Prenatal retinoic acid upregulates connexin 43 (Cx43) gene expression in pulmonary hypoplasia in the nitrofen-induced congenital diaphragmatic hernia rat model.
OBJECTIVE
Connexin 43 (Cx43), a major gap junction protein, is necessary for alveologenesis and plays an important role in the differentiation of type II to type I alveolar epithelial cells. Knockout mice of Cx43 display severe pulmonary hypoplasia (PH). Prenatal administration of retinoic acid (RA) is known to stimulate alveologenesis in nitrofen-induced PH. Recent studies revealed that retinoids upregulate Cx43 expression. We hypothesized that gene expression of Cx43 is downregulated during alveologenesis and that administration of RA upregulates Cx43 expression in the nitrofen-induced PH.


METHODS
Pregnant rats were exposed to olive oil or nitrofen on day 9 (D9) of gestation. Retinoic acid was given intraperitoneally on D18, D19, and D20. Fetal lungs were harvested on D18 and D21 and divided into control, nitrofen, control+RA (D21), and nitrofen+RA (D21). The Cx43 expression levels were determined using reverse transcription polymerase chain reaction and immunohistochemistry.


RESULTS
On D18 and D21, Cx43 relative messenger RNA expression levels were significantly downregulated in nitrofen compared with those in the control group. On D21, expression levels of Cx43 were significantly upregulated in nitrofen+RA and control+RA compared with those in nitrofen group. Immunohistochemical studies confirmed these results.


CONCLUSIONS
Downregulation of Cx43 expression may interfere with normal alveologenesis. Upregulation of Cx43 pulmonary gene expression after RA treatment may promote lung growth by stimulating alveologenesis in nitrofen-induced PH.
National Children's Research Centre, Our Lady's Children's Hospital, Dublin, Ireland.
Elke Maria
EM
Ruttenstock
Takashi
T
Doi
Jens
J
Dingemann
Prem
P
Puri
D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D018031:Connexin 43 / Q000096:biosynthesis* / Q000235:genetics; D004195:Disease Models, Animal; D004353:Drug Evaluation, Preclinical; D004847:Epithelial Cells / Q000187:drug effects; D005260:Female; D046128:Fetal Therapies; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D006548:Hernia, Diaphragmatic / Q000139:chemically induced / Q000196:embryology / Q000378:metabolism; D065630:Hernias, Diaphragmatic, Congenital; D007274:Injections, Intraperitoneal; D008168:Lung / Q000196:embryology* / Q000378:metabolism / Q000473:pathology; D010647:Phenyl Ethers / Q000633:toxicity; D011247:Pregnancy; D012333:RNA, Messenger / Q000096:biosynthesis; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D020545:Respiratory Mucosa / Q000166:cytology / Q000196:embryology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014212:Tretinoin / Q000494:pharmacology / Q000627:therapeutic use*; D015854:Up-Regulation / Q000187:drug effects
D018031:Connexin 43; D010647:Phenyl Ethers; D012333:RNA, Messenger; D014212:Tretinoin; C007350:nitrofen