Trophoblast cell invasiveness and the mechanisms of its regulation

滋养细胞是哺乳动物胎盘的重要组成部分，具有独特的生物学特性。特别是在怀孕的前三个月，滋养细胞开始侵入子宫壁，远至子宫脊髓动脉。有趣的是，这种侵入行为受到严格的管制，因此侵入不会超出子宫血管。近年来，一些整合素的特定成员被描述为在滋养细胞上表达。已有证据表明，这些整合素在上述侵袭性行为的调节中起着至关重要的作用。研究表明，细胞与细胞和细胞与细胞外基质（ECM）相互作用涉及两种主要机制：通过配体受体结合的相互作用，以及可溶性生长因子或细胞因子如表皮生长因子（EGF）、白细胞介素-6 （IL-6）、转化生长因子-β (TGF-β)或白血病抑制因子（LIF）的相互作用。本研究利用人BeWo绒毛膜癌细胞，进一步研究了表皮生长因子是否影响BeWo细胞表面整合素的表达。流式细胞术检测的整合素分子中，α2整合素在刺激10 nM EGF后12、24和48 h的表达最明显。这种增加与人绒毛膜促性腺激素（hCG）分泌的增加同时发生，这表明滋养细胞的功能分化。此外，α2整合素转录本早在添加EGF后3小时就被诱导响应。结合以往的知识，我们推测α2整合素的增加在子宫内膜的侵袭活性中起作用。侵袭实验表明，在生物浓度下，EGF增加了BeWo细胞的侵袭活性。抗α2整合素抗体对egf处理细胞的侵袭活性比未处理细胞更有效，这可能表明细胞表面α2整合素的增加可能有助于增强对Matrigel的侵袭能力。此外，我们分别通过黏附实验和Boyden Chamber实验检测了EGF对BeWo细胞粘附胶原和趋化的影响。EGF不改变BeWo细胞对胶原基质的粘附。另一方面，EGF增强BeWo细胞的趋化活性呈剂量依赖性。值得注意的是，与侵袭实验结果相似，EGF处理后，抗α2整合素抗体能更有效地抑制趋化活性的增加。综上所述，我们认为i) α2整合素是EGF的诱导分子。ii) EGF增加α2整合素在一定程度上解释了BeWo细胞侵袭性的增强，可能是由于趋化活性的增加。少

Trophoblast, an important component of mammalian placenta has a unique biological features. Particularly, during the first trimester of pregnancy, trophoblasts start invading into uterine wall as far as uterine spinal arteries. Interestingly, this invasive behavior is strictly regulated so that the invasion would not go beyond uterine vessels. Recently, particular members of integrins have been described to be expressed on trophoblast. Evidence has been accumulated that these integrins play an essential role for the regulation of the invasive behavior described above. It has been shown that two main mechanisms are involved in cell-to-cell and cell-to extracellular matrix (ECM) interactions : interaction via ligand receptor binding, and comunication by soluble growth factors or cytokines such as epidermal growth factor (EGF), interleukin-6 (IL-6), transforming growth factor-beta (TGF-β), or leukemia inhibitory factor (LIF).In this study, utilizing human BeWo choriocarcinoma cells, we ex … More amined whether epidermal growth factor influences integrin expression on the surface of BeWo cells. Among integrin molecules examined by flow cytometry, α2 integrin expression was increased most effectively at 12, 24 and 48 hours after stimulation of 10 nM EGF. This increase concurrently occurred along the increase of human choriogenic gonadotropin (hCG) secretion, which indicates functional differentiation of trophoblasts. In addition, the α2 integrin transcripts were induced in response to EGF as early as 3 hours after addition.Combined with previous knowledge, we speculated that the increase of α2 integrin play a role in the invasion activity into endometrium. An invasion assay indicated that EGF increased invasion activity of BeWo cells at biological concentration. Antibody against α2 integrin suppressed the invasion activity more effectively on EGF-treated cells than untreated cells, which may indicate that the increase of cell surface α2 integrin may contribute to augmented invasiveness into Matrigel. Furthermore, we examined the effects of EGF on BeWo cell adhesion on collagen and chemokinasis by EGF by adhesion assay and Boyden Chamber assay, respectively. EGF did not alter the adhesion of BeWo cells to collagen matrix. On the other hand, EGF augmented chemokinasis activity of BeWo cells in dose-dependant manner. Noteworthy was that the increase of chemokinasis activity was suppressed by antibody against α2 integrin antibody more effectively when the cells were treated with EGF reimniscently to the invasion assay results. Given these results, we concluded that i) α2 integrin is an inducible molecule by EGF. ii) the increase of α2 integrin by EGF accounts in part for the augmentation of invasiveness of BeWo cells, presumably due to increase of chemokinasis activity. Less