The role of transforming growth factors beta1 and beta3 in pre- and post-natal pulmonary surfactant development

The aim was to explore the pulmonary surfactant regulatory effect of TGF-β1 and TGF-β3 during pre- and post-natal porcine development. Pigs on embryonic day 99 (E94) (term = 114 days) and 1-h (D0) and 15-day (D20) neonates were killed to obtain whole lungs. DSPC (disaturated phosphatidylcholine) was separated from other phospholipids, and chemical methods were used to determine the amounts of DSPC, TPL (total phospholipids) and TP (total protein) in BALF (bronchoalveolar lavage fluid). TPL was elevated at E94. DSPC in TPL was significantly higher in the D20 group than in the E94 group. Reductions in TP correlated with developmental age. The levels of TGF-β1 and TGF-β3 mRNA were determined by RT (reverse transcription)-PCR and Northern blot. The expression of TGF-β1 mRNA was low at E94, increased at D0 and then decreased at D20. The expression of TGF-β3 was high at E94, reduced at D0, and then elevated at D20. We further examined the effect of exogenously administered TGF-1 on the expression of SPs (surfactant proteins) and cytidine triphosphorylate: CCT (phosphocholine cytidylyltransferase) activity in porcine fetal lung cells cultured for 5 days. The results indicated that TGF-β1 inhibited the expression of all three SPs (SP-A, SP-B and SP-C) and CCT activity, but did not alter the expression level of SP-D transcripts. We conclude that TGF-1 inhibits the expression of surfactant components. The alterations of TGF-β3 seem to partly explain the pulmonary surfactant changes observed in development, but this result needs further investigation.