Abstract 133: Heterozygous Deletion of Transferrin Receptor 1 Suppresses Angiogenesis in a Mouse Model of Hind Limb Ischemia

Objective: Angiogenesis can be triggered under conditions of ischemia and plays a protective role in peripheral artery disease. Iron is an essential trace mineral in the living body whose intracellular metabolism is regulated by transferrin receptor 1 (TfR1). Excess iron causes tissue damage and has been reported in patients with peripheral artery disease. Therefore, we hypothesized that TfR1 contributes to the pathophysiology of hind limb ischemia through iron overload. The aim of this study is to examine whether TfR1 deletion effects angiogenesis in hind limb ischemia. Methods and Results: Since homozygous TfR1 deletion is embryonically lethal, mice with heterozygous TfR1 deletion and their wild type littermates were used in this study. To induce hind limb ischemia, the left femoral artery in 8 - 9 week-old male mice was ligated and stripped. The non-ligated right hind limb was used as a control. Blood flow was measured by laser Doppler blood flowmetry at both a baseline of 1 hour and 28 days after the surgery. In wild type, the ratio of ischemc/non-ischemic hind limb blood flow was significantly decreased to 12% at baseline, and recovered to 62% at day 28. On the other hand, TfR1 deleted mice also showed similar reduction of blood flow at baseline, whereas blood flow recovery at day 28 was attenuated to 42%. Subsequently, both right and left adductor muscles were harvested for Western blot and immunohistochemistry. TfR1 expression in the adductor muscle was decreased in TfR1 deleted mice compared to wild type, regardless of the ligation. Ferritin, a marker for iron storage, was 10 times higher in ischemic muscles than in wild type non-ischemic muscles. In contrast, ferritin levels in TfR1 deleted mice were not altered by the surgery. Finally, immunohistochemistry for CD31 was performed to evaluate angiogenesis. The ischemic adductor muscle of TfR1 deleted mice had few CD31 positive vascular structures. Conclusions: Heterozygous deletion of TfR1 attenuated iron overload and angiogenesis in a mouse model of hind limb ischemia. TfR1 may be a novel therapeutic target for the treatment of peripheral artery disease.