Vascular endothelial growth factor isoform and receptor expression during compensatory lung growth

Background: Vascular endothelial growth factor (VEGF) is required for blood vessel formation during lung growth and repair. Alteration of VEGF isoform expression has been demonstrated in response to fetal tracheal occlusion and in models of lung injury. The purpose of this study was to investigate VEGF expression during compensatory lung growth in the mouse.

Methods: Under general anesthesia, adult mice underwent left thoracotomy with (n = 5) or without (sham, n = 5) pneumonectomy. The right lungs were harvested at 1, 3, and 7 d after the operation. Lung-to-body weight ratio as well as total DNA and protein content were measured. VEGF protein expression was analyzed by Western blot and ELISA. VEGF isoform expression was evaluated using semi-quantitative PCR followed by Imagequant optical densitometry. Values were compared by Student's t-test and ANOVA using Fisher's protected least significant difference post-hoc test where appropriate.

Results: Compensatory lung growth was observed as measured by increases in right lung-to-body weight ratio and in DNA and protein content. Total VEGF RNA and protein expression did not change after pneumonectomy. However, on post-operative day 1, there was a decrease in the relative percentage of VEGF188 mRNA (P < 0.01), and an increase in the relative percentage of VEGF164 mRNA (P = 0.05). At 3 d postpneumonectomy, low relative VEGF188 expression persisted (P < 0.05), VEGF164 expression normalized, and relative VEGF120 expression increased (P < 0.01). Isoform expression in the pneumonectomy animals was identical to sham animals by the seventh d. There were no differences observed in VEGF receptor expression.

Conclusion: During compensatory lung growth, we have observed an early postoperative reversion of VEGF isoform expression to the pattern seen during fetal lung development and in lung injury models.