Nucleic acids have considerable potential as therapeutic agents in the treatment of pathologies including genetic diseases, viral infections and cancer therapies. The major challenge for the use of nucleic acids in therapy lies in safely delivering these anionic macromolecules to their intended sites of action. The increasing use of viral vectors in Human Gene Therapy clinical trials has emphasized the potential of nucleic acid-based approaches to address the unmet needs of drug-based treatments. While viral vector-based Gene Therapy is on everyone's mind with recently approved Luxturna™, as well as other viral vector-based treatments under Fast Track Designation, it is key to remember that non-viral vectors present considerable advantages in terms of reliability, safety and costs for nucleic-acid based therapies. At Polyplus-transfection ® , we develop powerful non-viral vectors to safely deliver nucleic acids in vivo to target a wide range of tissues, through various routes of administrations. Of these reagents, in vivo-jetPEI ® and its highest quality grade cGMP in vivo-jetPEI ® are acknowledged as a non-viral vector of choice to deliver nucleic acids respectively in animal preclinical studies and in human clinical trials, notably for cancer and immunotherapy.

Leukocyte extravasation is an essential step during the immune response and requires the destabilization of endothelial junctions. We have shown previously that this process depends in vivo on the dephosphorylation of VE-cadherin-Y731. Here, we reveal the underlying mechanism. Leukocyte-induced stimulation of PECAM-1 triggers dissociation of the phosphatase SHP2 which then directly targets VE-cadherin-Y731. The binding site of PECAM-1 for SHP2 is needed for VE-cadherin dephosphorylation and subsequent endocytosis. Importantly, the contribution of PECAM-1 to leukocyte diapedesis in vitro and in vivo was strictly dependent on the presence of Y731 of VE-cadherin. In addition to SHP2, dephosphorylation of Y731 required Ca 2+ -signaling, non-muscle myosin II activation, and endothelial cell tension. Since we found that βcatenin/plakoglobin mask VE-cadherin-Y731 and leukocyte docking to endothelial cells exert force on the VE-cadherin-catenin complex, we propose that leukocytes destabilize junctions by PECAM-1-SHP2-triggered dephosphorylation of VE-cadherin-Y731 which becomes accessible by actomyosin-mediated mechanical force exerted on the VE-cadherin-catenin complex.

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