Epithelium-specific adenoviral transfer of a dominant-negative mutant TGF-beta type II receptor stimulates embryonic lung branching morphogenesis in culture and potentiates EGF and PDGF-AA.
Although exogenous transforming growth factor-beta (TGF-beta) is known to inhibit branching morphogenesis in mouse embryonic lungs in culture, whether the principal negative function of endogenous TGF-beta signaling resides in lung epithelium or mesenchyme remains unresolved. A recombinant adenovirus was constructed, containing a mutated human TGF-beta type II receptor with a truncated cytoplasmic kinase domain. We examined whether this dominant-negative receptor could abolish epithelium-specific endogenous TGF-beta signaling. We introduced the recombinant adenovirus into lung explants via intra-tracheal micro-injection. This resulted in over-expression of exogenous truncated TGF-beta type II receptor only in airway epithelium, not in mesenchyme, as assessed by mRNA level and protein localization. Blockade of endogenous TGF-beta receptor signaling in epithelial endoderm by the mutated dominant-negative TGF-beta type II receptor resulted in significant (65%) stimulation of epithelial branching morphogenesis, while exogenous TGF-beta no longer downregulated epithelial PCNA immunoreactivity and surfactant protein C (SP-C) expression. Additionally, the mitogenic responses to epidermal growth factor (EGF) and platelet-derived growth factor, PDGF-AA were potentiated by 33 and 31%, respectively. We conclude that epithelium-specific adenovirus-mediated over-expression of a dominant-negative TGF-beta type II receptor completely and specifically abolished the anti-proliferative effects of both endogenous and exogenous TGF-beta. Therefore, epithelium-specific TGF-beta signaling is sufficient to negatively regulate embryonic lung-branching morphogenesis in culture. We speculate that abrogation of TGF-beta signaling stimulates lung morphogenesis by potentiating the inductive and permissive effects of other endogenous peptide growth factors such as EGF and PDGF-AA.
Zhao
J
J
Center for Craniofacial Molecular Biology, Departments of Surgery and Pediatrics, The Children's Hospital Los Angeles Research Institute, University of Southern California Schools of Dentistry and Medicine Los Angeles, CA 90033, USA.
Sime
P J
PJ
Bringas
P
P
Gauldie
J
J
Warburton
D
D
D000256:Adenoviridae; D000818:Animals; D046508:Culture Techniques; D003720:Densitometry; D004815:Epidermal Growth Factor / Q000502:physiology*; D004847:Epithelial Cells / Q000502:physiology*; D005260:Female; D006801:Humans; D008168:Lung / Q000196:embryology*; D051379:Mice; D009024:Morphogenesis; D010982:Platelet-Derived Growth Factor / Q000502:physiology*; D011247:Pregnancy; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000502:physiology
D010982:Platelet-Derived Growth Factor; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; C075278:platelet-derived growth factor A; D004815:Epidermal Growth Factor; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II