Simple new method for making a rat carotid artery post-angioplasty stenosis model

How to Establish a Minimal Invasive and Stable Carotid Artery Stenosis Rabbit Model? A Simple and Effective Carotid Artery Balloon Strain Technique

Background: The objective of this study is to establish a minimally invasive technique to create a stable carotid artery stenosis rabbit model. This article summarizes the specific methods and key points of this technology. Methods: The experiment studied a rabbit that was anesthetized through the vein. After the femoral artery was exposed, a minimally invasive needle was used to puncture the femoral artery, then the sheath was placed into the artery. We primarily put a catheter in the ascending aorta for angiography and then used a PT2 guidewire for super-selection. The PT2 guidewire was retained, and a balloon was placed in the right common carotid artery (CCA) through a guidewire to inflate it three times. Six rabbits in the 2- (2W) and 4-week (4W) groups were examined at 14 and 28 days, respectively. The rabbits in the control group received angiography at the beginning and 28 days later but without balloon injury. After angiography assessment, specimens of right CCA were dissected. Pathological and immunohistochemical examinations were performed on the collected specimens, and iFlow analysis was performed as well. Results: All the 18 animals which survived were observed. The rabbits in the 2W and 4W groups showed stenosis of the right CCA. Digital subtraction angiography showed the diameter was lower than that in the control group (1.04 ± 0.1, 0.71 ± 0.12, and 1.83 ± 0.08 mm in 2W, 4W, and control group, P < 0.05). Pathology also suggested carotid stenosis and obvious intimal hyperplasia. The results of immunohistochemistry showed that α-smooth muscle actin was highly expressed in the 2W and 4W groups, and the integrated optical density (IOD) value was higher than that in the control group (14,807.11 ± 1,822.3, 22,245.96 ± 1,212.82, and 6,537.16 ± 1,186.62 in the 2W, 4W, and control group, P < 0.05). Meanwhile, a cluster of differentiation 31 (CD31) was low expressed in the 2W and 4W groups, and the IOD value was lower than that in the control group (519.14 ± 44.4, 1,029.64 ± 98.48, and 1,502.05 ± 88.79 in the 2W, 4W, and control group, P < 0.05), which suggested endothelial damage and partial repair. The analysis by iFlow showed that the time-to-peak after balloon strain in the 2W and 4W groups were longer than that in the control group. Conclusion: We established a minimally invasive, effective, and safe method to establish a carotid artery stenosis rabbit model. The highlights of this technology were the application of minimally invasive methods, reducing surgical bleeding, infection, and related complications. This technology avoided the influence of tissue around CCA in the traditional carotid artery balloon injury model, which might lead to more accurate treatment outcomes.

Asymmetric radial expansion and contraction of rat carotid artery observed using a high-resolution ultrasound imaging system

The geometry of carotid artery bifurcation is of high clinical interest because it determines the characteristics of blood flow that is closely related to the formation and development of atherosclerotic plaque. However, information on the dynamic changes in the vessel wall of carotid artery bifurcation during a pulsatile cycle is limited. This pilot study investigated the cyclic changes in carotid artery geometry caused by blood flow pulsation in rats. A high-resolution ultrasound imaging system with a broadband scanhead centered at 40 MHz was used to obtain longitudinal images of the rat carotid artery. A high frame rate retrospective B-scan imaging technique based on the use of electrocardiogram to trigger signal acquisition was used to examine precisely the fast arterial wall motion. Two-dimensional geometry data obtained from nine rats showed that the rat carotid artery asymmetrically contracts and dilates during each cardiac cycle. Systolic/diastolic vessel diameters near the upstream and downstream regions from the bifurcation were 0.976 ± 0.011/0.825 ± 0.015 mm and 0.766 ± 0.015/0.650 ± 0.016 mm, respectively. Their posterior/anterior wall displacement ratios in the radial direction were 41.0 ± 14.9% and 2.9 ± 1.6%, respectively. These results indicate that in the vicinity of bifurcation, the carotid artery favorably expands to the anterior side during the systolic phase. This phenomenon was observed to be more prominent in the downstream region near the bifurcation. The cyclic variation pattern in wall movement varies depending on the measurement site, which shows different patterns at far upstream and downstream of the bifurcation. The asymmetric radial expansion and contraction of the rat carotid artery observed in this study may be useful in studying the hemodynamic etiology of cardiovascular diseases because the pulsatile changes in vessel geometry may affect the local hemodynamics that determines the spatial distribution of wall shear stress, one of important cardiovascular risk factors. Further systematic study is needed to clarify the effects of wall elasticity, branch angle and vessel diameter ratio on the asymmetric wall motion of carotid artery bifurcation.

Cilostazol activates function of bone marrow-derived endothelial progenitor cell for re-endothelialization in a carotid balloon injury model

BACKGROUND

Cilostazol(CLZ) has been used as a vasodilating anti-platelet drug clinically and demonstrated to inhibit proliferation of smooth muscle cells and effect on endothelial cells. However, the effect of CLZ on re-endothelialization including bone marrow (BM)-derived endothelial progenitor cell (EPC) contribution is unclear. We have investigated the hypothesis that CLZ might accelerate re-endothelialization with EPCs.

METHODOLOGY/PRINCIPAL FINDINGS

Balloon carotid denudation was performed in male Sprague-Dawley rats. CLZ group was given CLZ mixed feed from 2 weeks before carotid injury. Control group was fed normal diet. CLZ accelerated re-endothelialization at 2 weeks after surgery and resulted in a significant reduction of neointima formation 4 weeks after surgery compared with that in control group. CLZ also increased the number of circulating EPCs throughout the time course. We examined the contribution of BM-derived EPCs to re-endothelialization by BM transplantation from Tie2/lacZ mice to nude rats. The number of Tie2-regulated X-gal positive cells on injured arterial luminal surface was increased at 2 weeks after surgery in CLZ group compared with that in control group. In vitro, CLZ enhanced proliferation, adhesion and migration activity, and differentiation with mRNA upregulation of adhesion molecule integrin αvβ3, chemokine receptor CXCR4 and growth factor VEGF assessed by real-time RT-PCR in rat BM-derived cultured EPCs. In addition, CLZ markedly increased the expression of SDF-1α that is a ligand of CXCR4 receptor in EPCs, in the media following vascular injury.

CONCLUSIONS/SIGNIFICANCE

CLZ promotes EPC mobilization from BM and EPC recruitment to sites of arterial injury, and thereby inhibited neointima formation with acceleration of re-endothelialization with EPCs as well as pre-existing endothelial cells in a rat carotid balloon injury model. CLZ could be not only an anti-platelet agent but also a promising tool for endothelial regeneration, which is a key event for preventing atherosclerosis or restenosis after vascular intervention.

Cerebral artery restenosis following transluminal balloon angioplasty for vasospasm after subarachnoid hemorrhage

Background:

Although percutaneous transluminal angioplasty (PTA) is a widely used less invasive method to treat coronary artery stenosis, 10% of treated patients experience restenosis. Restenosis also occurs in approximately 5% of patients subjected to carotid artery stenting. Animal and human data suggested that restenosis is a response to injury incurred during PTA. As PTA has come into wide use to manage symptomatic cerebral vasospasm after subarachnoid hemorrhage (SAH) we studied the incidence of restenosis after PTA for cerebral vasospasm.

Methods:

Our study population consisted of 32 patients who had undergone PTA. They were followed by cerebral or 3DCT angiography or MRA for 6 126 months post-PTA (mean 48.65 months) to diagnose restenosis of the cerebral artery. We compared the size of the cerebral artery on the PTA and the contralateral side.

Results:

All 32 patients underwent successful PTA of 38 vascular territories and all manifested angiographic improvement of vasospasm. None suffered restenosis during the follow up period.

Conclusion:

PTA resulted in a significant improvement in the vessel diameter in patients with vasospasm after SAH and they did not suffer restenosis in the course of prolonged follow-up.

In vitro and in vivo platelet targeting by cyclic RGD-modified liposomes

Cell-selective delivery using ligand-decorated nanoparticles is a promising modality for treating cancer and vascular diseases. We are developing liposome nanoparticles surface-modified by RGD peptide ligands having targeting specificity to integrin GPIIb-IIIa. This integrin is upregulated and stimulated into a ligand-binding conformation on the surface activated platelets. Activated-platelet adhesion and aggregation are primary events in atherosclerosois, thrombosis, and restenosis. Hence, platelet-targeted nanoparticles hold the promise of vascular site-selective delivery of drugs and imaging probes. Here, we report in vitro and ex vivo microscopy studies of platelet-targeting by liposomes surface-modified with a cyclic RGD peptide. The peptide-modified liposomes were labeled either with a lipophilic fluorophore or with lipid-tethered Nanogold(R). For in vitro tests, coverslip-adhered activated human platelets were incubated with probe-labeled liposomes, followed by analysis with fluorescence microscopy, phase contrast microscopy, and scanning electron microscopy (SEM). For in vivo tests, the liposomes were introduced within a catheter-injured carotid artery restenosis model in rats and post-euthanasia, the artery was imaged ex vivo by fluorescence microscopy and SEM. All microscopy results showed successful platelet-targeting by the peptide-modified liposomes. The in vitro SEM results also enabled visualization of nanoscopic liposomes attached to activated platelets. The results validate our nanoparticle design for site-selective vascular delivery.