Hypoxia Inhibits De Novo Vascular Assembly of Adipose-Derived Stromal/Stem Cell Populations, but Promotes Growth of Preformed Vessels
Hypoxia Inhibits De Novo Vascular Assembly of Adipose-Derived Stromal/Stem Cell Populations, but Promotes Growth of Preformed Vessels
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DOI：
10.1089/ten.tea.2015.0421
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发表时间：
2016-01-01
影响因子：
4.1
通讯作者：
Grayson, Warren L.
中科院分区：
文献类型：
--
作者：
Hutton, Daphne L.;Grayson, Warren L.
在组织工程移植物中，血管形成是细胞存活的关键。脂肪基质/干细胞(ASCs)是一种临床相关的干细胞和内皮祖细胞来源，广泛应用于组织工程领域。先前研究表明，在常氧(20%O-2)培养条件下，ASCs可以自组装成周细胞稳定的血管网络。这种新生血管组装的能力可能会加速体内移植物血管的形成，而不是仅仅依赖血管新生生长。然而，大细胞移植体内的氧气消耗将是迅速的，目前尚不清楚这种日益恶化的低氧环境将如何影响移植细胞的血管组装。本研究的目的是确定ASC来源的血管是否可以在缺氧中生长，并评估血管成熟度(即单个细胞与预形成的血管)是否影响这种缺氧反应。利用体外血管形成模型，将ASCs包裹在纤维蛋白凝胶中，在常氧(20%O-2)和低氧(0.2%或2%O-2)中体外培养6天。在随后的实验中，允许血管在常氧下预成型6天，然后再进行6天的常氧或低氧。对每种实验方法的存活率、血管生长、周细胞覆盖率、增殖、代谢和血管生成因子的表达进行评估。在中度和重度缺氧(血管总长度分别为47%和11%，与常氧相比)下，血管生长受到显著抑制，尽管在低氧条件下保持了高细胞存活率，并上调了血管内皮生长因子的内源性表达。溴脱氧尿嘧啶核苷标记显示缺氧时内皮细胞的增殖显著降低。相反，当血管网络在常氧中预形成6天时，血管在低氧中不仅存活，而且比常氧中保持的血管继续生长得更多。这些发现表明，血管的组装和生长受到氧分压的严格控制，并可能受到基于血管成熟度的低氧条件的不同影响。了解这种关系对于开发有效的方法在体内设计可存活的组织工程移植物至关重要。
Vascularization is critical for cell survival within tissue-engineered grafts. Adipose-derived stromal/stem cells (ASCs) are widely used in tissue engineering applications as they are a clinically relevant source of stem cells and endothelial progenitor cells. ASCs have previously been shown to self-assemble into pericyte-stabilized vascular networks in normoxic (20% O-2) cultures. This capacity for de novo vascular assembly may accelerate graft vascularization in vivo rather than relying solely on angiogenic ingrowth. However, oxygen depletion within large cell-seeded grafts will be rapid, and it is unclear how this worsening hypoxic environment will impact the vascular assembly of the transplanted cells. The objectives of this study were to determine whether ASC-derived vessels could grow in hypoxia and to assess whether the vessel maturity (i.e., individual cells vs. preformed vessels) influenced this hypoxic response. Utilizing an in vitro vascularization model, ASCs were encapsulated within fibrin gels and cultured in vitro for up to 6 days in either normoxia (20% O-2) or hypoxia (0.2% or 2% O-2). In a subsequent experiment, vessels were allowed to preform in normoxia for 6 days before an additional 6 days of either normoxia or hypoxia. Viability, vessel growth, pericyte coverage, proliferation, metabolism, and angiogenic factor expression were assessed for each experimental approach. Vessel growth was dramatically inhibited in both moderate and severe hypoxia (47% and 11% total vessel length vs. normoxia, respectively), despite maintaining high cell viability and upregulating endogenous expression of vascular endothelial growth factor in hypoxia. Bromodeoxyuridine labeling indicated significantly reduced proliferation of endothelial cells in hypoxia. In contrast, when vascular networks were allowed to preform for 6 days in normoxia, vessels not only survived but also continued to grow more in hypoxia than those maintained in normoxia. These findings demonstrate that vascular assembly and growth are tightly regulated by oxygen tension and may be differentially affected by hypoxic conditions based on the maturity of the vessels. Understanding this relationship is critical to developing effective approaches to engineer viable tissue-engineered grafts in vivo.