Simvastatin augments revascularization and reperfusion in a murine model of hind limb ischemia – Multimodal imaging assessment

Introduction: Peripheral artery disease can lead to severe disability and limb loss. Therapeutic strategies focussing on macrovascular repair have shown benefit but have not significantly reduced amputation rates in progressive PAD. Proangiogenic small molecule therapies may substantially improve vascularisation in limb ischemia. The purpose of the current study was to assess the proangiogenic effects of simvastatin in a murine model of hind limb ischemia using longitudinal multimodal imaging. Methods: Mice underwent surgical intervention to induce hind limb ischemia, and were treated with simvastatin orally for 28 days. Neovascularisation was assessed using ^99mTc-RGD SPECT imaging, and macrovascular volume was assessed by quantitative time of flight MRI. At each imaging time point, VEGF expression and capillary vessel density were quantified using immunohistochemical analysis. Results: Simvastatin significantly increased ^99mTc-RGD retention in the ischemic hind limb by day 3 post-surgery, with maximal retention at day 8. Vascular volume was significantly increased in the ischemic hind limb of simvastatin treated animals, but only by day 22. Immunohistochemical analysis shows that simvastatin significantly augmented tissue VEGF expression from day 8 with increase in capillary density (CD31⁺) from day 14. Conclusions: Early assessment of proangiogenic therapy efficacy can be identified using ^99mTc-RGD SPECT, which displays significant increases in retention before macrovascular volume changes are measureable with MRI. Advances in knowledge and implications for patient care: Simvastatin offers an effective proangiogenic therapy as an adjunct for management of limb ischemia. Simvastatin induces integrin expression and vascular remodeling leading to neovascularisation and improved perfusion.