Mochizuki M, Maruo T, Matsuo H, Samoto T, Ishihara N
Department of Obstetrics and Gynecology, Japan Kobe University School of Medicine Japan.
Int J Gynaecol Obstet. 1998 Apr;60 Suppl 1:S21-S28. doi: 10.1016/S0020-7292(95)02403-4.
In order to elucidate the regulation of placental growth, we have characterized the expression of proliferating cell nuclear antigen (PCNA), apoptotic DNA fragmentation and bc1-2 protein in human placenta during pregnancy. PCNA and bc1-2 protein expression were examined by immunohistochemical techniques, while the occurrence of apoptotic DNA fragmentation was assessed by in situ analysis of DNA 3'-end labeling method. Both PCNA expression and apoptotic DNA fragmentation were found in cytotrophoblasts (C-cells), being most abundant in early placenta, less abundant in midterm placenta and least abundant in term placenta. In contrast, bc1-2 protein expression was found in syncytiotrophoblasts (S-cells), being least abundant in early placenta, less abundant in midterm placenta and most abundant in term placenta. These data indicate that early placenta is characterized by the highly proliferative activity of C-cells associated with the increased occurrence of apoptosis, whereas term placenta is characterized by the abundant expression of bc1-2 protein in S-cells. Furthermore, effects of EGF on the proliferative activity and differentiated function of trophoblasts were investigated using an organ culture system. Expiants of trophoblastic tissues were cultured with or without EGF, in the presence or absence of 10 M triiodo-L-thyronine (T3) in a serum-free condition. In 4-5 week placentas, EGF and EGF receptor were almost exclusively localized in C-cells, and EGF augmented the proliferative activity of C-cells without affecting the ability to secrete hCG and hPL. By contrast, in 6-12 week placentas, EGF and EGF receptor were predominantly localized in S-cells, and EGF stimulated hCG and hPL secretion without affecting the proliferative activity of C-cess. The addition of T (10 M) resulted in an increased secretion of immunoreactive EGF by cultured placental explants. These findings suggest that EGF acts as a local factor in regulating early placental growth and function in synergy with thyroid hormone. On the other hand, progesterone selectively inhibited pleise hCG (α, β) mRNAs expression and decreased hCG secretion in normal placental tissues, whereas choriocarcinoma did not respond to progesterone. This suggests that inhibitory regulation of hCG synthesis in choriocarcinoma is different from normal placenta. It was also found that in molar trophoblasts and choriocarcinoma cells PCNA expression was high, but both bc1-2 protein and apoptotic signal expression were low. Characterization of choriocarcinoma hCG revealed that there are striking differences in carbohydrate structures between normal hCG and choriocarcinoma hCG. Sialic acid content in choriocarcinoma hCG was extremely lower compared to that in normal hCG. The detection of the alteration in hCG sugar chains is useful for biochemical diagnosis of choriocarcinoma.
为阐明胎盘生长的调节机制，我们对妊娠期间人胎盘增殖细胞核抗原（PCNA）、凋亡性DNA片段化及bcl-2蛋白的表达进行了特征性研究。采用免疫组织化学技术检测PCNA和bcl-2蛋白的表达，同时通过DNA 3'-末端标记法原位分析评估凋亡性DNA片段化的发生情况。PCNA表达和凋亡性DNA片段化均见于细胞滋养层细胞（C细胞），在早期胎盘最为丰富，中期胎盘较少，足月胎盘最少。相反，bcl-2蛋白表达见于合体滋养层细胞（S细胞），在早期胎盘最少，中期胎盘较少，足月胎盘最多。这些数据表明，早期胎盘的特征是C细胞具有高度增殖活性且凋亡发生率增加，而足月胎盘的特征是S细胞中bcl-2蛋白表达丰富。此外，利用器官培养系统研究了表皮生长因子（EGF）对滋养层细胞增殖活性和分化功能的影响。在无血清条件下，将滋养层组织外植体在有或无EGF、有或无10μM三碘-L-甲状腺原氨酸（T3）的情况下进行培养。在4 - 5周的胎盘中，EGF和EGF受体几乎仅定位于C细胞，EGF增强了C细胞的增殖活性，而不影响分泌人绒毛膜促性腺激素（hCG）和人胎盘催乳素（hPL）的能力。相比之下，在6 - 12周的胎盘中，EGF和EGF受体主要定位于S细胞，EGF刺激hCG和hPL分泌，而不影响C细胞的增殖活性。添加T3（10μM）导致培养的胎盘外植体分泌免疫反应性EGF增加。这些发现提示EGF作为一种局部因子，与甲状腺激素协同调节早期胎盘的生长和功能。另一方面，孕酮选择性抑制正常胎盘组织中多聚体hCG（α、β）mRNA的表达并降低hCG分泌，而绒毛膜癌对孕酮无反应。这表明绒毛膜癌中hCG合成的抑制调节与正常胎盘不同。还发现，在葡萄胎滋养层细胞和绒毛膜癌细胞中PCNA表达较高，但bcl-2蛋白和凋亡信号表达均较低。绒毛膜癌hCG的特征显示，正常hCG与绒毛膜癌hCG的碳水化合物结构存在显著差异。绒毛膜癌hCG中的唾液酸含量与正常hCG相比极低。检测hCG糖链的改变对绒毛膜癌的生化诊断有用。
