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Serum Heat Shock Protein 27 (HSP27) has been shown to attenuate genesis of atherosclerosis and levels decrease with advanced disease. The role of extracellular HSP27 following mechanical injury has not been investigated.
Endothelial progenitor cells (EPCs) were treated with recombinant HSP27 or the biologically inactive C1 terminal fragment. Quantitative PCR arrays were used to identify differentially regulated genes in an unbiased fashion. In vitro endothelial scratch assays were used to assess paracrine effect of EPCs on re–endothelialization (RE). HSP27 over–expressing mice were utilized to assess effect of serum HSP27 following femoral artery injury. Finally, HSP27 eluting stents were evaluated in a rabbit carotid artery stenting model.
Differential regulated genes were identified in HSP27 treated EPCs by quantitative PCR arrays. Vascular endothelial growth factor (VEGF) mRNA was confirmed to be 10–fold higher and a 6–fold increase in secretion was observed. The importance of this increased secretion was confirmed in vitro by co–culture of EPCs with endothelial cells following scratch assay. Pre–treatment with HSP27 of EPCs resulted in a 60% reduction in RE time and the effect was blocked by VEGF neutralizing antibodies. In vivo efficacy of HSP27 was assessed in two models. First, HSP27 over–expressing mice demonstrated more robust mobilization of EPCs at time of injury as assessed by flow cytomtery. This was associated with a 67% increase in RE and a 45% reduction in neointima formation at 28 days (0.29± 0.04 vs. 0.55±0.04, p<0.05). Finally, the efficacy of local delivery was tested by implantation of HSP27 eluting stents in rabbit carotid arteries. RE at 7 and 28 days was markedly greater with HSP27 elution (98.3 ± 0.8% vs. 77.3 ± 2.8%; p<0.001). Neointimal formation, while 50% reduced at 7 days (p<0.05), demonstrated a catch–up phenomenon and was not significantly different by 28 days.
Extracellular HSP27 improves paracrine effects of EPCs via up–regulation of the production and secretion of VEGF. Systemic over–expression or local delivery in vivo markedly improves RE following vascular injury resulting in improved arterial remodeling.
Poster Sessions, Expo North
Sunday, March 10, 2013, 3:45 p.m.–4:30 p.m.
Session Title: Preclinical and Translational Research
Abstract Category: 52. TCT@ACC–i2: Translation and Pre–clinical Research
Presentation Number: 2111–240
- 2013 American College of Cardiology Foundation