。这些结果表明，增加局部 EGFL6 浓度可能是治疗受损骨折愈合和骨缺损修复的新策略。
