Premature implantation may be prevented by an inhibitory system regulated by epidermal growth factor

Endometriotic Cells Exhibit Metaplastic Change and Oxidative DNA Damage as Well as Decreased Function, Compared to Normal Endometrium

A widely accepted theory of the etiology of endometriosis is that it originates from the implantation and invasion of cells from retrograde menstruation to various sites in the body particularly the pelvic peritoneal cavity. Little is known of the function of these cells in ectopic sites. Normal endometrium was compared with endometriotic tissue using an antibody to Placental Cadherin (P Cadherin), a recently studied cadherin that is implicated in metaplasia and early neoplasia and also 8-hydroxyguanine, an indicator of oxidative DNA damage. Comparisons of endometrial tissue function were made using expression of transforming growth factor beta-1 (TGFbeta-1) and insulin-like growth factor-I (IGF-I). There was no labelling for anti-P Cadherin or anti-8-hydroxydeoxyguanosine in normal endometrium but marked labelling for both on the apical surface of the endometriotic epithelium. Studies of markers of normal endometrial function were all de-expressed in endometriosis. This study indicates that endometriosis cells are abnormal and exhibit oxidative DNA damage, metaplasia and markedly reduced function compared to normal endometrium.

Heparin binding-epidermal growth factor improves blastocyst hatching and trophoblast outgrowth in the golden hamster

The effect of heparin binding-epidermal growth factor (HB-EGF) on the in-vitro development of hamster 8-cell embryos was investigated. Supplementation of HB-EGF to culture medium accelerated zona escape of blastocysts (63 +/- 9% compared with 33 +/- 9% after 36 h; P < 0.05). Complete zona escape of blastocysts persisted even after 48 h (61 +/- 11% versus 30 +/- 4%) and 60 h (75 +/- 6% versus 42 +/- 8%). Addition of anti-HB-EGF antibody drastically reduced the percentage of zona escaped-blastocysts (30.0 +/- 5.0% versus 92.3 +/- 2.8%; P < 0.05). Interestingly, a significant increase in the area of trophoblast outgrowth occurred in the presence of HB-EGF (116 x 10(3) +/- 8 x 10(3) microm(2) versus 74 x 10(3) +/- 8 x 10(3) microm(2) at 48 h; P < 0.05). This, however, was not due to an increased number of trophectodermal cells in HB-EGF-treated blastocysts. Immunoreactive HB-EGF was localized in blastocysts and uterine sections, visible by intense immunostaining in the luminal epithelium, particularly on the apical surface. Moreover, the expression of HB-EGF in the uterus was maximum on day 4 of pregnancy, coinciding with the timing of zona escape and implantation. The receptor of HB-EGF, viz. EGF receptor was also detected in blastocysts and the luminal epithelium of day 4 pregnant uterus. These results show that HB-EGF improves blastocyst hatching and trophoblast outgrowth in hamsters.

Tenascin, E-cadherin and P2X calcium channel receptor expression is increased during rat blastocyst implantation

The calcium-activated cell-adhesion proteins tenascin, E-cadherin and the purinergic (P2X) calcium channel receptors are expressed in an identical spatial and temporal pattern in uterine epithelium in the rat during implantation. On Day 1 of pregnancy (estrous), a diffuse cytoplasmic and specific basement membrane label for each of the proteins was observed throughout the uterine epithelium. On Day 3 of pregnancy, a specific and prominent lateral plasma membrane label for each protein was seen. At the time of implantation on Day 6, an additional and significant increase in the label for each was observed on the apical epithelium. At this time, the label for tenascin in the apical epithelium was increased 2.1-fold (p < 0.0004), that of E-cadherin was increased 2.5-fold (p < 0.0001) and the P2X receptor label was increased 2.0-fold (p < 0.0001). These observations suggest a major role for the calcium-activated adhesion proteins tenascin and E-cadherin in attachment and implantation, with ionic calcium for protein activation possibly provided by the P2X calcium channels. These events occur along the entire length of the uterine epithelium in preparation for blastocyst adhesion.

Distributional changes of purinergic receptor subtypes (P2X 1-7) in uterine epithelial cells during early pregnancy

Expression of each of the purinergic receptor subtypes (P2X7) was studied by immunohistochemical localization in the apical, lateral and basal plasma membranes of rat uterine epithelial cells during early pregnancy to the time of implantation on Day 6. Labelling for each P2X subtype was seen in the apical, lateral and basal compartments on Days 1 and 3, except for P2X2 which was only observed in the basement membrane. The P2X5 signal was similar in temporal and spatial expression to the other subtypes, but with a greatly reduced intensity. At the time of implantation on Day 6, this pattern altered dramatically. Apical expression markedly increased for most subtypes while the lateral and basal signals were markedly reduced. The exceptions to this pattern were P2X2, which displayed both a strong basal and apical label, and P2X4 which became de-expressed in all areas. We propose that the changing spatial and temporal expression of the P2X receptors is a significant factor in the regulation of events during early pregnancy. They are expressed in the same location as remodelling. apoptosis, and protein activation events prior to implantation on Day 6. These observations suggest an up-regulation of calcium-mediated events, including cytoskeletal alterations, a decrease in luminal pH and transmembrane molecule activation.

Differential expression of insulin-like growth factors in the uterine epithelium and extracellular matrix during early pregnancy

We have studied the simultaneous expression of insulin-like growth factor I (IGF-I) and insulin-like growth factor II (IGF-II) in the uterine epithelium and extracellular matrix during the time of trophoblast attachment and implantation. These studies reveal that IGF-I and IGF-II display different spatial and temporal patterns of expression during early pregnancy, and suggest a role for them in the process of attachment and implantation. Specifically, IGF-I is strongly expressed in the basal lamina which is the site of trophoblast invasion into the maternal stroma, and also in the apical epithelium, the site of initial trophoblast attachment. IGF-II is expressed to a lesser extent in the basal lamina, lateral plasma membranes and apical epithelium on day 3 but is only prominent apically at the time of implantation, suggesting a role in attachment.