Narematsu Mayu, Kamimura Tatsuya, Yamagishi Toshiyuki, Nakajima Yuji
Department of Anatomy and Cell Biology, Graduate School of Medicine, Osaka City University, Osaka 545-8585, Japan.
Department of Anatomy and Cell Biology, Graduate School of Medicine, Osaka City University, Osaka 545-8585, Japan.
J Mol Cell Cardiol. 2020 Oct;147:62-73. doi: 10.1016/j.yjmcc.2020.08.001. Epub 2020 Aug 7.
During the formation of the coronary artery stem, endothelial strands from the endothelial progenitor pool surrounding the conotruncus penetrate into the aortic wall. Vascular endothelial growth factors (VEGFs) as well as CXCL12/CXCR4 signaling are thought to play a role in the formation of the coronary stem. However, the mechanisms regulating how endothelial strands exclusively invade into the aorta remain unknown.
Immunohistochemistry showed that before the formation of endothelial strands, Sema3a was highly expressed in endothelial progenitors surrounding the great arteries. At the onset of/during invasion of endothelial strands into the aorta, Sema3a was downregulated and CXCR4 was upregulated in the endothelial strands. In situ hybridization showed that Cxcl12 was highly expressed in the aortic wall compared with in the pulmonary artery. Using avian embryonic hearts, we established two types of endothelial penetration assay, in which coronary endothelial strands preferentially invaded into the aorta in culture. Sema3a blocking peptide induced an excess number of endothelial strands penetrating into the pulmonary artery, whereas recombinant Sema3a inhibited the formation of endothelial strands. In cultured coronary endothelial progenitors, recombinant VEGF protein induced CXCR4-positive endothelial strands, which were capable of being attracted by CXCL12-impregnated beads. Monoazo rhodamine detected that hypoxia was predominant in aortic/subaortic region in ovo and hypoxic condition downregulated the expression of Sema3a in culture.
Results suggested that hypoxia in the aortic region downregulates the expression of Sema3a, thereby enhancing VEGF activity to induce the formation of CXCR4-positive endothelial strands, which are subsequently attracted into the Cxcl12-positive aortic wall to connect the aortic lumen.
在冠状动脉干形成过程中，圆锥动脉干周围内皮祖细胞池的内皮条索侵入主动脉壁。血管内皮生长因子（VEGFs）以及CXCL12/CXCR4信号通路被认为在冠状动脉干形成中发挥作用。然而，调节内皮条索如何特异性侵入主动脉的机制尚不清楚。
免疫组织化学显示，在内皮条索形成前，Sema3a在大动脉周围的内皮祖细胞中高表达。在内皮条索侵入主动脉开始时/侵入过程中，内皮条索中Sema3a表达下调，CXCR4表达上调。原位杂交显示，与肺动脉相比，Cxcl12在主动脉壁中高表达。利用鸡胚心脏，我们建立了两种内皮细胞穿透试验，在培养中冠状动脉内皮条索优先侵入主动脉。Sema3a阻断肽诱导过多内皮条索侵入肺动脉，而重组Sema3a抑制内皮条索形成。在培养的冠状动脉内皮祖细胞中，重组VEGF蛋白诱导产生CXCR4阳性内皮条索，其能够被包被CXCL12的珠子吸引。单偶氮罗丹明检测到卵内主动脉/主动脉下区域缺氧占主导，缺氧条件下调培养中Sema3a的表达。
结果提示主动脉区域的缺氧下调Sema3a表达，从而增强VEGF活性以诱导形成CXCR4阳性内皮条索，随后这些内皮条索被吸引到Cxcl12阳性的主动脉壁以连接主动脉腔。
