Search

The non-classical human leucocyte antigen (HLA) class I molecule HLA-G is widely known to play a major role in feto-maternal tolerance. We tested the hypothesis that HLA-G expression is altered in placentas of women with gestational diabetes mellitus (GDM) in a specific pattern that depends on fetal sex. HLA-G expression was analysed in a total of 80 placentas (40 placentas from women with GDM and 40 healthy controls) by immunohistochemistry using the semi-quantitative immunoreactive score (IRS). Double immunofluorescence staining identified the cells expressing HLA-G in the decidua and allowed evaluation of the expression pattern. We found a significant (p < 0.001) reduction of HLA-G expression in extravillous cytotrophoblasts (EVTs) in the placentas of women with GDM as compared to the healthy controls and were able to demonstrate that this downregulation was not due to a loss of cell number, but to a loss of expression intensity. A special change in the cell pattern of EVTs was observed, with these cells showing an obvious decrease in HLA-G expression on their cell surface. No significant differences according to fetal sex were found. These data show a possible association between decreased HLA-G expression and presence of GDM and provide new insights into altered placental function in women with GDM., (© 2022. The Author(s).)

During first trimester pregnancy, trophoblast cells invade from the placenta into the maternal decidua where they anchor the placenta and remodel luminal structures like spiral arteries. This process depends on proteases secreted by invading trophoblasts, which degrade extracellular matrix (ECM). We here aimed to identify proteases particularly important for trophoblast invasion. We generated a list of proteases capable of degrading decidual ECM and trophoblast integrins using MEROPS database and compared expression of these proteases between primary trophoblasts isolated from first trimester placenta (FT, n = 3), representing an invasive phenotype, vs trophoblasts isolated from term pregnancy (TT, n = 3), representing a non-invasive trophoblast phenotype. Matrix metalloproteinase 12 (MMP12) revealed highest expression levels in FT, with absent expression in TT. In situ hybridisation and immunofluorescence localised MMP12 specifically to extravillous trophoblasts (evCT) whilst Ki67 co-staining revealed that proliferating trophoblasts of the cell columns were almost negative for MMP12. Quantification revealed a decline in MMP12 positive evCT at the end of first trimester, when oxygen levels start rising. MMP12 promoter analysis identified potential binding sites for hypoxia-inducible factor (HIF-1) and other oxygen-sensitive transcription factors. Moreover, MMP12 protein was increased by low oxygen in FT in vitro and by addition of a HIF-1α activator. Collectively, MMP12 is a highly expressed protease specific for invasive evCT during the first trimester. MMP12 down regulation by increasing oxygen concentration enables temporal expression control of MMP12 and involves several mechanisms including HIF-1α. These findings suggest MMP12 involved in trophoblast invasion during the first trimester.

In the original publication, the contribution of Dr. Christian Eyth as equal first author was not indicated. This has been corrected confirming that U. Hidden and C. Eyth contributed equally to this work.

Binding of endothelial cell (EC) integrins to extracellular-matrix (ECM) components is one of the key events to trigger intracellular signaling that will ultimately result in proper vascular development. Even within one tissue, the endothelial phenotype differs between arteries and veins. Here, we tested the hypothesis that anchorage dependent processes, such as proliferation, viability, survival and actin organization of venous (VEC) and arterial EC (AEC) differently depend on ECM proteins. Moreover,because of different oxygen tension in AEC and VEC, we tested oxygen as a co-modulator of ECM effects. Primary human placental VEC and AEC were grown in collagens I and IV, fibronectin, laminin, gelatin and uncoated plates and exposed to 12 and 21% oxygen. Our main findings revealed that VEC are more sensitive than AEC to changes in the ECM composition. Proliferation and survival of VEC, in contrast to AEC, were profoundly increased by the presence of collagen I and fibronectin when compared with gelatin or uncoated plates. These effects were reversed by inhibition of focal adhesion kinase (Fak) and modulated by oxygen. VEC were more susceptible to the oxygen dependent ECM effects than AEC. However, no differential ECM effect on actin organization was observed between the two cell types. These data provide first evidence that AEC and VEC from the same vascular loop respond differently to ECM and oxygen in a Fak-dependent manner.

As cell cycle regulation is fundamental to the normal growth and development of the placenta, the aim of the present study was to determine the immunolocalizations of cell cycle related proteins, which have key roles in proliferation, differentiation and apoptosis during the development of the rat placenta. Here immunohistochemistry has been used to localize G1 cyclins (D1, D3, E), which are major determinants of proliferation, CIP/KIP inhibitors (p21, p27, p57), p53 as a master regulator and proliferating cell nuclear antigen in all cell types of the rat term placenta. The proportion of each cell type immunolabeled was counted. Cyclin D1 and cyclin D3 were present mostly in cells of the fetal aspect of the placenta, whereas the G1/S cyclin E was present only in the spongio- and labyrinthine trophoblast populations. Among the CIP/KIP inhibitors, p21 was present only in cells of the fetal aspect whereas p27 and p57 were found in all cell types studied. p53 was only found in a small proportion of cells with no co-localization of p53 and p21. The data suggest that the cells of the fetal side of the rat placenta still have some proliferation potential which is kept in check by expression of the CIP/KIP cell cycle inhibitors, whereas cells of the maternal aspect have lost this potential. Apoptosis is only marginal in the term rat placenta. In conclusion, proliferation and apoptosis in rat placental cells appears controlled mostly by the CIP/KIP inhibitors in late pregnancy.

Although placental development and implantation depend on the coordination of trophoblast proliferation, differentiation and invasion, little is known about the cell cycle regulators that govern the control of these events. The hypothesis that the coordinated expression of cell cycle progression and inhibition factors will determine whether cytotrophoblasts proliferate or undergo cell cycle arrest or cell cycle exit allowing subsequent differentiation was tested. The cell cycle promotors cyclin A, cyclin B1, PCNA, Ki67 and the cell cycle inhibitors p21, p27 and p57 were immunolocalized in tissue sections of first trimester pregnancies (weeks 6 and 9-12). Double staining with cytokeratin 7 allowed unambiguous identification of extravillous cytotrophoblast (EVT) in the decidua. Villous cytotrophoblasts were immunolabelled for Ki67 and cyclin A but only few were stained with anti-cyclin B1. The syncytiotrophoblast was devoid of immunoreactivity for any of the cell cycle progression factors. It expressed especially p21, whereas p27 and p57 were predominantly found in villous cytotrophoblasts. PCNA, Ki67, cyclin A and cyclin B1 were immunolocalized in proximal and distal EVTs of anchoring villi and in EVT which had invaded the upper decidual segments. All EVTs strongly expressed p27 and p57, but not p21. These data clearly suggest different functions for p21, p27 and p57 in placental development with distinct roles for p21 and p57 in syncytiotrophoblast and EVT differentiation, respectively. p27 appears to be involved in both the processes. The results may also challenge the concept of differential mitotic activity in the proximal and distal parts of the first trimester cytotrophoblast cell column, but more functional studies are clearly needed. The presence of p27 and p57 in EVT cells, which invade the deciduas deeply, may account for the loss of mitogenic potential of these cells.

Human placenta regulates the transport of maternal molecules to the fetus. It is known that glucose transport occurs via glucose transporters (GLUTs) in the feto-placental unit. Data on the expression of GLUTs during implantation are very scarce. Moreover, the question of how the decidual leukocytes obtain the energy for their activation during implantation mechanism is still under investigation. We studied the distributions of GLUT1, GLUT3, and GLUT4 in tissue sections of first trimester pregnancies the human maternal-fetal interface. GLUT1 was present in apical microvilli of the syncytiotrophoblast, in cytotrophoblast, and in vascular patterns of the villous core, whereas GLUT3 was localized in cytotrophoblasts of placental villi and in some fetal endothelial cells. Moreover, the proliferating cells of the proximal cell columns were also immunopositive for GLUT1 and GLUT3. We did not observe any positive immunoreactivity for GLUT4 in placental and decidual tissues. Essentially, GLUT3 and also to some extent GLUT1 was present in maternal leukocytes and platelets. In conclusion, our results suggest that the glucose taken up via GLUT1 and GLUT3 from the maternal circulation might not only be needed for placental functions but also for successful implantation by trophoblast invasion, proliferation and also by having a role to support energy for maternal leukocytes.

Mercurochrom [2,7-dibromo-4-(hydroxymercuri)-fluorescein disodium salt] used for staining of protein thiols in addition binds to other groups of proteins. Experimental evidence is provided that mercurochrom bound to non-thiol groups forms a 1:1 adduct with protein (mixed) disulfides. The disulfide contents of three different types of cells determined biochemically correlated with the corresponding mean integrated optical densities determined microphotometrically after mercurochrom staining of groups other than thiols. Intracellular disulfide exchange has been studied, leading to a transformation of protein mixed disulfides to protein disulfides and an equimolar loss of protein thiols. Protein mixed disulfides were generated from protein thiols using both methyl methanethiosulfonate (MMTS) and 2,2'-dihydroxy-6,6'-dinaphthyldisulfide (DDD). Loss of thiols as well as the equimolar increase of protein mixed disulfides were followed using both mercurochrom staining for thiols and for disulfides. Generation of protein mixed disulfides due to the DDD reaction was also followed by azocoupling with Fast blue B. On the basis of the observed stoichiometry between the loss of protein thiols and the quantity, increase or conversion of protein disulfides determined microphotometrically using both mercurochrom staining and DDD Fast blue B staining, we conclude that: (1) 1 mol of mercurochrom is bound per mol of protein (mixed) disulfide; and (2) the molar absorptivity of mercurochrom bound to disulfides is epsilon 520 = 34940. This study demonstrates that mercurochrom can be used for the quantitative determination of the oxidative status of protein thiols in cells.