title: Retinoid receptors in the developing human lung.
abstract: Nuclear receptors and their ligands are known to play very important roles in lung development. Among these receptors, retinoid receptors, members of the steroid/thyroid hormone receptor superfamily, are classified into retinoic acid receptor (RAR) isoforms alpha, beta, and gamma and retinoid X receptor (RXR) isoforms alpha, beta, and gamma. In addition, isoforms I and II of the orphan receptor chicken ovalbumin upstream promoter-transcription factor (COUP-TF) have been shown to negatively regulate the activation of retinoid receptors. Both of these receptors have been shown to regulate lung development in the mouse. In the present study we utilized immunohistochemistry and real-time quantitative PCR to examine the expression of RAR-alpha, -beta and -gamma, RXR-alpha, -beta and -gamma and COUP-TFII in the human fetal lung at 13-16 gestational weeks, a very critical stage of human pulmonary development, in order to study possible roles in pulmonary morphogenesis by comparing these findings with those of the adult lung. RXR-gamma immunoreactivity was detected at both proximal (epithelia and mesenchyme of the trachea and bronchi associated with cartilage) and distal (epithelia and mesenchyme of smaller distal bronchi) sites in the fetal lung, but was markedly weaker in the adult lung. RAR-beta immunoreactivity was detected in distal mesenchymal cells of the fetal lung, but was not discernible in distal mesenchymal cells in the adult lung (bronchioles, alveolar ducts and alveolus). Relatively intense RAR-gamma immunoreactivity was detected in the chondrocytes of bronchial cells. COUP-TFII immunoreactivity was detected with a similar pattern to that of RAR-beta. Real-time quantitative PCR analyses revealed that mRNA levels of RXR-gamma at proximal and distal sites (ratio of fetal lung/adult lung: 3.4+/-0.05-fold and 3.1+/-0.03-fold respectively; P <0.01), RAR-beta at distal sites (2.4+/-0.01-fold; P <0.05) and RAR-gamma at proximal sites (2.2+/-0.11-fold; P <0.05) were significantly higher in the fetus than in the adult.
authors.affiliation: Department of Pathology, Tohoku University School of Medicine, Tohoku University, Sendai, Japan. kimuyu@patholo2.med.tohoku.ac.jp
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Kimura
authors.forename: Takashi
authors.initials: T
authors.lastname: Suzuki
authors.forename: Chika
authors.initials: C
authors.lastname: Kaneko
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Darnel
authors.forename: Takuya
authors.initials: T
authors.lastname: Moriya
authors.forename: Satoshi
authors.initials: S
authors.lastname: Suzuki
authors.forename: Masashi
authors.initials: M
authors.lastname: Handa
authors.forename: Masahito
authors.initials: M
authors.lastname: Ebina
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Nukiwa
authors.forename: Hironobu
authors.initials: H
authors.lastname: Sasano
mesh_terms: D000328:Adult; D051837:COUP Transcription Factor II; D051836:COUP Transcription Factors; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D008168:Lung / Q000196:embryology* / Q000378:metabolism*; D009024:Morphogenesis; D016133:Polymerase Chain Reaction / Q000379:methods; D020033:Protein Isoforms / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000378:metabolism*; D011987:Receptors, Steroid / Q000378:metabolism; D047488:Retinoid X Receptors; D014157:Transcription Factors / Q000378:metabolism; D000097768:Retinoic Acid Receptor gamma
chemical_list: D051837:COUP Transcription Factor II; D051836:COUP Transcription Factors; D004268:DNA-Binding Proteins; D020033:Protein Isoforms; D018168:Receptors, Retinoic Acid; D011987:Receptors, Steroid; D047488:Retinoid X Receptors; D014157:Transcription Factors; D000097768:Retinoic Acid Receptor gamma; C082925:retinoic acid receptor beta; C095569:NR2F2 protein, human