Mechanism of hepatocyte proliferation through vascular mediators secreted by sinusoidal endothelial cells

血管内皮细胞分泌各种化学介质，从而控制周围各种细胞的功能。肝脏具有一种独特的结构，称为肝窦，其中肝细胞和肝窦内皮细胞直接面对Disse间隙。我们认为这种结构适合肝脏再生；肝脏独特的生理功能。首先建立了大鼠肝窦内皮细胞的原代培养体系，并与目前广泛应用于该领域实验研究的牛核苷酸内皮细胞进行了比较。两种细胞都能分泌典型的血管介质--内皮素，但分泌量不同。它们分泌的主要前列腺素分别是PGE2和PGI2。胞外ATP通过嘌呤能受体调节窦状内皮细胞PGE2的分泌。肝窦内皮细胞分泌的前列腺素与枯否细胞分泌的前列腺素不同。PGE2是在胰岛素和EGF存在下刺激培养肝细胞DNA合成的主要前列腺素，它通过PGE2受体与百日咳毒素抑制的抑制性G蛋白偶联起作用。这表明该受体为EP3亚型，通过突变RT-PCR方法检测该亚型上的mRNA表达，证实了该受体为EP3亚型。这些发现似乎支持我们的假设，并在另一页列出的文献中得到了证实。

Vascular endothelial cells secretes various chemical mediators, and thus they control the function of various cells around them. Liver is characterized by a unique structure named sinusoids, where hepatocytes and sinusoidal endothelial cells face directly across Disse spaces. We thought that this structure was suitable for liver regeneration ; unique physiological function of the liver. We hypothesized that sinusoidal endothelial cells would regulate the proliferation of hepatocytes through secretion of vascular mediators.We first established the primary culture system for rat sinusoidal endothelial cells, and compared them with bovine carotide endothelial cells, widely used cell priparation for experimental research of this field. Both cells secreted endothelin, typical vascular mediator, although there was difference in secreted amount. Main prostanoid they secreted were PGE2 and PGI2, respectively. PGE2 secretion of sinusoidal endothelial cells was regulated by extracellular ATP through purinergic receptors. The profile of prostanoid secreted by sinusoidal endothelial cells was diffrent from that by Kupffer cells. PGE2 was the main prostanoid that stimulated DNA systhesis of cultured hepatocytes in the presence of insulin and EGF.It acted through PGE2 receptor, which was coupled with inhibitory G protein suppressed by pertussis toxin. This suggested that the receptor was EP3 subtype, which was confirmed by examining the expression of mRNA on this subtype with mutagenic RT-PCR method.These findings seems to support our hypothesis, and were pulished in literature as listed in the other page.