Nanoparticle-Mediated Delivery of Pioglitazone Enhances Therapeutic Neovascularization in a Murine Model of Hindlimb Ischemia

Objective-Critical limb ischemia is a severe form of peripheral artery disease (PAD) for which neither surgical revascularization nor endovascular therapy nor current medicinal therapy has sufficient therapeutic effects. Peroxisome proliferator activated receptor-gamma agonists present angiogenic activity in vitro; however, systemic administration of peroxisome proliferator-activated receptor-gamma agonists is hampered by its side effects, including heart failure. Here, we demonstrate that the nanoparticle (NP)-mediated delivery of the peroxisome proliferator activated receptor-gamma agonist pioglitazone enhances its therapeutic efficacy on ischemia-induced neovascularization in a murine model. Methods and Results-In a nondiabetic murine model of hindlimb ischemia, a single intramuscular injection of pioglitazone-incorporated NP (1 mu g/kg) into ischemic muscles significantly improved the blood flow recovery in the ischemic limbs, significantly increasing the number of CD31-positive capillaries and a-smooth muscle actin-positive arterioles. The therapeutic effects of pioglitazone-incorporated NP were diminished by the peroxisome proliferator activated receptor-gamma antagonist GW9662 and were not observed in endothelial NO synthase-deficient mice. Pioglitazone-incorporated NP induced endothelial NO synthase phosphorylation, as demonstrated by Western blot analysis, as well as expression of multiple angiogenic growth factors in vivo, including vascular endothelial growth factor-A, vascular endothelial growth factor-B, and fibroblast growth factor-1, as demonstrated by real-time polymerase chain reaction. Intramuscular injection of pioglitazone (1 mu g/kg) was ineffective, and oral administration necessitated a > 500 mu g/kg per day dose to produce therapeutic effects equivalent to those of pioglitazone-incorporated NP. Conclusion-NP-mediated drug delivery is a novel modality that may enhance the effectiveness of therapeutic neovascularization, surpassing the effectiveness of current treatments for peripheral artery disease with critical limb ischemia. (Arterioscler Thromb Vasc Biol. 2012; 32: 2427-2434.)