MK2 inhibitory peptide delivered in nanopolyplexes prevents vascular graft intimal hyperplasia

Nanopolyplexes formulated from a pH-responsive, endosomolytic polymer with a peptide inhibitor of MAPKAP kinase 2 block inflammatory and migratory signaling in vascular smooth muscle cells and prevent intimal hyperplasia in human saphenous vein grafts. Nano keeps MK2 inhibitor intact, on-target A peptide, currently in clinical trials, that can penetrate cells and block the activity of MAPKAP kinase 2 (MK2) may be able to stop inflammation and fibrosis after vein grafting, but it has low bioavailability and is degraded easily once inside the cell. To more effectively translate this inhibitory peptide, called MK2i, Evans et al. formulated it in electrostatically complexed nanoparticles—nanopolyplexes—for delivery to vascular cells and tissues. The MK2i nanopolyplexes were taken up readily by vascular smooth muscle cells and endothelial cells in human saphenous veins and significantly inhibited neointima formation ex vivo. In rabbit vein grafts, treatment with the MK2 nanopolyplexes prevented intimal hyperplasia for 1 month after transplant; by contrast, free MK2i peptide had no effect. Thus, complexing the MK2 inhibitor peptide with an endosomolytic polymer could improve long-term graft patency. Both treatments were able to block macrophage recruitment and/or signaling in vivo, possibly leading to less inflammation. In human saphenous veins, the MK2i nanopolyplexes similarly reduced proinflammatory cytokines and were also shown to reduce vascular smooth muscle cell migration. Such new insights into the effects of MK2i on intimal hyperplasia could open doors to new therapeutic options in this multifactorial disease. Furthermore, this nanoencapsulation approach could be broadly applied to other therapeutic cell-penetrating peptides to prolong bioavailability and enhance stability in vivo. Autologous vein grafts are commonly used for coronary and peripheral artery bypass but have a high incidence of intimal hyperplasia (IH) and failure. We present a nanopolyplex (NP) approach that efficiently delivers a mitogen-activated protein kinase (MAPK)–activated protein (MAPKAP) kinase 2 inhibitory peptide (MK2i) to graft tissue to improve long-term patency by inhibiting pathways that initiate IH. In vitro testing in human vascular smooth muscle cells revealed that formulation into MK2i-NPs increased cell internalization, endosomal escape, and intracellular half-life of MK2i. This efficient delivery mechanism enabled MK2i-NPs to sustain potent inhibition of inflammatory cytokine production and migration in vascular cells. In intact human saphenous vein, MK2i-NPs blocked inflammatory and migratory signaling, as confirmed by reduced phosphorylation of the posttranscriptional gene regulator heterogeneous nuclear ribonucleoprotein A0, the transcription factor cAMP (adenosine 3′,5′-monophosphate) element–binding protein, and the chaperone heat shock protein 27. The molecular effects of MK2i-NPs caused functional inhibition of IH in human saphenous vein cultured ex vivo. In a rabbit vein transplant model, a 30-min intraoperative graft treatment with MK2i-NPs significantly reduced in vivo IH 28 days posttransplant compared with untreated or free MK2i–treated grafts. The decrease in IH in MK2i-NP–treated grafts in the rabbit model also corresponded with decreased cellular proliferation and maintenance of the vascular wall smooth muscle cells in a more contractile phenotype. These data indicate that nanoformulated MK2 inhibitors are a promising strategy for preventing graft failure.