Background-Prolonged myocardial ischemia results in cardiomyocyte loss despite successful revascularization. We have reported that retrograde application of embryonic endothelial progenitor cells (eEPCs) provides rapid paracrine protection against ischemia-reperfusion injury. Here, we investigated the role of thymosin β4 (Tβ4) as a mediator of eEPC-mediated cardioprotection.

Alterations in glomerular podocyte cell-cell and cell-matrix contacts are key events in progressive glomerular failure. Integrin-linked kinase (ILK) has been implicated in podocyte cell-matrix interaction and is induced in proteinuria. For evaluation of ILK function in vivo, mice with a Cre-mediated podocyte-specific ILK inactivation were generated. These mice seemed normal at birth but developed progressive focal segmental glomerulosclerosis and died in terminal renal failure. The first ultrastructural lesions that are seen at onset of albuminuria are glomerular basement membrane (GBM) alterations with a significant increase in true harmonic mean GBM thickness. Podocyte foot process effacement and loss of slit diaphragm followed with progression to unselective proteinuria. No significant reduction of slit membrane molecules (podocin and nephrin), key GBM components (fibronectin, laminins, and collagen IV isoforms), or podocyte integrins could be observed at onset of proteinuria. However, ␣3-integrins were relocalized into a granular pattern along the GBM, consistent with altered integrin-mediated matrix assembly in ILK-deficient podocytes. As the increased GBM thickness precedes structural podocyte lesions and key components of the GBM were expressed at comparable levels to controls, these data suggest an essential role of ILK for the close interconnection of GBM structure and podocyte function.

Whereas HO-1 deficiency exacerbates post-ischemic cardiac inflammation in mice, hHO-1 gene therapy attenuates inflammation after ischemia and reperfusion in murine and porcine hearts. Regional hHO-1 gene therapy provides cardioprotection in a pre-clinical porcine ischemia/reperfusion model.

Retroinfusion of rAAV.VEGF-A alone induces angiogenesis, but fails to enhance collateralization and perfusion, unless PDGF-B is cotransfected. In addition to neovascularization, rAAV.VEGF-A/PDGF-B improves regional and global myocardial function in hibernating myocardium.

Embryonal endothelial progenitor cells (eEPCs) are capable of inducing therapeutic angiogenesis in a chronic hind limb model. However, the proportion of eEPCs recruited to the ischemic tissue appears to be a limiting step for the induction of cell-based therapeutic neovascularization. In the present study, we primed eEPCs with the human cathelicidin LL37 (hCAP-18) ex vivo to selectively enhance the eEPC-dependent gain of perfusion in vivo and elucidated the mechanism of action of LL37 on eEPCs. Seven days after femoral artery excision, 5 3 10 6 eEPCs (wt, wild type; p65t, transiently p65 transient; p65s, stable p65-transfected; LL37-eEPCs, LL37 peptide preincubated) were retroinfused into the anterior tibial vein. Recruitment of diI-labeled eEPCs in the ischemic gastrocnemic muscle was investigated 2 days later, whereas collateral growth and perfusion score (obtained by fluorescent microspheres) were assessed at day 7 and day 35 and are given as percentage of day 7 level. Capillary/muscle fiber ratio in the ischemic lower limb was obtained at day 35. Embryonic EPC recruitment in vitro and in vivo was found elevated after LL37 and p65t pretreatment, but not in p65s-eEPCs displaying increased IkBa or after LL37 in IkB-DN overexpressing eEPCs. Using LL37-and p65t-eEPCs, collateral growth (181 6 10% and 165 6 8%, respectively) surpassed that of wt-eEPCs (135 6 7%), increasing perfusion ratio (208 6 20% and 210 6 17% vs. 142 6 12% in wt-eEPCs, respectively), whereas p65s-eEPCs exerted no additive effect (collateral growth 130 6 8%; perfusion ratio 155 6 15%). Moreover, p65t-eEPCinduced neovascularization was abrogated by blocking antibodies against E-selectin and P-selectin glycoprotein ligand-1 (PSGL-1). We conclude that NF kB activation by LL37 or transient p65-transfection increases functionally relevant eEPC recruitment to ischemic muscle tissue via induction of PSGL-1 and E-selectin. STEM CELLS

Retroinfusion of Ad2/Hif-1α/VP16, combining a master pro-angiogenic protein with regional myocardial application, may offer an efficient approach to cardiac gene therapy of chronic ischemic cardiomyopathy.

Therapeutic neovascularization is a concept well validated in animal models, however, without clear-cut success in clinical studies. To achieve prolonged transgene expression, recombinant adeno-associated virus (rAAV) was used in a chronic ischemic hind-limb model and the human antimicrobial peptide cathelicidin (LL-37/hCAP-18) was used as proangiogenic factor. Seven days after femoral artery excision, 0.5 x 10(11) rAAV particles encoding for green fluorescent protein (rAAV.GFP), cathelicidin (rAAV.cath), or vascular endothelial growth factor A (rAAV.VEGF-A) were retroinfused into the anterior tibial vein of rabbits (n = 5 per group). In addition, one rAAV.cath-treated group obtained a constant infusion with the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin into the ischemic tissue starting on day 7. On day 7 and day 35 angiography of both hind limbs was performed for collateral quantification and frame count score (cinedensitometry). Capillary-to-muscle fiber ratios were obtained on day 35. Compared with controls, application of rAAV.cath induced a gain of perfusion (153 +/- 12 vs. 107 + 9% of day 7 controls) via increased collateral growth (length index, 161 +/- 14 vs. 97 +/- 9%, controls), but no significant capillary growth (1.16 +/- 0.09 vs. 0.99 +/- 0.08, controls). Wortmannin application completely abolished the effects of rAAV.cath, indicating the involvement of the PI3K signal pathway. In conclusion, rAAV-mediated cathelicidin expression is capable of inducing functionally relevant neovascularization, preferentially by collateral growth. The rAAV-based vectors as long-expressing vector expression systems and cathelicidin as proangiogenic factor provide a promising new combination in the treatment of peripheral artery disease.

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