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| PPAR-δ Activation Regulates Endothelial Progenitor Cells through Genomic and Non-genomic Activations of the PI3K/Akt Pathway, leading to Vasculogenesis. |
| ¹서울대학교의과대학 심혈관줄기세포 연구실, ²충남대학교의과대학 생리학교실, ³한국과학기술원 생명과학과, ⁴Department of Veterinary and Biomedical Sciences and The Center of Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, 5서울대학교병원 심혈관센터 |
| 한정규¹, 이현숙¹, 양한모¹, 허진¹, 전수인¹, 김주영¹, 조정현², 고규영³, Jeffrey M. Peters⁴, 박경우¹ 5, 조현재¹ 5, 이해영¹ 5, 강현재¹ 5, 오병희¹ 5, 박영배¹ 5, 김효수¹ 5 |
Background: PPARs form a subfamily of the nuclear receptor superfamily and three isoforms have been identified. Among these, PPAR-δ is the least understood subtype. Especially, the impact of PPAR-δ activation in vascular biology is virtually unknown. Thus we investigated the effect of PPAR-δ activation on EPC, vasculogenesis and its signal pathway.
Methods and Results: In Western blot assays, GW501516, a potent and highly selective PPAR-δ agonist, phosphorylated Akt in EPC in PPAR-δ dependent manner, which was reversed by PPAR-δ antisense oligodeoxynucleotides transfection. The Akt phosphorylation occurred in a bimodal pattern at less than 1 hour and at 4-8hours. The late phosphorylation was dependent on transcription, which was suppressed by actinomycin D, whereas the early induction was not. Immunoprecipitation assay showed the early rapid/nontranscriptionally mediated phosphorylation occurred by binding between PPAR-δ and p85α, a regulatory subunit of PI3K. In trypan blue exclusion assay, PPAR-δ agonist (GW501516 or L-165041) treatment enhanced EPC proliferation, and inhibited hypoxia-induced apoptosis. These were reconfirmed by cell cycle and apoptosis FACS. In Matrigel tube formation and transendothelial migration assay, PPAR-δ agonist (GW501516 or L-165041) treated EPCs showed more tube formation and migration. PI3K blocker LY-294002 abolished these several in vitro effects of PPAR-δ activation on EPC. In murine ischemic hindlimb models, transplantation of GW501516-treated human EPCs enhanced blood flow recovery to ischemic limbs compared with vehicle-treated EPCs. Treated mouse EPCs also showed the same effects. In EPCs from PPAR-δ knockout mice, however, GW501516 treatment did not enhance in vivo vasculogenic potential. Systemic administration of GW501516 to mice increased hematopoietic stem cells in bone marrow and EPCs in peripheral. In a corneal neovascularization model, this led to improved vasculogenesis with incorporation of bone marrow-derived cells to new vessels, and in ischemic hindlimb model, limb salvage with better blood flow.
Conclusions: The results of our study suggest that PPAR-δ agonist may be a novel therapeutic option in the treatment of ischemic vascular diseases.
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