Tissue engineering of heart valves: biomechanical and morphological properties of decellularized heart valves

Biological scaffolds are widely used in the process of cardiac valve tissue engineering. Scaffold characteristics are decisive for valve durability. Herein, the influence of three different decellularization protocols on the morphological and biomechanical properties of porcine pulmonary valve conduits was evaluated.

Pulmonary valve conduits were decellularized with 1% sodium deoxycholate (SD), 1% sodium dodecylsulfate (SDS), or 0.05% trypsin/0.02% EDTA. The degree of decellularization and morphological integrity of the treated pulmonary valve cusp, wall and myocardial cuff were analyzed with hematoxylin and eosin staining, Movat-Pentachrome staining, electron microscopy, and DNA assay. The conservation of extracellular matrix (ECM) proteins was evaluated by immunohistochemical staining against collagens I and IV, and laminin. The biomechanical properties of the obtained scaffolds were evaluated using uniaxial tension tests. Native grafts served as controls.

All treatments resulted in complete decellularization of the cusp, whereas only SD and SDS treatments were able to remove completely all cells from the pulmonary valve wall and subvalvular myocardial cuff. The morphological integrity and preservation of ECM proteins was clearly superior in both detergent-treated groups. Enzyme treatment resulted in destruction of the basement membrane. Wall longitudinal tension parameters (stiffness, elasticity modulus, ultimate force; stress and strain) were significantly inferior in the trypsin/EDTA group (p < 0.05). No significant differences were observed between detergent-treated and native samples. The results of transversal tension parameters were comparable in all groups.

Both, SD and SDS treatment of the pulmonary valve may better preserve the morphological and biomechanical properties of the scaffold than the chosen enzymatic treatment. In the authors' opinion, detergent-based decellularization should be used in preference to enzyme treatment in the tissue engineering of heart valves.