Cancer Bioscience, AstraZeneca, Alderley Park, Macclesfield, Cheshire SK10 4TG, UK.
Angiogenesis. 2010 Dec;13(4):337-47. doi: 10.1007/s10456-010-9190-0. Epub 2010 Oct 16.
Vascular Endothelial Growth Factor Receptor (VEGFR) mediated signalling drives angiogenesis. This is predominantly attributed to the activity of VEGFR-2 following binding of VEGF-A. Whether other members of the VEGFR and ligand families such as VEGFR-1 and its ligand Placental Growth Factor (PlGF) can also contribute to developmental and pathological angiogenesis is less clear. We explored the function of PlGF in VEGF-A dependent angiogenesis using an in vitro co-culture assay in which endothelial cells are cultured on a fibroblast feeder layer. In the presence of 2% FS MCDB media (containing limited growth factors) in vitro endothelial tube formation is driven by endogenous angiogenic stimuli which are produced by the fibroblast and endothelial cells. Under these conditions independent sequestration of either free VEGF-A or PlGF with polyclonal and monoclonal antibodies inhibited tube formation suggesting that both ligands are required to drive an angiogenic response. Endothelial tube formation could only be driven within this assay by the addition of exogenous VEGF-A, VEGF-E or VEGF-A/PlGF heterodimer, but not by PlGF alone, implying that activation of either VEGFR-2/VEGFR-1 heterodimers or VEGFR-2 homodimers were responsible for eliciting an angiogenic response directly, but not VEGFR-1 homodimers. In contrast to results obtained with an endogenous angiogenic drive, sequestration of PlGF did not affect endothelial tube formation when the assay was driven by 1 ng/ml exogenous VEGF-A. These data suggest that although neutralising PlGF can be shown to reduce endothelial tube formation in vitro, this effect is only observed under restricted culture conditions and is influenced by VEGF-A. Such data questions whether neutralising PlGF would have a therapeutic benefit in vivo in the presence of pathological concentrations of VEGF-A.
血管内皮生长因子受体 (VEGFR) 介导的信号转导驱动血管生成。这主要归因于 VEGF-A 结合后 VEGFR-2 的活性。其他 VEGFR 和配体家族成员，如 VEGFR-1 和其配体胎盘生长因子 (PlGF)，是否也能促进发育和病理性血管生成尚不清楚。我们使用体外共培养测定法探索了 PlGF 在 VEGF-A 依赖性血管生成中的作用，其中内皮细胞在成纤维细胞饲养层上培养。在体外，在含有有限生长因子的 2% FS MCDB 培养基中（含有有限生长因子），内皮细胞的管形成由成纤维细胞和内皮细胞产生的内源性血管生成刺激驱动。在这些条件下，用多克隆和单克隆抗体分别封闭游离 VEGF-A 或 PlGF 均可抑制管形成，表明这两种配体都需要驱动血管生成反应。只有在该测定中添加外源性 VEGF-A、VEGF-E 或 VEGF-A/PlGF 异二聚体才能驱动内皮管形成，而不是单独添加 PlGF，这意味着激活 VEGFR-2/VEGFR-1 异二聚体或 VEGFR-2 同源二聚体都可以直接引发血管生成反应，但不是 VEGFR-1 同源二聚体。与内源性血管生成驱动的结果相反，当测定由 1ng/ml 外源性 VEGF-A 驱动时，封闭 PlGF 并不影响内皮管形成。这些数据表明，尽管中和 PlGF 可以显示减少体外内皮管形成，但这种效应仅在受限制的培养条件下观察到，并且受 VEGF-A 的影响。这些数据质疑在存在病理性浓度的 VEGF-A 的情况下，中和 PlGF 是否会在体内具有治疗益处。
