Endothelial injury and vascular dysfunction associated with the Fogarty balloon catheter

Ovine Iliac Vein Model for Endovascular Thrombectomy of Acute Deep Venous Thrombosis

An ovine iliac vein thrombosis model was devised to test a wall-contacting rotational thrombectomy device. Thrombosis was successfully induced in 9 sheep with an average clot length of 31 mm ± 12 and >60% vessel occlusion on angiography. The thrombus was subsequently removed, maintaining normal intraoperative pulmonary arterial pressure (5.9 mm Hg ± 3.6) and complete distal reperfusion after thrombectomy. Additionally, the sheep were without signs of vascular trauma or embolic complications on gross necropsy and histopathologic analysis. The findings from this study support the use of an ovine iliac deep vein thrombosis model for testing of a lower extremity thrombectomy device.

Janus Kinase 3 Deficiency Promotes Vascular Reendothelialization-Brief Report

[Figure: see text].

Trombectomia com cateter de Fogarty no tratamento da tromboflebite jugular experimental em eqüinos

Trombose da veia jugular é problema freqüente na medicina eqüina, implicando muitas vezes em conseqüências fatais. O objetivo deste trabalho foi avaliar em eqüinos a aplicabilidade da trombectomia com cateter de Fogarty, técnica rotineiramente empregada pela medicina humana, no restabelecimento da perviedade vascular. Foram utilizados 10 eqüinos divididos em dois grupos de cinco animais, em que se induziu a trombose da veia jugular direita, através do acesso cirúrgico à veia e aplicação de sutura estenosante e injeção de glicose a 50%. No grupo controle avaliou-se a evolução da tromboflebite sem qualquer tipo de intervenção terapêutica. Os animais do grupo tratado foram submetidos à trombectomia com cateter de Fogarty. Foram avaliados os parâmetros clínicos gerais, regionais, ultra-sonográficos e angiográficos, nos momentos pré-indução (M-PRÉ), indução da trombose (MTI) e 10 dias de evolução da trombose (M10). A técnica empregada induziu a tromboflebite, que obstruiu completamente um segmento da veia jugular de todos os animais. Os animais do grupo controle mantiveram os trombos obstruindo totalmente o lume vascular até o final do período de avaliação, sendo que avaliações regionais mostraram principalmente o edema parotídeo e o ingurgitamento vascular, cranial à tromboflebite da veia jugular. O grupo tratado apresentou as veias jugulares pérvias ao final do experimento, confirmadas pelos exames ultra-sonográficos e angiográficos, com remissão total dos sinais clínicos. Concluiu-se que a técnica da trombectomia com cateter de Fogarty foi eficiente na desobstrução da veia jugular submetida à trombose experimental.

Poly(N-isopropylacrylamide) copolymer films as vehicles for the sustained delivery of proteins to vascular endothelial cells

The aim of this study was to establish the capacity of thermoresponsive poly(N-isopropylacrylamide) copolymer films to deliver bioactive concentrations of vascular endothelial growth factor (VEGF165) to human aortic endothelial cells (HAEC) over an extended time period. Films were prepared using a 50:50 (w/w) mixture of non-crosslinkable and crosslinkable copolymers of the following monomer compositions (w/w): 85:15, N-isopropylacrylamide (NiPAAm):N-tert-butylacrylamide (NtBAAm); and 85:13:2 NiPAAm:NtBAAm:acrylamidobenzophenone (ABzPh, crosslinking agent), respectively. After crosslinking by UV irradiation, the ability of films to incorporate a fluorescently labeled carrier protein (FITC-labeled BSA, 1 mg loaded per film), at 4 degrees C, was first established. Incorporation into the matrix was confirmed by the observation that increasing film thickness from 5 to 10 microm increased release from collapsed films at 37 degrees C (1.76 +/- 0.15 and 10.98 +/- 3.38 microg/mL, respectively, at 24 h postloading) and that this difference was maintained at 5 days postloading (1.81 +/- 0.25 and 13.8 +/- 2.3 microg/mL, respectively). Incorporation was also confirmed by visualization using confocal microscopy. When 10-microm films were loaded with a BSA solution (1 mg/mL) containing VEGF165 (3 microg/mL), sustained release of VEGF165 was observed (10.75 +/- 3.11 ng at 24 h; a total of 31.32 +/- 8.50 ng over 7 days). Furthermore, eluted VEGF165 increased HAEC proliferation by 18.2% over control. The absence of cytotoxic species in medium released from the copolymer films was confirmed by the lack of effect of medium (incubated with copolymer films for 3 days) on HAEC viability. In conclusion this study has shown that NiPAAm:NtBAAm copolymers can be loaded with a therapeutic protein and can deliver bioactive concentrations to human vascular endothelial cells over an extended time period.

In vitro evaluation of vascular endothelial growth factor (VEGF)-eluting stents

BACKGROUND

Vascular endothelial growth factor (VEGF) is a specific endothelial cell mitogen. It promotes re-endothelialisation of the damaged vessel surface seen after stenting. Stent thrombosis and in-stent restenosis are partly related to endothelial denudation caused by stent implantation. We propose using hydrocarbon polymer-coated stents immersed in VEGF to speed re-endothelialisation and reduce the risk of stent thrombosis and restenosis.

METHODS

Stents (3 x 20 mm) were immersed in VEGF solutions and maximal VEGF absorption calculated. VEGF release from these stents was measured in a perfusion circuit. Delivery of VEGF to arterial wall was measured. Sterile VEGF-loaded stents were cultured with human umbilical vein endothelial cells.

RESULTS

18.5 +/- 4.1 microg VEGF was absorbed, 80% of which was released over 9 days; 11 +/- 6.8% of the initial VEGF loaded was delivered to the vessel wall. Cells exposed to VEGF-eluting stents showed an 11% increase in growth relative to controls.

CONCLUSION

VEGF may be a candidate for stent-based delivery and may increase the rate of endothelialisation in vivo.

Dexamethasone suppresses vascular smooth muscle cell proliferation

BACKGROUND

Experimental studies in vivo have demonstrated that dexamethasone inhibits neointimal hyperplasia following arterial injury. The mechanisms of this inhibition have not been clearly defined. Our objective was to test the hypothesis that dexamethasone directly suppresses smooth muscle cell (SMC) proliferation by inhibiting cell cycle progression and the expression of key cell cycle-dependent genes.

METHODS

Cultured rat aortic SMC were treated with incremental concentrations of dexamethasone and cell number was determined after 72 h. To determine if dexamethasone inhibited cell cycle progression, cells were synchronized, then restimulated to enter the cell cycle, and treated with or without dexamethasone. DNA synthesis was determined 24 h after restimulation by measuring [3H]thymidine incorporation. To define the point of action of dexamethasone in the cell cycle, synchronized SMC were treated with dexamethasone (10(-7) M) at various time points after entry into the cell cycle. Flow cytometry and Northern blots were performed to examine cell cycle progression and the expression of smooth muscle cell cycle-dependent genes c-fos, c-myc, and thymidine kinase (TK).

RESULTS

Dexamethasone treatment induced a concentration-dependent inhibition of SMC proliferation and DNA synthesis. The cell cycle progression of synchronized SMC from G1 into S phase was inhibited by dexamethasone, even when added as late as 16 h after restimulation. The expression of TK was suppressed by dexamethasone, while c-fos and c-myc were not affected.

CONCLUSIONS

Dexamethasone inhibits the proliferation of SMC in a concentration-dependent fashion. This inhibition is associated with a block in cell cycle progression late in G1 phase of the cell cycle. Consistent with this finding, dexamethasone does not alter the expression of the early cell cycle-dependent genes c-fos and c-myc, but significantly inhibits the expression of TK, a marker of late G1 phase.

Nitroglycerin decreases medial smooth muscle cell proliferation after arterial balloon injury

PURPOSE

Nitroglycerin and its effector molecules nitric oxide and cyclic guanosine monophosphate decrease smooth muscle cell proliferation in vitro. We examined the in vivo effect of nitroglycerin on intimal hyperplasia.

METHODS

We treated rats after carotid artery balloon injury with nitroglycerin delivered paraarterially with a miniosmotic pump for 1 week.

RESULTS

High nitroglycerin serum levels were achieved, and the level of cyclic guanosine monophosphate in the carotid artery wall was significantly increased (1.48 +/- 0.37 vs 0.86 +/- 0.39 pmol/mg protein; p < 0.05) in the nitroglycerin-treated group. Cellular proliferation in the arterial wall was assessed by incorporation of 5-bromo-2'-deoxyuridine 6 days after the injury and was lower in the nitroglycerin-treated group (15.2 +/- 3.4 vs 36.3 +/- 5.5 positive cells/section; p < 0.005). This was due to a decrease in the number of proliferating cells in the media (6.3 +/- 1.2 vs 21.8 +/- 4.5; p < 0.005), whereas in the budding neointima, the difference in the number of proliferating cells was not significant. Neointimal lesions 21 days after the injury did not differ in cross-sectional intimal area, in intimal/medial area ratio, and in cell density.

CONCLUSION

Nitroglycerin decreased medial cellular proliferation after balloon injury and had no significant effect on intimal proliferation. The size of the neointimal lesion was not affected by nitroglycerin therapy.

Impairment of vascular endothelial function by high-potassium storage solutions

High-potassium cold storage solutions are currently used to preserve myocardial function during heart transplantation. However, the effects of high potassium concentration on vascular endothelial function are not well known. We therefore tested vascular rings for endothelial-dependent and endothelial-independent relaxation during storage in normokalemic, normothermic buffers and then in buffers supplemented with 10 to 110 mmol/L KCl. Maximal endothelial-dependent relaxation was significantly reduced at all high potassium concentrations. Endothelial-independent relaxation was impaired only with 80 and 110 mmol/L KCl buffers. Both endothelial-dependent relaxation and endothelial-independent relaxation returned to normal values after washout of excess potassium. Similarly, endothelial-dependent relaxation and endothelial-independent relaxation were assessed in rings after 24 hours of hypothermic storage in normokalemic Krebs buffer, and in buffers containing 20 and 110 mmol/L KCl. Maximal endothelial-dependent relaxation was significantly reduced after preservation in the high-potassium solutions, whereas endothelial-independent relaxation was not impaired. We conclude that there is significant impairment of endothelial function after cold storage in a high-potassium buffer. Inadequate washout of potassium during normothermic conditions may lead to further functional impairment of vascular responsiveness. A low-potassium storage medium is recommended for improved vascular protection.

A biological basis for re-stenosis after percutaneous transluminal angioplasty: possible underlying mechanisms

Intravascular catheterization is a commonly used diagnostic tool and percutaneous transluminal angioplasty is used to dilate stenosed blood vessels. Although these techniques are very successful diagnostically and therapeutically they may precipitate a number of acute and chronic complications. Chronic intimal changes following balloon angioplasty can result in re-stenosis. Intimal hyperplasia can be a long-term complication of both diagnostic and interventional vascular catheterization. This article details these long-term structural changes, specifically relating experimental in vivo and in vitro changes to those seen clinically.

Influence of transluminal angioplasty on the prostanoid release from the arterial wall

Vasospasm and thrombosis complicate percutaneous transluminal angioplasty (PTA). To study if the release of the prostanoids PGI2 and TxA2 are affected by PTA, the following experiment was undertaken: In ten rabbits, the upper or lower half of the aorta was randomised either to transluminal angioplasty or control segment. After excision the segments were simultaneously but separately perfused ex vivo with Hank's balanced salt solution for five consecutive 15 min periods. Arachidonic acid was added to the perfusate for the last 15 min period. PGI2 and TxA2 were measured by radioimmunoassay in the perfusate as the stable degradation products 6-keto-PGF1 alpha and TxB2. After perfusion, the two aortic segments were prepared for scanning electron microscopy (SEM). Angioplasty decreased the basic release of PGI2 as well as the response to arachidonic acid. This is likely to be due to endothelial denudation as seen by SEM. The release of TxA2 from the vessel wall was very low and was not increased by dilatation. The influence of angioplasty on the prostanoid system may be of importance in the complications of vasospasm and thrombosis.