Hydrated versus lyophilized forms of porcine extracellular matrix derived from the urinary bladder

Biologic scaffolds composed of naturally occurring extracellular matrix (ECM) are currently in clinical use for the repair and reconstruction of damaged or missing tissues. The material and structural properties of the ECM scaffold are important determinants of the potential clinical applications and these properties may be affected by manufacturing steps, processing steps, and storage conditions. The present study compared the structural properties of hydrated and lyophilized forms of a biologic scaffold derived from the porcine urinary bladder (urinary bladder matrix or UBM). The structural properties evaluated include: maximum load and elongation, maximum tangential stiffness, energy absorbed, suture retention strength, ball-burst strength, and the hydrostatic permeability index. Other properties that were investigated include changes in the water content, structural morphology, and thickness and the ability to support in vitro growth of NIH 3T3 cells. Lyophilization caused no changes in the structural properties evaluated with the exception of a decrease in maximum elongation. NIH 3T3 cells showed invasion of the scaffold when seeded on the abluminal side of both hydrated and lyophilized UBM, and there were more cells present on lyophilized UBM when compared to hydrated UBM devices after the 7-days culture period. Irreversible changes were observed in the microstructure and ultrastructure of lyophilized UBM devices. We conclude that lyophilization affects the overall in vitro cell growth of NIH 3T3 cells and the ultrastructural morphology of UBM devices, but does not result in significant changes in structural properties. (C) 2008 Wiley Periodicals, Inc. J Biomed Mater Res 87A: 862-872, 2008