TGF-beta expression during rat pregnancy and activity on decidual cell survival.
BACKGROUND
During early rat pregnancy, trophoblast of the tiny embryo joins with the endometrium and epithelial cells undergo apoptosis. Near the end of pregnancy, regression of the decidua basalis (DB) is also observed (from day 14 to 20). However, little is known about the intra-cellular and molecular mechanisms involved in apoptosis regulation in the uterus during pregnancy. The objective of the present study was to investigate the presence and the developmental expression of transforming growth factor-beta isoforms (TGF-beta well known differentiation factor) in the rat endometrium throughout pregnancy and its action in vitro using cultured endometrial stromal cells.


METHODS
In vivo: Rats were killed at different days of pregnancy (days 2-20) and uteri removed to collect endometrial protein extracts or the uteri were fixed, embedded and sectioned for immunohistochemistry (IHC) and in situ cell death analyses using TdT-mediated dUTP nick end labeling (TUNEL). In vitro: Rats were ovariectomized and decidualization was induced using sex steroids. Endometrial stromal decidual cells were then collected and cultured.


RESULTS
An increase of apoptosis in the DB on days 14, 16 and 18 was observed. Cleaved caspase-3 was clearly detected during regression of the DB by Western analysis and immunofluorescence. Western analyses using endometrial protein extracts demonstrated that TGF-beta1, TGF-beta2 and TGF-beta3 were highly expressed at the time of DB regression (day 14). During early pregnancy, TGF-beta1 and -beta2 expressions raised at days 5.5 to 6.5. TGF-beta3 protein was not detected during early pregnancy. IHC analyses revealed that TGF-beta1 and -2 were found surrounding both epithelium (luminal and glandular) in the stroma compartment at the implantation site, and TGF-beta3 was mainly located surrounding endometrial epithelium in the stroma compartment. Smad2 phosphorylation was increased at the time of DB regression. In vitro studies using decidual endometrial stromal cells revealed that TGF-beta1 induced apoptosis and Smad2 phosphorylation. Moreover, TGF-beta1 reduced both Akt (a well known survival factor) phosphorylation and XIAP (X-linked inhibitor of apoptosis protein) expression in decidual endometrial stromal cells in vitro.


CONCLUSIONS
Taken together, these results suggest that TGF-beta isoforms are regulated differently during pregnancy and may have an important role in the control of apoptosis and cell survival at specific stages during pregnancy.
Shooner
Carl
C
Département de Chimie-Biologie, Université du Québec à Trois-Rivières, C.P. 500, Trois-Rivières, Québec, G9A 5H7, Canada. SHOONECA@CollegeSherbrooke.qc.ca
Caron
Pierre-Luc
PL
Fréchette-Frigon
Guylaine
G
Leblanc
Valérie
V
Déry
Marie-Claude
MC
Asselin
Eric
E
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology; D002470:Cell Survival; D002478:Cells, Cultured; D003656:Decidua / Q000166:cytology*; D004717:Endometrium / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D010766:Phosphorylation; D011247:Pregnancy / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D051899:Smad2 Protein / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D053773:Transforming Growth Factor beta1; D053781:Transforming Growth Factor beta2; D053782:Transforming Growth Factor beta3; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism
D000911:Antibodies, Monoclonal; D051899:Smad2 Protein; C497784:Smad2 protein, rat; C508962:Tgfb1 protein, rat; C509046:Tgfb3 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D053781:Transforming Growth Factor beta2; D053782:Transforming Growth Factor beta3; D051636:X-Linked Inhibitor of Apoptosis Protein; D051057:Proto-Oncogene Proteins c-akt