Measurements of the effects of decellularization on viscoelastic properties of tissues in ovine, baboon, and human heart valves.

School of Engineering, Brown University, Providence, Rhode Island 02912, USA.
Tissue Engineering Part A (Impact Factor: 4.64). 09/2011; 18(3-4):423-31. DOI: 10.1089/ten.TEA.2010.0677
Source: PubMed

ABSTRACT In the development of tissue-engineered heart valves based on allograft decellularized extracellular matrix scaffolds, the material properties of the implant should be ideally comparable to the native semilunar valves. This investigation of the viscoelastic properties of the three functional aortic/pulmonary valve tissues (leaflets, sinus wall, and great vessel wall) was undertaken to establish normative values for fresh samples of human valves and to compare these properties after various steps in creating scaffolds for subsequent bioreactor-based seeding protocols. Torsional wave methods were used to measure the viscoelastic properties. Since preclinical surgical implant validation studies require relevant animal models, the tests reported here also include results for three pairs of both ovine and baboon aortic and pulmonary valves. For human aortic valves, four cryopreserved valves were compared with four decellularized scaffolds. Because of organ and heart valve transplant scarcity for pulmonary valves, only three cryopreserved and two decellularized pulmonary valves were tested. Leaflets are relatively soft. Loss angles are similar for all tissue samples. Regardless of species, the decellularization process used in this study has little effect on viscoelastic properties.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The field of tissue engineering has been growing in the recent years as more products have made it to the market and as new uses for the engineered tissues have emerged, motivating many researchers to engage in this multidisciplinary field of research. Engineered tissues are now not only considered as end products for regenerative medicine, but also have emerged as enabling technologies for other fields of research ranging from drug discovery to biorobotics. This widespread use necessitates a variety of methodologies for production of tissue engineered constructs. In this review, these methods together with their non-clinical applications will be described. First, we will focus on novel materials used in tissue engineering scaffolds; such as recombinant proteins and synthetic, self assembling polypeptides. The recent advances in the modular tissue engineering area will be discussed. Then scaffold-free production methods, based on either cell sheets or cell aggregates will be described. Cell sources used in tissue engineering and new methods that provide improved control over cell behavior such as pathway engineering and biomimetic microenvironments for directing cell differentiation will be discussed. Finally, we will summarize the emerging uses of engineered constructs such as model tissues for drug discovery, cancer research and biorobotics applications.
    IEEE reviews in biomedical engineering. 12/2012;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Aortic valve (AV) performance is closely linked to its structural components. Glycosaminoglycans (GAGs) are thought to influence the time-dependent properties of living tissues. This study investigates the effect of GAGs on the viscoelastic behaviour of the AV. Fresh porcine AV cusps were either treated enzymatically to remove GAGs or left untreated (control). The specimens were tested for stress relaxation and tensile properties under equibiaxial load conditions. The stress relaxation curves were fitted using a double exponential decay equation and the early relaxation constant (τ(1)) and late relaxation constant (τ(2)) calculated for each specimen. Immunohistochemistry confirmed the successful depletion of both sulphated and non-sulphated GAGs from the AV cusps. A statistical increase in τ(1) was found for both the radial and circumferential directions between the control and -GAGs group (radial, control 17.37s vs. -GAGs 25.65s; circumferential, control 21.47s vs. -GAGs 27.37s). It was also found that τ(1) differed between the two directions for the control group but not after GAG depletion (control, radial 17.37s vs. circumferential 21.47s; -GAGs, radial 25.65s vs. circumferential 27.37s). No effect on stiffness was found. The results showed that the presence of GAGs influences the mechanical viscoelastic properties of the AV but has no effect on the stiffness. The natural anisotropy, which reflects the relaxation kinematics, is lost after GAG depletion.
    Acta biomaterialia 09/2012; · 5.68 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: There is a major need for scaffold-based tissue engineered vascular grafts and heart valves with long-term patency and durability to be used in diabetic cardiovascular patients. We hypothesized that diabetes, by virtue of glycoxidation reactions, can directly crosslink implanted scaffolds, drastically altering their properties. In order to investigate the fate of tissue engineered scaffolds in diabetic conditions, we prepared valvular collagen scaffolds and arterial elastin scaffolds by decellularization and implanted them subdermally in diabetic rats. Both types of scaffolds exhibited significant levels of advanced glycation end products (AGEs), chemical crosslinking and stiffening -alterations which are not favorable for cardiovascular tissue engineering. Pre-implantation treatment of collagen and elastin scaffolds with penta-galloyl glucose (PGG), an antioxidant and matrix-binding polyphenol, chemically stabilized the scaffolds, reduced their enzymatic degradation, and protected them from diabetes-related complications by reduction of scaffold-bound AGE levels. PGG-treated scaffolds resisted diabetes-induced crosslinking and stiffening, were protected from calcification, and exhibited controlled remodeling in vivo, thereby supporting future use of diabetes-resistant scaffolds for cardiovascular tissue engineering in patients with diabetes.
    Biomaterials 10/2012; 34(3). · 8.31 Impact Factor

Full-text (2 Sources)

Available from
May 28, 2014