TY - JOUR
T1 - Biomechanics of mitral valve leaflets
T2 - Second harmonic generation microscopy, biaxial mechanical tests and tissue modeling
AU - Sadeghinia, Mohammad Javad
AU - Skallerud, Bjørn
AU - Holzapfel, Gerhard A.
AU - Prot, Victorien
N1 - Funding Information:
We acknowledge Dr. Stig Urheim (Haukeland University Hospital, Department of Heart Disease, Bergen, Norway) for insightful discussions on mitral valve disease. We also thank Kathrin Torseth (Department of Cancer Research and Molecular Medicine, Faculty of Medicine, NTNU, Trondheim, Norway) for her assistance with tissue fixation and dehydration, and Astrid Bjørkøy (Department of Physics, NTNU, Trondheim, Norway) for her useful discussions on second harmonic generation microscopy.
Publisher Copyright:
© 2022 The Authors
PY - 2022/3/15
Y1 - 2022/3/15
N2 - Collagen fibers are the main load carrier in the mitral valve (MV) leaflets. Their orientation and dispersion are an important factor for the mechanical behavior. Most recent studies of collagen fibers in MVs lack either entire thickness study or high transmural resolution. The present study uses second harmonic generation (SHG) microscopy in combination with planar biaxial mechanical tests to better model and examine collagen fibers and mechanical properties of MV leaflets. SHG in combination with tissue clearing enables the collagen fibers to be examined through the entire thickness of the MV leaflets. Planar biaxial mechanical tests, on the other hand, enable the characterization of the mechanical tissue behavior, which is represented by a structural tissue model. Twelve porcine MV leaflets are examined. The SHG recording shows that the mean fiber angle for all samples varies on average by ±12° over the entire thickness and the collagen fiber dispersion changes strongly over the thickness. A constitutive model based on the generalized structure tensor approach is used for the associated tissue characterization. The model represents the tissue with three mechanical parameters plus the mean fiber direction and the dispersion, and predicts the biomechanical response of the leaflets with a good agreement (average r2=0.94). It is found that the collagen structure can be represented by a mean direction and a dispersion with a single family of fibers despite the variation in the collagen fiber direction and the dispersion over the entire thickness of MV leaflets. Statement of significance: Despite its prominent role in the mechanical behavior of mitral valve (MV) leaflets, the collagen structure has not yet been investigated over the entire thickness with high transmural resolution. The present study quantifies the detailed through thickness collagen fiber structure and examines the effects of its variation on MV tissue modeling. This is important because the study evaluates the assumption that the collagen fibers can be modeled with a representative single fiber family despite the variation across the thickness. In addition, the current comprehensive data set paves the way for quantifying the disruption of collagen fibers in myxomatous MV leaflets associated with disrupted collagen fibers.
AB - Collagen fibers are the main load carrier in the mitral valve (MV) leaflets. Their orientation and dispersion are an important factor for the mechanical behavior. Most recent studies of collagen fibers in MVs lack either entire thickness study or high transmural resolution. The present study uses second harmonic generation (SHG) microscopy in combination with planar biaxial mechanical tests to better model and examine collagen fibers and mechanical properties of MV leaflets. SHG in combination with tissue clearing enables the collagen fibers to be examined through the entire thickness of the MV leaflets. Planar biaxial mechanical tests, on the other hand, enable the characterization of the mechanical tissue behavior, which is represented by a structural tissue model. Twelve porcine MV leaflets are examined. The SHG recording shows that the mean fiber angle for all samples varies on average by ±12° over the entire thickness and the collagen fiber dispersion changes strongly over the thickness. A constitutive model based on the generalized structure tensor approach is used for the associated tissue characterization. The model represents the tissue with three mechanical parameters plus the mean fiber direction and the dispersion, and predicts the biomechanical response of the leaflets with a good agreement (average r2=0.94). It is found that the collagen structure can be represented by a mean direction and a dispersion with a single family of fibers despite the variation in the collagen fiber direction and the dispersion over the entire thickness of MV leaflets. Statement of significance: Despite its prominent role in the mechanical behavior of mitral valve (MV) leaflets, the collagen structure has not yet been investigated over the entire thickness with high transmural resolution. The present study quantifies the detailed through thickness collagen fiber structure and examines the effects of its variation on MV tissue modeling. This is important because the study evaluates the assumption that the collagen fibers can be modeled with a representative single fiber family despite the variation across the thickness. In addition, the current comprehensive data set paves the way for quantifying the disruption of collagen fibers in myxomatous MV leaflets associated with disrupted collagen fibers.
KW - Collagen fiber
KW - Mitral valve leaflet
KW - Planar biaxial mechanical test
KW - Second harmonic generation microscopy
KW - Tissue model
UR - http://www.scopus.com/inward/record.url?scp=85124403747&partnerID=8YFLogxK
U2 - 10.1016/j.actbio.2022.01.003
DO - 10.1016/j.actbio.2022.01.003
M3 - Article
C2 - 35007783
AN - SCOPUS:85124403747
VL - 141
SP - 244
EP - 254
JO - Acta Biomaterialia
JF - Acta Biomaterialia
SN - 1742-7061
ER -