Poster Presentation Annual Meetings of the Endocrine Society of Australia and Society for Reproductive Biology and Australia and New Zealand Bone and Mineral Society 2016

Uterine remodelling during pregnancy in the brush tail possum (Trichosurus vulpecula; Marsupialia) (#466)

Melanie K Laird 1 , Bronwyn M McAllan 1 , Mike B Thompson 1 , Chris R Murphy 1
  1. University of Sydney, Camperdown, NSW, Australia

Mammalian pregnancy involves a predictable suite of morphological changes to the uterine epithelium to ensure the uterus is receptive to the implanting embryo. Morphological remodelling facilitates attachment, and often invasion, of the embryo to the uterine epithelium in early pregnancy, and is essential for formation of a placenta. Yet while remodelling has well been described for eutherian mammal species with invasive implantation (i.e. the embryo invades uterine tissue as it implants), receptivity in species with non-invasive implantation, particularly marsupial species, may require a different suite of uterine cellular changes. To test this possibility, we identified morphological changes to the uterus of the brush tail possum (Trichosurus vulpecula), a marsupial species in which the embryo implants non-invasively, using both scanning and transmission electron microscopy. We found that uterine remodelling occurs in this species, yet morphological changes in T. vulpecula were largely related to secretory activity and differed from those described for species with invasive implantation. Uterine epithelial cells become dramatically domed leading up to implantation in T. vulpecula, which contrasts with the typical cell flattening in species with invasive implantation. In addition, these domed luminal cells become highly secretory while gland cell activity decreases as gestation progresses. This finding suggests that a shift from glandular to luminal cell secretion occurs during pregnancy in T. vulpecula and that species with non-invasive implantation may have a greater dependence on uterine secretions than those with less superficial attachment. Thus, remodelling appears to be a ubiquitous feature of mammalian pregnancy, but the specific uterine changes are likely to be influenced by mode of embryonic attachment.