The Tissue-Engineered Vascular Graft-Past, Present, and Future

Cardiovascular disease is the leading cause of death worldwide, with this trend predicted to continue for the foreseeable future. Common disorders are associated with the stenosis or occlusion of blood vessels. The preferred treatment for the long-term revascularization of occluded vessels is surgery utilizing vascular grafts, such as coronary artery bypass grafting and peripheral artery bypass grafting. Currently, autologous vessels such as the saphenous vein and internal thoracic artery represent the gold standard grafts for small-diameter vessels (<6 mm), outperforming synthetic alternatives. However, these vessels are of limited availability, require invasive harvest, and are often unsuitable for use. To address this, the development of a tissue-engineered vascular graft (TEVG) has been rigorously pursued. This article reviews the current state of the art of TEVGs. The various approaches being explored to generate TEVGs are described, including scaffold-based methods (using synthetic and natural polymers), the use of decellularized natural matrices, and tissue self-assembly processes, with the results of various in vivo studies, including clinical trials, highlighted. A discussion of the key areas for further investigation, including graft cell source, mechanical properties, hemodynamics, integration, and assessment in animal models, is then presented

Poly(ethylmethacrylate-co-diethylaminoethyl acrylate) coating improves endothelial re-population, bio-mechanical and anti-thrombogenic properties of decellularized carotid arteries for blood vessel replacement

Decellularized vascular scaffolds are promising materials for vessel replacements. However, despite the natural origin of decellularized vessels, issues such as biomechanical incompatibility, immunogenicity risks and the hazards of thrombus formation, still need to be addressed. In this study, we coated decellularized vessels obtained from porcine carotid arteries with poly (ethylmethacrylate-co-diethylaminoethylacrylate) (8g7) with the purpose of improving endothelial coverage and minimizing platelet attachment while enhancing the mechanical properties of the decellularized vascular scaffolds. The polymer facilitated binding of endothelial cells (ECs) with high affinity and also induced endothelial cell capillary tube formation. In addition, platelets showed reduced adhesion on the polymer under flow conditions. Moreover, the coating of the decellularized arteries improved biomechanical properties by increasing its tensile strength and load. In addition, after 5 days in culture, ECs seeded on the luminal surface of 8g7-coated decellularized arteries showed good regeneration of the endothelium. Overall, this study shows that polymer coating of decellularized vessels provides a new strategy to improve re-endothelialization of vascular grafts, maintaining or enhancing mechanical properties while reducing the risk of thrombogenesis. These results could have potential applications in improving tissue-engineered vascular grafts for cardiovascular therapies with small caliber vessels

Bioreactors as engineering support to treat cardiac muscle and vascular disease

Cardiovascular disease is the leading cause of morbidity and mortality in the Western World. The inability of fully differentiated, load-bearing cardiovascular tissues to in vivo regenerate and the limitations of the current treatment therapies greatly motivate the efforts of cardiovascular tissue engineering to become an effective clinical strategy for injured heart and vessels. For the effective production of organized and functional cardiovascular engineered constructs in vitro, a suitable dynamic environment is essential, and can be achieved and maintained within bioreactors. Bioreactors are technological devices that, while monitoring and controlling the culture environment and stimulating the construct, attempt to mimic the physiological milieu. In this study, a review of the current state of the art of bioreactor solutions for cardiovascular tissue engineering is presented, with emphasis on bioreactors and biophysical stimuli adopted for investigating the mechanisms influencing cardiovascular tissue development, and for eventually generating suitable cardiovascular tissue replacements

Przykłady ważnych stanowisk geologicznych w Sudetach czeskich

Artykuł daje reprezentatywny wgląd w kilka głównych geologicznych stanowisk czeskiej części Sudetów (region luzytański). Omówione zostały przykłady stanowisk o znaczeniu europejskim, reprezentujące krystaliczne kompleksy skalne, paleozoiczne osady z fauną (sylur, dewon, karbon) oraz platformowe utwory jury i kredy. Stanowiska te znajdują się już pod ochroną rzędu czeskiego, jako narodowe rezerwaty i pomniki przyrody, albo ich status ochrony jest przygotowywany

Magnetostratigraphy susceptibility of the Přídolian-Lochkovian (Silurian-Devonian) GSSP (Klonk, Czech Republic) and a coeval sequence in anti-atlas Morocco

The magnetosusceptibility event and cyclostratigraphy (MSEC) record for the Přídolian-Lochkovian (Silurian-Devonian) Global Boundary Stratotype Section and Point (GSSP) (Klonk, Prague Basin, Czech Republic) is described and used to establish a magnetostratigraphy susceptibility profile for the GSSP. GSSP MSEC data are summarized into three magnetozones (MSZ). The Tmaň MSZ (Late Přídolian) with 13 MSSZs (MSSZ), the Klonk MSZ (latest Přídolian and earliest Lochkovian) with 17 MSSZs, and the Voskop MSZ (Early Lochkovian) with 7 MSSZs. The base of Klonk MSSZ 2 is coincident with the base of Lochkovian and the Devonian. The proposed magnetostratotype for the Přídolian-Lochkovian boundary is supported by MS data from a nearby core through the GSSP sequence and into the upper Ludlow. Three additional MSZs are recognized for the portion of the core sequence older than the GSSP boundary sequence. The extension of the MSZs and MSSZs away from the proposed magnetostratotype is tested by comparison with a Lochkovian sequence in the western Sahara of southeastern Morocco. MSZs are the result of global sea level fluctuations that alter base level and the pattern of erosion and influx of detrital paramagnetic mineral components into the marine environment. Large-scale transgressive and regressive patterns interpreted from the MSEC data establish that the Silurian-Devonian boundary in the Barrandian region falls between a short-lived transgressive pulse in the latest Přídolian and an equally short-lived regressive pulse in the earliest Lochkovian. MSSZs identified in the GSSP and core sequences are the result of variation in climate cycles and the resulting periodicity can explained by either the 38.9 Ka Silurian and Devonian equivalent of the modern 54 Ka obliquity cycle or the eccentricity cycle of 106 Ka periodicity. Use of the obliquity periodicity gives a duration for the Barrandian Lochkovian of 4.46 Ma which agrees with the most recent geochronometric estimate of 4.5 Ma for the Lochkovian. Use of the eccentricity periodicity gives a duration for the Barrandian Lochkovian of 12.16 Ma which agrees with the previous geochronometric estimates of 12.2 and 12.5 Ma for the Lochkovian. In any case the cyclic nature of the MSEC data established by the MSSZs can be explained by variations in the rate of supply of weathered terrigenous paramagnetic grains to the marine system. These variations in supply occurred due to climate changes resulting from the either the obliquity or eccentricity of the Earth\u27s orbit. Knowledge of the periodicity of Lochkovian cycles in the Barrandian area allows estimation of the rates of sediment accumulation, the duration of fossil ranges, and the rates of evolution. Depending on the choice of obliquity or eccentricity to explain the cyclicity in the Barrandian Lochkovian, the estimated rate of sediment accumulation in the GSSP outcrop averaged either 51 or 140 Ka/m. The range of the graptoloid Monograptus uniformis angustidens, wholly contained within the Lochkovian sequence at the GSSP, is also estimated at either 51 or 140 Ka. © 2001 Elsevier Science B.V