Increased growth factor transcription after pulmonary artery banding

OBJECTIVE: Several mechanisms are known to produce mechanical stress during and after cardiac surgery, e.g. aortic cross-clamping and pulmonary artery banding (PAB). However, little is known about the transcription of myocardial genes which are changed during mechanical overload. This study was performed to investigate growth factor mRNA expression after PAB in porcine hearts. METHODS: The experiment was performed in 35 pigs (five groups). Each group consisted of three sham-pigs (S-pigs) and four banding-pigs (B-pigs). The mean transbanding gradient in B-pigs was 29 +/- 2.5 mm Hg. The hearts were excised after different time intervals. The probes were snap-frozen in liquid nitrogen and stored at -80 degrees C. Analysis was performed by Northern blot. RESULTS: Right ventricular weight increased significantly after 7 and 24 days (P < 0.05). There was an upregulation of transcriptional and growth factors in B-pigs: c-jun mRNA: 412 +/- 12.1% after 2 h (P < 0.001); c-fos mRNA: 303 +/- 18.5% after 2 h (P < 0.001); vascular endothelial growth factor (VEGF) mRNA: 203 +/- 18.2% after 2 h (P < 0.001); Flk-1 mRNA: 156 +/- 16% after 2 h (P < 0.05), 253 +/- 5% after 24 h (P < 0.01) and 184 +/- 12% after 3 days (P < 0.01); transforming growth factor-beta1 (TGF-beta1) mRNA: 255 +/- 21.5% after 24 h (P < 0.002). Fibroblast growth factors 1 and 2 (FGF-1 and FGF-2) were constitutively expressed in B- and S-pigs and did not change their expression. CONCLUSIONS: Pulmonary artery banding results in significant right ventricular hypertrophy and upregulation of different growth factors. However, growth factors known to induce hypertrophy in vitro, like the FGFs, showed unchanged expression. We think that myocardial growth factors may have trophic functions in the heart which may be useful for cardiac surgery in future.