Over the last two centuries there has been a drastic decline in mammalian biodiversity, with Australian marsupials facing disproportionate rates of extinction. A deficit in understanding of marsupial reproduction in comparison to eutherians may be one reason underpinning the limited success of captive breeding programs, hence there is a pressing need to further our understanding of marsupial reproduction. Research into the structure of the uterus and glandular secretions, on which the preimplantation embryo heavily relies, will provide insight into the structural and functional adaptations of the uterus required to meet the increasing metabolic demands of the developing embryo.
Uteri from fat-tailed dunnarts (Sminthopsis crassicaudata) were collected across gestation. PFA fixed uteri were stained using histological (H&E, PAS, orcein, Masson’s Trichrome), immunohistochemistry (E-Cadherin, Vimentin, Aquaporin 1, Fibronectin) techniques to characterise structural components of the uterus.
Gestation was accompanied by significant alterations to the stromal compartment and the luminal epithelium. The stromal compartment of the uterus expanded over gestation, with fibroblastic cells appearing to line epithelial structures. By embryonic neurulation luminal folds develop. Initially characterised by a layer of highly polarised simple columnar epithelial cells, the luminal epithelium undergoes a transition to a more mesenchymal, cobblestone-like morphology emerging by the time of embryo neurulation, just prior to shell coat breakdown and embryo adhesion. There was a visually obvious increase in size and diameter of PAS positive uterine glands and blood vessels over the duration of pregnancy.
Gestation is accompanied by significant structural alterations to the marsupial uterine environment which are likely related to the increasing metabolic demands of the developing embryo. A comprehensive understanding of the marsupial uterine environment is a necessary foundation for developing assisted reproduction technologies to support the reproduction of marsupial species threatened with extinction.