INSERM U845, Research Center Growth and Signalling, Université Paris Descartes, Hôpital Necker, Paris, France.
Diabetes. 2010 Mar;59(3):662-9. doi: 10.2337/db09-0891. Epub 2009 Dec 15.
Recent evidence indicates that low oxygen tension (pO2) or hypoxia controls the differentiation of several cell types during development. Variations of pO2 are mediated through the hypoxia-inducible factor (HIF), a crucial mediator of the adaptative response of cells to hypoxia. The aim of this study was to investigate the role of pO2 in beta-cell differentiation.
We analyzed the capacity of beta-cell differentiation in the rat embryonic pancreas using two in vitro assays. Pancreata were cultured either in collagen or on a filter at the air/liquid interface with various pO2. An inhibitor of the prolyl hydroxylases, dimethyloxaloylglycine (DMOG), was used to stabilize HIF1alpha protein in normoxia.
When cultured in collagen, embryonic pancreatic cells were hypoxic and expressed HIF1alpha and rare beta-cells differentiated. In pancreata cultured on filter (normoxia), HIF1alpha expression decreased and numerous beta-cells developed. During pancreas development, HIF1alpha levels were elevated at early stages and decreased with time. To determine the effect of pO2 on beta-cell differentiation, pancreata were cultured in collagen at increasing concentrations of O2. Such conditions repressed HIF1alpha expression, fostered development of Ngn3-positive endocrine progenitors, and induced beta-cell differentiation by O2 in a dose-dependent manner. By contrast, forced expression of HIF1alpha in normoxia using DMOG repressed Ngn3 expression and blocked beta-cell development. Finally, hypoxia requires hairy and enhancer of split (HES)1 expression to repress beta-cell differentiation.
These data demonstrate that beta-cell differentiation is controlled by pO2 through HIF1alpha. Modifying pO2 should now be tested in protocols aiming to differentiate beta-cells from embryonic stem cells.
最近的证据表明，低氧张力（pO2）或缺氧控制着几种细胞类型在发育过程中的分化。pO2 的变化是通过缺氧诱导因子（HIF）介导的，HIF 是细胞对缺氧适应反应的关键介质。本研究旨在探讨 pO2 在β细胞分化中的作用。
我们使用两种体外测定方法分析了大鼠胚胎胰腺中β细胞分化的能力。将胰腺分别在胶原或在空气/液体界面的滤器上进行培养，采用不同的 pO2。脯氨酰羟化酶抑制剂二甲氧乙二酰甘氨酸（DMOG）用于在常氧条件下稳定 HIF1α 蛋白。
当在胶原中培养时，胚胎胰腺细胞呈缺氧状态，并表达 HIF1α，且罕见的β细胞分化。在滤器上培养的胰腺（常氧）中，HIF1α 表达减少，大量β细胞发育。在胰腺发育过程中，HIF1α 水平在早期升高，随时间降低。为了确定 pO2 对β细胞分化的影响，将胰腺在胶原中于不同浓度的 O2 下进行培养。这些条件抑制了 HIF1α 的表达，促进了 Ngn3 阳性内分泌祖细胞的发育，并以 O2 浓度依赖的方式诱导β细胞分化。相比之下，使用 DMOG 在常氧下强制表达 HIF1α 会抑制 Ngn3 的表达并阻断β细胞的发育。最后，缺氧需要 hairy 和 enhancer of split（HES）1 的表达来抑制β细胞分化。
这些数据表明，β细胞分化受 HIF1α 通过 pO2 调控。改变 pO2 应该在试图从胚胎干细胞中分化β细胞的方案中进行测试。
