Fisher S J, Cui T Y, Zhang L, Hartman L, Grahl K, Zhang G Y, Tarpey J, Damsky C H
Department of Stomatology, University of California, San Francisco 94143.
J Cell Biol. 1989 Aug;109(2):891-902. doi: 10.1083/jcb.109.2.891.
Human fetal development depends on the embryo rapidly gaining access to the maternal circulation. The trophoblast cells that form the fetal portion of the human placenta have solved this problem by transiently exhibiting certain tumor-like properties. Thus, during early pregnancy fetal cytotrophoblast cells invade the uterus and its arterial network. This process peaks during the twelfth week of pregnancy and declines rapidly thereafter, suggesting that the highly specialized, invasive behavior of the cytotrophoblast cells is closely regulated. Since little is known about the actual mechanisms involved, we developed an isolation procedure for cytotrophoblasts from placentas of different gestational ages to study their adhesive and invasive properties in vitro. Cytotrophoblasts isolated from first, second, and third trimester human placentas were plated on the basement membrane-like extracellular matrix produced by the PF HR9 teratocarcinoma cell line. Cells from all trimesters expressed the calcium-dependent cell adhesion molecule cell-CAM 120/80 (E-cadherin) which, in the placenta, is specific for cytotrophoblasts. However, only the first trimester cytotrophoblast cells degraded the matrices on which they were cultured, leaving large gaps in the basement membrane substrates and releasing low molecular mass 3H-labeled matrix components into the medium. No similar degradative activity was observed when second or third trimester cytotrophoblast cells, first trimester human placental fibroblasts, or the human choriocarcinoma cell lines BeWo and JAR were cultured on radiolabeled matrices. To begin to understand the biochemical basis of this degradative behavior, the substrate gel technique was used to analyze the cell-associated and secreted proteinase activities expressed by early, mid, and late gestation cytotrophoblasts. Several gelatin-degrading proteinases were uniquely expressed by early gestation, invasive cytotrophoblasts, and all these activities could be abolished by inhibitors of metalloproteinases. By early second trimester, the time when cytotrophoblast invasion rapidly diminishes in vivo, the proteinase pattern of the cytotrophoblasts was identical to that of term, noninvasive cells. These results are the first evidence suggesting that specialized, temporally regulated metalloproteinases are involved in trophoblast invasion of the uterus. Since the cytotrophoblasts from first trimester and later gestation placentas maintain for several days the temporally regulated degradative behavior displayed in vivo, the short-term cytotrophoblast outgrowth culture system described here should be useful in studying some of the early events in human placen
人类胎儿发育依赖于胚胎迅速接入母体循环。形成人类胎盘胎儿部分的滋养层细胞通过短暂展现某些肿瘤样特性解决了这个问题。因此，在妊娠早期，胎儿细胞滋养层细胞侵入子宫及其动脉网络。这个过程在妊娠第12周达到顶峰，此后迅速下降，这表明细胞滋养层细胞高度专业化的侵袭行为受到密切调控。由于对其中实际涉及的机制知之甚少，我们开发了一种从不同妊娠阶段胎盘分离细胞滋养层细胞的方法，以研究它们在体外的黏附及侵袭特性。从妊娠早期、中期和晚期人类胎盘分离出的细胞滋养层细胞被接种到由PF HR9畸胎瘤细胞系产生的类基底膜细胞外基质上。所有妊娠阶段的细胞都表达钙依赖性细胞黏附分子细胞-CAM 120/80（E-钙黏蛋白），在胎盘中，它是细胞滋养层细胞特有的。然而，只有妊娠早期的细胞滋养层细胞降解它们所培养的基质，在基底膜底物上留下大的间隙，并将低分子量的3H标记基质成分释放到培养基中。当妊娠中期或晚期的细胞滋养层细胞、妊娠早期的人类胎盘成纤维细胞或人类绒毛膜癌细胞系BeWo和JAR在放射性标记基质上培养时，未观察到类似的降解活性。为了开始理解这种降解行为的生化基础，采用底物凝胶技术分析妊娠早期、中期和晚期细胞滋养层细胞表达的细胞相关和分泌的蛋白酶活性。几种明胶降解蛋白酶是妊娠早期侵袭性细胞滋养层细胞特有的，并且所有这些活性都可被金属蛋白酶抑制剂消除。到妊娠中期早期，即细胞滋养层细胞在体内侵袭迅速减少的时候，细胞滋养层细胞的蛋白酶模式与足月非侵袭性细胞的相同。这些结果是首个证据，表明专门的、受时间调控的金属蛋白酶参与滋养层细胞对子宫的侵袭。由于来自妊娠早期和晚期胎盘的细胞滋养层细胞在数天内维持在体内显示的受时间调控的降解行为，这里描述的短期细胞滋养层细胞生长培养系统应该有助于研究人类胎盘的一些早期事件。
