Quantitative magnetic resonance imaging assessment of matrix development in cell-seeded natural urinary bladder...

The approach of cell-seeded natural scaffolds holds great promise for tissue engineering complicated soft-tissue organs such as the urinary bladder and heart. However, relatively little is known about cell-natural scaffold interactions or their influence on magnetic resonance imaging (MRI) characterization, which is valuable for noninvasive monitoring. Ideally, MRI should provide information on tissue biochemistry in addition to structure and function. In this study, quantitative MRI was performed on control and smooth muscle cell-seeded natural bladder matrices at different time points up to 7 days postseeding. Measurements of MR relaxation times (T1 and T2) and diffusion coefficient (D) showed an overall change that was incompatible with cell presence. Multicomponent T2 provided greater specificity, revealing time-course changes in the short T2 fraction that were consistent with biochemically determined matrix degradation from collagenase released from seeded cells. These matrix alterations are noted for the first time, and their relatively early occurrence may be unique to soft-tissue matrices compared with synthetic materials. More importantly, they are not evident on histology but are revealed on quantitative MRI. We conclude that quantitative MRI may provide specific information on cell-matrix interaction and is a promising noninvasive approach to understand and monitor cell-seeded natural scaffold-based regeneration.