Background: Placentas of guinea pig-related rodents are appropriate animal models for human placentation because of their striking similarities to those of humans. To optimize the pool of potential models in this context, it is essential to identify the occurrence of characters in close relatives.

Foetal membranes are essential tissues for embryonic development, playing important roles related to protection, breathing, nutrition and excretion. The amnion is the innermost extraembryonic membrane, which surrounds the foetus, forming an amniotic sac that contains the amniotic fluid (AF). In recent years, the amniotic membrane has emerged as a potential tool for clinical applications and has been primarily used in medicine in order to stimulate the healing of skin and corneal diseases. It has also been used in vaginal reconstructive surgery, repair of abdominal hernia, prevention of surgical adhesions and pericardium closure. More recently, it has been used in regenerative medicine because the amniotic-derived stem cells as well as AF-derived cells exhibit cellular plasticity, angiogenic, cytoprotective, immunosuppressive properties, antitumoural potential and the ability to generate induced pluripotent stem cells. These features make them a promising source of stem cells for cell therapy and tissue engineering. In this review, we discussed the development of the amnion, AF and amniotic cavity in different species, as well as the applicability of stem cells from the amnion and AF in cellular therapy.

BackgroundSigmodontinae, known as "New World rats and mice," is a large subfamily of Cricetidae for which we herein provide the first comprehensive investigation of the placenta.MethodsPlacentas of various gestational ages ranging from early pregnancy to near term were obtained for five genera, i.e. Necromys, Euryoryzomys, Cerradomys, Hylaeamys, and Oligoryzomys. They were investigated by means of histology, immunohistochemistry, a proliferation marker, DBA-lectin staining and transmission electron microscopy.ResultsThe chorioallantoic placenta was organized in a labyrinthine zone, spongy zone and decidua and an inverted yolk sac persisted until term. The chorioallantoic placenta was hemotrichorial. The interhemal barrier comprised fetal capillary endothelium and three layers of trophoblast, an outermost, cellular layer and two syncytial ones, with interspersed trophoblast giant cells (TGC). In addition, accumulations of TGC occurred below Reichert's membrane. The junctional zone contained syncytial trophoblast, proliferative cellular trophoblast, glycogen cells and TGC that were situated near to the maternal blood channels. In three of the genera, TGC were also accumulated in distinct areas at the placental periphery. PAS-positive glycogen cells derived from the junctional zone invaded the decidua. Abundant maternal uNK cells with positive response to PAS, vimentin and DBA-lectin were found in the decidua. The visceral yolk sac was completely inverted and villous.ConclusionThe general aspect of the fetal membranes in Sigmodontinae resembled that found in other cricetid rodents. Compared to murid rodents there were larger numbers of giant cells and in some genera these were seen to congregate at the periphery of the placental disk. Glycogen cells were found to invade the decidua but we did not identify trophoblast in the walls of the deeper decidual arteries. In contrast these vessels were surrounded by large numbers of uNK cells. This survey of wild-trapped specimens from five genera is a useful starting point for the study of placentation in an important subfamily of South American rodents. We note, however, that some of these rodents can be captive bred and recommend that future studies focus on the study of time dated pregnancies.

The principle processes of placentation in caviomorphs follow an extraordinarily stable pattern that is independent of specializations, such as polyovulation.

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BackgroundIsolation of mesenchymal stem cells (MSCs) in equines, has been reported for different tissues including bone marrow, adipose, umbilical cord, peripheral blood, and yolk sac. In regard to the MSCs derived from synovial fluid (SF) or membrane (SM), there is data available for humans, dogs, pigs, goats and horses. Especially in equines, these cells have being considered promising candidates for articular regeneration. Herein, we established and characterized MSCs obtained from equine SF and SM. Samples were obtained during arthroscopy and cultured using MEM (Minimum Essential Medium). MSCs were characterized by morphology and expression of specific markers for stem cells, pluripotency, inflammation, and cell cycle.ResultsThe medium MEM was more effective (97 % ± 2) to maintain both cultures. The cultures were composed by adherent cells with fibroblast-like shape, which had a growth pattern represented by a sigmoidal curve. After the expansion, the cells were analyzed by flow cytometry for stem cells, inflammatory, and cell cycle markers, and both lineages showed significant expression of CD45, Oct3/4, Nanog, CD105, CD90, CD34, CD117, CD133, TRA-1-81, VEGF, and LY6a. In contrast, there were differences in the cell cycle phases between the lineages, which was not observed in relation to the mitochondrial electrical potential.ConclusionGiven the large impact that joint pathology has on the athletic performance horses, our results suggested that the SF and SM are promising sources of stem cells with satisfactory characteristics of growth and gene expression that can be used in equine regenerative medicine.

Assisted reproduction techniques have improved agricultural breeding in the bovine. However, important development steps may differ from the situation in vivo and there is a high mortality rate during the first trimester of gestation. To better understand these events, we investigated the development of embryos and fetal membranes following fixed-time AI (FTAI), IVF and nuclear transfer (NT). The onset of yolk-sac development was not normal in cloned embryos. Later steps differed from conditions in vivo in all three groups; the yolk-sac was yellowish and juxtaposed with the amniotic membrane. Vascularisation of the chorioallantoic membrane was relatively late and low in NT gestations, but normal in the others. The overall development of the embryos was normal, as indicated by morphology and regression analysis of growth rate. However, NT conceptuses were significantly smaller, with the livers in some embryos occupying the abdominal cavity and others exhibiting heart abnormalities. In conclusion, the yolk-sac and the cardiovascular system seem to be vulnerable to morphogenetic alterations. Future studies will focus on gene expression and early vascularisation processes to investigate whether these changes may be responsible for the high incidence of intrauterine mortality, especially in clones.

Maternal immunity is the main early defense against infectious agents in newborns. Immunoglobulin G (IgG) is indispensable for immune defense against infectious agents. IgG is transported through either the colostrum or the placenta. Immunoglobulins are antibodies, and the five different classes of these antibodies are IgG, IgA, IgM, IgD and IgE. Through their biological function of binding antigens, antibodies facilitate the removal of antigens from the body. The placenta is a temporary maternal-fetal organ, whose principal function is to allow the controlled exchange of metabolites between mother and embryo/fetus during gestation. The placenta types in different species are classified by the number of membranes separating the maternal and fetal blood circulation. Humans, lagomorphs and rodents have hemochorial placentas, which require a receptor for IgG transfer. In other animals, such as horse and pig (epitheliochorial placenta), ruminants (synepitheliochorial placenta) and carnivores (endotheliochorial placenta), antibodies are transferred via the colostrum and absorbed by passive diffusion. This review covers immunoglobulin transport in several types of placentas.