A placenta is defined as structural approximation of maternal and foetal tissues to perform physiological exchange. Associated processes of differentiation and the establishment of its cells take place within the extracellular matrix (ECM) that provides a rich environment of collagens, fibronectins, cytokines and other components. Placental ECM is promising for tissue regeneration purposes, because it has immune tolerance capacities that may cause only minimal rejections of transplants with immunological differences between donor and recipient. However, specific characteristics of ECM during evolution of the structurally very diverse mammalian placenta are not yet revealed. We here address the major aspects of placental types, that is non-invasive (epitheliochorial), medium (endotheliochorial)-to-high (haemochorial) invasive nature of the interhemal barrier between the foetal and maternal blood system as well as their main components of ECM with special reference to species that are commonly used as animal models for human placentation and in the potential applications for regenerative medicine.

The existence of neurogenesis in the adult brain is a widely recognized phenomenon, occurring in the subventricular zone (SVZ) of the lateral ventricles and the subgranular zone of the dentate gyrus in several vertebrate species. Neural precursors originated in the SVZ migrate to the main olfactory bulb (MOB), originating the rostral migratory stream (RMS) in the process. To better understand the formation of the adult neurogenic niches in dogs, we investigated the cellular composition and morphological organization of these areas in 57 days-old dog fetuses. Using multiple immunohistochemical markers, we demonstrated that the SVZ in the canine fetus is remarkably similar to the adult SVZ, with glial GFAP-immunoreactive (-ir) cells, DCX-ir neuroblasts and SOX2-ir neuronal progenitors tangentially organized along the dorsal lateral ventricle. The fetal RMS has all the features of its adult counterpart and closely resembles the RMS of other mammalian species. The late-development canine MOB has most of the neurochemical features of the adult MOB, including an early-developed TH-ir population and maturing CALR-ir interneurons, but CALB-ir neurons in the granule cell layer will only appear in the post-partum period. Taken together, our results suggest that the canine fetal development of adult neurogenic niches closely resembles those of primates, and dogs may be suitable models of human adult neurogenesis. Anat Rec, 301:1570-1584, 2018. © 2018 Wiley Periodicals, Inc.

The incidence of diabetes mellitus in dogs is increasing in recent years, mainly because of genetic and/or environmental factors, including endocrine disorders (like in humans); failure of suitable control of blood sugar levels, which triggers hyperglycemia; glycosuria and weight loss, which demands the development of innovative treatments to cure or treat this complex disease in dogs. The present study established for the first time a protocol to obtain and characterize cells derived from pancreas of canine fetuses. Those fetuses do not have a defined breed and were at the final stage of gestation. The protocol aims to provide morphological data to enable future applications of these cells for therapeutic approaches. In cell culture, pancreatic cells showed a fibroblastlike appearance with a mono-layered growth pattern and were not tumorigenic. They exhibited a positive expression for the pluripotent proliferation markers NANOG and PCNA and expressed PDX1, a transcription factor that is important for activation of the insulin gene promoter. In addition, Tyrosine Hydroxylase-positive (TH+) sympathetic nerve fibers were identified. Histologically, the pancreatic epithelium was developed, pancreatic glands in the fetuses were like those in the parenchyma of postconception dogs and pancreatic islets were unevenly distributed and organized in small clusters along the glands close to the vasculature. Staining with dithizone indicated the presence of insulin in the cells. A large number of beta cells were confirmed by immunofluorescence. In conclusion, the canine fetal pancreas cells could be an alternative and adequate source of cell lineages for stem

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