Peripheral arterial disease and restenosis after balloon angioplasty to treat arterial blockages is a significant cause of disability and death in the veteran population. Endovascular interventions are among the fastest growing treatments for peripheral arterial disease;however, restenosis secondary to intimal hyperplasia (IH) remains a major cause of failure from these procedures. Thrombospondin-1 (TSP-1) clearly contributes to IH by regulating the arterial response to injury. However, the mechanisms by which dyslipidemia enhances TSP- 1's actions, how TSP-1 induces IH, and optimal therapies to prevent IH after angioplasty in patients with peripheral arterial disease represent important gaps in our knowledge and is addressed by this application. Our long-term goal is to understand how TSP-1 signaling pathways can be manipulated therapeutically to prevent IH in vivo. The objective of this proposal is to investigate the mechanisms by which TSP-1, dyslipidemia and enhanced statin delivery regulate IH development. Our central hypothesis is that dyslipidemia enhances and that statin therapy will effectively inhibit the pro-stenotic effects of TSP-1. This hypothesis has been formulated on the basis of our strong preliminary data. The rationale for the proposed project is that understanding the underlying mechanisms of TSP-1 and dyslipidemia on IH and establishing optimal statin delivery to inhibit IH, will result in novel and innovative approaches to prevent restenosis after angioplasty. Our hypothesis will be tested by pursuing the following Specific Aims: 1) investigate how dyslipidemia modifies TSP-1-induced chemotaxis and signaling;2) elucidate the mechanisms of acute statin inhibition on TSP-1-induced signaling;3) determine the magnitude of TSP-1's role in statin efficacy;and 4) ascertain the optimal modality of statin delivery to reduce IH. The methodologies utilized to investigate these Specific Aims include: 1) modified Boyden chamber to assess vascular smooth muscle cell chemotaxis;2) western blot and ELISA for cell signaling;3) quantitative real time polymerase chain reaction for gene expression;4) two animal models of IH - carotid artery ligation in the TSP-1 knockout mouse and balloon injury of the common carotid artery in normal and dyslipidemic rats;5) different statin delivery methods in vivo - oral, intraluminal (using targeted micelles) and topical (using pluronic gel);and 6) morphometric analysis, immunohistochemical staining and in situ hybridization for analysis of the arterial specimens. The significance of the proposed research is that the findings will provide a major advance which is expected to result in the development of new treatment strategies to prevent restenosis after angioplasty for peripheral arterial disease lesions. The proposed research in this application is innovative, in our opinion, because the proposed development and testing of a targeted drug delivery system using statins for the treatment of these lesions would be a new treatment modality. The findings from this application will advance efforts to improve the quality of life and longevity by providing safer and more effective therapeutic options for veterans with peripheral arterial disease.
The proposed research is relevant to veterans'health because peripheral arterial disease and restenosis after balloon angioplasty to treat arterial blockages is a significant cause of disabiliy and death in the veteran population. Intimal hyperplasia is an important process in arterial restenosis development. These studies will: 1) expand our understanding of the pathophysiology of dyslipidemia and the acute phase reactant protein, thrombospondin-1, on intimal hyperplasia;2) determine whether vascular protective pleiotropic statin effects are thrombospondin-1 dependent;and 3) establish the optimal method(s) of statin delivery to decrease intimal hyperplasia. Thus, the findings from the proposed research are relevant to the VA's mission to decrease disability by providing safer, more effective care for veterans with peripheral arterial disease.