Growth factors gene expression in the developing lung

Aim: This is the first systematic study using quantitative real-time PCR to analyze and compare the expression profiles for critical members of the epidermal growth factor (EGF), transforming growth factor beta (TGF beta), and vascular endothelial growth factor (VEGF) families in developing rat lungs. Methods: mRNA expression was quantified at embryonic (E) day 15, 17, 19, 2 1, and postnatal age 1 day, 2 weeks, 12 weeks. Results: EGF and EGFR increased during gestation and development, then decreased in adulthood, whereas TGF alpha was highest at birth and remained unchanged afterwards. All TGF beta isoforms increased slightly during pregnancy, reached highest expression during development, and returned to neonatal levels in adulthood. TGF beta RI and TGF beta RII patterns were similar to TGFP2 and TGF beta 1 respectively, whereas TGF beta RIII expression was lowest at the postnatal time points. VEGF(164) and VEGF(120) showed a steady increase up to 2 weeks and declined at 12 weeks, whereas highest VEGF(188) expression occurred at 12 weeks. VEGF-A receptors expression paralleled the summation of all three isoforms, increasing steadily with age. Conclusion: Expression of growth factors in the developing lung is characterized by highly regulated distinctive patterns that may be critical to understand the early origin and progression of pulmonary diseases in childhood as well as in adulthood. Quantitative real-time PCR analysis revealed several differences compared to previously reported expression patterns defined with older methodologies.