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

Boerboom RA, Rubbens MP, Driessen NJ, Bouten CV, Baaijens FP - Ann Biomed Eng (2007)

Bottom Line: To ultimately regulate the biochemical processes, it is essential to quantify the effect of mechanical loading on the properties of engineered cardiovascular constructs.The results suggest that when the tissues are exposed to prolonged mechanical stimulation, the production of collagen with a higher fraction of crosslinks is induced.In addition, dynamic straining induced a different alignment of cells and collagen in the superficial layers compared to the deeper layers of the construct.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Soft Tissue Biomechanics and Engineering, Eindhoven University of Technology, PO Box 513, 5600 MB, Eindhoven, The Netherlands. r.a.boerboom@tue.nl

ABSTRACT
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. Corp., USA) straining system was modified to simultaneously apply various strain magnitudes to individual samples during one experiment. In addition, porous polyglycolic acid (PGA) scaffolds, coated with poly-4-hydroxybutyrate (P4HB), were partially embedded in a silicone layer to allow long-term uniaxial cyclic mechanical straining of cardiovascular engineered constructs. The constructs were subjected to two different strain magnitudes and showed differences in biochemical properties, mechanical properties and organization of the microstructure compared to the unstrained constructs. The results suggest that when the tissues are exposed to prolonged mechanical stimulation, the production of collagen with a higher fraction of crosslinks is induced. However, straining with a large strain magnitude resulted in a negative effect on the mechanical properties of the tissue. In addition, dynamic straining induced a different alignment of cells and collagen in the superficial layers compared to the deeper layers of the construct. The presented model system can be used to systematically optimize culture protocols for engineered cardiovascular tissues.

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Tangent stiffness (MPa) of 3-weeks-old engineered cardiovascular constructs as a function of different strain magnitudes. *Indicates significant difference with reference condition 0% (*p  <  0.05) and  +indicates significant difference with 4% loading condition (+p  <  0.05)
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Fig4: Tangent stiffness (MPa) of 3-weeks-old engineered cardiovascular constructs as a function of different strain magnitudes. *Indicates significant difference with reference condition 0% (*p  <  0.05) and  +indicates significant difference with 4% loading condition (+p  <  0.05)

Mentions: To characterize the effect of different strain magnitudes on engineered cardiovascular tissue properties, the tangent stiffness of the constructs and the amount of DNA, GAG, collagen, and HP crosslinks (Table 1) were quantified. Cyclic strain did not increase the amount of DNA per dryweight within the engineered tissue constructs relative to unstrained engineered tissue constructs. However, collagen per DNA and GAG per DNA in mechanically strained constructs, were significantly reduced compared to unstrained tissue constructs. The number of HP crosslinks per triple helix on the other hand were significantly increased for both strain conditions. The tangent stiffness of the 4% strained constructs was equal to the stiffness of the unstrained tissue constructs, whereas the 8% strained constructs showed a significant reduction in stiffness relative to both the unstrained and the 4% strained constructs (Fig. 4).Figure 4


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

Boerboom RA, Rubbens MP, Driessen NJ, Bouten CV, Baaijens FP - Ann Biomed Eng (2007)

Tangent stiffness (MPa) of 3-weeks-old engineered cardiovascular constructs as a function of different strain magnitudes. *Indicates significant difference with reference condition 0% (*p  <  0.05) and  +indicates significant difference with 4% loading condition (+p  <  0.05)
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2211363&req=5

Fig4: Tangent stiffness (MPa) of 3-weeks-old engineered cardiovascular constructs as a function of different strain magnitudes. *Indicates significant difference with reference condition 0% (*p  <  0.05) and  +indicates significant difference with 4% loading condition (+p  <  0.05)
Mentions: To characterize the effect of different strain magnitudes on engineered cardiovascular tissue properties, the tangent stiffness of the constructs and the amount of DNA, GAG, collagen, and HP crosslinks (Table 1) were quantified. Cyclic strain did not increase the amount of DNA per dryweight within the engineered tissue constructs relative to unstrained engineered tissue constructs. However, collagen per DNA and GAG per DNA in mechanically strained constructs, were significantly reduced compared to unstrained tissue constructs. The number of HP crosslinks per triple helix on the other hand were significantly increased for both strain conditions. The tangent stiffness of the 4% strained constructs was equal to the stiffness of the unstrained tissue constructs, whereas the 8% strained constructs showed a significant reduction in stiffness relative to both the unstrained and the 4% strained constructs (Fig. 4).Figure 4

Bottom Line: To ultimately regulate the biochemical processes, it is essential to quantify the effect of mechanical loading on the properties of engineered cardiovascular constructs.The results suggest that when the tissues are exposed to prolonged mechanical stimulation, the production of collagen with a higher fraction of crosslinks is induced.In addition, dynamic straining induced a different alignment of cells and collagen in the superficial layers compared to the deeper layers of the construct.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Soft Tissue Biomechanics and Engineering, Eindhoven University of Technology, PO Box 513, 5600 MB, Eindhoven, The Netherlands. r.a.boerboom@tue.nl

ABSTRACT
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. Corp., USA) straining system was modified to simultaneously apply various strain magnitudes to individual samples during one experiment. In addition, porous polyglycolic acid (PGA) scaffolds, coated with poly-4-hydroxybutyrate (P4HB), were partially embedded in a silicone layer to allow long-term uniaxial cyclic mechanical straining of cardiovascular engineered constructs. The constructs were subjected to two different strain magnitudes and showed differences in biochemical properties, mechanical properties and organization of the microstructure compared to the unstrained constructs. The results suggest that when the tissues are exposed to prolonged mechanical stimulation, the production of collagen with a higher fraction of crosslinks is induced. However, straining with a large strain magnitude resulted in a negative effect on the mechanical properties of the tissue. In addition, dynamic straining induced a different alignment of cells and collagen in the superficial layers compared to the deeper layers of the construct. The presented model system can be used to systematically optimize culture protocols for engineered cardiovascular tissues.

Show MeSH
Related in: MedlinePlus