Expression of cyclooxygenase-2 in embryonic and fetal tissues during organogenesis and late pregnancy.
BACKGROUND
Cyclooxygenase (COX) catalyzes the committed step in prostaglandin biosynthesis and exists as two related but unique isoforms, COX-1 (constitutive) and COX-2 (inducible). Prostaglandins (PGs) are known to have many important functions in reproduction, such as placentation and decidualization. Studies with the COX-1 and COX-2 knockout mice have demonstrated that COX-2, but not COX-1, is crucial for normal ovulation, implantation, and decidualization, suggesting that COX-2-derived PGs are important during the initial stages of pregnancy. Although the COX-2 knockout mice did not exhibit any abnormalities at birth, relatively little information exists with regard to the expression of COX-2 in the fetus during development.


METHODS
In order to understand the role of COX-2 throughout pregnancy, we characterized the cell type and the temporal expression of inducible COX-2 throughout embryonic and fetal development in the rat (n = 22) by immunohistochemistry and in situ hybridization.


RESULTS
High levels of COX-2 expression were seen in decidualized uterine tissue on gestation days 7-13 and then in the fetal membranes on gestation days 17-20. Cyclooxygenase-2 expression was not detectable in any tissues from developing embryos during gestation days 7-13, but was observed in the fetal growth period (gestation days 15-20) in the skin, heart, cartilage, and the kidney.


CONCLUSIONS
No COX-2 expression was seen in fetal tissues at days 7-13 of gestation, but was seen in various tissues at days 15-17 of gestation. These observations suggest that COX-2 may be important in mid to late pregnancy through an effect on fetal organ growth, but not in the organogenetic phase of fetal development.
Stanfield
K M
KM
Searle/Pharmacia Corp., Skokie, Illinois, USA.
Bell
R R
RR
Lisowski
A R
AR
English
M L
ML
Saldeen
S S
SS
Khan
K Nasir M
KN
D000818:Animals; D051546:Cyclooxygenase 2; D003656:Decidua / Q000201:enzymology; D004622:Embryo, Mammalian / Q000378:metabolism*; D005260:Female; D005333:Fetus / Q000378:metabolism*; D005865:Gestational Age; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000196:embryology / Q000201:enzymology; D038081:Organogenesis; D011247:Pregnancy; D011270:Pregnancy, Animal; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000196:embryology / Q000201:enzymology; D014327:Trophoblasts / Q000201:enzymology; D014599:Uterus / Q000201:enzymology
D007527:Isoenzymes; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases