Fetal tracheal occlusion in the rat model of nitrofen-induced congenital diaphragmatic hernia

Abstract

Prenatal tracheal occlusion (TO) consistently accelerates lung growth in the sheep model of congenital diaphragmatic hernia (CDH). However, significant variability in lung growth has been observed in early clinical trials of TO. We hypothesized that lung hypoplasia created at relatively late stages of lung development may not be equivalent to human CDH-induced lung hypoplasia, which begins early in gestation. To test this hypothesis, we performed TO in the rat model of nitrofen-induced CDH. Left-sided CDH was induced by administering 100 mg of nitrofen to timed pregnant rats on day 9 of gestation. On day 19 of gestation, four to five fetuses per dam underwent surgical ligation of the trachea. At death (day 21.5), lungs from non-CDH (non-CDH group), left-CDH (CDH group), and trachea-occluded left-CDH fetuses (CDH-TO group) were harvested and compared by weight, DNA and protein content, and stereological morphometry. Wet and dry lung weight-to-body weight ratio, total lung DNA and protein contents, the volume of lung parenchyma, and the total saccular surface area of the CDH-TO group were significantly increased relative to the CDH group and were either greater than or comparable to the non-CDH controls. We conclude that TO accelerates lung growth and increases lung parenchyma in an early-onset model of CDH-induced lung hypoplasia.

Changes in Fetal Lung Distension Alter Expression of Vascular Endothelial Growth Factor and Its Isoforms in Developing Rat Lung

“…In our study, this resulted in pulmonary hypoplasia (Table 3) but did not affect fetal body weights, findings consistent with the previous report by Kitano et al (52). In contrast to effects of increased lung distension from TO as discussed above, CDH did not affect expression of total VEGF-A mRNA nor its isoforms when normalized to 18S rRNA (Fig.…”

“…4C). Therefore, in addition to being a potent stimulus to lung growth (32,34, 51,52,63) and to hastening morphologic maturation of lung parenchyma (32-34,51,52), TO accelerates the maturational patterns of expression of total VEGF-A mRNA and its isoforms that occur in normal fetuses.…”

“…To produce fetal CDH, timed-pregnant rats (gestation 9.5 d) were gavage fed nitrofen (2,4-dichloro-4'-nitrodiphenyl ether, Wako Chemicals, Osaka, Japan), 100 mg dissolved in 1 mL of olive oil. This produces CDH in 40 -60% of fetuses (52). In some dams, TO was performed on fetuses at ED 20 as described above.…”

Airway and vascular maturation stimulated by tracheal occlusion do not correlate in the rabbit model of diaphragmatic hernia

“…In addition, TO promotes vascular growth and development, reducing the thickness of the muscular layer in pulmonary arteries in sheep, rabbit, and rat models of DH (10)(11)(12)(13)(14)(15). Our group demonstrated hemodynamic improvement in rabbit fetuses with DH following TO (16).…”

Tracheal Ligation and Corticosteroids in Congenital Diaphragmatic Hernia: For Better for Worse?

“…The supposed "lung growth" resulting from tracheal ligation is not founded on clean concepts of underlying mechanisms, although a variety of factors has been suggested (15)(16)(17).…”