Nanotechnology And Nitric Oxide: A Novel Approach To Inhibit Neointimal Hyperplasia

Muneera R Kapadia¹, Lesley A Chow¹, Sadaf S Ahanchi¹, Jason Eng¹, Jozef Murar¹, Janet Martinez¹, Nick D Tsihlis¹, Daniel A Popowich¹, Qun Jiang¹, James F Hulvat¹, Samuel I Stupp¹, Joseph Hrabie², Joseph E Saavedra², Larry K Keefer², Melina R Kibbe.^1
1Northwestern University, Chicago, IL;²National Cancer Institute, Frederick, MD.

OBJECTIVES: Nitric oxide (NO) has been shown to inhibit neointimal hyperplasia following arterial interventions in several animal models. However, to date NO-based therapies have not been used in the clinical arena. Our objective is to combine nanotechnology with NO chemistry to create a novel, more potent NO-releasing therapy that can be used clinically. The aim of this study is to evaluate perivascular application of spontaneous self-assembling NO-releasing nanofiber gels in the prevention of neointimal hyperplasia.

METHODS: Gels consisted of a heparin-binding peptide amphiphile (HBPA), heparin, and a diazeniumdiolate (DPTANO or PROLINO). NO release was evaluated by the Greiss reaction. In vitro vascular smooth muscle cell (VSMC) proliferation and apoptosis were assessed by 3H-thymidine incorporation and Guava PCA. Neointimal hyperplasia was evaluated using the rat carotid artery injury model at 14 days (n=6/group). Inflammation and proliferation were examined with immunofluorescent staining at 3 days. Endothelialization was assessed by Evans blue injection at 7 days.

RESULTS: Both DPTANO and PROLINO nanofiber gels released NO for 4 days. In vitro, DPTANO inhibited VSMC proliferation and induced apoptosis to a greater extent than PROLINO. However, the DPTANO nanofiber gel only reduced neointimal hyperplasia by 45% (intima/media area ratio [I/M] 0.45±0.07) whereas the PROLINO nanofiber gel reduced neointimal hyperplasia by 77% (I/M 0.19±0.03, P<.05) versus control (injury alone I/M 0.83±0.07; P<.05). Both DPTANO and PROLINO nanofiber gels significantly inhibited proliferation in vivo (1.06±0.30, 0.19±0.11 vs injury alone, 2.02±0.20, P<.05), yet had minimal effect on apoptosis. Only the PROLINO nanofiber gel inhibited inflammation (monocytes and leukocytes). Both NO-releasing nanofiber gels stimulated re-endothelialization.

CONCLUSIONS Perivascular application of NO-releasing self-assembling nanofiber gels is an effective and simple therapy to prevent neointimal hyperplasia following arterial injury. Our study demonstrates that the PROLINO nanofiber gel is more robust and resulted in less inflammation than the DPTANO nanofiber gel. This therapy has great clinical potential to prevent neointimal hyperplasia following open vascular interventions in patients.