Adventitial Microvessel Formation After Coronary Stenting and the Effects of SU11218, a Tyrosine Kinase Inhibitor

Adventitial Microvessel Formation After Coronary Stenting and the Effects of SU11218, a Tyrosine Kinase Inhibitor Asim N. Cheema, Tony Hong, Nafiseh Nili, Amit Segev, John G. Moffat, Kenneth E. Lipson, Anthony R. Howlett, David W. Holdsworth, Michael J. Cole, Beiping Qiang, Frank Kolodgie, Renu Virmani, Duncan J. Stewart, Bradley H. Strauss In a porcine coronary artery model, stenting caused tissue hypoxia within the vessel wall and resulted in an exuberant adventitial microvessel (Ad-MV) response that correlated with the amount of in-stent intimal hyperplasia (IH). A tyrosine kinase inhibitor (TKI), SU11218 inhibited platelet-derived growth factor receptor–beta phosphorylation, endothelial cell and smooth muscle cell DNA synthesis, and migration in vitro and significantly inhibited Ad-MV response and reduced IH by approximately 80% in vivo. The TKI SU11218 represents a promising therapeutic agent to prevent in-stent restenosis. The aim of this study was to delineate the temporal profile of adventitial microvessel (Ad-MV) formation after stenting, its relationship to arterial wall hypoxia, and the effects of a tyrosine kinase inhibitor (TKI), SU11218, on Ad-MV and in-stent intimal hyperplasia (IH). Adventitial microvessels have been reported after arterial injury; however, the underlying stimulus for this response and its relationship to IH is unknown. Coronary stenting was performed in 40 pigs randomized to SU11218 (n = 20) or placebo (n = 20). Vessel wall hypoxia was assessed by pimonidazole adducts and hypoxia-inducible factor (HIF)-1 alpha expression. Adventitial microvessels were quantified by three-dimensional microscopic computed tomography (3D micro CT). Intimal hyperplasia was measured by intravascular ultrasound (IVUS), 3D micro CT, and morphometry. The effects of SU11218 were assessed in vitro on smooth muscle cell (SMC) and endothelial cell (EC) functions and in vivo on Ad-MV and IH. Hypoxia was evident in the vessel wall at 48 h and persisted for four weeks. Adventitial microvessels increased significantly at one week (24 ± 7 microvessels/segment) and four weeks (23 ± 7 microvessels/segment) compared with uninjured arteries (16 ± 2 microvessels/segment; p < 0.001) and correlated with IH (r = 0.77, p < 0.001). The TKI SU11218 inhibited platelet-derived growth factor receptor–beta phosphorylation, EC and SMC DNA synthesis, and migration in a dose-dependent manner in vitro and significantly inhibited Ad-MV (16 ± 5 vs. 23 ± 7 microvessels/segment