age analysis of neointimal hyperplasia and vascular wall transformation after balloon angioplasty. Physiol Genomics 25: 286 -293, 2006. First published January 24, 2006 doi: 10.1152/physiolgenomics.00135.2005.-Neointimal hyperplasia (NIH), a result of vascular injury, is due to the migration and proliferation of smooth muscle cells through the media and internal elastic lamina leading to vascular occlusion. We used a rat model to find the genetic regions controlling NIH after endothelial denudation in two divergent inbred strains of rats. The Brown Norway (BN) and spontaneously hypertensive rat (SHR) strains have a 2.5-fold difference in injury-induced NIH. A population of 301 F2 (SHR ϫ BN) rats underwent a standard vascular injury followed by phenotyping 8 wk after injury to identify quantitative trait loci (QTL) responsible for this strain difference. Interval mapping identified two %NIH QTL on rat chromosomes 3 and 6 [logarithm of odds (LOD) scores 2.5, 2.2] and QTL for other injured vascular wall changes on rat chromosomes 3, 4, and 15 (LOD scores 2.0 -4.6). Also, QTL for control vessel media width (MW) and media area (MA) were found on chromosome 6 with LOD scores of 2.3 and 2.5, suggesting that linkage exists between these control vessel parameters and NIH production. These results represent the first genetic analysis for the identification of NIH QTL and QTL associated with the vascular injury response.quantitative trait loci; restenosis; vascular injury; inbred strains; Brown Norway rat; spontaneously hypertensive rat INTERVENTIONS IN THE CARDIOVASCULAR system such as arterial grafts, stents, and balloon angioplasties often fail because of the development of neointimal hyperplasia (NIH). There are no effective therapies to prevent or treat this complication. For example, restenosis secondary to NIH occurs in 30 -40% of patients after balloon angioplasty for coronary artery disease (27). Drug-eluting stents reduce the occurrence of short-term NIH to 20 -30%, but the long-term efficacy of these devices is not known (27). NIH is also associated with the development of significant restenosis in 20% of patients undergoing carotid endarterectomy (1) and is a major contributor to graft failure in coronary and peripheral arteries (24).NIH is triggered by vascular endothelial cell (VEC) disruption and injury that leads to smooth muscle cell (SMC) migration to subendothelial injury sites, followed by SMC proliferation and apoptosis. Significant neointimal thickening and decreased lumen areas are seen within 2 wk after vascular injury (16, 32). However, vascular occlusion can continue after 2 wk as SMC size increases (16, 32) and proteoglycan matrix deposits continue to thicken the neointima (8,28,36,37,45). Many factors are involved in, and possibly responsible for, genetically determined variations in the NIH injury response between different strains of animals and among individual patients (1). We postulate that heritable variations in the genes for these vascular injury response elements are possible candidate...

Neointimal Hyperplasia (NIH) can lead to restenosis after clinical vascular interventions. NIH results from complex, and poorly understood, interactions between signaling cascades in the extracellular matrix and disrupted endothelium which leads to vessel occlusion. Quantitative Trait Loci (QTLs) were previously reported on rat chromosomes 3 and 6 through linkage analysis of post-injury NIH in mid-iliac arterial sections. In the current study, substitution mapping validated the RNO3 NIH QTL but not the RNO6 NIH QTL. The SHR.BN3 congenic strain had a three-fold increase in %NIH compared to the parental SHR strain. A double congenic study of RNO3+RNO6 NIH QTL segments suggested less than additive effects of these two genomic regions. To test the hypothesis that changes in vessel dynamics account for the differences in NIH formation, we performed vascular reactivity studies in the BN, SHR, SHR.BN3 and SHR.BN6 strains. De-endothelialized left common carotid artery rings of the SHR.BN3 showed an increased vascular responsiveness when treated with serotonin or prostaglandin F2α, with significant differences in EC50 and Emax (p < 0.01) values compared to the SHR parental strain. Since both vascular reactivity and %NIH formation in the SHR.BN3 strain are significantly higher than the SHR strain, we postulate that these traits may be associated and are controlled by genetic elements on RNO3. In summary, these results confirm that the RNO3 NIH QTL carries the gene(s) contributing to post-injury NIH formation.