File talk:Human uterine tube ciliated epithelium SEM.jpg

A high resolution SEM study of the effects of RU486, used as a postcoital contraceptive, on the rat uterus during early pregnancy

Cell Biol Int. 2008 Apr;32(4):436-46. doi: 10.1016/j.cellbi.2007.12.015. Epub 2008 Jan 11.

Scholtz KE, Penny CB, Hosie MJ. Source School of Anatomical Sciences, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg, South Africa.

Abstract

During the window of receptivity, a narrow range of time under the control of the ovarian hormones progesterone and oestrogen, when a blastocyst can attach to the uterine surface, the plasma membrane of the uterine epithelial cells undergoes a remarkable change in structure, known as 'the plasma membrane transformation' of early pregnancy. RU486, the controversial abortion drug (Mifegyne), acts as a progesterone receptor antagonist, resulting in transcriptionally inactive progesterone receptors. In view of this, a change in the well-documented sequences of the plasma membrane transformation is postulated. This study therefore aims to investigate the effects of RU486 on this sequence of events in the implantation and non-implantation sites of the rat uterus. In both RU486 treated and control animals, on days 4.5, 5.5 and 6.5 of pregnancy, scanning electron microscopy revealed a distinct pattern of folding of the uterine surface in non-implantation sites. In contrast, folding was not observed within the implantation sites. These results indicate that surface alterations are probably not under the control of progesterone signalling. The lack of folding at the implantation sites possibly ensures maximum close contact between the blastocyst and the maternal tissue thus promoting implantation. During early pregnancy, specifically on day 5.5, the microvilli of the uterine epithelial cells in the treated animals were more dense than those in the untreated animals. Such microvilli are characteristic of the uterine epithelial cells of a uterus under-stimulated by hormones. Flattening of the apical cell borders usually seen at the time of blastocyst attachment and implantation was not observed following RU486 treatment. Large apical protrusions were observed in the RU486 treated animals only, possibly linked in some way to apoptosis. The antiprogestin properties of RU486 may further elucidate the progesterone effects associated with early pregnancy.

PMID 18280758

Uterine receptivity and the plasma membrane transformation

Cell Res. 2004 Aug;14(4):259-67.

Murphy CR. Source Department of Anatomy and Histology, The University of Sydney, NSW 2006, Australia. histology@anatomy.usyd.edu.au Abstract This review begins with a brief commentary on the diversity of placentation mechanisms, and then goes on to examine the extensive alterations which occur in the plasma membrane of uterine epithelial cells during early pregnancy across species. Ultrastructural, biochemical and more general morphological data reveal that strikingly common phenomena occur in this plasma membrane during early pregnancy despite the diversity of placental types--from epitheliochorial to hemochorial, which ultimately form in different species. To encapsulate the concept that common morphological and molecular alterations occur across species, that they are found basolaterally as well as apically, and that moreover they are an ongoing process during much of early pregnancy, not just an event at the time attachment, the term 'plasma membrane transformation' is suggested which also emphasises that alterations in this plasma membrane during early pregnancy are key to uterine receptivity.

Rodent

progesterone alone - short regular microvilli
oestrogen alone - long thin regular microvilli

Human

human 'pinopodes' do not have a significant pinocytotic function
suggested that the human structures be referred to as 'uterodomes'
represent a transformation of a microvillous plasma membrane into a smooth and flattened plasma membrane (bulging one)

PMID 15353123

http://www.nature.com/cr/journal/v14/n4/full/7290227a.html

Cytoskeletal alterations in the microvilli of uterine epithelial cells during early pregnancy

Acta Histochem. 1989;87(2):131-6.

Luxford KA, Murphy CR. Source Department of Histology and Embryology, University of Sydney, Australia. Abstract We have studied the arrangement of microfilaments in uterine microvilli during early pregnancy, using transmission electron microscopy and immunofluorescence microscopy. Observations indicate that changes in actin microfilament organization occur in association with the alterations to the uterine cell surface which precede blastocyst implantation. We consider these findings with reference to the possible mechanisms involved.

PMID 2516678