Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA.
Department of Animal Science, Texas A&M University, College Station, Texas, USA.
Reproduction. 2020 Apr;159(4):465-478. doi: 10.1530/REP-19-0358.
Angiogenesis is fundamental to the expansion of the placental vasculature during pregnancy. Integrins are associated with vascular formation; and osteopontin is a candidate ligand for integrins to promote angiogenesis. Endothelial progenitor cells (EPCs) are released from bone marrow into the blood and incorporate into newly vascularized tissue where they differentiate into mature endothelium. Results of studies in women suggest that EPCs may play an important role in maintaining placental vascular integrity during pregnancy, although little is known about how EPCs are recruited to these tissues. Our goal was to determine the αv integrin mediated effects of osteopontin on EPC adhesion and incorporation into angiogenic vascular networks. EPCs were isolated from 6 h old piglets. RT-PCR revealed that EPCs initially had a monocyte-like phenotype in culture that became more endothelial-like with cell passage. Immunofluorescence microscopy confirmed that the EPCs express platelet endothelial cell adhesion molecule, vascular endothelial cadherin, and von Willebrand factor. When EPCs were cultured on OPN-coated slides, the αv integrin subunit was observed in focal adhesions at the basal surface of EPCs. Silencing of αv integrin reduced EPC binding to OPN and focal adhesion assembly. In vitro siRNA knockdown in EPCs,demonstrated that OPN stimulates EPC incorporation into human umbilical vein endothelial cell (HUVEC) networks via αv-containing integrins. Finally, in situ hybridization and immunohistochemistry localized osteopontin near placental blood vessels. In summary, OPN binds the αv integrin subunit on EPCs to support EPC adhesion and increase EPC incorporation into angiogenic vascular networks.
血管生成对于妊娠期间胎盘血管系统的扩张至关重要。整合素与血管形成有关；骨桥蛋白是整合素促进血管生成的候选配体。内皮祖细胞（EPCs）从骨髓释放到血液中，并整合到新形成的血管化组织中，在那里分化为成熟的内皮细胞。女性研究结果表明，EPCs 可能在维持妊娠期间胎盘血管完整性方面发挥重要作用，尽管对于 EPCs 如何被招募到这些组织中知之甚少。我们的目标是确定骨桥蛋白对 EPC 黏附和整合到血管生成血管网络中的 αv 整合素介导的影响。EPCs 从小猪出生后 6 小时分离。RT-PCR 显示，EPCs 在培养物中最初具有单核样表型，随着细胞传代，其变得更具内皮样表型。免疫荧光显微镜证实 EPCs 表达血小板内皮细胞黏附分子、血管内皮钙黏蛋白和血管性血友病因子。当 EPCs 在 OPN 涂层载玻片上培养时，αv 整合素亚基在 EPC 基底表面的焦点附着处观察到。αv 整合素沉默减少了 EPC 对 OPN 的结合和焦点附着的组装。EPCs 的体外 siRNA 敲低表明，OPN 通过含有 αv 的整合素刺激 EPC 整合到人脐静脉内皮细胞（HUVEC）网络中。最后，原位杂交和免疫组织化学将骨桥蛋白定位在胎盘血管附近。总之，OPN 结合 EPCs 上的 αv 整合素亚基，以支持 EPC 黏附和增加 EPC 整合到血管生成血管网络中。
