Transforming growth factor-β1 antisense treatment of rat vein grafts reduces the accumulation of collagen and increases the accumulation of h-caldesmon

BackgroundThe main cause of occlusion and vein graft failure after peripheral and coronary arterial reconstruction is intimal hyperplasia. Transforming growth factor β-1 (TGF-β1) is a pleiotropic cytokine known to have powerful effects on cell growth, apoptosis, cell differentiation, and extracellular matrix synthesis.MethodsTo investigate the role of TGF-β1 in intimal hyperplasia, we used adenovirus to deliver to superficial epigastric vein messenger RNA (mRNA) antisense to TGF-β1 (Ad-AST) or the sequence encoding the bioactive form of TGF-β1 (Ad-BAT). Infection with “empty” virus was used as a control (Ad-CMVpLpA). The treated vein was then used for an interposition graft into rat femoral artery. Grafts were harvested at 1, 2, 4, and 12 weeks and formalin-fixed for histologic studies or placed in liquid nitrogen for mRNA studies.ResultsAd-AST treatment resulted in an overall reduction of TGF-β1 expression (P = .001), and Ad-BAT treatment resulted in an overall increase in TGF-β1 expression (P = .007). Histologic analysis showed Ad-AST caused reduced collagen build up in the neointima at 12 weeks (P = .0001). Immunohistochemical staining for h-caldesmon at 12 weeks indicated Ad-AST increased smooth muscle cells throughout the vessel wall compared with Ad-CMVpLpA (P = .0024) or Ad-BAT (P = .04). Ad-AST also resulted in reduced CD68-positive cells in the media/adventitia (P = .005 vs Ad-CMVpLpA, P = .01 vs Ad-BAT). To further understand how Ad-AST was influencing the build up of collagen, we performed quantitative polymerase chain reaction on complimentary DNA (cDNA) from homogenates of the vein grafts. Tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) was increased at 1 week by Ad-BAT (P = .048 vs Ad-CMVpLpA) and decreased by Ad-AST at all time points (P ≤ .038). The mRNA for collagen-1 α-1 was decreased by Ad-AST at 2, 4, and 12 weeks (P ≤ .05) and increased by Ad-BAT at 1 week (P = .01).ConclusionsTGF-β1 antisense treatment of vein grafts prevents the accumulation of collagen in the neointima in part by (1) changing the proportions of the cell types populating the vein graft wall, (2) reducing the mRNA for TIMPs, and (3) reducing the amount of collagen mRNA. With the Ad-AST and Ad-BAT treatments, we have been able to tip the maturation of the vein graft toward positive remodeling (artery-like phenotype) or toward negative remodeling (fibroproliferation and stenosis), respectively.

Clinical RelevanceThe main cause of occlusion and graft failure after peripheral and cardiac arterial reconstruction is intimal hyperplasia. The study of the mechanisms and mediators of intimal hyperplasia, including TGF-β1, should lead to future gene therapies to prevent or limit intimal hyperplasia. Ultimately, the goal of this research is to provide the clinician with a safe and reliable method of preconditioning vein to make it a more reliable conduit for arterial repair.