Pulmonary arteriole muscularization in lambs with diaphragmatic hernia after combined tracheal occlusion/glucocorticoid therapy.

Abstract

A morphometric study was performed to examine the effects of prenatal glucocorticoids, which were administered 48 hours before birth, on muscularization of small pulmonary arterioles (<60 microm diameter) in lambs with diaphragmatic hernia (DH) after fetal tracheal occlusion (TO). DH was created in 23 fetal sheep at 65 days gestation. TO was performed in 16 of 24 fetuses between 110 and 140 days of gestation; 9 of the fetuses were exposed prenatally to betamethasone (0.5 mg/kg body weight) 48 hours before delivery. Six sham-operated animals served as controls. Sections of paraffin that were embedded in lung tissues were stained with Elastin-Van Gieson, and the percentage of medial wall thickness (MWT) was determined. The percentage of MWT in DH lambs (29.6% +/- 1.9%) was increased compared with sham animals (18.1% +/- 1.3%) and was not different from that of DH/TO animals (30.3% +/- 1.7%). In DH/TO + glucocorticoid lambs, the percentage of MWT (24.6% +/- 1.2%) was significantly lower than in the DH/TO group but was higher than the sham group. In fetuses who underwent prolonged TO therapy for severe DH, prenatal glucocorticoid treatment decreased medial hypertrophy of pulmonary arterioles by approximately 19%. We speculate that such structural changes may have contributed to improve gas exchange that was observed in this model.