Rapamycin-Loaded Leukosomes Reverse Vascular Inflammation

Rationale: Through localized delivery of rapamycin via a biomimetic drug delivery system, it is possible to reduce vascular inflammation, and thus the progression of vascular disease. Objective: Use biomimetic nanoparticles to deliver rapamycin to the vessel wall to reduce inflammation in an in-vivo model of atherosclerosis after a short dosing schedule. Methods and Results: Biomimetic nanoparticles ("leukosomes") were synthesized using membrane proteins purified from activated J774 macrophages. Rapamycin loaded nanoparticles were characterized using dynamic light scattering and were found to have a diameter of 108 +/- 2.3 nm, a surface charge of -15.4 +/- 14.4 mV and a polydispersity index of 0.11 +/ 0.2. For in vivo studies, ApoE-/- mice were fed a high-fat diet for 12 weeks. Mice were injected with either phosphate-buffered saline, free rapamycin (5mg/kg), or rapamycin-loaded leukosomes (Leuko-Rapa) (5mg/kg) once daily for seven days. In mice treated with Leuko-Rapa flow cytometry of disaggregated aortic tissue revealed fewer proliferating macrophages in the aorta (15.6 +/- 9.79 %) compared to untreated mice (30.2 +/- 13.34 %) and rapamycin alone (26.8 +/- 9.87 %). Decreased macrophage proliferation correlated with decreased levels of monocyte chemoattractant protein (MCP-1) and Il-b1 in mice treated with Leuko-Rapa. Furthermore, Leuko-Rapa treated mice also displayed significantly decreased MMP activity in the aorta (Mean Difference 2554 plus minus 363.9, p= 9.95122E-06). No significant changes in metabolic or inflammation markers observed in liver metabolic assays. Histological analysis showed improvements in lung morphology, with no alterations in heart, spleen, lung, or liver in Leuko-Rapa treated mice. Conclusions: We showed that our biomimetic nanoparticles showed a decrease in proliferating macrophage population that was accompanied by the reduction of key pro-inflammatory cytokines and changes in plaque morphology. This proof-of-concept showed that our platform was capable of suppressing macrophage proliferation within the aorta after a short dosing schedule (seven days) and with a favorable toxicity profile. This treatment could be a promising intervention for the acute stabilization of late-stage plaques.