Biocompatibility and immunogenicity of decellularised allogeneic aorta in the orthotopic rat model

Background and aim of the study: Peripheral arterial disease causes blood vessel dysfunction that requires surgical intervention. Current surgical interventions employ synthetic or allogeneic vascular grafts, which offer biocompatible materials solutions that are not able to regenerate or grow with the patient. Decellularised scaffolds have gained significant momentum in the past few years, since they have the potential to regenerate in the patient. The aim of this study was to investigate the effects of modified decellularisation protocol on the biocompatibility and immunogenicity of allogeneic rat abdominal aorta in an orthotopic rat model. Methods: Native syngeneic Wistar (W) and allogeneic Dark Agouti (DA) aortas, together with decellularised allogeneic DA aortas, were assessed histologically, immunohistochemically and biomechanically. The immunogenicity of the untreated and decellularized syngeneic and allogeneic grafts was assessed in W rats, implanted orthotopically. Following implantation for 6 weeks, the grafts were explanted and assessed for the presence of T cells and macrophages by immunohistochemistry, and for their biomechanical integrity and histoarchitecture. Results: No obvious histoarchitectural differences were observed between the native W and DA aortas, with both presenting similar three-layered structures. Histological analysis of decellularized DA aortas did not reveal any remaining cells. Explanted native DA allografts showed media necrosis, partial elastic fibre degradation and adventitia thickening, as well as infiltration by lymphocytes (CD3+, CD4+) and macrophages (CD68+) in the adventitia. The explanted decellularized DA allografts indicated reduced immune injury compared to the explanted native DA allografts. The explanted native W syngeneic grafts showed a mild immune response, with an intact media and no lymphocyte infiltration. The explanted native DA allografts showed significantly lower collagen phase slope than the decellularized DA allografts prior implantation, and significantly higher thickness than the explanted decellularized DA allografts. Conclusions: The results indicated that the modified decellularization protocol did not affect significantly the mechanical and histological properties of the native DA rat aorta. Overall, the immune response was improved by decellularization. Native DA allografts induced an adverse immune response in W rats, whereas syngeneic W grafts showed good tissue integration

Investigation of the biomechanical integrity of decellularized rat abdominal aorta

Objectives. The loss or damage of an organ or tissue is one of the most common and devastating problems in healthcare today. Tissue engineering applies the principles of engineering and biology toward the development of functional biological replacements that are able to maintain, improve, or restore the function of pathological tissues. The aim of the overall project is to study an already existing method for the decellularization of homograft vascular grafts for use in vascular surgery. Materials and Methods. The biomechanical integrity of native and decellularized rat aortas was assessed under uniaxial tension tests. For this purpose, 36 male rats (12 Wistar and 24 Dark Agouti [DA]) were used to excise their abdominal aortas. Twelve of the aortas were tested fresh (Wistar and DA rats), within 24 hours from euthanasia, and the rest were decellularized using a modified protocol (DA rats only). Fresh and decellularized samples (n ¼ 12) were subjected to uniaxial tensile loading to failure, and the recorded stress-strain behaviour of each specimen was assessed in terms of 6 biomechanical parameters. Results. No statistically significant differences were found in any of the biomechanical parameters studied between the decellularized DA rat aorta group and both the native DA and Wistar rat aorta groups (P > .05). Also, no significant difference was shown between the native DA and native Wistar rat aorta groups. Conclusions. The results from this study have shown that the decellularization protocol did not affect the mechanical properties of the native rat aorta. In addition to this, both native Wistar and native/decellularized DA rat aorta groups shared similar mechanical properties

Vitrified human umbilical arteries as potential grafts for vascular tissue engineering

Background: The development of a biological based small diameter vascular graft (d < 6 mm), that can be properly stored over a long time period at − 196 °C, in order to directly be used to the patients, still remains a challenge. In this study the decellularized umbilical arteries (UAs) where vitrified, evaluated their composition and implanted to a porcine model, thus serving as vascular graft. Methods: Human UAs were decellularized using 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) and sodium dodecyl sulfate (SDS) detergents. Then, vitrified with vitrification solution 55 (VS55) solution, remained for 6 months in liquid nitrogen and their extracellular matrix composition was compared to conventionally cryopreserved UAs. Additionally, total hydroxyproline, sulphated glycosaminoglycan and DNA content were quantified in all samples. Finally, the vitrified umbilical arteries implanted as common carotid artery interposition graft to a porcine animal model. Results: Decellularized and vitrified UAs characterized by proper preservation of extracellular matrix proteins and tissue architecture, whereas conventionally cryopreserved samples exhibited a disorganized structure. Total hydroxyproline content was preserved, although sulphated glycosaminoglycan and DNA contents presented significantly alterations in all samples. Implanted UAs successfully recellularized and remodeled as indicated by the histological analysis. Conclusion: Decellularized and vitrified UAs retained their structure function properties and can be possible used as an alternative source for readily accessible small diameter vascular grafts

Body-weight and plasma levels of glucose, total cholesterol, and triglycerides at the intervention start and the end of the study.

<p>Body-weight and plasma levels of glucose, total cholesterol, and triglycerides at the intervention start and the end of the study.</p

Co-localized stains of serial sections of the aortic arch in Apo-E−/− mouse. Section thickness was set at 5 µm and original magnification at 100x.

<p>A: Haematoxylin-Eosin stain for morphometry. B: Sirius red for collagen stain. C: Orcein for elastin stain. D: Immunohistochemistry, MMP-2 stain.</p

Representative images from zymograms for the identification of metalloproteinase activity and reverse zymograms for the identification of TIMP activity.

<p>A) Zymograhy, MMP-2, MMP-9 and proMMP-2 identification. B) Reverse zymography, TIMP-1 and TIMP-2 identification.</p

Morphometry and immunohistochemistry results for total plaque area in all examined aortic regions, collagen and elastin content, MMP, TIMP, mac-3, a-actin and iNOS intra-plaque localization and activity.

<p>*: p value vs CO group <.05; ▴: ANOVA significance value <.05 and post hoc Tuckey HSD test p value vs AT group <.05; ▪: ANOVA significance value <.05 and post hoc Tuckey HSD test p value vs EX group <.05.</p

The Complementary Effects of Atorvastatin and Exercise Treatment on the Composition and Stability of the Atherosclerotic Plaques in ApoE Knockout Mice

<div><p>Aim</p><p>This study aimed to investigate the effects of combined atorvastatin and exercise treatment on the composition and stability of the atherosclerotic plaques in apolipoproteinE (apoE) knockout mice.</p><p>Methods</p><p>Forty male, apoE^−/− mice were fed a high-fat diet for 16 weeks. Thereafter, while maintained on high-fat diet, they were randomized into four (n = 10) groups for 8 additional weeks: Group CO: Control. Group AT: Atorvastatin treatment (10 mg/Kg/day). Group EX: Exercise-training on treadmill. Group AT+EX: Atorvastatin and simultaneous exercise training. At the study’s end, plasma cholesterol levels, lipids and triglycerides were measured, along with the circulating concentrations of matrix-metalloproteinases (MMP-2,3,8,9) and their inhibitors (TIMP-1,2,3). Plaque area and the relative concentrations of collagen, elastin, macrophages, smooth muscle cells, MMP-2,3,8,9 and TIMP-1,2,3 within plaques were determined. Lastly, MMP activity was assessed in the aortic arch.</p><p>Results</p><p>All intervention groups showed a lower degree of lumen stenosis, with atheromatous plaques containing more collagen and elastin. AT+EX group had less stenosis and more elastin compared to single intervention groups. MMP-3,-8 -9 and macrophage intra-plaque levels were reduced in all intervention groups. EX group had increased TIMP-1 levels within the lesions, while TIMP-2 was decreased in all intervention groups. The blood levels of the above molecules increased during atherosclerosis development, but they did not change after the therapeutic interventions in accordance to their intra-plaque levels.</p><p>Conclusion</p><p>The two therapeutic strategies act with synergy regarding the extent of the lesions and lumen stenosis. They stabilize the plaque, increasing its content in elastin and collagen, by influencing the MMP/TIMP equilibrium, which is mainly associated with the macrophage amount. While the increased MMP-2,-3,-8 -9, as well as TIMP-1 and TIMP-2 circulating levels are markers of atherosclerosis, they are not correlated with their corresponding concentrations within the lesions after the therapeutic interventions, and cannot serve as markers for the disease development/amelioration.</p></div

Circulating concentrations of MMPs and TIMPs at the beginning and the end of the study (in ng/ml).

<p>Circulating concentrations of MMPs and TIMPs at the beginning and the end of the study (in ng/ml).</p

Densitometry measurements in zymography and reverse zymography gels.

<p>Densitometry measurements in zymography and reverse zymography gels.</p