A Hydrogel Strategy to Augment Tissue Adenosine to Improve Hindlimb Perfusion

Objective: Adenosine is an important vasodilatory, anti-inflammatory, and antithrombotic agent; however, its delivery for the treatment of cardiovascular diseases is challenging due to the drug's short half-life and dose-limiting side effects. Peripheral artery disease, one of the most prevalent atherosclerotic diseases of the cardiovascular system, remains without adequate nonsurgical treatments, resulting in significant morbidity due to ischemia and inflammation. Here, we hypothesize that we can use an enzyme-loaded synthetic hydrogel for local adenosine production. Approach and Results: We engineer a protease-sensitive poly(ethylene glycol)-maleimide-based hydrogel and characterize its rheological parameters when modulating poly(ethylene glycol) density and tethering a peptide to the gel backbone, then test degradation in response to collagenase. We load the gel with an ecto-nucleotidase, CD73, which catalyzes adenosine production from phosphorylated substrates, and use the CD73-loaded gel to generate adenosine in vitro and inhibit neutrophils' oxidative burst. When delivered in vivo, the CD73 hydrogel augments adenosine levels in hindlimb skeletal muscles 24 hours after induction of peripheral arterial ischemia and increases lower limb perfusion compared with control gel in healthy mice on laser Doppler imaging. Conclusions: This enzyme-delivering hydrogel provides a strategy for local and sustained adenosine generation to improve perfusion, and future work will optimize its use for disease modulation.