Effects of decellularization on the mechanical and structural properties of the porcine aortic valve leaflet

Abstract

The potential for decellularized aortic heart valves (AVs) as heart valve replacements is based on the assumption that the major cellular immunogenic components have been removed, and that the remaining extracellular matrix (ECM) should retain the necessary mechanical properties and functional design. However, decellularization processes likely alter the ECM mechanical and structural properties, potentially affecting long term durability. In the present study we explored the effects of an anionic detergent (SDS), enzymatic agent (Trypsin), and a non-ionic detergent (Triton X-100) on the mechanical and structural properties of AV leaflets (AVLs) to provide greater insight into the initial functional state of the decellularized AVL. The overall extensibility represented by the areal strain under 60 N/m increased from 68.85% for the native AV to 139.95%, 137.51%, and 177.69% for SDS, Trypsin, and Triton X-100, respectively, after decellularization. In flexure, decellularized AVLs demonstrated a profound loss of stiffness overall, and also produced a nonlinear moment-curvature relation compared to the linear response of the native AVL. Effective flexural moduli decreased from 156.0±24.6 kPa for the native AV to 23.5±5.8 kPa, 15.6±4.8 kPa, and 19.4 ±8.9 kPa for SDS, Trypsin, and Triton X-100 treated leaflets, respectively. While the overall leaflet fiber architecture remained relatively unchanged, decellularization resulted in substantial microscopic disruption. In conclusion, changes in mechanical and structural properties of decellularized leaflets were likely associated with disruption of the ECM, which may impact the durability of the leaflets.

Decellularization of pericardial tissue and its impact on tensile viscoelasticity and glycosaminoglycan content

“…The decellularization of collagenous tissues has been explored as ECM may serve as appropriate biological scaffold for cell attachment. However, alterations both in the structural composition and in the mechanical properties of the remaining ECM can be induced during the decellularization protocols [20,32]. The mechanical integrity can be affected and it may be associated either to the denaturation of the collagen triple helix or to the loss of macromolecular substances such as glycoproteins [21].…”

“…For example, the decellularization of porcine heart valve with SDS appeared to maintain critical mechanical and structural properties of the leaflets of valves [32] while decellularization of bovine pericardium with SDS resulted in a reduction in denaturation temperature [21] and a reduction of almost 50% on tensile strength when compared to native and TX100 treated tissue respectively [24]. Courtman et al proposed that an anionic detergent binds to protein, increases negative charges and results in tissue irreversible swelling [21].…”

Whole-organ engineering with natural extracellular materials

“…These scaffolds retain the original architecture of organs and tissue interfaces, giving rise to a source of allogenic and xenogenic whole--organ grafts. Decellularization has been carried out on a variety of tissues of various organs such as the urinary bladder, small intestinal submucosa, blood vessels, heart valves, pericardium, tooth buds, trachea and esophagus, as well as musculoskeletal regions such as the temporomandibular joint [9][10][11][12][13][14][15][16][17][18][19][20][21][22]. This method of creating acellular scaffolds has resulted in commercial products and tissue substitutes [23][24][25][26][27].…”

“…Accordingly, protocols should be designed to detect and minimize destruction, while preserving the mechanical integrity of the tissue. Often, retention of ECM architecture is validated in comparison to untreated cadaveric tissue with microscopy to ensure tissue integrity is not compromised [12,13,17,22,28,32,35]. Using histological methods, the extent of ECM damage in collagen-dominated tissue has been quantified by measuring collagen crimping amplitude and periodicity, which can result from exposure to detergents such as sodium dodecyl sulfate [17,35].…”

“…Often, retention of ECM architecture is validated in comparison to untreated cadaveric tissue with microscopy to ensure tissue integrity is not compromised [12,13,17,22,28,32,35]. Using histological methods, the extent of ECM damage in collagen-dominated tissue has been quantified by measuring collagen crimping amplitude and periodicity, which can result from exposure to detergents such as sodium dodecyl sulfate [17,35]. Other imaging techniques such as scanning-electron microscopy have been used to visualize and compare nanostructures (e.g., the weave, coil and strut fibers in the decellularized heart study) in decellularized and non-decellularized cadaveric tissue [32].…”