Abstract 14682: The Pi 3-kinase Isoform p110alpha is Essential for Neointima Formation Following Percutaneos Coronary Intervention (pci) by Mediating Vascular Smooth Muscle Cell Proliferation, Migration and Survival
Proliferation, migration and survival of vascular smooth muscle cells (VSMC) play a pivotal role in the development of neointima formation following percutaneos coronary intervention (PCI) and are mainly mediated by peptide growth factor induced activation of receptor tyrosine kinases (RTKs). RTK-induced responses are mostly mediated by activation of phosphatidylinositol 3'-kinase (PI3K).
Previously, we were able to demonstrate that in vitro inhibition of the catalytic PI3K isoform p110alpha completely abrogated growth factor mediated proliferation of VSMCs.
Therefore we generated SMC-specific p110alpha deficient mice in order to analyse in vivo the relevance of p110 alpha in restenosis formation after PCI. Four weeks following PCI of carotid arteries the extend of neointima formation was quantified in wild-type (WT), p110alpha knock out(ko) and in heterozygous animals. Additionally, we isolated aortic VSMCs from these mice and analysed growth factor-mediated cellular proliferation, migration and apoptosis using BrdU incorporation assay (proliferation), modified Boyden-chamber (chemotaxis) and nucleosome ELISA (apoptosis).
Platelet-derived growth factor BB (PDGF, 30 ng/ml) caused a 5.13 ± 0.87 fold increase (x-fold increase compared to unstimulated VSMCs ± s.e.m., n ≥ 3) in the proliferation of WT VSMCs. In comparison to WT SMCs, proliferation of p110alpha ko SMCs (1.90 ± 0.18) and heterozygous cells (3.49 ± 0.28) was significantly reduced (p < 0.05). PDGF (30 ng / ml) also induced chemotaxis (x-fold increase ± s.e.m., n ≥ 3) of WT VSMCs (6.28 ± 0.63). The migration of p110alpha ko VSMCs (2.44 ± 0.18) and heterozygous VSMCs (3.36 ± 0.41) was also significantly (p <0.05) reduced compared to WT VSMCs. Application of PDGF significantly reduced H2O2 (25 µM) induced apoptosis of WT VSMCs by 30% ± 14% (n=4) whereas PDGF had only poor effects on H2O2 induced apoptosis of heterozygous SMCs (22% ± 19%, n=4, not significant) and p110alpha ko VSMCs (0% ± 13%, n=3, not significant). In summary, these data indicate that the p110alpha subunit of PI3K is crucially involved in growth factor-mediated proliferation, migration and survival of VSMCs. For the prevention of restonosis following PCI p110alpha represents a promising therapeutic target.
- © 2012 by American Heart Association, Inc.