title: Different roles for PDGF-alpha and -beta receptors in embryonic lung development.
abstract: Platelet-derived growth factor (PDGF) is implicated in the process of normal lung development. We have previously shown the presence of PDGF-AA and BB homodimers in embryonic rat lung. Also, we reported that PDGF-AA is involved in embryonic lung branching, whereas PDGF-BB influences embryonic lung growth. PDGF isoforms bind with different affinities to two related receptors, denoted the PDGF alpha- and beta-receptors, respectively. The alpha-receptor binds both PDGF isoforms, whereas the beta-receptor binds only PDGF-BB. In the present study, we investigated the role of both receptors in early embryonic rat lung development. Reverse-transcriptase-polymerase chain reaction (RT-PCR) analysis revealed that both PDGF alpha- and beta-receptor mRNAs are mainly expressed in the mesenchyme. Phosphorothioate antisense receptor oligonucleotides decreased PDGF receptor mRNA expression in early lung explants. PDGF-induced receptor tyrosine phosphorylation was also reduced by the antisense oligonucleotides. Incubation of embryonic lung explants with antisense beta-receptor oligonucleotides inhibited lung growth but not early lung branching. Neither growth nor branching were affected by sense beta-receptor oligonucleotides. The inhibitory effect of antisense beta-receptor oligonucleotides on embryonic lung growth was reversed by the addition of PDGF-BB or PDGF-AA, suggesting that the alpha-receptor can transduce similar mitogenic signals as the beta-receptor in early lung development. Antisense alpha-receptor oligonucleotides reduced both embryonic lung growth and branching. Sense alpha-receptor treatment had no effect on lung growth and branching. PDGF-BB but not PDGF-AA partially attenuated the inhibitory effect of antisense alpha-receptor oligonucleotides on lung growth. In contrast, PDGF-BB did not overcome the inhibitory effect on early lung branching, indicating that the beta-receptor cannot replace this biologic role of the alpha-receptor in early lung development. These data suggest that PDGF-BB stimulation of both receptors leads to lung growth, whereas PDGF-AA stimulation of the alpha-receptor induces transduction pathways that lead lung branching.
authors.affiliation: Department of Pediatrics, Hospital for Sick Children Research Institute, University of Toronto, Ontario, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Souza
authors.forename: A K
authors.initials: AK
authors.lastname: Tanswell
authors.forename: M
authors.initials: M
authors.lastname: Post
mesh_terms: D000818:Animals; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D008168:Lung / Q000196:embryology* / Q000378:metabolism; D008297:Male; D009024:Morphogenesis / Q000187:drug effects; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D020796:Receptor, Platelet-Derived Growth Factor alpha; D020797:Receptor, Platelet-Derived Growth Factor beta; D017479:Receptors, Platelet-Derived Growth Factor / Q000235:genetics / Q000378:metabolism*
chemical_list: D016376:Oligonucleotides, Antisense; D020796:Receptor, Platelet-Derived Growth Factor alpha; D020797:Receptor, Platelet-Derived Growth Factor beta; D017479:Receptors, Platelet-Derived Growth Factor