Comparison of bare metal and statin-coated coils on rates of intra-aneurysmal tissue organization in a rat model of aneurysm

Polymers and Nanoparticles for Statin Delivery: Current Use and Future Perspectives in Cardiovascular Disease

Atherosclerosis-related coronary artery disease (CAD) is one of the leading sources of mortality and morbidity in the world. Primary and secondary prevention appear crucial to reduce CAD-related complications. In this scenario, statin treatment was shown to be clinically effective in the reduction of adverse events, but systemic administration provides suboptimal results. As an attempt to improve bioavailability and effectiveness, polymers and nanoparticles for statin delivery were recently investigated. Polymers and nanoparticles can help statin delivery and their effects by increasing oral bioavailability or enhancing target-specific interaction, leading to reduced vascular endothelial dysfunction, reduced intimal hyperplasia, reduced ischemia-reperfusion injury, increased cardiac regeneration, positive remodeling in the extracellular matrix, reduced neointimal growth and increased re-endothelization. Moreover, some innovative aspects described in other cardiovascular fields could be translated into the CAD scenario. Recent preclinical studies are underlining the effect of statins in the stimulation and differentiation of endogenous cardiac stem cells, as well as in targeting of local adverse conditions implicated in atherosclerosis, and statin delivery through poly-lactic-co-glycolic acid (PLGA) appears the most promising aspect of current research to enhance drug activity. The present review intends to summarize the current evidence about polymers and nanoparticles for statin delivery in the field of cardiovascular disease, trying to shed light on this topic and identify new avenues for future studies.

Intra-aneurysmal embolization of cellulose porous beads to regenerate vessel wall: an experimental study

PURPOSE

Although the treatment of intracranial cerebral aneurysms with detachable coils is now widely accepted, the problem of coil compaction and recanalization remains unsolved. If the vessel wall can be regenerated at the neck orifice of an aneurysm, thereby reducing the blood flow into the aneurysm, the recurrence rate of the aneurysm would decrease. Accordingly, we aimed to insert cellulose porous beads (CPBs) into rat models of external carotid artery (ECA) aneurysm and study their efficacy in promoting vessel wall regeneration.

METHODS

Using a rat aneurysm model, we examined the tissue response to CPBs that were inserted into the ligated ECA sac of rats. The sacs were removed on days 14, 42, 84, and 180 after insertion and subjected to conventional and immunohistochemical examination. We evaluated the tissue response in the ECA sacs and observed the vessel wall regeneration progress.

RESULTS

At the neck orifice of the aneurysm in which the CPB was inserted, a layer of regenerating α-smooth muscle actin-positive spindle cells was observed on day 14. The regenerative cell layer gradually thickened until day 42 and, thereafter, the thickness remained unchanged until day 180. A monolayer of factor VIII-positive cells also appeared at the neck orifice on day 14 and covered the entire orifice until day 180. The CPBs were stably localized in the sac without degradation or signs of inflammation.

CONCLUSION

CPBs may be promising as embolic materials that can induce stable vessel wall regeneration at the neck orifice of an aneurysm without surrounding inflammatory reactions.

Mesenchymal stem cells and endothelial progenitor cells accelerate intra-aneurysmal tissue organization after treatment with SDF-1α-coated coils

Recurrences of aneurysms remain the major drawback of detachable coils for the endovascular treatment of intracranial aneurysms. The aim of the present study is to develop new modified coils, coating the surface of platinum coils with silk fibroin (SF) consisting of stromal cell-derived factor-1α (SDF-1α), and evaluate its acceleration of organization of cavities and reduction of lumen size in a rat aneurysm model. The morphological characteristics of SDF-1α-coated coils were examined using scanning electron microscopy (SEM). Fifty experimental aneurysms were created and randomly divided into five groups: three groups were embolized with SDF-1α-coated coils (8 mm) and two of these groups need transplantation of mesenchymal stem cells (MSCs) or endothelial progenitor cells (EPCs); one group was embolized with bare coils (8 mm) and another group severed as control. After coil implantation for 14 or 28 days, the coils were harvested and histological analysis was performed. SEM photographs showed that SF/SDF-1α-coated coils have uniform size and a thin film compared with bare coils. In the group treated with SDF-1α-coated coils, tissue organization was accelerated and the proliferation of α-smooth muscle actin positive cells was promoted in the aneurysmal sac. Compared with unmodified coils, on day 28, tissue organization was significantly greater in the group treated with SDF-1α-coated coils and MSC or EPC transplantation. These results suggest that SDF-1α-coated coils with MSC or EPC transplantation may be beneficial in the aneurysm healing and endothelialization at the orifice of embolized aneurysm.

Statins are not associated with short-term improved aneurysm healing in a rabbit model of unruptured aneurysms

Background

Owing to their anti-inflammatory effects and ability to stimulate production of extracellular matrix and chemotactic migration of mesenchymal progenitor cells, statins could potentially improve aneurysm healing after endovascular treatment.

Objective

To test the hypothesis that systemic administration of simvastatin would improve aneurysm healing in a rabbit model of unruptured intracranial aneurysms.

Methods

Experimental aneurysms were created in female rabbits and were embolized with platinum coils. Six rabbits served as controls and six rabbits received oral administration of simvastatin. Digital subtraction angiography was used to evaluate stability after embolization. Subjects were euthanized 4 weeks after coil embolization. Histologic samples were examined with a grading system (0–12) based on neck and dome features. Aneurysm occlusion data were compared using a Student t test.

Results

No significant differences in the mean aneurysm size were found between groups. No coil compaction occurred in either group. All aneurysms in both the statin and control groups showed stable occlusion. There were no significant differences in the histologic grade of occlusion in either group (statin group 2.6±0.8 vs control group 2.7±3.2, p=0.94).

Conclusions

Systemic statin administration after platinum coil embolization of unruptured aneurysms in a rabbit model does not improve aneurysm occlusion rates at 4 weeks.

Could Statin Use Be Associated with Reduced Recurrence Rates following Coiling in Ruptured Intracranial Aneurysms?

BACKGROUND AND PURPOSE

A number of studies have examined the role of matrix metalloproteinases in aneurysm healing following endovascular coiling. Because ruptured aneurysms are known to express higher levels of matrix metalloproteinases, we hypothesized that patients with subarachnoid hemorrhage who were on a statin at the time of coil embolization would have lower aneurysm recanalization and retreatment rates than patients not on statins.

MATERIALS AND METHODS

We performed a retrospective chart review of patients who underwent intrasaccular coil embolization of ruptured intracranial aneurysms of ≤10 mm with at least 6 months of imaging follow-up. Patients were separated into 2 groups: 1) those on an oral statin medication at the time of coiling, and 2) those who were not. Outcomes studied were aneurysm recurrence and aneurysm retreatment after endovascular coiling. Student t and χ(2) tests were used for statistical significance of differences between groups.

RESULTS

One hundred thirty-two patients with 132 ruptured aneurysms were included in our study. Sixteen were on statins (12.1%) and 116 were not (87.9%). The recurrence rate was 6.3% in the statin group (1/16) and 36.2% in the nonstatin group (42/107) (P = .02). Unplanned retreatment rates were 6.3% (1/16) for the statin group and 25.9% (30/116) for the nonstatin group (P = .08).

CONCLUSIONS

Statins were associated with a lower rate of aneurysm recurrence following endovascular coiling of small- and medium-sized ruptured aneurysms in this small retrospective study. Further studies are needed to confirm this finding to determine whether statins can be used to reduce recurrence rates in these aneurysms.

Acceleration of aneurysm healing by P(DLLA-co-TMC)-coated coils enabling the controlled release of vascular endothelial growth factor

Since the introduction of the detachable coil in endovascular treatment of intracranial aneurysms, the in-hospital mortality rate has been significantly decreased. Recurrence of the aneurysm remains the major drawback of using detachable coils. We prepared a bioactive coil coated with poly(d,l-lactide)-7co-(1,3-trimethylene carbonate) (P(DLLA-co-TMC)), a novel copolymer for controlling the release of vascular endothelial growth factor (VEGF). Platinum coils were prepared by successive coating with cationic P(DLLA-co-TMC) and anionic heparin. Then, recombinant human VEGF-165 (rhVEGF) was immobilized by affinity binding to heparin. The morphological characteristics and sustained in vitro release of rhVEGF were examined using scanning electron microscopy and enzyme-linked immunosorbent assay, respectively. The efficacy of these novel coils modified by P(DLLA-co-TMC)/rhVEGF was tested using a common carotid artery aneurysm model in rats. Experimental aneurysms were embolized with unmodified, P(DLLA-co-TMC)/heparin-coated or P(DLLA-co-TMC)/rhVEGF-coated platinum coils (n = 18). The coils were removed on days 15, 30 and 90 after insertion, and the histological and immunohistochemical analysis of factor VIII was performed to confirm the presence of endothelial cells in the organized area. In addition, the controlled in vivo release of VEGF was confirmed by Western blotting analysis. The release of VEGF tended to increase during the whole period and no burst release was observed. In the group treated with P(DLLA-co-TMC)/rhVEGF-coated platinum coils, clot organization and endothelial cell proliferation were accelerated. The immunohistochemistry study showed that the expression of factor VIII was found in the P(DLLA-co-TMC)/rhVEGF-coated coil group but not in the other two groups. Furthermore, Western blotting analysis confirmed that the major released VEGF in the aneurysm sac was from the P(DLLA-co-TMC)/VEGF-coated coil. P(DLLA-co-TMC)/rhVEGF-coated platinum coils can promote clot organization and endothelial cell proliferation in a rat aneurysm model.

Inflammation and human cerebral aneurysms: current and future treatment prospects

The formation of cerebral aneurysms and their rupture propensity is of immediate clinical importance. Current management includes observation with expectant management, microsurgical clipping and/or endovascular coiling. The surgical options are invasive and are not without increased risk despite the technological advances. Recent human and animal studies have shown that inflammation plays a critical role in aneurysm formation and progression to rupture. Modulating this inflammatory process may prove to be clinically significant. This review will discuss cerebral aneurysm pathogenesis with a focus on current and future research of potential use of pharmaceutical agents that attenuate inflammation in the aneurysm wall leading to decreased risk of aneurysm rupture.