A single nucleotide polymorphism in the p27Kip1 gene is associated with primary patency of lower extremity vein bypass grafts

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Objective About 30% of autogenous vein grafts develop luminal narrowing and fail because of intimal hyperplasia or negative remodeling. We previously found that vein graft cells from patients that later develop stenosis proliferate more in vitro in response to growth factors than cells from patients that maintain patent grafts. To discover novel determinants of vein graft outcome we have analyzed gene expression profiles of these cells using a systems biology approach to cluster the genes into modules based on their co-expression patterns and to correlate the results with growth data from our prior study and with new studies of migration and matrix remodeling. Methods RNA from 4 hour serum- or PDGF-BB-stimulated human saphenous vein cells obtained from the outer vein wall (20 cell lines), was used for microarray analysis of gene expression followed by weighted gene co-expression network analysis. Cell migration in microchemotaxis chambers in response to PDGF-BB and cell-mediated collagen gel contraction in response to serum were also determined. Gene function was determined using siRNA to inhibit gene expression before subjecting cells to growth or collagen gel contraction assays. These cells were derived from samples of the vein grafts obtained at surgery, and the long term fate of these bypass grafts was known. Results Neither migration nor cell-mediated collagen gel contraction showed a correlation with graft outcome. While 1,188 and 1,340 genes were differentially expressed in response to treatment with serum and PDGF, respectively, no single gene was differentially expressed in cells isolated from patients whose grafts stenosed compared to those that remained patent. Network analysis revealed 4 unique groups of genes, which we term modules, associated with PDGF responses, and 20 unique modules associated with serum responses. The “Yellow” and “Skyblue” modules, from PDGF and serum analyses respectively, both correlated with later graft stenosis (P=.005 and .02, respectively). In response to PDGF, Yellow was also associated with increased cell growth. For serum, Skyblue was also associated with inhibition of collagen gel contraction. The hub genes for Yellow and Skyblue (i.e. the gene most connected to other genes in the module), SCARA5 and SBSN, respectively, were tested for effects on proliferation and collagen contraction. Knockdown of SCARA5 increased proliferation by 29.9 ± 7.8% (P<.01), while knockdown of SBSN had no effect. Knockdown of SBSN increased collagen gel contraction by 24.2 ± 8.6% (P<.05), while knockdown of SCARA5 had no effect. Conclusion Using weighted gene co-expression network analysis of cultured vein graft cell gene expression, we have discovered two small gene modules, which comprise 47 genes, that are associated with vein graft failure. Further experiments are needed to delineate the venous cells that express these genes in vivo and the roles these genes play in vein graft healing starting with the module hub genes SCARA5 and SBSN, which have been shown to have modest effects...

Section: Discussionmentioning

confidence: 97%

Scavenger receptor class A member 5 ( SCARA5 ) and suprabasin ( SBSN ) are hub genes of coexpression network modules associated with peripheral vein graft patency

Kenagy

Civelek

Kikuchi

et al. 2016

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“…Despite technological advances and improvements in surgical techniques, the precise factors that determine whether a vein graft adopts an adaptive, outwardly remodeling phenotype, versus an occlusive phenotype, are largely unknown. A SNP of the p27 kip1 gene, a key cell-cycle inhibitor, has recently been associated with improved revascularization outcomes following both coronary angioplasty and lower extremity vein graft bypass 1, 2 , yet the mechanisms underlying this clinical observation remain undefined. Here we attempted to dissect the gene pathways and networks at play in shaping these divergent outcomes.…”

Section: Discussionmentioning

confidence: 99%

“…and van Tiel et. al., in fact, have identified a single nucleotide polymorphism (SNP) in the promoter region of the p27 kip1 gene that is associated with divergent clinical outcomes following lower extremity vein bypass grafting and coronary artery stenting, respectively 1, 2 . Both clinical studies demonstrated the p27 kip1 -838C>A SNP to be associated with significantly increased rates of clinical success compared to the -838CC and -838CA genotypes.…”

Section: Introductionmentioning

confidence: 99%

Time and flow-dependent changes in the p27 gene network drive maladaptive vascular remodeling

DeSart

Butler

O’Malley

et al. 2015

Objectives Although clinical studies have identified that a single nucleotide polymorphism in the p27kip1 gene is associated with success or failure following vein bypass grafting, the underlying mechanisms for this difference are not well defined. Using a high-throughput approach in a flow-dependent vein graft model, we explored the differences in p27kip1 -related genes that drive the enhanced hyperplastic response under low flow conditions. Methods Bilateral rabbit carotid artery interposition grafts with jugular vein were placed with unilateral distal outflow branch ligation to create differential flow states. Grafts were harvested at 2hr, 1d, 3d, 7d, 14d, and 28 days after implantation, measured for neointimal area, and assayed for cell proliferation. Whole-vessel mRNA was isolated and analyzed using an Affymetrix gene array platform. Ingenuity Pathway Analysis (IPA) was utilized to identify the gene networks surrounding p27kip1. This gene set was then analyzed for temporal expression changes following graft placement and for differential expression in the alternate flow conditions. Results Outflow branch ligation resulted in an 8-fold difference in mean flow rates throughout the 28d perfusion period (P<.001). Flow reduction led to a robust hyperplastic response, resulting in a significant increase in intimal area by 7d (0.13±0.04 vs. 0.014±0.006mm2, P<.005) and progressive growth to 28d (1.37±0.05 vs. 0.39±0.06mm2, P<.001). At 7 days, low flow grafts demonstrated a burst of actively dividing intimal cells (36.4 cells/mm2 ± 9.4 vs. 11.5 ± 1.9, P=.04). 65 unique genes within the microarray were identified as components of the p27kip1 network. At a false discovery rate of 0.05, 26 genes demonstrated significant temporal changes and two dominant patterns of expression was identified. Class comparison analysis identified differential expression of 11 genes at 2h and 7 genes and 14d between the high and low flow grafts (P<.05). At 2h, Oncostatin M and cadherin 1 were the most differentially expressed. Cadherin 1 and PKB exhibited the greatest differential expression at 14d. Conclusions Alterations in flow and shear stress result in divergent patterns of vein graft remodeling. Associated with the dramatic increase in neointimal expansion observed in low flow versus high flow grafts is a subset of differentially expressed p27kip1-associated genes that correlate with critical stages in the adaptive response. These represent potential biologic targets whose activity may be altered to augment maladaptive vascular remodeling.

“…But rather, intimal hyperplasia develops within a dynamic conduit, molded by hemodynamics, under the influence of systemic and regional factors. Thus inflammation,[22] race,[25] gender,[28] and genetics[29] can act globally on the entire vein graft to influence its adaptation in the arterial circulation. However, should local levels of shear stress and wall tension be impeded from reaching or reestablishing baseline conditions – due to either local environmental conditions, flow disturbances, or intrinsic vein disease - the proliferative intimal reaction would be expected to continue and stenosis to supervene.…”

Section: The Remodeling Of Human Vein Bypassmentioning

confidence: 99%

Vein graft failure

Owens

Gasper

Rahman

et al. 2015

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123

107

Following the creation of an autogenous lower extremity bypass graft, the vein must undergo a series of dynamic structural changes to stabilize the arterial hemodynamic forces. These changes, commonly referred to as remodeling, include an inflammatory response, the development of a neointima, matrix turnover, and cellular proliferation and apoptosis. The sum total of these processes results in dramatic alterations in the physical and biomechanical attributes of the arterialized vein. The most clinically obvious and easily measured of these is lumen remodeling of the graft. However, though somewhat less precise, wall thickness, matrix composition, and endothelial changes can be measured in vivo within the healing vein graft. Recent translational work has demonstrated the clinical relevance of remodeling as it relates to vein graft patency and the systemic factors influencing it. By correlating histologic and molecular changes in the vein, insights into potential therapeutic strategies to prevent bypass failure and areas for future investigation are explored.