Abstract 17550: PPAR-δ Activation Induces Angiomyogenesis Through the Potentiation of Endothelial Progenitor Cell Paracrine Network

Abstract

Background Endothelial progenitor cells (EPCs) paracrine network has been known to play a key role in neovascularization. We focused on skeletal muscle regeneration as well as new vessel formation by EPCs and their modulation by PPAR-δ. Methods and Results GW501516 , a PPAR-δ agonist enhanced MMP-9 mRNA expression, protein excretion and enzyme activity among several paracrine factors in EPCs. MMP-9 in conditioned media (CM) from GW501516 treated EPCs degraded IGFBP-3 in Western blot. The CM treatment phosphorylated IGF-1 receptor (R) in HUVECs, enhancing BrdU incorporation, Matrigel tube formation and migration. It also induced proliferation of C2C12 myoblast cells and protected them from hypoxia. Systemic treatment of GW501516 in mice increased MMP-9 expression in EPCs and degraded IGFBP-3 in serum Western. In mice which received bone marrow transplantation (BMT) from WT mice, continuous infusion of GW501516 phosphorylated IGF-1R in ECs and skeletal muscle. It increased capillary density and regenerating myotubes with central nuclei, and decreased muscle fibrosis in MT stain. IF for Ki67 and TUNEL stain demonstrated the in vivo proliferation and protection from apoptosis of ECs and skeletal muscle cells by GW501516. Limb perfusion recovery was also enhanced in LDPI. BMT from MMP-9 KO mice or IGFBP-3 systemic infusion abolished these effects. Intramuscular injection of ex vivo GW501516 treated EPCs to ischemic limbs showed the same effects. But EPCs from MMP-9 KO mice reversed the results. In skin punch wound model, GW501516 systemic administration enhanced wound healing with increased angiogenesis in WT mice, not in MMP-9 KO mice. Conclusion EPC paracrine network through MMP-9 mediated IGF-1 signaling pathway is important in angiomyogenesis, and is potentiated by PPAR-δ activation. Our results suggest PPAR-δ agonist as a good candidate drug for patients with peripheral vascular diseases who need angiomyogenesis for recovery.