Characterization of decellularized arterial conduits

John Charles Fitzpatrick

doi:10.17918/etd-3364

Sterilization processes used on biologically-derived, intact arteries may change the vessel's structural integrity and biocompatibility from its native state. Remodeling processes that occur in biologically-derived vessels serve to restore homeostatic levels of shear and circumferential stresses, which arise from fluid flow and pressure loads. If the mechanical compliance of a decellularized artery changes from its native state, the vessel may be vulnerable to biological remodeling processes that occlude the vessel when used for small-diameter arterial bypass or replacement procedures. The effects of three distinct detergent-enzymatic decellularization protocols on porcine artery were characterized by mechanical and spectroscopic methods to evaluate cell removal efficacy, preservation of structural integrity, and altered mechanical behavior under physiological loading. Longitudinal porcine aortic strip samples were tested under uniaxial tension, and parameters optimized to a nonlinear rubber model were compared. Molecular-level changes between treated and untreated arterial tissue were assessed by observing shifts in Fourier Transform Infrared (FTIR) spectra processed by baseline-correction between amide I and II bands and optimized to Gaussian-Lorenztian curve distributions. Quasi-static inflation-extension tests were used to characterize effects of temperature and decellularization on the modeled distensibilities of native porcine carotid artery. Parameters for a nonlinear, orthotropic strain energy function were optimized to inflation-extension data to predict internal stresses at physiological loads. A four-step, 72-hour decellularizaton protocol that utilized TritonX-100, sodium-deoxycholate, RNase-A, DNase-I, and magnesium chloride as reagents was the most effective option for decellularizing porcine aorta. This protocol lysed all smooth muscle cells from porcine aorta and reduced the hyperelastic response of the vessel in the physiologic loading range. Analysis of FTIR spectra confirms that this decellularization method does not denature collagen protein structure in arterial tissue, but does alter intermolecular hydrogen bonding that supports the observed increase in bulk mechanical compliance. Three-dimensional mechanical characterization of porcine carotid artery suggests that room temperature testing conditions and the selected decellularization protocol increase arterial residual strains. Increased levels of residual strain increase the vessel's modeled distensibility and, consequently, its internal stresses. Use of a constitutive model that incorporates residual strains leads to better prediction of local circumferential stresses in comparison to mean circumferential stress approximations.

Characterization of decellularized arterial conduits

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Characterization of decellularized arterial conduits

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