Onyx Migration Into the Anterior Spinal Artery During Lumbar Artery Embolisation: an Adverse Event.

INTRODUCTION: The impact of sequential lumbar and intercostal artery occlusion on the risk of spinal cord ischaemia was evaluated; however, an adverse event (paraplegia) was encountered, which resulted in study interruption. Investigations were carried out to understand the reasons for the paraplegia. REPORT: To develop a porcine model of spinal cord ischaemic preconditioning prior to extensive thoraco-abdominal aneurysm endovascular aortic repair, the lumbar arteries were selectively embolised with Onyx 5 days prior to an extended thoracic aortic stent graft. Six pigs were used in this preliminary work. Four cases of paraplegia secondary to accidental migration of Onyx to the anterior spinal artery from the lumbar arteries are reported. Histological analysis confirmed severe spinal ischaemic injury and the presence of Onyx particles in the anterior spinal artery. DISCUSSION: Onyx is used for lumbar artery embolisation in type II endoleak treatment after endovascular aortic repair, and while migration in lumbar arteries is frequent, the risk of spinal cord ischaemia has never been described. The current study demonstrates the risk of paraplegia following Onyx migration to the anterior spinal artery from the lumbar artery in an experimental model. Thus, Onyx treatment for type II endoleaks from lumbar arteries should be used cautiously.

Preclinical study on an animal model of a new non-adhesive cyanoacrylate (Purefill®) for arterial embolization.

PURPOSE: The goal of this study was to assess the distal dispersion, the adhesion strength to catheter, the vascular toxicity and the ability in excluding embolized vessels using Purefill® (α-hexil-cyanoacrylate) as embolic material, which is a new high purity cyanoacrylate and compare these results with those obtained with N-butyl-2-cyanoacrylate (Histoacryl®) and a mixture of N-butyl-2-cyanoacrylate and methacryloxysulfolane. MATERIAL AND METHODS: In six pigs, the right rete mirabile (RM) and right renal arteries were embolized with α-hexil-cyanoacrylate, and the left rete mirabile and left renal artery were embolized with N-butyl-2-cyanoacrylate and N-butyl-2-cyanoacrylate+Methacryloxysulfolane for comparison. One minute after glue injection through the microcatheter, displacements of the kidney and the pharyngeal artery were measured on angiographic images, before exercising any traction and during catheter pulling, when the forces were maximal. Displacement was measured in terms of distance (mm) with respect to renal pedicles and in terms of angle (°) with respect to the rete. After acute embolization (4 pigs) or three-month follow-up (2 pigs), the kidneys and the RM were removed and further analysed using computed tomography and histopathological examination. RESULTS: Similar short and long-term embolic efficacies were observed with the three glues. The mean displacement distances of renal pedicles were 2.6mm for α-hexil-cyanoacrylate, 22.6mm for N-butyl-2-cyanoacrylate and 19.8mm for N-butyl-2-cyanoacrylate+Methacryloxysulfolane (P=0.021). The mean angles of displacement of the ascending pharyngeal arteries were for 12.2° for α-hexil-cyanoacrylate, 23.5° for N-butyl-2-cyanoacrylate and 30° for N-butyl-2-cyanoacrylate+Methacryloxysulfolane (P=0.070). Histopathologically, findings were similar for the three glues, immediately and 90 days after embolization. CONCLUSION: α-hexil-cyanoacrylate has occlusive efficacy in the short and long term similar to those of N-butyl-2-cyanoacrylate and N-butyl-2-cyanoacrylate+Methacryloxysulfolane. In addition, histopathological changes are similar with the three glues immediately or 90 days after embolization. Conversely, α-hexil-cyanoacrylate results in a reduced angle and distance of displacement compared to the other two glues, assumably reflecting a limited adhesive strength.

Minimal portal vein stenosis is a promising preconditioning in living donor liver transplantation in porcine model.

BACKGROUND & AIMS: The main hindrance in promoting living donor liver transplantation remains the morbi-mortality risk for the donor. Considering the opposed remodeling influence of portal and hepatic artery flows, our working hypothesis was to identify a lobar portal vein stenosis capable of inducing a contralateral liver mass compensatory enlargement, without the downstream ipsilateral atrophic response. METHODS: Twenty-four pigs entered this study. Six of them were used to establish hemodynamic changes following a progressive left portal vein (LPV) stenosis, in blood flow, pressure and vessel diameter of the LPV, main portal vein and hepatic artery. Sixteen pigs were divided into 4 groups: sham operated animals, 20% LPV stenosis, 50% LPV stenosis, and 100% LPV stenosis. Daily liver biopsies were collected until post-operative day 5 to investigate liver regeneration and atrophy (Ki67, STAT3, LC3, and activated caspase 3) according to the degree of LPV stenosis. Finally, changes in liver volumetry after 20% LPVS were investigated. RESULTS: A 20% LPV stenosis led to dilatation of the hepatic artery and a subsequent four-fold increase in hepatic arterial flow. Concomitantly, liver regeneration was triggered in the non-ligated lobe and the cell proliferation peak, 5 days after surgery, was comparable to that obtained after total LPV ligation. Moreover, 20% LPV stenosis preconditioning did not induce left liver atrophy contrary to 50 and 100% LPV stenosis. CONCLUSIONS: A 20% LPV stenosis seems to be the adequate preconditioning to get the remnant liver of living donor ready to take on graft harvesting without atrophy of the future graft.

An experimental porcine model of heterotopic renal autotransplantation.

OBJECTIVE: The aim of the present study was to validate an experimental model of heterotopic renal allotransplantation. Such a model, more relevant to the human situation, has never been previously described. MATERIALS AND METHODS: Pietrin pigs (40 to 50 kg) were used in the study. Through a midline incision, the left kidney was removed, washed, and preserved in a standard preservation solution (Celsior, Genzyme, France) for 20 hours at 4 °C. Heterotopic autotransplantation was performed into the right iliac fossa onto the external iliac vessels with an end-to-side anastomosis and a nonstented uretero-ureteral anastomosis was performed. RESULTS: Twenty-five renal allotransplantations were performed over a 5-month time period. Mean operating time progressively decreased and stabilized after 15 procedures (mean ± SD: 78.2 ± 19 minutes and 187.4 ± 18 minutes for left nephrectomy and transplantation, respectively) as morbidity decreased concomitantly. Suturing times for end-to-side anastomosis of the renal artery and vein onto the external iliac artery and vein were 21.9 ± 7 minutes and 34 ± 8 minutes (mean ± SD), respectively. Ten pigs died before the end of the experiment. CONCLUSIONS: We have developed and validated the first nonrodent animal model of heterotopic renal autotransplantation relevant to the human anatomy and physiology. The procedure was easy to learn and safe. This model could be used to teach junior surgeons renal transplantation techniques and could also be used as a model to study ischemia-reperfusion injury in renal transplantation.

[Pathological features of radiofrequency ablation (RFA) renal scar CT-imaging in a swine model]. / Cicatrice de radiofréquence rénale : corrélations anatomopathologiques-tomodensitométriques chez le porc. Applications pratiques pour le suivi en imagerie.

PURPOSE: To analyze the changes in vicinal kidney parenchyma after percutaneous RFA. MATERIALS AND METHODS: [corrected] Twenty-four CT-guided RFA procedures were performed on six pigs using 2 cm LeVeen coaxial needles. We studied volume, morphology, cavitation and enhancement of the ablation zones (AZ) before and after the procedure on contrast-injected CT-scans. The kidneys were removed four weeks later and studied in the path lab. RESULTS: All the procedures were successfully completed. Four weeks later, the CT-scans showed AZ that were either clearly circumscribed or with unclear borders, heterogenous areas associating necrosis and infarct tissue and mesenchyma showing a process of apoptosis around the edges. A treatment considered as incomplete on the CT-scan (presenting as an enhancement) was always associated with necrosis on the histology slides, although the necrotic areas behaved in various different ways on the CT-scan after injection of contrast medium: an enhancement of more than 10 HU did not mean that no necrotic tissue was present. CONCLUSION: RFA causes heterogenous tissue changes, associating necrotic and ischemic zones and an apoptotic reaction. The mechanisms of these changes and their therapeutic significance should be studied. CT-scans performed immediately after RFA procedure and one month later are not predictive of the efficacy of the treatment because an enhancement of the AZ does not mean that it is not necrotic. The value of a CT-scan performed one month after the procedure is debatable, because the tissue remodeling that occurs in the kidneys is not definitive at this time-point.

The haemodynamics of the distal arterial Y-shaped autograft bypass-flap in a porcine experimental model.

BACKGROUND: The haemodynamic effects of revascularisation with combined bypass and free-muscle flap remain controversial. In a porcine experimental model, we investigated the transplantation-induced changes in the haemodynamics of a Y-shaped combined arterial autograft bypass-muscle flap (AABF). METHODS: Anatomy of AABF was identified in eight dissections in four porcine cadavers. In five animals, AABF served as a superficial femoral artery (SFA) defect replacement. Modelled, triggered pulsatile pressure (P) and flow (Q) waves delivered mean haemodynamics and PQ hysteresis loops before and after transplantation at days 0 and 10. RESULTS: Anatomically, AABF combined subscapular and circumflex-scapular arteries, and thoracodorsal artery as latissimus dorsi flap pedicle. Surgical feasibility and AABF patency were confirmed in each case. At day 0, the proximal flow was increased in the grafted Y-shaped AABF, which also adopted the specific SFA pulsatile haemodynamics. Regulatory mechanisms of AABF vasomotricity were preserved and AABF-flow-dependence amplified the flow in the distal segment, which otherwise preserved its own flow dependence. At 10 days, the AABF flow was unchanged in the distal segment, and remained elevated in the proximal and pedicle segments. CONCLUSIONS: Combined AABF, as a single one-piece arterial autograft, was shown highly adaptive to the receiving arteries. The transplantation-induced changes in AABF pulsatile flow profile and vascular reactivity improve the overall graft flow, and strongly advocate for beneficial effects on the blood propelling capacity of the grafted circulation.

Embolization-driven occlusion of the abdominal aortic aneurysmal sac as the basis of prevention of endoleaks in a new swine model.

OBJECTIVES: To assess the effect of a new polymer in embolization of endoleaks using an animal model. METHODS: A modified aortic stent-graft was placed in 20 pigs. Embolization was performed at the time of graft insertion with non-cytotoxic n-butyl-2-cyanoacrylate-metacryloxysulpholane and lipiodol (0.2:0.8ratio, 2 ml). Angiography, scanning electron microscopy and immuno-histochemistry were obtained at day 0, 1 week and 3 months. RESULTS: In control animals both type I and II endoleaks were demonstrated. In treated animals, neither type-I nor type-II endoleaks were observed and a fibro-proliferative response was demonstrated within the aneurysm thrombus. CONCLUSIONS: Host vascular responses govern the fate of the excluded aneurysm. Embolization of the sac and feeding arteries with non-cytotoxic glue sealed all occlusions by stimulating a massive restenosis-like process.

Compliance matching stent placement in the carotid artery of the swine promotes optimal blood flow and attenuates restenosis.

OBJECTIVES: We assessed the value of a gradient-compliant stent in an animal model. METHODS: Bilateral carotid arteries were stented with nitinol stents having variable-oversizing, variable-stiffness, and with (CMS, 10 animals) and without (SMART, four animals) compliance-matching endings. Angiography, hemodynamic, scanning-electron-microscopic and histological analyses were performed at 3-month. The protocol was completed in 14 among 19 swines. RESULTS: Transient (1-month) exaggerated recoil, attributable to stress-induced phasic inhibition of vasorelaxation, developed at CMS endings. At mid-term, all stents were endothelialized; CMS-stents, but not SMART-stents, were incorporated into walls (one-strut-thickness). Restenosis developed outside SMART-stents (cell migration+wall-compensatory enlargement) whereas CMS-stents elicited no or focalized cell-accumulations at endings that bulged vascular walls radially outward. SMART-stents were blood-flow neutral, whereas CMS-stents favored (higher-stiffness, higher-oversizing) or opposed (lower-stiffness, less-oversizing) carotid blood flow. CONCLUSIONS: Direct carotid stenting with stents having compliance-matched endings and specific requirements of stiffness and oversizing can optimize blood flow to the brain and restrict local restenosis.

Efficacy and low vascular toxicity of embolization with radical versus anionic polymerization of n-butyl-2-cyanoacrylate (NBCA). An experimental study in the swine.

BACKGROUND AND PURPOSE: To compare the efficacy and vascular toxicity of embolization with radical (NBCA+metacryloxysulpholane=CS) versus conventional anionic (NBCA alone=CA) polymerization of NBCA. MATERIALS AND METHODS: Under continuous digital subtracted angiography (DSA) recordings, a 0.2 mL volume of identical glue mixtures were injected in a single-step procedure, concomitantly, in left and right (with CS and CA, respectively) renal arterial branches (RAB) and ascending pharyngeal arteries (APA) in 8 swines. Arterial histopathology and morphometry of inflammation were investigated at 2 weeks. RESULTS: Complete embolization was achieved with equivalent cast homogeneity on DSA with both NBCA mixtures in RAB and APA. Inflammatory crowns in APA and RAB were significantly lower in CS - than in CA-treated sites (p<0.001). CS plug was scarcely adhesive to the vascular wall, and pulled apart from the wall by a residual thrombotic lining; in contrast with CA casts that were strongly adhesive to walls with endothelium stripping. CONCLUSIONS: Anionic and radical polymerization of NBCA embolization was identical with regards to occlusion rate; whereas radical pathway of polymerization with cyanoacrylates lowered histotoxicity with a less sustained adhesiveness of casts against vascular walls.

Local perivascular application of low amounts of a plasmid encoding for vascular endothelial growth factor (VEGF165) is efficient for therapeutic angiogenesis in pigs.

Clinical trials have demonstrated therapeutic benefit in inducing angiogenesis in chronic occlusive arterial disease. The route of application mostly used was the intramuscular injection of high dosages of plasmid. Therefore, a local perivascular application of low amounts of vascular endothelial growth factor (VEGF) plasmid was used in an interventional occlusion model, and the effect of VEGF on coronary and peripheral occlusions compared in the same animal model. Coronary and peripheral arteries were chronically occluded in Pietrain pigs using a non-surgical, interventional approach. Adventitial delivery of the DNA for VEGF was performed with a needle injection catheter. The DNA was applied as lipoplexes using the novel cationic liposomes DOCSPER. Optimized transfer conditions were used. Angiography, polymerase chain reaction (PCR), reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry were undertaken within a follow-up period of 6 months. Expression of the transfected VEGF gene was observed at 1 and 3 weeks following application. The DNA was detected up to 5 months following application. Around occluded coronary arteries, there was formation of new collaterals and arterial prolongation, whereas surrounding occluded peripheral arteries there was no collateralization but development of new arterial branches was seen. Results demonstrate that the response to VEGF is also sufficient, when minimal amounts of plasmid encoding for VEGF are applied locally into the perivasculature allowing for more safety of this therapy. Comparison of treatment of chronic coronary and peripheral arterial disease revealed differences in angiogenesis following VEGF application during a total follow-up period of almost 6 months which may be related to their different developmental origins. This may have important implications for developing future therapeutic strategies using VEGF in different vessels.

Local delivery of NO-donor molsidomine post-PTA improves haemodynamics, wall mechanics and histomorphometry in atherosclerotic porcine SFA.

OBJECTIVES: we investigated the therapeutic effect of angioplasty with local drug delivery (LDD) of the wall-accumulating NO-donor molsidomine (M) in the superficial femoral arteries (SFA) of atherosclerotic swine. MATERIALS AND METHODS: atherosclerotic Pietrin swines (n=14) underwent PTA-LDD-M (4 mg/2 ml) vs contralateral PTA-LDD-Placebo in the SFA using a channelled balloon angioplasty catheter. Invasive and colour Doppler energy (CDE) assessments of haemodynamics and wall mechanics were performed at 24 h (n=4) and 5 months (n=10). Immuno-histolabelling of cell proliferation and histomorphometry were serially performed in perfusion fixed SFA samples. RESULTS: at 24 h, PCNA-positive nuclei revealed 33+/-14 and 12+/-3 proliferating cells/mm2 at placebo and molsidomine PTA-LDD sites, respectively (p<0.001). At 5 months, PTA-LDD-M vessels, compared with PTA-LDD-P, had increased compliance (66+/-9 vs 11+/-4 ml/mmHg) and lowered impedance (0.11+/-0.05 vs 0.45+/-0.14 mmHg/ml x min(-1)) (p<0.05). CDE revealed low, middle and high velocity peaks at 7.5, 20 and 35, and 8, 15 and 22 cm x s(-1) in systolic and diastolic flows, respectively; and PTA-LDD-M prevented emergence of restenosis-associated increases in low blood velocities (p<0.01). PTA-LDD-M inhibited restenotic intimal thickening and medial thinning which decreased mean lumenal diameter in placebo-treated (2.6+/-0.3) as compared to molsidomine-treated (3.4+/-0.3 mm) vessels (p<0.05). CONCLUSIONS: in the atherosclerotic porcine SFA model, PTA-LDD with molsidomine consistently improved haemodynamic wall mechanics, lowered cell proliferation and prevented late lumen loss observed with PTA-LDD with placebo.

Evaluation of endovascular techniques for creating a porcine femoral artery occlusion model.

PURPOSE: To determine the optimal endovascular approach to achieve long-term occlusion of large arteries, while preserving the integrity of periarterial tissue, in an animal model of ischemia. METHODS: Femoral artery occlusions were created in 16 pigs using detachable balloons, coils, or blinded stent-grafts. Feasibility, safety, primary and long-term success, and the degree of neovascularization were determined over a 6-month period by serial angiography and histological analyses. Four animals served as untreated controls. RESULTS: Overall primary success for all occlusion devices was 100%. The 6-month occlusion rate using detachable balloons or coils was 33% and 0%, respectively; however, all arteries occluded with blinded stent-grafts remained obstructed to the end of the study. There was no significant difference in capillary densities and collateralization of periarterial areas when occluded arteries were compared with nonoccluded controls in the same animal. No increase in collateralization was observed following endovascular arterial occlusion. CONCLUSIONS: Percutaneous insertion of blinded stent-grafts easily, safely, and reliably creates long-term arterial occlusion in pigs, which may make this a more appropriate model for studying the effects of angiogenic factors in vivo.

Simultaneous measurements of arterial diameter and blood pressure to determine the arterial compliance, wall mechanics and stresses in vivo.

BACKGROUND: to develop a periarterial dimensional clip-probe which, associated with endovascular pressure measurement, real-time digital signal processing/data treatment systems, enables characterisation of the basic wall mechanics in given arterial sites. DESIGN: experimental study. MATERIAL: a facing pair of ultrasonic crystals was incorporated in periarterial highlight probes, made of sterilisable silicone and manufactured from computer-designed stainless steel casts. The A/D converted diameter and pressure (from an endovascular micro-tip probe) signals, triggered by the ECG, were on-line processed to provide their respective profiles during an averaged cardiac cycle, and subsequently the arterial wall physics. The technique was tested in the iliac and renal arteries in eight pigs. RESULTS: the technique was found to indicate adequately that arterial responses to distending blood pressure, as given by Petersons modulus and relative pulsatility, were identical in renals and iliacs. In contrast, the compliance, circumferential incremental elastic modulus and midwall circumferential stress were higher in iliacs than in renals, whereas arterial stiffness of the renals surpassed that of the iliacs. DISCUSSION: the technique with sterilisable probes produces in vivo pressure-diameter relationships, arterial compliance, and wall mechanics and stresses, whatever the arterial size. The porcine iliacs and renals are elastic and viscorigid arteries, respectively.

Optimization of nonviral gene transfer of vascular smooth muscle cells in vitro and in vivo.

Gene therapy strategies for the prevention of restenosis postangioplasty are promising. Nonviral gene transfer to the arterial wall in vivo has so far been limited by poor efficiency. This study aimed to optimize transfection of primary vascular smooth muscle cells using cationic nonviral formulations based on cholesterol derivates (DC-, DAC-, DCQ-, and Sp-Chol), double-chained amphiphils (LipofectAMINE, DOTMA, DOSGA, DOSPER, and DOCSPER), or heterogeneous reagents (Superfect, Effectene, and Tfx-50). Estimation of transfection efficiencies was performed using galactosidase assays at different ratios of transfection reagent to plasmid DNA with reporter gene. Toxicity was monitored by analyzing cell metabolism. Transfer efficiency and safety were determined in a porcine restenosis model for local gene therapy using morphometry, histology, galactosidase assays, and reverse-transcriptase polymerase chain reaction. The highest in vitro transfection efficiency was achieved using the recently developed DOCSPER liposomes, with transfer rates of at least 20% in vascular smooth muscle cells. Transfer efficiency was further enhanced up to 20% by complexing with poly-L-lysine. Transfection efficiency in vivo in a porcine restenosis model was up to 15% of adventitial cells using DOCSPER versus 0.1% using LipofectAMINE. Toxicity in vivo and in vitro was lowest using DOCSPER. Increased biological effects were demonstrated following optimization of transfer conditions.

Hemodynamics and wall mechanics after stent placement in swine iliac arteries: comparative results from six stent designs.

PURPOSE: To compare the hemodynamics and wall mechanics of swine iliac arteries after placement of six types of stent. MATERIALS AND METHODS: Stents were placed in the iliac artery of 18 pigs (three pigs each underwent placement with one of six types of stent); 16 untreated pigs served as control animals. Iliac arterial hemodynamics and wall mechanics were measured 4 days after placement. RESULTS: Four stents (Palmaz-Schatz, Cordis, Warren, NJ; and Strecker, Cragg, and Symphony, Boston Scientific/Vascular, Natick, Mass) caused decreased pulsatile flow rate in the treated and contralateral iliac arteries; one (Memotherm; Bard, Covington, Ga) caused increased flow pulsatility; and one (Wallstent; Schneider, Plymouth, Minn) had no effect. No compliance mismatching was noted for the Cragg, Symphony, and Memotherm stents, whereas a decrease in compliance was noted for the Palmaz-Schatz, Strecker, and Wallstent designs. The Palmaz-Schatz and Strecker stents caused increased arterial wall rigidity, the Symphony and Wallstent designs had no effect, and the Memotherm and Cragg stents caused decreased wall rigidity. Stents made of stiff metal yielded different early results than did stents made of the less rigid nitinol. CONCLUSION: Soon after implantation, the six stent designs elicited varying changes in blood flow, arterial compliance, and arterial wall mechanics. Contralateral arterial flow also was affected.

Effects of folate supplementation in hyperhomocysteinemic pigs.

OBJECTIVES: The aim of this study was to evaluate the therapeutic effects of folic acid in the pig model of hyperhomocysteinemia. BACKGROUND: We have previously shown that pigs fed a methionine-rich diet develop hyperhomocysteinemia, arterial lesions and thrombotic events. Elevated homocysteine level is an independent risk factor for atherosclerosis that can be markedly lowered with daily folic acid administration. However, it is not known whether this treatment can prevent arterial lesions. METHODS: Three groups of pigs were studied: 8 control subjects received a standard diet; 8 received a methionine-rich diet for four months; 8 received a methionine-rich diet for 1 month and then the methionine-rich diet + 5 mg/day folic acid for 3 months. At month 4 after hemodynamic investigation, all the pigs were sacrificed. RESULTS: Control animals developed few usual vascular streaks. All the pigs fed a methionine-rich diet without folic acid treatment developed hyperhomocysteinemia (10.3+/-1.3 micromol/liter at basal state, 18.2+/-2.5 micromol/liter at one month and 14.6+/-3.8 micromol/liter at four months), hemodynamic abnormalities and diffuse arterial lesions with smooth muscle cell hyperplasia, endothelial alterations and elastic lamina dislocation. In this group, one pig died of venous thromboembolism and one of myocardial infarction. The pigs fed a methionine-rich diet + folic acid displayed similar arterial lesions and two had thrombotic events (one myocardial infarction and one pulmonary embolism), despite normalization of homocysteine levels (10.9+/-1.3 micromol/liter at basal state, 19.5+/-2.5 micromol/liter at one month and 11.4+/-3.8 micromol/liter at four months). CONCLUSIONS: In the pig model of hyperhomocysteinemia, 5 mg/day folic acid did not prevent arterial lesions or thrombotic events.

Association of mild hyperhomocysteinemia with cardiac graft vascular disease.

In non-transplant patients mild hyperhomocysteinemia is an independent risk factor for vascular disease. The aim of this study was to determine whether hyperhomocysteinemia is associated with graft vascular disease. Fasting total plasma homocysteine was assessed in 18 patients with graft vasculopathy and 18 transplanted patients without graft vasculopathy matched for age, sex and the time since transplant. All were on cyclosporin. Graft vasculopathy was defined at coronary angiography as stenoses > or = 25%, or aneurysms. We found that hyperhomocysteinemia ( > or = 15 micromol/l) is common among transplanted heart recipients and significantly more frequent in the patients with graft vasculopathy (17/18 versus 11/18). Accordingly, the mean homocysteinemia was significantly higher in the group with graft vasculopathy (23.6+/-7.8 versus 16.9+/-7.1 micromol/l, P=0.01). The elevation of homocysteine plasma levels in the heart transplant recipients has probably multiple causes. The main cause seems to be renal failure. Additional causes could be azathioprine treatment or genetic polymorphisms. These results suggest that besides the immunological factors, homocysteine can play an additional role in the pathogenesis of graft vascular disease.

Hyperhomocysteinemia induces elastolysis in minipig arteries: structural consequences, arterial site specificity and effect of captopril-hydrochlorothiazide.

Hyperhomocysteinemia is a risk factor for arterial diseases, and the deterioration of the arterial elastic structures is one of the possible mechanisms underlying this epidemiological association. The aim of this paper is to quantitatively characterize such structural alterations and to explore their causes in a previous model of dietary induced mild hyperhomocysteinemia in minipigs. After four months, both a morphodensitometrical analysis of the elastic structure and a biochemical analysis of elastin and elastase activities were performed on the infrarenal abdominal aorta (IRAA) and the proximal left interventricular coronary artery (LIVCA) of control (C), hyperhomocysteinemic (H) and captopril-hydrochlorothiazide (Cp-Htz, 25 + 12.5 mg/d)-treated (H+/-Cp) minipigs (n = 8/group). Hyperhomocysteinemia was found to induce an increase in parietal elastolytic metalloproteinase activities. It resulted in opening and enlargement of fenestrae through the medial elastic laminae and in a decrease in medial elastin content (p < 10(-3)), expressed as well as volume density (%) as weight concentration (microg elastin/mg dry tissue). The thickness of the media and its basic lamellar organization was unchanged. The reduction in volume density was more dramatic in LIVCA (H: 4.7 +/- 0.9 vs C: 8.8 +/- 2.4), where it was evenly distributed within the media, than in IRAA (H: 6.7 +/- 1.1 vs C: 9.3 +/- 1.2), where the deep medial layers were less affected. Cp-Htz partly prevented the hyperhomocysteinemia-induced reduction of the medial elastin content in LIVCA (5.7 +/- 1.2) and IRAA (7.9 +/- 1.4). This effect, occurring in the subintimal layers of the media in both arteries but not in the deeper layers, resulted in a less beneficial effect in LIVCA than in IRAA. This result parallels the moderate beneficial therapeutic effect of ACE inhibitors against coronary atherosclerosis in humans. This paper reports for the first time a quantitative analysis of the arterial site-dependent deterioration of the elastic structure caused by mild hyperhomocysteinemia and the involvement of metalloproteinases in this process. These results confirm that the plaque-independent damage to elastic structure previously described in hyperhomocysteinemic-atherosclerotic minipigs was mainly due to homocysteine. This highlights that the metalloproteinase-related elastolysis and the subsequent structural deterioration is one of the major events underlying the epidemiological association between mild hyperhomocysteinemia and arterial diseases.