Pax3 mRNA is decreased in the hearts of rats with experimental diaphragmatic hernia.

Rats with nitrofen-induced congenital diaphragmatic hernia (CDH) have heart hypoplasia and cardiovascular malformations. The mechanism of action of nitrofen involves changes in neural crest signaling. Pax3 function is required for cardiac neural crest cells to complete their migration to the developing heart. The aim of this study was to examine whether Pa x 3 expression is changed at two gestational endpoints in rat embryos or fetuses exposed to nitrofen. On day E9.5 of gestation, pregnant rats received either 100 mg of nitrofen (n=10) or vehicle alone (control, n=10). The fetuses were recovered on E15 or E21. Their hearts were dissected out and weighed. Pax3 mRNA expression was determined by real-time polymerase chain reaction. We used two-tailed Student's t-tests to compare groups, with a threshold of significance of p<0.05. Compared with controls, nitrofen-exposed fetuses had heart hypoplasia in terms of heart/body weight ratio (0.62+/-0.10% vs. 0.77+/-0.17%, p<0.05). Pax3 mRNA expression in the heart was significantly decreased on E15 in nitrofen-treated embryos (32.94+/-17.11 U vs. 55.09+/-11.56 U, p<0.05), and it was still decreased, although not significantly, in the hearts of nitrofen-exposed fetuses recovered on E21 (15.67+/-5.56 U vs. 20.51+/-5.92 U, not significant). In conclusion, Pax3 is underexpressed in the hearts of nitrofen-exposed embryonal rats before the end of gestation. The mechanism of action of Pax3 should be further investigated because it could be one of the targets for future prenatal transplacental intervention.