Delivery of Thrombospondin-2 Small Interfering RNA for Suppression of Intimal Hyperplasia

Treatments of peripheral arterial disease, which affects >8.5 million individuals in the United States, include angioplasty and stenting and graft bypass. However, these have been limited by the pervasive development of intimal hyperplasia, which leads to in-stent restenosis and reduced graft patency. We propose a novel technique to suppress the progression of intimal hyperplasia using bioengineered hydrogels (ClickGels) for localized small interfering RNA (siRNA) delivery and suppression of thrombospondin-2 (TSP2), an upregulated gene of intimal hyperplasia, in an in vivo rat carotid angioplasty model. The rat carotid angioplasty model is an established in vivo animal model for intimal hyperplasia. Vessel injury was induced by Fogarty catheter angioplasty of the left common carotid artery in 32 rats, which were equally divided into three control arms (control injury, ClickGel, and control siRNA delivery) and one experimental arm (ClickGel delivering TSP2-suppressing siRNA). On postoperative day 21, the bilateral common carotid arteries were harvested for evaluation of intimal hyperplasia via an intima/media ratio calculation, polymerase chain reaction quantification of TSP2 mRNA expression, and immunohistochemical analysis of CD31, CD68, and Ki-67 expression. Masson's trichrome stain demonstrated an injured left carotid artery (Fig 1) with significant intimal hyperplasia compared with an uninjured right carotid artery (Fig 1) from the same rat. The intima/media ratio was significantly increased (Fig 2) in the control injury arm compared with the TSP2 siRNA experimental arm (2.02 ± 0.55 vs 1.24 ± 0.57; P = .01). Quantitative real-time polymerase chain reaction demonstrated successful TSP2 mRNA expression knockdown (Fig 2) in the TSP2 siRNA experimental arm compared with the control injury arm (0.081 ± 0.01 vs 6.32 ± 5.47; P = .063). The Results from preliminary in vivo experiments suggest the promising ability of ClickGel delivery of TSP2 siRNA to successfully suppress TSP2 expression and limit the development of intimal hyperplasia in a rat carotid angioplasty model. Further translational research with larger animal models is warranted for continued optimization of this delivery system, with the eventual aim of clinical trials.Fig 2View Large Image Figure ViewerDownload Hi-res image Download (PPT)