Spontaneous embryonic death in plains viscacha (Lagostomus maximus - Rodentia), a species with unique reproductive characteristics

Pulmonary trophoblastic deportation in the hystricomorph rodent Lagostomus maximus

INTRODUCTION

Trophoblast has been reported in the lungs of gestating eutherian mammals with hemochorial placenta, including humans, cotton rats, and American hares. This study describes the discovery of trophoblastic-like cells in the lungs of Lagostomus maximus.

METHODS

Lung and placenta samples from non-pregnant and pregnant plains viscachas were analyzed using histology and immunohistochemistry.

RESULTS

Macroscopically, the lungs of females in both groups showed no alterations, but microscopic examination of the lungs from pregnant females revealed lesions and trophoblast-like cells. Markers such as pancytokeratin, MMP-2, MMP-9, and progesterone receptors were found in both pulmonary trophoblastic cells and the various types of trophoblasts in the placenta and subplacenta. Notably, cytokeratin-7 showed similarity with the placenta but not with the subplacenta. Cells identified in the lungs that were positive for markers similar to trophoblast giant cells in the maternal blood chambers suggest that the trophoblast that reaches the lungs may originate from giant cells that enter maternal blood circulation rather than those that invade the uterine artery. Immunohistochemical analysis indicated that, unlike placental trophoblast, the lung cells exhibited no proliferative activity.

DISCUSSION

The lack of this process in mice and the difficulty of developing in vivo experimental models have prompted the exploration of in vitro models. L. maximus may serve as an alternative model to study this process, necessitating further research to determine the timing of this phenomenon during gestation and whether pulmonary alterations persist after parturition.

Differential Remodelling of Endometrial Extracellular Matrix in the Non-Pregnant Uterus of Lagostomus maximus as a Potential Mechanism Underlying Embryonic Death

During development, the remodelling of fibrillar components of the uterine extracellular matrix (ECM), mediated by the matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs), plays an essential role in embryonic survival. Previously, we observed that in the plains viscacha (Lagostomus maximus), only caudal implantation sites (IS) contain viable embryos, whereas embryos at cranial and middle IS die and are reabsorbed. The objective of this study was to analyse the distribution and expression of key components of the endometrial ECM, including fibrillar collagens, MMPs 2 and 9, and TIMPs 1 and 2, in three uterine segments (US) of the non-pregnant adult viscachas. In sections from three US, we observed a significant craniocaudal increase in collagen fibres (Van Gieson and Picrosirius red staining) and elastic fibres (Verhoeff-Van Gieson trichrome staining), along with the immunolabelling levels of MMP-2, MMP-9, TIMP-1, and TIMP-2 (immunohistochemistry). Zymography revealed similar gelatinolytic activity of MMP-2 in the three US but higher than the MMP-9 activity. However, MMP-9 activity in the caudal segment was significantly higher than that in the cranial and middle ones. These findings suggest that uterine ECM variations along the craniocaudal axis may contribute to uterine remodelling processes that regulate embryonic survival during gestation.

Morphology and Immunoexpression of Selenoproteins in Term Placenta of Alpaca (Vicugna pacos) from the Peruvian Andes

South American camelids inhabit high-altitude environments characterized by hypoxia, influencing embryonic, fetal, and placental development. This study examined the term placenta morphology of alpacas (Vicugna pacos, N = 12) and the immunoexpression of antioxidant selenoproteins (SP). We hypothesize that the placenta of alpacas, adapted to high altitudes, has characteristics with other species also adapted to altitude. Placentas were paraffin-embedded, sectioned (3-5 µm), stained with hematoxylin-eosin (H&E), Masson's trichrome, and picrosirius red, and analyzed via light and polarized light microscopy. The chorion showed simple cuboidal epithelium with binucleated cells, a subepithelial mesenchyme rich in blood capillaries (area: 124.90 ± 9.82 µm2), and type III collagen fibers. The chorionic villi measured 2740.22 ± 132.75 µm. The allantois contained a simple columnar epithelium and mesenchyme with type I collagen fibers. Immunohistochemistry localized SP-N, SP-P, Dio-3, and GPx-3 in the blood capillaries and mesenchymal tissue of the chorion but not in the allantois. These findings were compared to human and sheep placentas from different altitudes due to a lack of camelid data at low levels. The morphological features resembled adaptations to hypoxia observed in other species. This preliminary study suggests a potential role for selenoproteins in hypoxia adaptation, providing a basis for future functional studies.

Changes in Immune Response during Pig Gestation with a Focus on Cytokines

Pigs have the highest percentage of embryonic death not associated with specific diseases of all livestock species, at 20-45%. During gestation processes, a series of complex alterations can arise, including embryonic migration and elongation, maternal immunological recognition of pregnancy, and embryonic competition for implantation sites and subsequent nutrition requirements and development. Immune cells and cytokines act as mediators between other molecules in highly complex interactions between various cell types. However, other non-immune cells, such as trophoblast cells, are important in immune pregnancy regulation. Numerous studies have shed light on the crucial roles of several cytokines that regulate the inflammatory processes that characterize the interface between the fetus and the mother throughout normal porcine gestation, but most of these reports are limited to the implantational and peri-implantational periods. Increase in some proinflammatory cytokines have been found in other gestational periods, such as placental remodeling. Porcine immune changes during delivery have not been studied as deeply as in other species. This review details some of the immune system cells actively involved in the fetomaternal interface during porcine gestation, as well as the principal cells, cytokines, and molecules, such as antibodies, that play crucial roles in sow pregnancy, both in early and mid-to-late gestation.

Embryonic-placental relationship in Lagostomus maximus as compared to other hystricognath rodents and eutherian mammals

Reproductive specializations in caviomorphs (infraorder Hystricognathi), are very peculiar within the Order Rodentia. These include long gestations, the birth of offspring with an extreme degree of precociality, and short lactation periods. This study describes the embryo-placental relationship of viable implantation sites (IS) of the plains viscacha, Lagostomus maximus, after 46 post-coital days. The observations recorded in this study are comparatively discussed with those of other hystricognaths and eutherians. At this stage, the embryo resembles that of other eutherians. At this time of embryo development, the placenta exhibits a size, shape, and organization similar to that it will have in its mature state. Besides, the subplacenta is already highly folded. These characteristics are adequate to sustain the development of future precocial offspring. The mesoplacenta, a structure present in other hystricognaths and related to uterine regeneration is described for the first time in this species. This detailed description of the placental and embryonic structure contributes to the knowledge of the reproductive and developmental biology of the viscacha, as well as that of hystricognaths. These characteristics will allow testing other hypotheses related to the morphology and physiology of the placenta and subplacenta, and their relationship with the growth and development of precocial offspring in Hystricognathi.

Placental glycotype of the caviomorph rodent Lagostomus maximus and its evolution within Eutheria

The main evolutionary milestone in the oviparity-viviparity transition is placentation. The placenta is an organ with great morphological diversity among eutherians. The expression of different glycosidic residues (Gr) in the near-term placenta constitutes its glycotype. In this study, the expression of different Gr was determined by lectin histochemistry in early, midterm, and near-term placentas of the plains viscacha (Lagostomus maximus), a caviomorph rodent with the highest poliovulatory rate and embryonic resorption rate among eutherians. Besides, a matrix with the expression of each Gr in the exchange trophoblast of viscacha and other eutherians was constructed to map and infer phylogenetic and evolutionary relationships. Between early, midterm, and near-term placentas, variations in the pattern expression of Gr were observed. The glycotype of the near-term placenta is composed of a high diversity of Gr. Reconstruction of the ancestral state for each Gr present in the near-term placenta showed a diverse scenario: some sugars were common to the species of Placentalia included in this study. In the analyzed species with synepitheliochorial and epitheliochorial placentas, no differential glycosylation patterns between them were observed. In species with invasive placentas, such as the endotheliochorial placentas of Carnivora, some common Gr were detected among them, while others were species-specific. In species with hemochorial placenta, the same Gr are shared. Particularly, in the viscacha greater differences with species of the Hominidae and even Muridae families were observed. Nevertheless, greater similarities with other caviomorph rodents were detected. Placental glycotype of each species constitutes an excellent tool to achieve phylogenetic and evolutionary inferences among eutherians.