The non-linear mechanical properties of soft engineered biological tissues determined by finite spherical indentation.

The mechanical properties of soft biological tissues in general and early stage engineered tissues in particular limit the feasibility of conventional tensile tests for their mechanical characterisation. Furthermore, the most important mode in development of deep tissue injury (DTI) is compression. Therefore, an inverse numerical-experimental approach using a finite spherical indentation test is proposed.

Nondestructive and noninvasive assessment of mechanical properties in heart valve tissue engineering.

Despite recent progress, mechanical behavior of tissue-engineered heart valves still needs improvement when native aortic valves are considered as a benchmark. Although it is known that cyclic straining enhances tissue formation, optimal loading protocols have not been defined yet. To obtain a better understanding of the effects of mechanical conditioning on tissue development, mechanical behavior of tissue constructs should be monitored and controlled during culture.

A microstructurally motivated model of the mechanical behavior of tissue engineered blood vessels.

Mechanical models have potential to guide the development and use of engineered blood vessels as well as other engineered tissues. This paper presents a microstructurally motivated, pseudoelastic, mechanical model of the biaxial mechanics of engineered vessels in the physiologic pressure range. The model incorporates experimentally measured densities and alignments of engineered collagen.

Stress related collagen ultrastructure in human aortic valves--implications for tissue engineering.

Understanding the response of tissue structures to mechanical stress is crucial for optimization of mechanical conditioning protocols in the field of heart valve tissue engineering. In heart valve tissue, it is unclear to what extent mechanical loading affects the collagen fibril morphology. To determine if local stress affects the collagen fibril morphology, in terms of fibril diameter, its distribution, and the fibril density, this was investigated in adult native human aortic valve leaflets.

Effect of strain magnitude on the tissue properties of engineered cardiovascular constructs.

Mechanical loading is a powerful regulator of tissue properties in engineered cardiovascular tissues. To ultimately regulate the biochemical processes, it is essential to quantify the effect of mechanical loading on the properties of engineered cardiovascular constructs. In this study the Flexercell FX-4000T (Flexcell Int.

Mechanical characterization of anisotropic planar biological soft tissues using finite indentation: experimental feasibility.

Heart valve tissue engineering offers a promising alternative for current treatment and replacement strategies, e.g., synthetic or bioprosthetic heart valves.

Remodelling of the angular collagen fiber distribution in cardiovascular tissues.

Understanding collagen fiber remodelling is desired to optimize the mechanical conditioning protocols in tissue-engineering of load-bearing cardiovascular structures. Mathematical models offer strong possibilities to gain insight into the mechanisms and mechanical stimuli involved in these remodelling processes. In this study, a framework is proposed to investigate remodelling of angular collagen fiber distribution in cardiovascular tissues.

Autologous human tissue-engineered heart valves: prospects for systemic application.

Background: Tissue engineering represents a promising approach for the development of living heart valve replacements. In vivo animal studies of tissue-engineered autologous heart valves have focused on pulmonary valve replacements, leaving the challenge to tissue engineer heart valves suitable for systemic application using human cells.

Methods And Results: Tissue-engineered human heart valves were analyzed up to 4 weeks and conditioning using bioreactors was compared with static culturing.

Mechanical characterization of anisotropic planar biological soft tissues using large indentation: a computational feasibility study.

Traditionally, the complex mechanical behavior of planar soft biological tissues is characterized by (multi)axial tensile testing. While uniaxial tests do not provide sufficient information for a full characterization of the material anisotropy, biaxial tensile tests are difficult to perform and tethering effects limit the analyses to a small central portion of the test sample. In both cases, determination of local mechanical properties is not trivial.

Modeling the mechanics of tissue-engineered human heart valve leaflets.

Mathematical models can provide valuable information to assess and evaluate the mechanical behavior of tissue-engineered constructs. In this study, a structurally based model is applied to describe and analyze the mechanics of tissue-engineered human heart valve leaflets. The results from two orthogonal uniaxial tensile tests are used to determine the model parameters of the constructs after two, three and four weeks of culturing.

Tissue engineering of human heart valve leaflets: a novel bioreactor for a strain-based conditioning approach.

Current mechanical conditioning approaches for heart valve tissue engineering concentrate on mimicking the opening and closing behavior of the leaflets, either or not in combination with tissue straining. This study describes a novel approach by mimicking only the diastolic phase of the cardiac cycle, resulting in tissue straining. A novel, yet simplified, bioreactor system was developed for this purpose by applying a dynamic pressure difference over a closed tissue engineered valve, thereby inducing dynamic strains within the leaflets.

A structural constitutive model for collagenous cardiovascular tissues incorporating the angular fiber distribution.

Accurate constitutive models are required to gain further insight into the mechanical behavior of cardiovascular tissues. In this study, a structural constitutive framework for cardiovascular tissues is introduced that accounts for the angular distribution of collagen fibers. To demonstrate its capabilities, the model is applied to study the biaxial behavior of the arterial wall and the aortic valve.

Improved prediction of the collagen fiber architecture in the aortic heart valve.

Living tissues show an adaptive response to mechanical loading by changing their internal structure and morphology. Understanding this response is essential for successful tissue engineering of load-bearing structures, such as the aortic valve. In this study, mechanically induced remodeling of the collagen architecture in the aortic valve was investigated.

Finite element model of mechanically induced collagen fiber synthesis and degradation in the aortic valve.

Tissue-engineered trileaflet aortic valves are a promising alternative to current valve replacements. However, the mechanical properties of these valves are insufficient for implantation at the aortic position. To simulate the effect of collagen remodeling on the mechanical properties of the aortic valve, a finite element model is presented.