Reproduction Abstracts

Introduction: Uterine epithelial cells (UECs) undergo a number of changes to become receptive to blastocyst implantation including the loss of integrin based focal adhesions (FA), and increase in basolateral plasma membrane (PM) curvature; despite these changes UECs maintain a polarised state. Caveolae are lipid rich invaginations of the PM which contribute to membrane curvature. Major caveolae proteins (caveolin 1, and 2, PTRF, and SDPR) were investigated to explore the possible roles they play in remodelling the basolateral PM of UECs during early pregnancy in the rat.

Methods: Western blotting, immunofluorescence (IFM) and transmission electron microscopy (TEM) was performed on rat uterus during early pregnancy; and in hormone treated ovariectomised rats.

Results and discussion: Cytoplasmic caveolin 1, 2 and SDPR was seen at time of fertilisation (TOF). Caveolins 1 and 2 shifted to the basal PM while SDPR was absent at time of implantation (TOI) and under progesterone influence. This corresponded to a 3× increase in morphological caveolae basally at the TOI. Protein analyses showed an increase in caveolin 1 and a decrease in caveolin 2 at this time. PTRF protein abundance did not change, while SDPR was present at the TOF only. Co-immunoprecipitation experiments confirmed associated between caveolin1 and PTRF in UECs at the TOI. While at the TOF caveolin1 demonstrated an association with integrin β1, indicating an association between FAs and caveolae. The increased caveolar formation and the accompanying increased turnover at the basal PM may be a mechanism to compensate for the loss of membrane junctional structures and maintain UEC polarity.