Vernon Hilary, Clark Katherine, Bressler Joseph P
Kennedy Krieger Institute and Center in Alternatives in Animal Testing, Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA.
Methods Mol Biol. 2011;758:153-68. doi: 10.1007/978-1-61779-170-3_10.
The blood brain barrier regulates the transport of chemicals from entering and leaving the brain. Brain capillaries establish the barrier and restrict transport into the brain by providing a physical and chemical barrier. The physical barrier is due to tight membrane junctions separating the capillary endothelial cells resulting in limited paracellular transport. The chemical barrier is due to the expression of multidrug transporters that mediate the efflux of a broad range of hydrophobic chemicals. Because of the unusual nutrient demands of the brain, this limited permeability is compensated by the expression of a large number of transporters that are responsive to the metabolic demands of the brain. Consequently, the blood brain barrier indirectly regulates brain function by directly controlling the uptake of nutrients. Two widely used methods for studying the blood brain are a cell culture model using rat, pig, or cow brain endothelial cells and isolated microvessels. The cell culture model is more popular likely because it is easier to use and less costly compared to isolated microvessels. In some laboratories, brain endothelial cells are cocultured with astrocyte- or astroglial-conditioned media. The endothelial cells express many of the transporters displayed in vivo but not all. Although cell culture models vary, none express the tight barrier observed in vivo. Because microvessels are isolated directly from the brain, they express all of the transporters displayed in vivo. Their disadvantage is that the preparation is laborious, requires animals, and has a shorter lifespan in vitro. We present an approach in which transport is first verified in isolated microvessels, and then the mechanism is studied in cell culture.
血脑屏障调节化学物质进出大脑的运输。脑毛细血管通过提供物理和化学屏障来建立屏障并限制进入大脑的运输。物理屏障是由于紧密的膜连接将毛细血管内皮细胞分隔开，导致细胞旁运输受限。化学屏障是由于多药转运蛋白的表达，这些转运蛋白介导多种疏水性化学物质的外排。由于大脑对营养物质的特殊需求，这种有限的通透性通过大量响应大脑代谢需求的转运蛋白的表达得到补偿。因此，血脑屏障通过直接控制营养物质的摄取间接调节大脑功能。两种广泛用于研究血脑屏障的方法是使用大鼠、猪或牛脑内皮细胞和分离微血管的细胞培养模型。细胞培养模型可能更受欢迎，因为与分离微血管相比，它更易于使用且成本更低。在一些实验室中，脑内皮细胞与星形胶质细胞或星形胶质细胞条件培养基共培养。内皮细胞表达许多在体内显示的转运蛋白，但并非全部。尽管细胞培养模型各不相同，但没有一个能表达在体内观察到的紧密屏障。由于微血管是直接从大脑中分离出来的，它们表达所有在体内显示的转运蛋白。它们的缺点是制备过程费力，需要动物，并且在体外寿命较短。我们提出了一种方法，首先在分离的微血管中验证运输，然后在细胞培养中研究其机制。
