Complete Static Repopulation of Decellularized Porcine Tissues for Heart Valve Engineering: An in vitro Study.

To date, a completely in vitro repopulated tissue-engineered heart valve has not been developed. This study focused on sequentially seeding 2 cell populations onto porcine decellularized heart valve leaflets (HVL) and pericardia (PER) to obtain fully repopulated tissues. For repopulation of the interstitium, porcine valvular interstitial cells (VIC) and bone marrow-derived mesenchymal stem cells (BM-MSC) or adipose tissue-derived stem cells (ADSC) were used. In parallel, the culture medium was supplemented with ascorbic acid 2-phosphate (AA) and its effect on recolonization was investigated. Subsequently and in order to obtain an endothelial surface layer similar to those in native HVL, valvular endothelial cells (VEC) were seeded onto the scaffolds. It was shown that VIC efficiently recolonized HVL and partially also PER. On the other hand, stem cells only demonstrated limited or no subsurface cell infiltration of HVL and PER. Interestingly, the addition of AA increased the migratory capacity of both stem cell populations. However, this was more pronounced for BM-MSC, and recolonization of HVL appeared to be more efficient than that of PER tissue. VEC were demonstrated to generate a new endothelial layer on HVL and PER. However, scanning microscopy revealed that these endothelial cells were not allowed to fully spread onto PER. This study provided a proof of concept for the future generation of a bioactive tissue-engineered heart valve by showing that bioactive HVL could be generated in vitro within 14 days via complete repopulation of the interstitium with BM-MSC or VIC and subsequent generation of an entirely new endothelium.

Non-Cytotoxic Crosslinkers for Heart Valve Tissue Engineering.

BACKGROUND AND AIM OF THE STUDY: Currently, no effective crosslinking reagents are available to treat xenogenic decellularized heart valve matrices. The study aim was to evaluate the crosslinking effect of quercetin, catechin, caffeic acid and tannic acid on porcine aortic valve matrices. METHODS: Cytotoxicity of the different crosslinkers was evaluated. The mechanical properties of crosslinked porcine matrices and control matrices (non-fixed) were examined by tensile strength testing, as was the cytocompatibility of the fixed matrices. Crosslinked and control matrices were implanted subcutaneously in Wistar rats (n = 9) and, after two weeks, their calcium contents were determined using inductively coupled plasma-mass spectrometry. The antibody reaction against porcine tissue in rat serum was also determined. RESULTS: Cytotoxicity studies showed that crosslinkers, even at high concentrations, did not inhibit cell viability. All crosslinkers except tannic acid improved the mechanical strength of acellular porcine matrices. Moreover, the tensile strength of quercetin-fixed matrices was comparable with that of glutaraldehyde (GTA)-fixed leaflets. Light microscopic evaluation showed that crosslinked matrices caused only a mild lymphocytic inflammatory reaction. Furthermore, quercetin-fixed leaflets exhibited a well-preserved matrix without infiltration of CD3+ cells. After two weeks, calcium levels were 206.33 µg/mg for controls (non-fixed), and 151.33 µg/mg, 181 µg/mg and 163.66 µg/mg for quercetin-, catechin-, and caffeic acid-fixed matrices, respectively. At two weeks after implantation the quercetin-crosslinked matrices also elicited the lowest levels of IgG antibodies. CONCLUSION: The study results identified quercetin as the most suitable crosslinker for heart valve tissue engineering, and a possible alternative to GTA. Further studies are essential to determine whether quercetin crosslinking will allow autologous cell repopulation in order to create a viable heart valve.

Shear stress and VEGF enhance endothelial differentiation of human adipose-derived stem cells.

Herein we combine chemical and mechanical stimulation to investigate the effects of vascular endothelial growth factor (VEGF) and physiological shear stress in promoting the differentiation human adipose derived stem cells (ADSCs) into endothelial cells. ADSCs were isolated and characterized; endothelial differentiation was promoted by culturing confluent cells in 50 ng/ml VEGF under physiological shear stress for up to 14 days. Afterwards, endothelial cells were seeded onto collagen or acellular aortic valve matrices and exposed to four culture conditions: shear stress + VEGF; shear stress - VEGF; static + VEGF and static - VEGF. After 7 days, phenotype was investigated. ADSCs subjected to shear stress and VEGF express a comprehensive range of specific endothelial markers (vWF, eNOS and FLT-1 after 7 days and CD31, FLk-1 and VE-cadherin after 14 days) and maintain the phenotype when seeded onto scaffolds. Our protocol proved to be an efficient source of endothelial-like cells for tissue engineering based on autologous ADSC.

An optimized growth factor cocktail for ovine mesenchymal stem cells.

Growth factors that regulate proliferation, migration, and invasion of ovine mesenchymal stem cells (oMSCs) are not well defined. In this study, we have evaluated five growth factors for their ability to initiate and support in vitro proliferation, migration, and invasion of oMSCs. oMSCs were exposed to different doses and combinations of the growth factors: basic fibroblast growth factor (bFGF), transforming growth factor-ß (TGF-ß), epidermal growth factor (EGF), insulin growth factor-I (IGF-I), connective tissue growth factor, and platelet-derived growth factor-AB (PDGF-AB). Cellular proliferation, motility, and invasiveness were assayed. The most proliferative stimulating growth factors are PDGF-AB+TGF-ß and PDGF-AB+IGF-I. Combinations EGF+bFGF and EGF+bFGF+PDGF-AB demonstrated the greatest ability to stimulate migration. Moreover, the triple cocktail EGF+bFGF+TGF-ß has the most significant effect on invasion. Different growth factor cocktails are required to enhance proliferation, migration, and invasion. These results may be useful for the development of a tissue-engineered heart valve by stimulating cellular repopulation.

Bioactive porcine matrices in heart valve tissue engineering.

BACKGROUND AND AIM OF THE STUDY: Platelet gel (PG), a storage vehicle of growth factors, can be considered for the application of growth factors in combination with mesenchymal stem cells (MSCs) to accelerate tissue regeneration. Moreover, the addition of bioactive factors to porcine aortic valves could result in a more rapid repopulation. The study aim was to load acellular porcine aortic valve matrices with the PG-rich growth factors and to evaluate the effect on MSC repopulation. METHODS: Ovine mesenchymal stem cells (oMSCs) were isolated from sheep bone marrow. Acellular porcine heart valve matrices (n = 3) were preloaded with heparin and incubated with the PG for 2 h. A quantitative sandwich enzyme immunoassay was used to examine the release of basic fibroblast growth factor (bFGF) and transforming growth factor-beta (TGF-beta) from the matrices, oMSC repopulation was stimulated by static and dynamic culture. RESULTS: The immunoassays revealed that heparin-preloaded PG-incubated matrices showed a sustained release of 56.28 pg/ml bFGF and 30.66 ng/ml TGF-beta1 after 24 h. Dynamic culture induced oMSC invasion in growth factor-loaded matrices. Cell density results showed that dynamic culture significantly enhanced the repopulation of growth factor-loaded matrices (75 +/- 21 cells/mm2) when compared to static culture (26 +/- 10 cells/mm2). CONCLUSION: The incubation of a porcine aortic valve matrix with a PG concentrate creates a bioactive matrix. However, further fine-tuning of the PG concentration is necessary to take full advantage of platelet growth factor interaction between cells and the extracellular matrix in order to optimize cellular repopulation.

Decellularization of heart valve matrices: search for the ideal balance.

OBJECTIVE: Currently used decellularization procedures have negative effects on extracellular matrix (ECM) integrity. The objective of this study is to evaluate four decellularization methods and their effect on the collagen ultrastructure, mechanical behavior and antigenicity of porcine aortic valves. METHODS: Aortic valves were placed in a trypsin, osmotic, trypsin-osmotic or detergent-osmotic solution. Leaflets were processed for histology and mechanical testing. Matrices were implanted subdermally in rats to evaluate immune reaction and calcification. RESULTS: Trypsin-osmotic methodology effected near-complete decellularization. Trypsin treatment resulted in cell removal only in the spongiosa layer. Osmotic and detergent-osmotic treatments did not remove any cells from the cusps. Mechanical strength was significantly inferior in the trypsin (p50,03) and trypsin-osmotic treated group (p50,04). Trypsin and trypsin-osmotic decellularized matrices evoked a strong CD31 inflammatory cell infiltration. CONCLUSION: Enzymatic-osmotic decellularization appears to be the only effective method to remove cellular components. However, the near cell free scaffolds still evokes a strong CD31 T-cell inflammatory reaction.

Sustained release and activation of the growth factor basic fibroblast growth factor from loaded scaffolds in heart valve tissue engineering.

OBJECTIVES: Loading of biological matrices offers an opportunity to induce specific cell behaviour. We previously reported the use of growth factors to promote cell invasion and proliferation in tissue valve engineering. We investigated biological matrices preloaded with heparin as an ionically attractive template for the binding, activation and sustained release of basic fibroblast growth factor (bFGF). METHODS: Heparin loading concentrations were evaluated and different incubation times were tested. Heparin and heparin-bound bFGF uptake and release were evaluated by (123)I radio-labelling. Biological activity of bFGF was evaluated in vitro. RESULTS: Maximum heparin uptake was observed for 2000 microg/ml at 2 h and stabilized thereafter. bFGF-loaded matrices showed an initial burst release of 15% within 4 h and thereafter sustained release reaching 21% at 24 h. Released bFGF was bioactive. CONCLUSIONS: This model would be useful in tissue engineering using porcine aortic matrices and could be applied using other growth factors or combinations.

Genipin blues: an alternative non-toxic crosslinker for heart valves?

BACKGROUND AND AIM OF THE STUDY: One approach in tissue-engineering involves the implantation of decellularized, xenogenic scaffolds, with the expectation of repopulation in vivo. However, a major limitation of this method is the propensity to induce a strong immune host response. The study aim was to mitigate this immunogenicity by employing a crosslinking treatment with genipin. METHODS: Porcine matrices were prepared using a detergent-enzymatic treatment and fixed in 0.01% or 0.001% aqueous genipin. The mechanical properties of the matrices were monitored by tensile strength testing. The survival of chicken fibroblasts was used to determine cell-friendliness of the matrices. Non-fixed, decellularized biological scaffolds (n = 3) were implanted in a sheep model and compared to an equal number of genipin-fixed scaffolds (n = 6). Matrices implanted in the pulmonary position were explanted after six weeks and examined using light and transmission electron microscopy. The antibody reaction against porcine tissue in sheep serum was also determined. RESULTS: Statistically significant differences were found between non-fixed leaflets, 0.001% genipin-and 0.6% glutaraldehyde (GA)-fixed leaflets for work to maximum load (non-fixed 0.00646 J; genipin-fixed 0.00509 J; GA-fixed 0.00543 J) and stiffness (non-fixed 9281 N/m; genipin-fixed 16214 N/m; GA-fixed 14401 N/m). Genipin-treated matrices were not cytotoxic. For all concentrations of genipin a high proportion of viable cells was present (79-100%). Low-dose GA (10 microg/ml) showed a distinct cytotoxicity (24.8% viability). At explant, an intense chronic inflammatory response was observed in non-fixed matrices, in contrast to genipin-fixed scaffolds. The sheep serum showed a marked decrease in IgG response in both 0.001% and 0.01% genipin-fixed matrices (IgG 30 and 20, respectively) when compared to non-fixed matrices (IgG 40). CONCLUSION: Genipin crosslinking of the matrices attenuated, but did not eliminate, the inflammatory host reaction. Whether genipin treatment might extend the durability of xenogenic scaffolds remains to be investigated.

Histological evaluation of autophagic cell death in calcified aortic valve stenosis.

BACKGROUND AND AIM OF THE STUDY: Calcification in aortic valves is the most common valvular lesion in western populations. This event is correlated with cellular degeneration in the valvular cusps, although there is no exact evidence how these cells die: this requires further exploration. METHODS: Twelve human severely calcified aortic valves obtained during cardiac surgery were studied by semi-quantitative analysis, and results compared with data from 12 human control aortic valves obtained during autopsy. Tissue analysis was by hematoxylin and eosin and Alcian blue staining. Detection of neurons was by immunohistochemical staining of PGP9.5 and neurofilament. In order to detect autophagy, an immunohistochemical staining for ubiquitin was used. The TUNEL technique was used to detect apoptosis. Co-localization of Alizarin red with ubiquitin labeling was performed on non-decalcified aortic valves. RESULTS: Hematoxylin and eosin staining showed moderate to severe mineralization in 10 of 12 patients in the surgical group, but in only one of 12 in the autopsy group. No significant observations were made with regard to PGP9.5 and neurofilament staining. Moderate to severe ubiquitin labeling was found initially in the majority of the surgical resection group (9/12) compared to a minority in the autopsy group (1/12). TUNEL-positive labeling was very rare and found mostly at the endothelial layer of the valvular cusps. CONCLUSION: Immunohistochemical methods showed the main cell death mechanism involved in the calcification of aortic leaflets to be autophagy rather than apoptosis. These findings suggest that autophagic cell death might play a role in the release of matrix vesicles in early degenerative aortic valves, thereby attracting inflammatory cells, and this could eventually lead to mineralization.

The histopathology of varicose vein disease.

Varicosity is a complex venous pathology affecting the lower extremities. The exact etiology and physiopathology of varicose vein disease remain, however, unclear. Several theories exist from incompetence of the valves to a disturbance of the smooth muscle cells (SMC) and extra-cellular matrix (ECM) organization providing a weakness of the venous wall. Multiple studies have been performed to explain the underlying mechanisms of varicosity inducing alterations in the expression patterns of the endothelium, SMC, and ECM. In that respect, most attention has been focused on the alteration of the endothelium due to blood stasis and hypoxia inducing migration/proliferation of the medial SMC into the intima. Also, studies in the deformation of the ECM induced by alterations of the expression patterns of the metalloproteinases (MMP) and their inhibitors (TIMPs) have been put forward to explain the etiology of varicosity. However, less attention has been paid to the hormonal changes that occur during pregnancy and menopause, crucial factors to be involved in the etiology of varicosity. Since alteration of the estrogen receptor-b (ERb) expression could enhance directly the cellular volume of SMC and thus the disorganization of the contractile-elastic units, hypertrophy of SMC must be accounted a pivotal role that could induce the weakness of the venous wall. Altogether, this review summarizes an overview of the latest findings of varicosity with respect to the histopathological changes of the different cellular components of the varicose vein wall related to functional and morphologic alterations.

Histopathology of calcific aortic valve stenosis.

Calcific aortic valve stenosis is the most common and increasing heart valve disease in the western world. In the last 30 years, diagnosis and management were revolutionized by the development of cardiac catheterisation, echocardiography, cardiac surgery, and medication. Recently, new strategies were introduced for aortic valve replacement using more sophisticated bioprosthetic heart valves. Moreover, tissue-engineered heart valves are under development to improve management strategies. In this article we review the current morphological and histopathological findings in the progression of calcific aortic valve stenosis. This is, to our understanding, important to contribute to the knowledge of fundamental management strategies of this disease.

Impact of Detergent-Based Decellularization Methods on Porcine Tissues for Heart Valve Engineering.

To date an optimal decellularization protocol of heart valve leaflets (HVL) and pericardia (PER) with an adequate preservation of the extracellular matrix (ECM) is still lacking. This study compares a 4 day Triton X-100-based protocol with faster SDC-based protocols for the decellularization of cardiac tissues. Decellularized and non-treated HVL and PER were processed for histological, biochemical and mechanical analysis to determine the effect of these agents on the structure, ECM components, and biomechanical properties. Tissues treated with SDC-based protocols still showed nuclear material, whereas tissues treated with Triton X-100 1% + ENZ ± TRYP were completely cell free. For both decellularized tissues, an almost complete washout of glycosaminoglycans, a reduction of soluble collagen and an alteration of the surface ultrastructure was observed. Interestingly, only the elastic fibers of pericardial tissue were affected and this tissue had a decreased maximum load. This study showed that both detergents had a similar impact on the ECM. However, Triton X-100 1% +DNase/RNase (ENZ) ± Trypsin (TRYP) is the only protocol that generated completely cell free bioscaffolds. Also, our study clearly demonstrated that the decellularization agents have more impact on pericardial tissues than on heart valve leaflets. Thus, for the purpose of tissue engineering of heart valves, it is advisable to use valvular rather than pericardial matrices.

Role of myocardial hypertrophy on acute and chronic right ventricular performance in relation to chronic volume overload in a porcine model: relevance for the surgical management of tetralogy of Fallot.

OBJECTIVES: The age for correction of tetralogy of Fallot has progressively declined to the postnatal period, often despite an increased rate of transannular patch repair. However, the long-term effect of premature exposure to chronic pulmonary insufficiency on the right ventricle remains unknown. On the basis of the relationship between the duration of pressure overload and age, the role of previous pressure load-related hypertrophy on right ventricular (RV) performance after chronic volume overload was investigated in a porcine model. METHODS: RV hypertrophy (RVH), induced by pulmonary artery banding, was studied in pigs with (RVH plus pulmonary insufficiency [PI]) and without (RVH) subsequent PI. The effect of volume overload was compared between these 2 groups and pigs without RVH but with PI and controls (sham). Both acute and chronic effects on RV function were studied using conductance technology and validated using echocardiography. RESULTS: After chronic volume overload, the end-systolic and end-diastolic volumes were smaller in the RVH+PI group than in the PI group, including a lower pulmonary regurgitation fraction (25% ± 5% vs 35% ± 5%; P = .002). RVH resulted in better preserved systolic function, confirmed by an increased preload recruitable stroke work slope (14.7 ± 1.8 vs 9.3 ± 1.3 Mw.s/mL; P = .025) and higher RV ejection fraction (51% ± 3% vs 45% ± 4%; P = .05). Myocardial stiffness was impaired in the RVH+PI group versus the PI group (ß, 0.19 ± 0.03 vs 0.12 ± 0.02 mL(-1); P = .001), presenting restrictive physiology only in the condition associating RVH and PI. CONCLUSIONS: The results of the present study have demonstrated that RVH attenuates the RV remodeling process related to chronic PI. It enables better preservation of contractility but at the cost of sustained diastolic impairment. These findings might help to determine the timing and strategy for repair of tetralogy of Fallot when RV outflow tract morphology indicates a definite need for transannular reconstruction.

Flexural mechanical properties of porcine aortic heart valve leaflets.

Freshly excised porcine aortic heart valve cusps were subjected to a uni-axial flexural indentation test, from which the rupture characteristics and a functional stiffness parameter were determined. It was found that the flexural mechanical properties of aortic valve cusps (i) are unaffected by their coronary position and (ii) are sensitive to the effect of mechanical preconditioning. The resulting values of the cusp's flexural mechanical properties are intended as a set of reference properties which scaffolds, meant for the tissue engineering of heart valves, must approximate in order to be considered as a functional replacement.

Acute and chronic effects of dysfunction of right ventricular outflow tract components on right ventricular performance in a porcine model: implications for primary repair of tetralogy of fallot.

OBJECTIVES: This study investigates the contribution of infundibular versus pulmonary valve (PV) dysfunction on right ventricular (RV) function in a porcine model. BACKGROUND: Clinical outcome after repair of tetralogy of Fallot is determined by the adaptation of the right ventricle to the physiological sequelae of the right ventricular outflow tract (RVOT) reconstruction. Recent surgical techniques are pursuing a PV-versus infundibulum-sparing approach. METHODS: In a porcine model, 3 types of RVOT dysfunction were created and compared with sham-operated controls: infundibular dysfunction (INF), PV insufficiency (PI), and combined infundibular-PV dysfunction (TAP). Both acute and chronic effects on RV function were studied by using conductance technology and magnetic resonance imaging. RESULTS: In animals with PI, pulmonary regurgitant fraction progressed more in the presence of concomitant INF (54% in TAP versus 14% in PI; p = 0.03). Subsequently, RV end-systolic and end-diastolic volume increased more in both groups, resulting in decreased ejection fraction after 3 months. Preload-independent systolic indices showed acute impairment of RV contractility in all treatment groups but most in animals with infundibular scarring (INF and TAP). Further chronic deterioration was observed in animals of the TAP group. RV compliance improved proportionally most in the PI and TAP groups in relation to the extent of RV dilation. CONCLUSIONS: Surgical RVOT dysfunction, whether it includes the infundibulum and/or the PV, has an immediate effect on RV performance. Although impaired RV contractility is due to intrinsic myocardial damage by infundibular distortion, it is chronically furthered by PI-related RV dilation. These findings support the adoption of a RVOT-sparing strategy to treat tetralogy of Fallot.

Lumen enhancement influences absolute noncalcific plaque density on multislice computed tomography coronary angiography: ex-vivo validation and in-vivo demonstration.

AIM: The purpose of this study was to define the in-vitro and in-vivo effects of intracoronary enhancement on the absolute density values of coronary plaques during multislice computed tomography. METHODS: We studied seven ex-vivo left coronary artery specimens surrounded by olive oil and filled with isotonic saline and four solutions with decreasing dilutions of contrast material: control (isotonic saline), 1/200, 1/80, 1/50, and 1/20. The multislice computed tomography protocol was: slice/collimation 32 x 2 x 0.6 mm and rotation time 330 ms. The attenuation (Hounsfield units) value of atherosclerotic plaques was measured for each dilution in lumen, plaque (noncalcified coronary wall thickening), calcium, and surrounding oil. In-vivo assessment was performed in 12 patients (nine men; mean age 58.7 +/- 9.9 years) who underwent two subsequent multislice computed tomography scans (arterial and delayed) after intravenous administration of a single bolus of contrast material. The attenuation values of lumen and plaques during arterial and delayed computed tomography were compared. The results were compared with one-way analysis of variance and correlated with Pearson's test. RESULTS: Mean lumen (45 +/- 38-669 +/- 151 HU) and plaque (11 +/- 35-101 +/- 72 HU) attenuation differed significantly (P < 0.001) among the different dilutions. The attenuation of lumen and plaque of coronary plaques showed moderate correlation (r = 0.54, P < 0.001). The mean attenuation value in vivo for the arterial and delayed phase scans differed significantly (P < 0.001) for lumen (325 +/- 70 and 174 +/- 46 HU, respectively) and plaque (138 +/- 71 and 100 +/- 52 HU, respectively). CONCLUSION: Coronary plaque attenuation values are significantly modified by differences in lumen contrast densities both ex vivo and in vivo. This should be taken into account when considering the distinction between lipid and fibrous plaques.

Gamma radiation alters the ultrastructure in tissue-engineered heart valve scaffolds.

OBJECTIVES: Xenogenic extracellular heart valve matrices have been suggested as scaffolds for tissue engineering. However, these matrices are immunogenic and stimulate an intense cell-mediated immune response and calcification. Mitigating the immunogenicity was attempted by different doses of gamma irradiation. METHODS: Mechanical properties of gamma-irradiated porcine matrices and control matrices (nonirradiated) were examined by tensile strength testing. Irradiated matrices (1, 10, 50, and 100 gray [Gy]) and control matrices were implanted subcutaneously in Wistar rats (n = 20). After 24 h, 1, 2, 3, and 4 weeks the explants were examined by light microscopy and transmission electron microscopy. Calcium (Ca) content was determined using inductively coupled plasma-mass spectrometry. Antibody reaction against porcine tissue in the rat serum was determined. RESULTS: Tensile strength increased in irradiated matrices at the expense of elasticity. Ten gray-irradiated leaflets showed minimal lymphocytic inflammatory infiltration with preservation of ultrastructure. Ca levels after 2 weeks were as follows: control (0 Gy), 388 +/- 264 microg/mg; 1 Gy, 240 +/- 95 microg/mg; 10 Gy, 188 +/- 54 microg/mg; 50 Gy, 289 +/- 94 microg/mg; 100 Gy, 651 +/- 57 microg/mg. All implants still elicit an antibody immunoglobulin G reaction. CONCLUSIONS: Exposure to 10 Gy gamma irradiation reduces lymphocytic inflammatory infiltrates and Ca levels in acellular porcine matrices with preservation of structural integrity. This could prolong the durability of these matrices.

Mechanical and chemical characteristics of an autologous glue.

The study evaluates the mechanical and chemical characteristics of autologous surgical glue made by mixing ultrafiltered plasma with glutaraldehyde (GTA). Human albumin 200 g/L mixed with different concentrations of GTA (25, 50, 75, or 100 g/L) was used as a single protein set-up for testing tensile strength, elasticity, and rate of crosslinking. Subsequently, ultrafiltered canine or human plasma to obtain autologous glue replaced human albumin. BioGlue, a surgical glue, and Tissucol Duo, a fibrin sealant, were used as controls. Tensile strength of human albumin 200 g/L mixed with 75 g/L GTA is 825 +/- 109 N versus 672 +/- 167 N for BioGlue. Ultrafiltered canine plasma showed a maximum tensile strength of 634 +/- 137 N when mixed with GTA 75 g/L. For human plasma, the maximum tensile strength of 436 +/- 69 N was reached after mixing with GTA 25 g/L. Autologous glue had a higher elasticity of 144 +/- 66 N versus 322 +/- 104 N for BioGlue at maximum load. Autologous glues for vascular repair can be easily prepared out of the patient's plasma. The optimal characteristics, compared to BioGlue, are obtained for ultrafiltered canine and human plasma by mixing with a GTA concentration of 50-75 g/L and 25-50 g/L, respectively. The autologous glue will exert less tensile strength than BioGlue but has a better compliance. In case where no plasma can obtained from the patient, mixing human albumin 200 g/L with GTA 75 g/L can be an alternative to BioGlue.

Autologous glue: part of the sticky mystery unraveled.

OBJECTIVE: The aim of the study was to evaluate the safety and efficacy of an autologous surgical tissue adhesive. METHODS: Autologous glue was made out of canine concentrated plasma proteins mixed with 7.5% glutaraldehyde. Tensile strength and cytotoxicity of the autologous glue were tested. In a dog model, 8 transectioned iliac arteries were reanastomosed by using the animal's glue as the sole fixation method. After 120 days, all animals were angiographically controlled for patency and killed for histologic and immunohistochemical examination of the anastomosis. RESULTS: The autologous glue showed sufficient tensile strength (557 +/- 135 N/mm2). The elasticity of the glue is influenced by variations of concentrations in both proteins and glutaraldehyde. Glutaraldehyde remained cytotoxic, even at low concentrations of 2.5%. All operative procedures were successful. Angiographs performed before animal death showed all but 1 vessel to be patent and showed manifest compression signs in 3 anastomoses. Histological examination revealed only a foreign-body reaction adjacent to the surface of the glue. The autologous glue does not trigger any immune response on immunochemistry. Because fibroblastic neo-endothelial lining was near to normal, potential glutaraldehyde leaching does not seem too harmful for the vascular juncture in the dog model. CONCLUSIONS: Autologous glutaraldehyde glue has been used successfully as a vascular adhesive. In contrast to our previous studies with heterologous glue, we did not find a fierce acute inflammatory reaction indicating immune triggering. Nevertheless, glutaraldehyde remains a cytotoxic cross-linker. It is yet not known whether autologous glutaraldehyde glue can be used safely in clinical practice.

Influence of convolution filtering on coronary plaque attenuation values: observations in an ex vivo model of multislice computed tomography coronary angiography.

Attenuation variability (measured in Hounsfield Units, HU) of human coronary plaques using multislice computed tomography (MSCT) was evaluated in an ex vivo model with increasing convolution kernels. MSCT was performed in seven ex vivo left coronary arteries sunk into oil followingthe instillation of saline (1/infinity) and a 1/50 solution of contrast material (400 mgI/ml iomeprol). Scan parameters were: slices/collimation, 16/0.75 mm; rotation time, 375 ms. Four convolution kernels were used: b30f-smooth, b36f-medium smooth, b46f-medium and b60f-sharp. An experienced radiologist scored for the presence of plaques and measured the attenuation in lumen, calcified and noncalcified plaques and the surrounding oil. The results were compared by the ANOVA test and correlated with Pearson's test. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. The mean attenuation values were significantly different between the four filters (p < 0.0001) in each structure with both solutions. After clustering for the filter, all of the noncalcified plaque values (20.8 +/- 39.1, 14.2 +/- 35.8, 14.0 +/- 32.0, 3.2 +/- 32.4 HU with saline; 74.7 +/- 66.6, 68.2 +/- 63.3, 66.3 +/- 66.5, 48.5 +/- 60.0 HU in contrast solution) were significantly different, with the exception of the pair b36f-b46f, for which a moderate-high correlation was generally found. Improved SNRs and CNRs were achieved by b30f and b46f. The use of different convolution filters significantly modifief the attenuation values, while sharper filtering increased the calcified plaque attenuation and reduced the noncalcified plaque attenuation.