Stent-mediated methylprednisolone delivery reduces macrophage contents and in-stent neointimal formation

Prednisolone-containing liposomes accumulate in human atherosclerotic macrophages upon intravenous administration

Drug delivery to atherosclerotic plaques via liposomal nanoparticles may improve therapeutic agents' risk-benefit ratios. Our paper details the first clinical studies of a liposomal nanoparticle encapsulating prednisolone (LN-PLP) in atherosclerosis. First, PLP's liposomal encapsulation improved its pharmacokinetic profile in humans (n=13) as attested by an increased plasma half-life of 63h (LN-PLP 1.5mg/kg). Second, intravenously infused LN-PLP appeared in 75% of the macrophages isolated from iliofemoral plaques of patients (n=14) referred for vascular surgery in a randomized, placebo-controlled trial. LN-PLP treatment did however not reduce arterial wall permeability or inflammation in patients with atherosclerotic disease (n=30), as assessed by multimodal imaging in a subsequent randomized, placebo-controlled study. In conclusion, we successfully delivered a long-circulating nanoparticle to atherosclerotic plaque macrophages in patients, whereas prednisolone accumulation in atherosclerotic lesions had no anti-inflammatory effect. Nonetheless, the present study provides guidance for development and imaging-assisted evaluation of future nanomedicine in atherosclerosis.

FROM THE CLINICAL EDITOR

In this study, the authors undertook the first clinical trial using long-circulating liposomal nanoparticle encapsulating prednisolone in patients with atherosclerosis, based on previous animal studies. Despite little evidence of anti-inflammatory effect, the results have provided a starting point for future development of nanomedicine in cardiovascular diseases.

Stent hypersensitivity and infection in sinus cavities

Persistent mucosal inflammation, granulation tissue formation, hypersensitivity, and multifactorial infection are newly described complications of retained drug-eluting stents from endoscopic sinus surgery for refractory rhinosinusitis. In an important report published in Allergy and Rhinology, a 45-year-old male patient suffering from recalcitrant chronic rhinosinusitis underwent functional endoscopic sinus surgery and was found, for the first time, to have steroid-eluting catheters that were inadvertently left in the ethmoid and frontal sinuses. The retained catheters had caused persistent mucosal inflammation and formation of granulation tissue denoting hypersensitivity reaction. These consequences had induced perpetuation of symptoms of chronic rhinosinusitis. Meticulous removal of the retained stents with the nitinol wings from inflamed tissues of the frontal, ethmoidal, and sphenoethmoidal recesses in which they were completely imbedded was successfully performed without polypoid regrowth. Cultures of specimens taken from both left and right stents showed heavy growth of Stenotrophomonas maltophilia and moderate growth of Klebsiella oxytoca, coagulase negative Staphylococcus, and beta-hemolytic Streptococcus anginosus. Fungal infection was not detected. The current knowledge and experience regarding stent hypersensitivity and infection in relation with the use of stents in sinus cavities is reviewed.

Stent‐based tempamine delivery on neointimal formation in a porcine coronary model

BACKGROUND

Tempamine is one of new class of antioxidant agents, the nitroxides, which have shown a wide range of biological effects like suppressing free radical driven reactions to maintain cell functions. The objectives of this study were to evaluate the effect of a biodegradable polymer coated stent loaded with tempamine on in-stent neointimal formation.

METHODS

Stainless steel stents were dip coated in biodegradable elastomeric poly (ester-amide) (co-PEA) or in polymer solution mixed with 50% (wt%) and 100% (wt%) tempamine. One group 100% (wt%) tempamine loaded stents were further dip coated in co-PEA polymer to form a top layer. Stainless steel bare, polymer-only, and different doses tempanine coated stents were implanted into porcine coronary arteries with a stent to artery ratio 1.2:1. Histomorphometric analysis was performed at 5 days and 6 weeks respectively.

RESULTS

Histomorphometric analysis showed that the bare, polymer-only and tempamine-coated stents elicited a similar tissue response at 5 days. At 6 weeks, the peri-strut inflammation and neointimal hyperplasia of polymer-only stents were comparable to the bare stents. Compared to the bare stents, 50% tempanine coated stents had a trend to decrease the arterial injury (0.62 +/- 0.41 versus 0.34 +/- 0.18, P = 0.075) and neointimal hyperplasia (1.80 +/- 0.77 versus 1.27 +/- 0.39 mm2, P = 0.085). However, 100% tempanine coated showed significantly increased inflammatory response and neointimal formation.

CONCLUSION

These co-PEA polymer coatings showed a biocompatible performance. Loaded with 50% tempamine had a trend to decrease neointimal hyperplasia. The 100% tempamine for stent-based delivery may have potential cytotoxic effects to arterial wall. Using a co-PEA polymer topcoat could effectively abolish these side effects.

Avoiding restenosis: is there a role for glucocorticoids in the drug-eluting stent era?

Restenosis is an important limitation of percutaneous coronary interventions (PCI). In-stent restenosis is mainly due to neointimal hyperplasia, a proliferative process modulated by inflammatory mechanisms. Numerous technical and pharmacological means have been tested to reduce restenosis rates, with frequently disappointing clinical results. Drug-eluting stents (DES) have demonstrated a high efficacy in reducing restenosis, but there are some associated problems that limit its generalized utilization. Glucocorticoids (GC), as potent anti-inflammatory agents, may exert beneficial effects on neointimal proliferation. Clinical studies with oral and intracoronary GC therapy have demonstrated reduction in restenosis rates in selected patients. Although further investigations are warranted, GC might have a potential role for restenosis prevention in selected cases.