Noninvasive monitoring of the development and treatment response of ischemic hindlimb by targeting matrix metalloproteinase-2 (MMP-2).

Critical limb ischemia (CLI) is a common cause of high vascular morbidity and mortality. Monitoring the development and treatment response of hindlimb ischemia (HI) in an animal model enables a better understanding of the pathological mechanisms underlying CLI, and evaluation of the efficacy of novel therapeutic approaches. Matrix metalloproteinase (MMP) activity is essential for remodeling of ischemic tissue including extracellular matrix degradation and angiogenesis. Herein, a mouse HI model is established and subjected to noninvasive optical imaging with a novel and ultra-sensitive MMP activatable probe, termed MMP-P12, for analyzing the development and treatment response of HI. Our results show that angiogenesis development during HI was well correlated with MMP-2 activity alteration as examined by western blot, histological staining and MMP-P12 fluorescence signal recovery. Moreover, vascular endothelial growth factor (VEGF) mediated HI treatment was also monitored by MMP-P12. Up-regulated MMP-2 expression and an enhancement of angiogenesis were observed after VEGF treatment, which peaked at 7 days after the treatment. Overall, our results showed that MMP-2 plays an important role in the monitoring of angiogenesis during HI development and therapy. Application of MMP-P12 to visualize MMP-2 activity alteration can serve as a promising noninvasive optical imaging strategy to monitor angiogenesis and its response to therapy in CLI.