Multhaupt H A, Mazar A, Cines D B, Warhol M J, McCrae K R
Department of Pathology, Pennsylvania Hospital, Philadelphia.
Lab Invest. 1994 Sep;71(3):392-400.
Through their ability to invade endometrium, remodel the uterine spiral arteries, and sustain placental blood fluidity, trophoblast cells play a central role in establishing and maintaining the integrity of the uteroplacental vasculature. The expression of urokinase receptors by trophoblast may facilitate these processes by focusing plasminogen activator activity to discrete sites on the cell surface and promoting the activation of cell-bound plasminogen. However, although urokinase receptors are expressed by cultured trophoblast, the expression of these receptors by trophoblast in vivo has not been examined.
Immunohistochemistry and immunoelectron microscopy were used to characterize the expression of urokinase receptors by villous and extravillous trophoblast at several points in gestation.
Urokinase receptors were expressed in a polarized fashion at the leading edge of migrating extravillous trophoblast cells. Receptors were also abundantly expressed during the first and second trimesters of gestation by villous trophoblast, where they were located on apical villous projections and within intracellular vacuoles, a subset of which were lysosomes.
The polarized expression of urokinase receptors by invasive extravillous trophoblast cells is consistent with a role for these receptors in mediating the extent and directionality of trophoblast migration. In contrast, the expression of urokinase receptors by villous trophoblast, which are not actively invasive in vivo, may serve to facilitate the generation of plasmin at the interface of these cells with maternal plasma, thereby limiting the deposition of fibrin within the placental intervillous spaces. Diminished urokinase receptor expression by villous trophoblast at term may represent a physiologic adaptation to diminish local fibrinolysis and limit hemorrhage at parturition.
通过侵入子宫内膜、重塑子宫螺旋动脉以及维持胎盘血流流动性的能力，滋养层细胞在建立和维持子宫胎盘血管系统的完整性方面发挥着核心作用。滋养层细胞表达尿激酶受体，可将纤溶酶原激活物活性集中于细胞表面的离散位点并促进细胞结合型纤溶酶原的激活，从而可能促进这些过程。然而，尽管培养的滋养层细胞表达尿激酶受体，但尚未检测过滋养层细胞在体内的这些受体表达情况。
采用免疫组织化学和免疫电子显微镜技术，对妊娠不同阶段绒毛和绒毛外滋养层细胞中尿激酶受体的表达进行表征。
尿激酶受体以极化方式表达于迁移的绒毛外滋养层细胞的前沿。在妊娠的前三个月和第二个月，绒毛滋养层细胞也大量表达受体，这些受体位于顶端绒毛突起和细胞内液泡中，其中一部分是溶酶体。
侵袭性绒毛外滋养层细胞中尿激酶受体的极化表达与这些受体在介导滋养层细胞迁移的程度和方向性方面的作用一致。相比之下，体内不具有活跃侵袭性的绒毛滋养层细胞表达尿激酶受体，可能有助于在这些细胞与母体血浆的界面处产生纤溶酶，从而限制纤维蛋白在胎盘绒毛间隙内的沉积。足月时绒毛滋养层细胞尿激酶受体表达减少可能是一种生理适应性变化，以减少局部纤维蛋白溶解并限制分娩时出血。
