Proceedings of The Physiological Society
University College Dublin (2009) Proc Physiol Soc 15, PC58
VEGF family members can inhibit angiogenesis in the hypoxic lung.
M. Sands1, K. Howell1, C. Costello1, P. McLoughlin1
1. School of Medicine and Medical Science, Conway Institute of Biomolecular and Biomedical Science, Dublin 4, Ireland.
Figure 1: Mean (±SEM) percentage wound closure over a 24 hour period in response to VEGF A alone (8ng/ml), VEGF A and PlGF (40ng/ml or 160ng/ml). * signifies a significant increase in wound healing compared to vehicle, † signifies significant increase compared to VEGF A alone (P<0.05, ANOVA, post hoc Student Newman Keuls). N=6 per group.
We have recently shown, for the first time, that angiogenesis occurs in the pulmonary circulation in response to chronic hypoxia, a common complication of chronic lung diseases. Much is known about the role of members of the vascular endothelial growth factor (VEGF) family in mediating neovascularisation in the systemic circulation. However, to date their role in hypoxia-induced pulmonary angiogenesis remains less clear. Male specific pathogen free Sprague Dawley rats (n= 7-8 per group) were exposed to normoxia or chronic hypoxia (10% O2) for 1, 3, 7, 14 and 21 days. Following the exposure period, the rats were deeply anaesthetised (70mg.kg-1 sodium pentobarbitone (i.p.)) and killed by exsanguination via the femoral vessels. The right lung was removed and flash frozen for later analysis of mRNA by real-time PCR. To examine the interactions of specific VEGF ligands in vitro, human pulmonary microvascular endothelial cells were grown under sterile cell culture conditions until confluent. A single wound was created in the cell monolayer by scraping with a sterile pipette tip, the cells treated with vehicle or recombinant proteins (PlGF, VEGF A, VEGF B) and the wound assessed 24 hours later. The percentage reduction in wound width was then calculated. VEGF A mRNA expression in the hypoxic lung was not altered at any time point examined in vivo (over a 3 week interval). VEGF B and PlGF mRNA expression was significantly increased at 7 and 14 days, with PlGF remaining augmented following 21 days exposure to chronic hypoxia. VEGF A (8ng/ml) augmented the mean (±SEM) rate of wound healing over vehicle alone. A low concentration of PlGF (40ng/ml) potentiated the rate of VEGF A induced wound healing. However, a higher concentration of PlGF protein (160ng/ml) did not alter the rate of VEGF A induced wound healing. VEGF B (20ng/ml) inhibited the actions of VEGF A. These results suggest that the interaction between VEGF ligands is complex and is critically concentration dependent. Thus, further in vivo experiments are required to fully elucidate the role of members of the VEGF family in hypoxic pulmonary angiogenesis.
Where applicable, experiments conform with Society ethical requirements