恒河猴胚胎浅表型植入机理的探讨

Molecular mechanism of the superficial implantation in the rhesus monkey (Macaca mulatta)

为揭示恒河猴胚胎浅表型植入的分子机理 ,实验采用免疫组化和原位杂交的方法研究了粘附侵润相关分子在妊娠恒河猴母胎界面的表达模式 ,发现层粘连蛋白 (LN)、Ⅳ型胶原 (ColⅣ )和基质金属蛋白酶 2(MMP 2 )在滋养层细胞柱的远端开始表达 ;整合素α1β1从柱的近端到远端表达逐渐升高 ,但在滋养层细胞鞘中上述分子的表达均降低 ;大量侵润母体血管的滋养层细胞高水平表达上述分子。此外 ,植入早期上皮斑和蜕膜基质细胞高表达MMPs组织抑制因子 2 (TIMP 2 )。结果提示 ,滋养层细胞鞘中α1β1、LN、MMP 2表达水平的降低及上皮斑、蜕膜和滋养层细胞中TIMP 2的高表达可能是导致浅表型植入形成的分子基础.

Embryo implantation involves in recognition and adhesion between receptive uterine epithelium and trophoblast; invasion of extravillous cytotrophoblast into endometrium; degradation and remodeling of ECM and angiogenesis. ECM and their integrin receptor, MMPs and TIMPs participate in the comprehensive course and play a critical role in mediating adhesion and invasion of trophoblast into maternal uterine. The different expression pattern of the molecules mentioned above in trophoblast as well as decidual tissue among various animals might result in the difference in implantation type and invading depth. Unlike the interstitial type of the embryo implantation in human being, it appears to be the superficial type in the rhesus monkey. Up to now it remains unclear in literatures whether the special expression pattern of the adhesion- and/or invasion-related molecules at the maternal-fetal interface is the underlying molecular basis for the shallow implantation in the rhesus monkey.To better understand the molecular mechanism underlining the superficial implantation in rhesus monkey, the expression pattern of laminin (LN), type Ⅳ collagen (Col Ⅳ), integrin α 1β 1, matrix metalloproteinases-2 (MMP-2) and its tissue inhibitor (TIMP-2) at the maternal-fetal interface at the gestational day 15, 25, 50 and 100 were investigated by immunohistochemistry and in situ hybridization. It was observed that the cytotrophoblast (CTB) column was well developed in a relatively long cylinder-like shape compared to the human's with packed CTB cells in the proximal region. The wondering trophoblast cells in maternal decidue were scarcely found. Under the implantation site, special groups of lumenal and glandular epithelial cells clumped to form an epithelial plaque before the gestational day 25. In trophoblast cells, the transcripts and immunoreactivities of LN, Col Ⅳ, integrin α 1β 1, MMP-2 and TIMP-2 were detected on the 15th day of pregnancy and reached a peak level (appeared) on the 25th day. From the 50th day on, their expression decreased obviously. Along the invasive pathway, the expression levels of LN and Col Ⅳ as well as their corresponding receptor (integrin α 1β 1) in the cytotrophoblast (CTB) cells increased gradually. However, their levels declined in the CTB cells which were adjacent to the maternal decidual cells. MMP-2 and TIMP-2 were strongly expressed by the CTB cells in the distal column. Meanwhile, most of the CTB cells invading into the maternal blood vessels exhibited high level of integrin α 1β 1, LN, and MMP-2.On the other hand, at the maternal part, strong expression of MMP-2 and TIMP-2 whereas low level of LN and Col Ⅳ were observed in the decidual stromal cells but the level of TIMP-2 in the stromal cells was elevated with the advancing of pregnancy. Notably, besides the moderate expression of integrin α 1β 1 and MMP-2, a high level of TIMP-2 and scarce LN were presented by the epithelial plaque cells. Conclusion: the data indicated that the active invasion of trophpblast cells was precisely restricted by the decreased expression of integrin α 1β 1 and its ligands (LN and Col Ⅳ) in the CTB shell as well as by a strong expression of TIMP-2 in decidual cells and the epithelial plaque which formed from the uterine lumenal and glandular epithelial cell. Thus it might be the essential mechanism involved in the superficial implantation in the rhesus monkey.