Immunohistochemical identification of the extravillous trophoblast during the placentation of the degu (Octodon degus)

Abstract

Recent data indicate that placentation in Octodon degus is similar to that in humans, making it a potential animal model for studies in human placental pathologies related to alterations in the migration of the extravillous trophoblast (EVT). Our objective was to immunohistochemically identify degu EVT during placentation by using cytoskeletal protein markers to establish the normal migratory pattern of the EVT. Fifteen O.degus were divided into three equal groups: day 27, 60, and 84 of gestation. The placentas were immunostained for cytokeratin (CK) and alpha smooth muscle actin (SMA). At day 27, the migrating EVT immunostained for SMA but not for CK. Once the EVT was incorporated in the maternal vessels (day 60) it was positive for CK but negative for SMA. The smooth muscle cells of the mesometrial arteries that remained after EVT invasion were positive for SMA. At day 84, the media muscular layer had partially regenerated but some EVT was still present. Furthermore, at day 27 cyclooxygenase-1 (COX-1) was detected in the endothelium of the maternal decidual vessels. Our results suggest that during the early stages of placentation, the cytoskeletal organization of the actin network of the migrating EVT corresponds to that of a cell with motile behavior. Once the EVT invaded the spiral arteries, the cytoskeleton reorganized, adopting the structure of an epithelial-like cell, expressing CK intermediate filaments. The media muscle layer regenerated near the end of gestation but some EVT remained. During EVT formation the endothelium of the maternal decidual vessels immunostained for COX-1.

Development of Some Organs Derived from the Three Embryonic Germ Layer in a Degus Ectopic Pregnancy and Presence of a Cytotrophoblast That Mimics Human Chorionic Placenta

“…This would give a stronger support to our proposal of the degu as an experimental animal model for the study of preeclampsia in the early stages of placentation [10,16].…”

“…It is important to note that the placenta of the degu is hemomonochorial and labyrinthine as in the guinea pig [9,15] and that the degus cytotrophoblast develops from the subplacenta, from which the syncytial labyrinthine placental barrier is formed [10,16]. On the other hand, Bland and Donovan [17] were able to induce abdominal implantation in guinea pig by introducing fertilized eggs into the peritoneal cavity.…”

“…In a histological micrograph, these authors showed a subplacenta and invasive trophoblast in the spleen but not the development of a real placental organ as we report in the present study. In addition, Bosco et al [10,16] demonstrated that in the degu the cytotrophoblast is found only in the subplacenta and not in the labyrinthine placental barrier as it is known to occur in the human villous placental barrier. In the human species, each villus consists of a central core of loose connective tissue surrounded by a double layer of trophoblast, an outer syncytiotrophoblast and an inner cytotrophoblast that differentiate to syncytiotrophoblast [8], as is the case in this report (see Figures 5(a), 5(b), 5(c), and 5(d)).…”

Chorioallantoic placentation in Galea spixii (Rodentia, Caviomorpha, Caviidae)

“…Ultrathin sections were made on an automatic ultramicrotome (Ultracut R, Leica Microsystems, Germany), contrasted with 2% uranyl acetate and 0.5% lead citrate and studied in a transmission electron microscope (Morgagni 268D, FEI Company, The Netherlands; Mega View III camera, Soft Imaging System, Germany). Immunohistochemistry was performed for vimentin to identify mesenchymal cells and stromal decidua and for α-smooth muscle actin to identify vessel walls, following methods established as standard for guinea pig-related rodents [ 3 , 6 - 8 , 13 - 15 , 25 ]. Additional immunohistochemistry was carried out for cytokeratin to identify epithelial cells and trophoblast, but this method did not result in fully specific reactions for guinea pig-related rodents [ 3 , 7 ].…”

Placentação em roedores da família Cricetidae - Sigmodontinae

“…Segundo proposto por King (1982) a condição labiríntica e hemomonocorial da placenta é uma característica de roedores caviomorfos (KAUFMANN, 1981;MOSSMAN, 1987;DANTZER et al, 1988;MESS, 2007b;BUFFET, 2008), o que corresponderia certamente a um carácter filogenético de grupo. Carter (2001) sugere que filogeneticamente a barreira-placentária evoluiu de um modelo mais complexo (hemotricorial) com três camadas de tecido separando a circulação materna e fetal, para um modelo mais simples com apenas uma camada de tecido fazendo essa divisão (hemomonocorial), passando antes por um modelo hemodicorial presente em algumas espécies, como no caso dos Lagomorfos (ENDERS et al, 1998).…”