Introduction: Diabetic patients suffer poor clinical outcomes after ischemic insult, as demonstrated by increased morbidity and mortality following cerebrovascular insult, myocardial infarction, and wounding. Proposed mechanisms of microvascular complications include micro-infarction, leaky capillaries, malformed vessels, or lack of new blood vessel growth. Here we employ a novel assay of pure neovascularization to demonstrate that diabetics do not form new blood vessels in response to ischemia. This process is reversed by blocking Fenton reactions, the physiologic process of iron oxidation that produces reactive oxygen species (ROS), with the FDA approved iron chelator deferoxamine.
Methods: A novel murine model of soft tissue ischemia was used to specifically isolate and quantify neovascularization in deferoxamine treated and untreated control and diabetic mice. After tissue harvest histology, vessel counts, and laser Doppler were used to quantify new blood vessel growth. Lineage depleted bone marrow cells from these mice were harvested and studied for their ability to mobilize, migrate, and incorporate into vascular structures.
Results: Ischemic flaps forced to survive completely on newly formed blood vessels in control animals exhibited no tissue loss, while diabetic animals exhibited approximately 50% reduction in gross tissue survival. Vessel counts and laser Doppler confirmed this functional defect was a result of decreased new blood vessel growth in the flap. Deferoxamine treatment returned new blood vessel growth to control levels and rescued flap survival. In-vitro assays demonstrated that deferoxamine corrected diabetes induced cellular deficits in mobilization and migration.
Conclusion: Diabetes results in impaired neovascularization, leading to functional deficits after ischemic injury. Scavenging of ROS corrects the functional deficit seen after ischemic insult and returns new blood vessel growth to control values in diabetic animals in part by reversing defects in bone marrow derived cells. Since deferoxamine is currently FDA approved, this observation will be rapidly translated into the clinic.