Immunosuppressive properties of murine trophoblast

The modification of the immunological response by murine trophoblast cells of different sources was investigated using the mixed lymphocyte reaction (MLR) and the cell mediated lympholysis (CML) test. MLR between C57BL (H-2b) stimulator splenocytes (mitomycin C treated in the unidirectional MLR) and BALB/c (H-2d) responder lymph node cells were markedly suppressed by trophoblast of ectoplacental cone (EPC) and placental origin. The same in vitro effect was observed with supernatants (SN) of trophoblast cells and with supernatants of blastocysts. Addition of anti-progesterone serum (APS), anti-testosterone serum (RAT), and anti-immunoglobulin serum (RAHIg) in serial dilutions to the trophoblast-MLR system revealed that the immunosuppressive effect of trophoblast giant cells and trophoblast giant cell culture supernatants can be abolished with APS. Identical results were obtained with APS added to immunosuppressive doses of progesterone. CML between C57BL responder lymph node cells and mitomycin C-treated BALB/c stimulator spleen cells was also markedly suppressed when trophoblast of EPC origin was added. A similar suppression of cytotoxic T-cell induction was seen when progesterone was added to the system. The immunosuppressive action of trophoblast as detected in vitro is likely to play an important role in the maintainance of pregnancy by protecting the semiallogeneic conceptus against immune aggression by the maternal immune system.     

Control of human trophoblast function

The trophoblast, i.e. the peripheral part of the human conceptus, exerts a crucial role in implantation and placentation. Both processes properly occur as a consequence of an intimate dialogue between fetal and maternal tissues, fulfilled by membrane ligands and receptors, as well as by hormone and local factor release. During blastocyst implantation, generation of distinct trophoblast cell types begins, namely the villous and the extravillous trophoblast, the former of which is devoted to fetal-maternal exchanges and the latter binds the placental body to the uterine wall. Physiological placentation is characterized by the invasion of the uterine spiral arteries by extravillous trophoblast cells arising from anchoring villi. Due to this invasion, the arterial structure is replaced by amorphous fibrinoid material and endovascular trophoblastic cells. This transformation establishes a low-resistance, high-capacity perfusion system from the radial arteries to the intervillous space, in which the villous tree is embedded. The physiology of pregnancy depends upon the orderly progress of structural and functional changes of villous and extravillous trophoblast, whereas a derangement of such processes can lead to different types of complications of varying degrees of gravity, including possible pregnancy loss and maternal life-threatening diseases. In this review we describe the mechanisms which regulate trophoblast differentiation, proliferation, migration and invasiveness, and the alterations in these mechanisms which lead to pathological conditions. Furthermore, based on the growing evidence that proper inflammatory changes and oxidative balance are needed for successful gestation, we explain the mechanisms by which agents able to influence such processes may be useful in the prevention and treatment of pregnancy disorders.     

Endomitosis in human trophoblast

Summary Endopolyploidy, which arises through the duplication of DNA without accompanying nuclear division, occurs in large numbers of lower and higher plants and animals, including the best known, the salivary gland nuclei of Drosophila. Endomitosis is one of the processes leading to endopolyploidy, in which the stages of mitosis (prophase, metaphase, anaphase) take place inside the nuclear membrane and without spindle formation. In mammals, endomitosis has been observed in the trophoblast of the placenta of the mouse, rat and rabbit. This is the first report of endomitosis in a normal human tissue, the trophoblast of first trimester human placenta.This research was supported in part by the Foundation for Reproductive Research and Education, Inc., Northwestern University, Department of Obstetrics and Gynecology.     

Oncofoetal antigens of human trophoblast.

Rabbits immunized with human trophoblast cell membranes produced antibodies that were detected, by immunofluorescence, to react with normal human tissues, and, by complement-mediated cytotoxicity, with several transformed human cell lines. Absorption with trophoblast abolished all of these reactions, whereas multiple absorptions with lymphocytes, liver or kidney failed to remove reactivity with either trophoblast or certain transformed cells. To further identify the antigens responsible for these antibodies, rabbits were immunized with a chromatographed fraction of deoxycholate-solubilzed membranes prepared from KCl-extracted, ultracentrifuge-prepared trophoblast microvilli. The resultant IgG antibody reacted specifically with syncytiotrophoblastic membranes in sections of human placentae, in addition to recognizing the membranes of viable Chang liver, AV3, HEp-2, Sw/156 (kidney) and Sw/527 (breast) cells. That normal tissues, baboon or monkey placentae, and HeLa or Daudi cell lines did not react with this antibody, indicates the presence of species- and organ-specific antigens in human trophoblast, as well as the existence of trophoblast cross-reactive antigens on some transformed cells. The selective localization of these antigens at the interface of the materno-foetal graft suggests that they function biologically in the host-parasite relation of human pregnancy; their appearance on many transformed cells implies a similar function in the host-parasite relation of some human cancers.     

Interplay between neutrophils and trophoblast cells conditions trophoblast function and triggers vascular transformation signals

Normal placentation entails highly regulated interactions of maternal leukocytes with vascular and trophoblast cells to favor vascular transformation. Neutrophil activation and neutrophil extracellular trap (NET) formation associate with poor placentation and severe pregnancy complications. To deepen into the mechanisms of trophoblast–neutrophil interaction, we explored the effects of NETs on trophoblast cell function and, conversely, whether trophoblast cell-derived factors condition neutrophils to favor angiogenesis and anti-inflammatory signals required for fetal growth. NETs isolated from activated neutrophils hindered trophoblast cell migration. Trophoblast conditioned media prevented the effect as well as the vasoactive intestinal peptide (VIP) known to regulate trophoblast and neutrophil function. On the other hand, factors released by trophoblast cells and VIP shaped neutrophils to a proangiogenic profile with increased vascular endothelial growth factor synthesis and increased capacity to promote vascular transformation. Results presented here provide novel clues to reconstruct the interaction of trophoblast cells and neutrophils in vivo during placentation in humans.     

Ectopic transplantation of equine invasive trophoblast

A system for transplanting invasive equine trophoblast (i.e., chorionic girdle) to ectopic sites has been developed as a means to study the differentiation of this tissue and to assess maternal immune responses to the conceptus tissue in a site outside the uterus. Chorionic girdle was isolated from Day 33 to 34 conceptuses and surgically placed into the vulvar mucosa or subdermal skin of recipient mares. Biopsy specimens of the graft sites for immunohistochemical staining were taken at weekly or biweekly intervals after grafting. Serum samples were collected from each recipient and tested for antibody to donor major histocompatibility complex (MHC) class I antigens using the lymphocyte microcytotoxicity assay. Transplanted trophoblast cells expressed differentiation markers associated with invading chorionic girdle and endometrial cup cells. The transplanted trophoblast cells were also labeled by an antibody to eCG. Strong cellular and humoral immune responses to the transplanted tissue were mounted by the recipients, similar to those occurring during normal equine pregnancy. Despite these responses, the invasive trophoblast transplants survived for at least 28 days after grafting and downregulated MHC class I antigens, as do the mature endometrial cup cells in equine pregnancy. These findings suggest that invasive equine trophoblast has the capacity to differentiate fully in equine nonuterine tissues, and that it can evade maternal immune responses independent of the physiological state of pregnancy and in sites other than the uterus.     

Erythrophagocytosis in the caprine trophoblast

The mechanism of iron transfer by extravasation of maternal blood in the maternal-fetal interface and the subsequent phagocytosis of the erythrocytes by the trophoblast cells was described in ovine, bovine and other species. This research was performed due to the absence of studies on this process in the goat. Fragments of placentomes were obtained from 9 adult goats of an unspecified breed and were separated into Groups A, B and C, based on 90, 120 and 150 d of gestation, respectively. Fragments of 3 placentomes were obtained from each animal of all groups. The first of them was removed from the base, the second from the middle part and the third from the end of the gestational uterine horn. The fragments were fixed in Bouin solution and histologically processed according to the usual paraffin inclusion techniques. The slides were stained by hematoxilin-eosin and potassium ferrocyanide and examined under light microscopy The erythrophagocytosis (EP) process of the trophoblast was identified in all the examined histological sections, throughout the gestation and for each placentome. An accumulation of spots of blood was observed only in the maternal-fetal interface located in the arcade zone of the placentome. The main cells of the trophoblast of these areas presented an intense phagocytic activity and the observation of erythrocytes with hemossiderin pigments in their citoplasm was possible. The trophoblast epithelium of these areas was thicker and with a columnar aspect than the cubic aspect observed in other areas. The trophoblast binucleate cells do not seem to participate in EP. Our findings indicate that the phagocitosis process of the maternal erythrocites by the trophoblast also occurs in caprine species, indicating that this could be a mechanism of transplacentary transfer of iron in this species.     

Control of trophoblast cell differentiation: Lessons from the genetics of early pregnancy loss and trophoblast neoplasia

Trophoblast cell differentiation is crucial to the morphogenesis of the placenta and thus the establishment of pregnancy and the growth and development of the embryo/fetus. In the present review, we discuss current evidence for the existence of regulatory genes crucial to trophoblast cell differentiation and placental morphogenesis. The elucidation of regulatory pathways controlling normal differentiation of trophoblast cells will facilitate the identification of sensitive junctures in the regulatory pathways leading to various developmental disorders, including those associated with the initiation of pregnancy, fetal growth retardation and gestational trophoblast disease.     

Identification of extra-villous trophoblast cells in human decidua using an apparently unique murine monoclonal antibody to trophoblast

Summary Murine monoclonal antibodies were raised to human first trimester trophoblast cells. Eleven antibodies reacted with first trimester trophoblast, tested by immunoperoxidase staining on frozen sections, but only one had apparent specificity for trophoblast after examining reactivities with a panel of other cells and tissues. This antibody, designated FD0161G, bound selectively to syncytiotrophoblast and non-villous trophoblast in first trimester and term placentae. Villous cytotrophoblast was negative. This was clearly demonstrated on freeze-dried, paraffin embedded tissue sections which have superior architecture to frozen sections. FD0161G reacted with extra-villous trophoblast cells in human decidua which are also delineated by a monoclonal anti-cytokeratin antibody. Unlike the latter, however, FD0161G did not react with decidual glands. Thus FD0161G could be used as a specific probe for extra-villous trophoblast in decidual tissue     

Function of caspase-14 in trophoblast differentiation

Background  

Within the human placenta, the cytotrophoblast consists of a proliferative pool of progenitor cells which differentiate to replenish the overlying continuous, multi-nucleated syncytiotrophoblast, which forms the barrier between the maternal and fetal tissues. Disruption to trophoblast differentiation and function may result in impaired fetal development and preeclampsia. Caspase-14 expression is limited to barrier forming tissues. It promotes keratinocyte differentiation by cleaving profilaggrin to stabilise keratin intermediate filaments, and indirectly providing hydration and UV protection. However its role in the trophoblast remains unexplored.     

Identification of bovine trophoblast protein-1, a secretory protein immunologically related to ovine trophoblast protein-1

This paper demonstrates that a group of proteins, representing a major secretory component of cattle conceptuses, is immunologically related to ovine trophoblast protein-1 (oTP-1), a principal product of culture Day 13 to 21 sheep conceptuses. Conceptuses from cows (Day 17-18) and ewes (Day 16-17) were cultured for 24 h in the presence of L-[3H]leucine. By using a rabbit antiserum to oTP-1 and Ouchterlony double-immunodiffusion analysis it was shown that material in the bovine conceptus culture medium was serologically related, but not identical, to oTP-1. A solid-phase radiobinding assay indicated that the cross-reacting bovine secretory component had an affinity for anti-oTP-1 antibody similar to that of oTP-1. Anti-oTP-1 antiserum specifically immunoprecipitated a group of 6-8 polypeptides from culture medium of cow conceptuses which, when analysed by two-dimensional gel electrophoresis, fell into two major molecular weight classes (22,000 and 24,000) with isoelectric points between 6.5 and 6.7. These immunoprecipitated polypeptides, defined as bTP-1, constituted the major secretory products of Day 16-25 cow conceptuses. They were larger and more basic than oTP-1 polypeptides (Mr about 18,000; pI 5.4-5.7). Anti-oTP-1 antiserum also recognized the major translation product of Day 17 bovine conceptus mRNA, a polypeptide significantly smaller (Mr approximately 18,000) than the secreted protein. It is suggested that oTP-1 and the homologous bovine protein may play similar roles in the phenomenon of maternal recognition of pregnancy in the two species.