Mackarel A J, Cottell D C, Fitzgerald M X, O'Connor C M
Department of Medicine and Therapeutics, University College Dublin, Ireland.
In Vitro Cell Dev Biol Anim. 1999 Jun;35(6):346-51. doi: 10.1007/s11626-999-0085-6.
A growing number of studies on the mechanism of leukocyte transendothelial migration use endothelial cells grown on microporous filters as an in vitro model of endothelium. Ultrastructural examination of such a model system previously demonstrated that human pulmonary artery endothelial cells (HPAEC) formed confluent monolayers on both sides of the 3-microm-pore filter (Mackarel et al., 1999). To determine whether this was a characteristic specific to pulmonary artery endothelial cells, the growth characteristics of a human pulmonary microvascular endothelial cell type (HMVEC-L) and the widely used human umbilical vein endothelial cells (HUVEC) on 3-microm microporous filters were examined by transmission electron microscopy (TEM). Similar to HPAEC, HMVEC-L and HUVEC were also found to grow on both sides of the filter. All three endothelial cell types were capable of migrating through the 3 microm pores of the filter to form a monolayer on the filter underside. The endothelial cells on the underside were orientated in an inverted position with the luminal surface facing away from the filter. Such 'bilayer' formation was observed at a range of seeding densities and in different culture media. Despite the presence of a bilayer of endothelial cells, TEM demonstrated that neutrophils migrated successfully across the cell-filter-cell system. Previous transmigration reports in which an in vitro model similar to ours was used have often assumed only one layer of endothelial cells. The observations reported here indicate that while endothelial cells on microporous filters are useful models for examining leukocyte-endothelial interactions, they are not appropriate for studies examining endothelial cell 'sidedness.'
越来越多关于白细胞跨内皮迁移机制的研究使用生长在微孔滤膜上的内皮细胞作为内皮的体外模型。此前对这种模型系统的超微结构检查表明，人肺动脉内皮细胞（HPAEC）在3微米孔径的滤膜两侧形成了汇合的单层（Mackarel等人，1999年）。为了确定这是否是肺动脉内皮细胞特有的特征，通过透射电子显微镜（TEM）检查了人肺微血管内皮细胞类型（HMVEC-L）和广泛使用的人脐静脉内皮细胞（HUVEC）在3微米微孔滤膜上的生长特性。与HPAEC相似，HMVEC-L和HUVEC也被发现在滤膜两侧生长。所有三种内皮细胞类型都能够穿过滤膜的3微米孔迁移，在滤膜下方形成单层。下方的内皮细胞呈倒置排列，管腔表面背向滤膜。在一系列接种密度和不同培养基中都观察到了这种“双层”形成。尽管存在内皮细胞双层，但TEM表明中性粒细胞成功地穿过了细胞-滤膜-细胞系统。以前使用类似于我们的体外模型的跨迁移报告常常只假设存在一层内皮细胞。此处报告的观察结果表明，虽然微孔滤膜上的内皮细胞是研究白细胞-内皮相互作用的有用模型，但它们不适用于研究内皮细胞的“方向性”。
