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J R Soc Interface. 2019 Jul 26;16(156):20190069. doi: 10.1098/rsif.2019.0069. Epub 2019 Jul 3.

An investigation of the glycosaminoglycan contribution to biaxial mechanical behaviours of porcine atrioventricular heart valve leaflets.

Author information

1
1 Biomechanics and Biomaterials Design Laboratory, School of Aerospace and Mechanical Engineering, The University of Oklahoma , Norman, OK , USA.
2
2 Stephenson School of Biomedical Engineering, The University of Oklahoma , Norman, OK , USA.
3
4 Advanced Magnetic Resonance Center, MS 60, Oklahoma Medical Research Foundation , Oklahoma City, OK , USA.
4
5 Department of Pathology, The University of Oklahoma Health Sciences Center , Oklahoma City, OK , USA.
5
6 Stephenson Cancer Center, The University of Oklahoma Health Sciences Center , Oklahoma City, OK , USA.
6
7 Division of Pediatric Cardiology, Department of Pediatrics, The University of Oklahoma Health Sciences Center , Oklahoma City, OK , USA.
7
8 Division of Cardiothoracic Surgery, Department of Surgery, The University of Oklahoma Health Sciences Center , Oklahoma City, OK , USA.
8
9 Institute of Biomechanics, Graz University of Technology , Graz , Austria.
9
10 Department of Structural Engineering, Norwegian University of Science and Technology (NTNU) , Trondheim , Norway.
10
3 Institute for Biomedical Engineering, Science and Technology, The University of Oklahoma , Norman, OK , USA.

Abstract

The atrioventricular heart valve (AHV) leaflets have a complex microstructure composed of four distinct layers: atrialis, ventricularis, fibrosa and spongiosa. Specifically, the spongiosa layer is primarily proteoglycans and glycosaminoglycans (GAGs). Quantification of the GAGs' mechanical contribution to the overall leaflet function has been of recent focus for aortic valve leaflets, but this characterization has not been reported for the AHV leaflets. This study seeks to expand current GAG literature through novel mechanical characterizations of GAGs in AHV leaflets. For this characterization, mitral and tricuspid valve anterior leaflets (MVAL and TVAL, respectively) were: (i) tested by biaxial mechanical loading at varying loading ratios and by stress-relaxation procedures, (ii) enzymatically treated for removal of the GAGs and (iii) biaxially mechanically tested again under the same protocols as in step (i). Removal of the GAG contents from the leaflet was conducted using a 100 min enzyme treatment to achieve approximate 74.87% and 61.24% reductions of all GAGs from the MVAL and TVAL, respectively. Our main findings demonstrated that biaxial mechanical testing yielded a statistically significant difference in tissue extensibility after GAG removal and that stress-relaxation testing revealed a statistically significant smaller stress decay of the enzyme-treated tissue than untreated tissues. These novel findings illustrate the importance of GAGs in AHV leaflet behaviour, which can be employed to better inform heart valve therapeutics and computational models.

KEYWORDS:

atrioventricular heart valves; biaxial mechanical testing; glycosaminoglycan removal; leaflet microstructure; stress relaxation

PMID:
31266416
DOI:
10.1098/rsif.2019.0069

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