Sustained Reduction of Vein Graft Neointima Formation by Ex Vivo TIMP-3 Gene Therapy

Abstract

Background— Coronary artery vein graft failure, resulting from thrombosis, intimal thickening, and atherosclerosis, is a significant clinical problem, with approximately 50% of vein grafts failing within 10 years. Intimal thickening is caused by migration of vascular smooth muscle cells from the media to the intima, where they proliferate. Interventions using gene transfer to inhibit vascular smooth muscle cells proliferation and migration are attractive because ex vivo access to the graft is possible. The involvement of matrix-degrading metalloproteinases in intimal thickening is well established, and we previously showed that adenoviral-delivered overexpression of an endogenous inhibitor, the tissue inhibitor of metalloproteinases-3 (TIMP-3), significantly retarded intimal thickening in short-term autologous porcine arteriovenous interposition grafts (28 days). However, it is essential to determine whether this approach will provide longer-term benefits. Methods and Results— We assessed whether a recombinant adenovirus that overexpresses TIMP-3 (RAdTIMP-3) affects vein graft intimal thickening in the longer term (at 3 months). Porcine saphenous veins were subjected to luminal infection with 2.5×10 10 pfu/mL RAdTIMP-3 or RAd60 (control virus) or vehicle control, for 30 minutes before implantation into the carotid artery. Analysis of grafts harvested 3 months after delivery revealed that RAdTIMP-3–infected grafts had significantly reduced intimal areas compared with both controls (3.2±0.4 mm 2 versus 5.6±0.7 mm 2 and 5.9±0.5 mm 2 , RAdTIMP-3, RAd60, and vehicle, respectively). Medial areas were also significantly decreased by TIMP-3 (3.8±0.3 mm 2 versus 6.7±1.0 mm 2 and 5.2±0.4 mm 2 , RAdTIMP-3, RAd60, and vehicle, respectively). Conclusions— Overexpression of TIMP-3 provides a sustained retardation of vein graft intimal thickening and highlights the translational potential for ex vivo TIMP-3 gene therapy.

Role of noncoding RNA in vascular remodelling

“…VSMCs are one of the major cellular components of the vessel wall and are implicitly involved in neointimal formation [25]. For example (and aligned to our own research) in vein graft disease, VSMC proliferation and migration contributes to the increased vein graft medial thickening, neointimal formation and superimposed atherosclerosis [26].…”

The atypical mechanosensitive microrna-712 derived from pre-ribosomal RNA induces endothelial inflammation and atherosclerosis

“…TIMP3 was selected for further study since the miR-712 interactome analysis (Figure 3a; Supplementary Figure S8) suggested its potential role as a key gene hub connected to numerous genes of interest, including matrix metalloproteinases-2/9 (MMP2/9) and a disintegrin and metalloproteinase 10/17 (ADAM10/17), ADAM with thrombospondin type 1 motif, 4 (ADAMTS4) and versican that are known to play a critical role in the regulation of vascular inflammation, permeability and atherosclerosis 23,24,25,26,27,28 .…”

Vein graft failure: current clinical practice and potential for gene therapeutics

“…62,63 Furthermore, direct proof of the involvement of MMPs in vein graft intimal thickening has been provided by the observation that overexpression of the endogenous MMP inhibitors tissue inhibitors of MMPs (TIMPs) significantly retarded intimal thickening. [64][65][66][67] Overproduction of superoxide (O 2 À ) is an important pathological component of vein graft failure, the principal source being nicotinamide adenine dinucleotide phosphate oxidase (for a review, see Jeremy et al 68 ). Nicotinamide adenine dinucleotide phosphate oxidase is upregulated by many platelets and leukocytes factors such as entothelin-1, leukotrienes and serotonin.…”

“…For example, some early studies showed enhanced neointima formation following arterial gene transfer in rabbits as well as high levels of inflammatory markers on endothelium; 82 however, we recently reported that there was no difference in inflammatory markers in long-term pig grafts using Ad5 vectors. 67 This may represent differences in responses in different models (rabbit/pig) and potential differences in virus quality control. Clearly, modulation of virus infection to maintain/improve target cell infection within the constraints imposed in the vein graft gene therapy setting would be advantageous.…”

“…66 We have recently performed longer term experiments in a pig vein graft model and shown sustained efficacy out to 3 months post gene transfer. 67 This is important since it illustrates that short-term transgene overexpression leads to lasting effects on neointima formation. Taken together with other studies, this presents a new opportunity to treat late vein graft failure using an Ad gene therapy approach and is a goal that we are aiming to test clinically in the future.…”