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Quantification of the temporal evolution of collagen orientation in mechanically conditioned engineered cardiovascular tissues.

Rubbens MP, Driessen-Mol A, Boerboom RA, Koppert MM, van Assen HC, TerHaar Romeny BM, Baaijens FP, Bouten CV - Ann Biomed Eng (2009)

Bottom Line: Engineered tissues often lack properly organized collagen and consequently do not meet in vivo mechanical demands.Most importantly, intermittent straining improved and accelerated the alignment of the collagen fibers, as compared to constraining the constructs.Both the method and the results are relevant to create and monitor load-bearing tissues with an organized anisotropic collagen network.

View Article: PubMed Central - PubMed

Affiliation: Soft Tissue Biomechanics & Engineering, Department of Biomedical Engineering, Eindhoven University of Technology, WH 4.107, Den Dolech 2, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands. m.p.rubbens@tue.nl

ABSTRACT
Load-bearing soft tissues predominantly consist of collagen and exhibit anisotropic, non-linear visco-elastic behavior, coupled to the organization of the collagen fibers. Mimicking native mechanical behavior forms a major goal in cardiovascular tissue engineering. Engineered tissues often lack properly organized collagen and consequently do not meet in vivo mechanical demands. To improve collagen architecture and mechanical properties, mechanical stimulation of the tissue during in vitro tissue growth is crucial. This study describes the evolution of collagen fiber orientation with culture time in engineered tissue constructs in response to mechanical loading. To achieve this, a novel technique for the quantification of collagen fiber orientation is used, based on 3D vital imaging using multiphoton microscopy combined with image analysis. The engineered tissue constructs consisted of cell-seeded biodegradable rectangular scaffolds, which were either constrained or intermittently strained in longitudinal direction. Collagen fiber orientation analyses revealed that mechanical loading induced collagen alignment. The alignment shifted from oblique at the surface of the construct towards parallel to the straining direction in deeper tissue layers. Most importantly, intermittent straining improved and accelerated the alignment of the collagen fibers, as compared to constraining the constructs. Both the method and the results are relevant to create and monitor load-bearing tissues with an organized anisotropic collagen network.

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Different steps of the orientation analysis. On the multiphoton image (a) coherence enhanced diffusion is applied (b). Using the Hessian matrix the principal curvature directions are calculated (c) which results in a histogram of orientations (d). Scale bar represents 50 μm
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Fig3: Different steps of the orientation analysis. On the multiphoton image (a) coherence enhanced diffusion is applied (b). Using the Hessian matrix the principal curvature directions are calculated (c) which results in a histogram of orientations (d). Scale bar represents 50 μm

Mentions: A representative example of the application of the orientation algorithm is shown in Fig. 3. In brief, to each multiphoton image of cells and collagen fibers (Fig. 3a), coherence enhanced diffusion is applied. This enhances the collagen fiber structures (Fig. 3b). Next, the principle curvature directions are calculated per pixel (Fig. 3c). Subsequently, the orientation analysis program generates a histogram of the orientations (Fig. 3d), from which the mean angle and vector length are calculated using circular statistics.Figure 3


Quantification of the temporal evolution of collagen orientation in mechanically conditioned engineered cardiovascular tissues.

Rubbens MP, Driessen-Mol A, Boerboom RA, Koppert MM, van Assen HC, TerHaar Romeny BM, Baaijens FP, Bouten CV - Ann Biomed Eng (2009)

Different steps of the orientation analysis. On the multiphoton image (a) coherence enhanced diffusion is applied (b). Using the Hessian matrix the principal curvature directions are calculated (c) which results in a histogram of orientations (d). Scale bar represents 50 μm
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2690830&req=5

Fig3: Different steps of the orientation analysis. On the multiphoton image (a) coherence enhanced diffusion is applied (b). Using the Hessian matrix the principal curvature directions are calculated (c) which results in a histogram of orientations (d). Scale bar represents 50 μm
Mentions: A representative example of the application of the orientation algorithm is shown in Fig. 3. In brief, to each multiphoton image of cells and collagen fibers (Fig. 3a), coherence enhanced diffusion is applied. This enhances the collagen fiber structures (Fig. 3b). Next, the principle curvature directions are calculated per pixel (Fig. 3c). Subsequently, the orientation analysis program generates a histogram of the orientations (Fig. 3d), from which the mean angle and vector length are calculated using circular statistics.Figure 3

Bottom Line: Engineered tissues often lack properly organized collagen and consequently do not meet in vivo mechanical demands.Most importantly, intermittent straining improved and accelerated the alignment of the collagen fibers, as compared to constraining the constructs.Both the method and the results are relevant to create and monitor load-bearing tissues with an organized anisotropic collagen network.

View Article: PubMed Central - PubMed

Affiliation: Soft Tissue Biomechanics & Engineering, Department of Biomedical Engineering, Eindhoven University of Technology, WH 4.107, Den Dolech 2, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands. m.p.rubbens@tue.nl

ABSTRACT
Load-bearing soft tissues predominantly consist of collagen and exhibit anisotropic, non-linear visco-elastic behavior, coupled to the organization of the collagen fibers. Mimicking native mechanical behavior forms a major goal in cardiovascular tissue engineering. Engineered tissues often lack properly organized collagen and consequently do not meet in vivo mechanical demands. To improve collagen architecture and mechanical properties, mechanical stimulation of the tissue during in vitro tissue growth is crucial. This study describes the evolution of collagen fiber orientation with culture time in engineered tissue constructs in response to mechanical loading. To achieve this, a novel technique for the quantification of collagen fiber orientation is used, based on 3D vital imaging using multiphoton microscopy combined with image analysis. The engineered tissue constructs consisted of cell-seeded biodegradable rectangular scaffolds, which were either constrained or intermittently strained in longitudinal direction. Collagen fiber orientation analyses revealed that mechanical loading induced collagen alignment. The alignment shifted from oblique at the surface of the construct towards parallel to the straining direction in deeper tissue layers. Most importantly, intermittent straining improved and accelerated the alignment of the collagen fibers, as compared to constraining the constructs. Both the method and the results are relevant to create and monitor load-bearing tissues with an organized anisotropic collagen network.

Show MeSH