Gastroschisis in mice lacking aortic carboxypeptidase-like protein is associated with a defect in neuromuscular development of the eviscerated intestine.

Mice lacking aortic carboxypeptidase-like protein (ACLP) exhibit a gastroschisis (GS) like abdominal wall defect. The objectives of this study were to evaluate the pathophysiological features of GS in ACLP mice and to characterize the neuromuscular development of the eviscerated intestine (EI). ACLP mice were created by heterozygous mating from previously generated mice with targeted disruption of ACLP. Specimens were processed for H&E, and immunohistochemistry for smooth muscle cells [SMC, alpha-smooth muscle actin (alpha-SMA) antibody], interstitial cells of Cajal (ICC, c-kit-antibody), neural crest cells (NCC, Hox-b5-antibody), and enteric neurons (EN, PGP9.5-, alpha-internexin, and synaptophysin antibody). From 47 fetuses genotyped, 13 (27.7%) were wild type, 20 (42.5%) were heterozygous, and 14 (29.8%) were ACLP homozygous. In GS mice, expression of c-kit, Hox-b5, PGP-9.5, alpha-internexin, and synaptophysin were almost completely absent and only faint alpha-SMA expression was seen in the EI. In contrast, c-kit, Hox-b5, PGP9.5, alpha-internexin, synaptophysin, and alpha-SMA expression in intra-abdominal intestine in GS fetuses was the same as control intestine. The defect observed in ACLP mice closely resembles GS. Absence of ICC, NCC, EN, and immature differentiation of SMC supports an associated defect in neuromuscular development that is restricted to the EI.

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

OBJECTIVE: 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). STUDY DESIGN: 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. RESULTS: 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. CONCLUSION: 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.

Prenatal glucocorticoids improve lung morphology and partially restores surfactant mRNA expression in lambs with diaphragmatic hernia undergoing fetal tracheal occlusion.

In fetal sheep with surgically created diaphragmatic hernia (DH), tracheal occlusion (TO) can restore lung growth but does not ameliorate the increase in inter-alveolar wall thickness (T(W)). We determined whether prenatal exposure to glucocorticoids (GC) could reduce T(w) in fetuses with DH undergoing TO. At 65 days of gestation, DH was created in 12 fetal sheep, and TO subsequently performed at 110 days (DH/TO). Six of these fetuses were exposed to betamethasone (DH/TO + GC; 0.5 mg/kg; maternal, IM) 48 hr before delivery; Sham operated fetuses (n = 7) served as controls. At 139 days, we measured alveolar surface density (S(V)), parenchymal tissue fraction, T(W), alveolar type 2 (AE2) cell density and lung surfactant protein (SP) mRNA expression. Prenatal GC decreased T(W) and S(V) by 33% and 27% respectively, and increased fixed lung volume (by 55%), AE2 cell density and partially restored SPmRNA expression. Our data indicate that prenatal exposure to GC can reverse some of the negative effects of prolonged fetal TO. We hypothesize that a GC-induced reduction in lung liquid volume during TO contributes, in part, to the observed increase in AE2 cell density and SPmRNA expression.