Abstract 5603: LL-37 Improves Adhesion and Therapeutic Effects of Embryonic EPCs in Chronic Ischemia (Rabbit Model)

Abstract

Therapeutic neovascularization can be achieved by vascular growth factors or by mobilisation or exogenous application of endothelial progenitor cells. We could already demonstrate that murine embryonal EPCs (eEPCs) are capable of inducing therapeutic angiogenesis in a chronic hindlimb model (rabbit). Furthermore we could show that homing of these cells can be enhanced by transient overexpression of the pro-inflammatory transcription factor nfkb subunit p65. In the present study, we aimed at peptide activation of NF kappa b in the eEPC population. For this purpose, we used the cathelicidin (LL-37), which binds to the receptor FPRL1 subsequently activating NF kappa B. Methods: Adhesion of wildtype (wt), p65 transfected (p65t) and LL37-activated eEPCs (100 μ g, LL37-eEPC) was examined in vitro in flow chamber experiments. In rabbits, at d7 after femoral artery excision, 5×106 eEPCs (n=5 per group) were retroinfused into the anterior tibial vein. At d7 and 35 angiography of both hindlimbs was performed for collateral quantification and frame count score (cinedensitometry, % of d7 level each). Capillary/muscle fiber (C/MF) ratio was assessed at d35. Results: eEPC adhesion was more than doubled after pre-treatment with LL-37 (326±13 cells/field vs. 153±19, wt). In vivo, no difference was found in C/MF ratio of p65t-eEPC- or wt-eEPC-treatment (1,44±0.10 vs. 1.41±0.09, respectively), whereas LL-37-eEPC treated animals showed a significant effect (1,93±0,13). Collateral growth (wt-eEPCs 129±5% vs. 109±4% in controls), was elevated by p65t-eEPCs (146±4%), and further increased in LL37-ePCs (179±8%). The wt-eEPC-induced gain of perfusion (151±5% vs. 109±10% in controls) was similarly improved by p65t-eEPC transfusion (205±24%) and LL-37-preincubation (244±22%). We conclude that induction of a pro-inflammatory phenotype in eEPCs by either transient p65 transfection or LL37 enhances recruitment and subsequent neovascularization in ischemic tissue.