New Regenerative Vascular Grafts for Hemodialysis Access: Evaluation of a Preclinical Animal Model.

The purpose of this study was to evaluate a suitable animal model for the in vivo evaluation of patency and vascular tissue regeneration in small intestinal submucosa (SIS) vascular grafts for hemodialysis access. First, a 4-mm U-shaped SIS vascular graft was implanted between the internal carotid artery (CA) and the external jugular vein (JV) in five sheep and six swine. The U-shape grafts remained functional for 53 ± 4 days in sheep and 32 ± 2 days in swine. The sheep model presented exaggerated inflammation, so the swine model was selected for the in vivo study. Based on these initial results, a 4-mm C-shape SIS vascular graft with SIS circumferential reinforcement was developed to mechanically improve the vascular graft and manage complications identified during surgery in both sheep and swine. The C-shape vascular graft was implanted in a swine model (n = 3) between the CA and JV. GORE-TEX® vascular grafts were used as controls in the contralateral side of the neck. C-shape grafts remained patent for 47 ± 4 days, whereas the GORE-TEX® grafts were patent for 30 ± 15 days. The C-shape vascular graft was easier to handle during surgery, and its circumferential reinforcement improved in vivo patency, avoiding kinks in the graft after implantation. Histological results showed neovascularization and some regeneration with the alignment of endothelial cells in the vascular wall of the grafts. The model developed may be helpful in other research involving in vivo studies of vascular grafts for hemodialysis access.

Neovascularization after surgical exposure of rat external jugular vein endothelium.

PURPOSE: To investigate the neovascularization after exposure of the external jugular venous endothelium in an experimental model. METHODS: The sample was composed of 60 male rats of Wistar OUT B breed provided by animal colony of the Medicine College of Juazeiro do Norte, weighing 250 to 350 g, aged 90-120 days. Randomized study in OUT B Wistar rats, open, with 60 days duration. The animals were distributed into three groups of 20 specimens and were subjected to the following: Group 1: neck incision with dissection, ligation and section of the external jugular vein. Group 2: neck incision with dissection and ligation of the external jugular vein. Group 3: cervicotomy without dissection of the external jugular vein without ligation or section. The animals were sacrificed, half of them in 30 days and the other half within 60 days. The material in block harvested from the operated site were sectioned and stained for immunohistochemistry with CD34 marker. RESULTS: Neovascularization occurred with level of significance when compared group 1 to group 3 at 30 days (p=0.0076) and the same occurred at 60 days (p=0.0001) (Newman-Keuls test). CONCLUSION: The group with exposure of the venous endothelium showed a significant increase of neovascularization when compared with other groups.

Neovascularization after surgical exposure of rat external jugular vein endothelium

PURPOSE: To investigate the neovascularization after exposure of the external jugular venous endothelium in an experimental model. METHODS: The sample was composed of 60 male rats of Wistar OUT B breed provided by animal colony of the Medicine College of Juazeiro do Norte, weighing 250 to 350g, aged 90-120 days. Randomized study in OUT B Wistar rats, open, with 60 days duration. The animals were distributed into three groups of 20 specimens and were subjected to the following: Group 1: neck incision with dissection, ligation and section of the external jugular vein. Group 2: neck incision with dissection and ligation of the external jugular vein. Group 3: cervicotomy without dissection of the external jugular vein without ligation or section. The animals were sacrificed, half of them in 30 days and the other half within 60 days. The material in block harvested from the operated site were sectioned and stained for immunohistochemistry with CD34 marker. RESULTS: Neovascularization occurred with level of significance when compared group 1 to group 3 at 30 days (p=0.0076) and the same occurred at 60 days (p=0.0001) (Newman-Keuls test). CONCLUSION: The group with exposure of the venous endothelium showed a significant increase of neovascularization when compared with other groups.

The endothelium modulates the arterial wall mechanical response to intra-aortic balloon counterpulsation: in vivo studies.

Intra-aortic balloon pump (IABP) benefits could depend on variations in the cardiovascular biomechanical properties associated with blood flow-induced endothelium-dependent changes. However, if IABP results in changes in the peripheral artery biomechanics and if the endothelium plays a role in these potential changes remains unknown. The aim of this study is to characterize acute IABP effects on peripheral artery biomechanics in control and acute heart failure (AHF) states and the role of the endothelium in IABP effects on peripheral artery biomechanics. Pressure and diameter were recorded in sheep (n= 7) iliac arteries (IAs), before and during 1:2 IABP, during four states: (i) control with intact IA; (ii) AHF with intact IA; (iii) control with de-endothelialized (DE) (mechanical rubbing) IA; and (iv) AHF with DE IA. Arterial distensibility, elastic modulus, and conduit function (CF) (1/characteristic impedance) were calculated. The results of this study include: (i) during control conditions, IABP resulted in intact IA dilatation, stiffness reduction, and CF increase; (ii) AHF induction determined a reduction in intact IA diameter and CF, and a stiffness increase. These changes reverted during IABP; (iii) the increase in IA stiffness observed after DE remained unchanged during IABP; (iv) in DE IA, AHF did not result in diameter or stiffness changes; and (v) IABP during AHF did not associate changes in diameter or stiffness in the DE IA. In conclusion, during control and AHF states, IABP results in IA dilatation and stiffness reduction. The integrity of the endothelial layer would be critical for the IABP-associated changes in IA biomechanics.

Arterial pressure and diameter waveforms analysis by means of wavelet transform: application to artery de-endothelization.

In this present paper, we showed that wavelet analysis (WA) has the potential for extracting specific features from measured arterial diameter and pressure waveforms. The fifth detail of the Daubechies 4 (Db4) wavelet appears to be the most appropriate level for application, in order to analyze artery waveforms and was used to characterized arterial de-endothelization (DE). Raises in smooth muscle tone induced by (DE) tended to increase arterial stiffness and therefore that WA details embed the information of the diameter and pressure pulse that contains the signature of effects of wave travel and reflection affected by arterial stiffness.

Hiperplasia endotelial papilar intravascular oral: uma entidade rara / Intravascular papillary endothelial hyperplasia: a rare entity

A hiperplasia endotelial papilar intravascular (HEPI) é uma lesão vascular reativa caracterizada pela proliferação endotelial excessiva localizada no interior de vasos sangüíneos comumente dilatados, associada a trombos em organização, ou secundária a outras lesões vasculares, como hemangiomas e granulomas piogênicos. A HEPI é um achado incomum na cavidade oral, onde os lábios são o principal sítio de acometimento, e surge clinicamente sob a forma de nódulos azulados de aspecto clínico semelhante ao de lesões como hemangioma, mucocele e varicosidades. Sob o aspecto histopatológico, observam-se projeções papilares de tecido conjuntivo fibroso revestidas por uma ou duas camadas de células endoteliais no interior de um lúmen vascular. A principal peculiaridade da HEPI reside em sua semelhança histológica com o angiossarcoma e na possível interpretação errônea como neoplasia maligna. Neste artigo, os autores descrevem um caso de HEPI oral e realizam uma breve revisão da literatura, enfatizando suas características histopatológicas e o diagnóstico diferencial.

Endotelização in vivo das biopróteses cardíacas: preservação convencional versus não-aldeídica / In vivo endothelialization of cardiac bioprostheses: conventional versus non-aldehyde preservation

OBJETIVO: O revestimento endotelial in vitro das biopróteses com células do hospedeiro parece ter ação protetora contra a calcificação, trombose, inflamação e o desgaste mecânico. O objetivo deste estudo é analisar o potencial para endotelização in vivo com um processo alternativo de preservação tecidual (L-HydroTM). MÉTODO: A preservação L-Hydro consiste na extração controlada de substâncias antigênicas pela ação do polietilenoglicol e na incorporação de um agente antiinflamatório e antitrombótico. Para testar a re-endotelização in vivo, foram implantadas em posição mitral de ovelhas jovens sete próteses porcinas L-Hydro (grupo teste) e três convencionais preservadas com glutaraldeído (GA - grupo controle). Estas próteses foram explantadas com 150 dias após avaliação ecocardiográfica e angiográfica. A avaliação histológica consistiu em microscopia de varredura e transmissão, e imuno-histoquímica (von Willebrand) para detecção da presença e viabilidade das células endoteliais, respectivamente. Utilizou-se o teste-t não pareado para análise estatística. RESULTADOS: Não houve diferença hemodinâmica significativa nos dois grupos (p>0.05). Entretanto, a microscopia mostrou no grupo teste um revestimento endotelial quase completo formado por células confluentes, viáveis com expressão do fator vW, as quais encontravam-se em contato direto com a matriz colagênica subjacente. No grupo controle (GA), as superfícies valvulares estavam recobertas por fibrina, macrófagos, cálcio, material trombótico e células endoteliais esparsas com expressão fraca do fator vW, e com pouco contato direto com o colágeno. CONCLUSÕES: Estes dados indicam que o processo L-HydroTM permite endotelização espontânea com boa adesividade celular à matriz colagênica, o que favoreceria maior durabilidade às biopróteses porcinas.

Endotelização in vivo das biopróteses cardíacas porcinas: comparação entre a preservação convencional e a não-aldeídica / In vivo endothelization of conventional and non-aldehyde-fixed porcine bioprostheses: comparative study

Este estudo analisa o potencial para endotelização in vivo das próteses cardíacas com a preservação L-Hydro. Foram implantadas em ovelhas jovens 7 próteses porcinas L-Hydro e 3 glutaraldeídicas convencionais. Após 150 dias de implante a microscopia mostrou que nas próteses L-Hydro houve revestimento endotelial quase completo formado por células confluentes, viáveis com expressão do fator von Willebrand, e em contato direto com o colagêno subjacente. Nas próteses glutaraldeídicas houve ausência de crescimento endotelial. Estes dados indicam que o processo não-aldeídico (L-Hydro) utilizado neste estudo permite a endotelização espontânea / This study demonstrates the potential for in vivo endothelialization of heart valves treated by the L-Hydro preservation. Seven stented porcine heart valves treated by the L-Hydro process and 3 Glutaraldehyde-fixed porcine heart valves were implanted in juvenile sheep. A nearly complete coverage of endothelial cells on the surfaces of all leaflets was observed in the L-Hydro-treated valves after 5 months of implantation. The endothelial cells were in direct contact with the underlying collagen layer and expressed von Willebrand-related antigens. The surfaces of the Glutaraldehyde-treated valves showed lack of endothelial cells. These data indicate that L-Hydro-treated heart valves are capable of inducing spontaneous endothelialization...

Atherosclerosis and acute arterial thrombosis in rabbits: a model using balloon desendothelization without dietary intervention.

Acute thrombosis can be induced in rabbits by a triggering protocol using Russell's viper venom and histamine given after 8 months of a 1% cholesterol diet and balloon desendothelization. In the present study, we tested the hypothesis that aortic desendothelization performed 4 months before the triggering protocol without a high cholesterol diet is a highly effective and less expensive way of producing arterial atherosclerosis and thrombosis. Nineteen male New Zealand white rabbits on a normal diet were studied. The control group (N = 9) received no intervention during the 4-month observation period, while the other group (N = 10) was submitted to aortic balloon desendothelization using a 4F Fogarty catheter. At the end of this period, all animals were killed 48 h after receiving the first dose of the triggering treatment. Eight of 10 rabbits (80%) in the balloon-trauma group presented platelet-rich arterial thrombosis while none of the animals in the control group had thrombus formation (P < 0.01). Thus, this model, using balloon desendothelization without dietary manipulation, induces arterial atherosclerosis and thrombosis and may provide possibilities to test new therapeutic approaches.

Atherosclerosis and acute arterial thrombosis in rabbits: a model using ballon desendothelization without dietary intervention

Acute thrombosis can be induced in rabbits by a triggering protocol using Russell's viper venom and histamine given after 8 months of a 1 per cent cholesterol diet and balloon desendothelization. In the present study, we tested the hypothesis that aortic desendothelization performed 4 months before the triggering protocol without a high cholesterol diet is a highly effective and less expensive way of producing arterial atherosclerosis and thrombosis. Nineteen male New Zealand white rabbits on a normal diet were studied. The control group (N = 9) received no intervention during the 4-month observation period, while the other group (N = 10) was submitted to aortic balloon desendothelization using a 4F Fogarty catheter. At the end of this period, all animals were killed 48 h after receiving the first dose of the triggering treatment. Eight of 10 rabbits (80 per cent) in the balloon-trauma group presented platelet-rich arterial thrombosis while none of the animals in the control group had thrombus formation (P<0.01). Thus, this model, using balloon desendothelization without dietary manipulation, induces arterial atherosclerosis and thrombosis and may provide possibilities to test new therapeutic approaches.

Carotid atherosclerosis. Immunocytochemical analysis of the vascular and cellular composition in endarterectomies.

Papers dealing with rupture of carotid plaque surface are few in spite of the growing importance of the subject. The aim of this study was to analyze the cellular and vascular components of surgically excised carotid endarterectomies in order to obtain information about their role in the pathogenesis of the plaque rupture and intraplaque hemorrhage. Seventy-six surgical specimens of carotid endarterectomies were used for this study. The findings of immunophenotyping of the cellular constituents of the plaques were: 1) endothelial lining: the fibrous cap at the site of the rupture showed an eroded surface with loss of the endothelial lining. Conversely, in the remaining surface a continuous, not damaged row of endothelial cells stained with anti-CD31 and anti-CD34 was observed; 2) fibrous cap: the collagenous fibrous cap at the site of erosion was attenuated and the phenotypic characterization of the cells showed inflammatory components consisting mainly of macrophages (CD68 positive), 2/3 of the total infiltration. The remaining 1/3 was composed of T-lymphocytes and scarce B-lymphocytes. A close interaction between macrophages and capillaries and macrophages and T-lymphocytes was observed; 3) lipid cores: two different types of lipid cores could be depicted. Avascular or mildly vascularized lipid cores and highly vascularized, with neoformed vessels stained with CD34 and CD31. CD34 stained endothelia of all kind of vessels; conversely, neoformed vessels showed a weak stain with CD31. T-lymphocytes were found to be in close contact with neoformed vessels, and in some cases, migrating through the endothelial cells; 4) deeper layers of the plaque: the base and the shoulder of the plaques showed in 28/76 cases neoformed vessels, thin or thick walled, CD34 positive, generally surrounded by mild to extensive mononuclear infiltrates. Atherosclerotic plaques were found to belong to six different lesions: plaque rupture plus thrombosis (18/76, 23.6%), plaque rupture plus intraplaque hemorrhage plus thrombosis (18/76, 23.6%), intraplaque hemorrhage without plaque rupture (16/76, 21.0%), plaque rupture plus intraplaque hemorrhage (5/76, 6.5%), stable calcified non complicated plaque (14/76, 18.4%) and unstable, soft, non complicated plaque (5/76, 6.5%). The first four lesions were considered as "complicated lesions". Complicated plaques presented neoformed vessels in the periphery, shoulder and base of the plaque in 22/57 (38.5%) cases. Conversely only 1/14 (7.1%) of non complicated, stable calcified plaques presented neoformed vessels, (p < 0.05). Of note, the 5 causes of unstable, soft non complicated plaque presented neoformed vessels surrounding the plaque. In 10/57 (17.5%) complicated plaques unequivocal histological signs of old hemorrhages were found surrounding those vessels. Irrespective of presenting no rupture, 11/35 plaques showed a mononuclear infiltrate in the fibrous cap. In conclusion, rupture of carotid plaques (50% of the cases), is characterized by the presence of a macrophagic infiltration of the caps and by the direct apposition of T-lymphocytes to macrophages and a close relation of these cells to endothelial cells. This highly suggests a cell-to-cell interaction, which results in an inflammatory process. Intraplaque hemorrhage without rupture represented 21% of the endarterectomies. These lesions are not related to cap erosion, but to plaque vascularization. Most lipid cores were highly vascularized with neoformed vessels with macrophages and T-cells in close contact and in some cases disrupting the endothelium. The abrupt growing of the lipid core and/or an overproduction of oxygen free radicals could lead to the breakdown of core vessels and intraplaque hemorrhage.

Intimal staining for visibility enhancement during microanastomoses.

Absolute perfection in microvascular surgery continues to be thwarted by technical inadequacies in construction of the microanastomosis. Occasionally this is a consequence of limited visualization or misidentification of the intima proper predisposing to thrombosis. At least in rats, we have demonstrated that intimal staining with clinically inert vital dyes has enhanced gross appreciation of the exact intimal location. This maneuver has simplified suture placement without evidence of any associated increased risk of anastomotic failure.