ImmunoPET of CD146 in a Murine Hindlimb Ischemia Model

Peripheral arterial disease (PAD) consists of a persistent obstruction of lower-extremity arteries further from the aortic bifurcation attributable to atherosclerosis. PAD is correlated with an elevated risk of morbidity and mortality as well as of deterioration of the quality of life with claudication and chronic leg ischemia being the most frequent complications. Therapeutic angiogenesis is a promising therapeutic strategy that aims to restore the blood flow to the ischemic limb. In this context, assessing the efficacy of pro-angiogenic treatment using a reliable noninvasive imaging technique would greatly benefit the implementation of this therapeutic approach. Herein, we describe the angiogenesis and perfusion recovery characteristics of a mouse model of PAD via in vivo positron emission tomography (PET) imaging of CD146 expression. For that, ischemia was generated by ligation and excision of the right femoral artery of Balb/C mice and confirmed through laser Doppler imaging. The angiogenic process, induced by ischemia, was noninvasively monitored and quantified through PET imaging of CD146 expression in the injured leg using a Cu-64-labeled anti-CD146 monoclonal antibody, Cu-64-NOTA-YY146, at post-operative days 3, 10, and 17. The CD146-specific character of Cu-64-NOTA-YY146 was verified via a blocking study performed in another cohort at day 10 after surgery. Tracer uptake was correlated with in situ CD146 expression by histological analysis. PET scan results indicated that Cu-64-NOTA-YY146 uptake in the injured leg was significantly higher, with the highest uptake with a value of 14.1 +/- 2.0 %ID/g at post-operative day 3, compared to the normal contralateral hindlimb, at all time points (maximum uptake of 2.2 +/- 0.2 %ID/g). The pre-injection of a blocking dose resulted in a significantly lower tracer uptake in the ischemic hindlimb on day 10 after surgery, confirming tracer specificity. CD146/CD31 immunofluorescent co-staining showed an excellent correlation between the high uptake of the tracer with in situ CD146 expression levels and a marked co-localization of CD146 and CD31 signals. In conclusion, persistent and CD146-specific tracer accumulation in the ischemic hindlimb was observed, confirming the feasibility of Cu-64-NOTA-YY146 to be used as an imaging agent to monitor the progression of angiogenesis and recovery in future PAD research.