MRI method for labeling and imaging decellularized extracellular matrix scaffolds for tissue engineering

Abstract

Purpose: To develop a facile method for labeling and imaging decellularized extracellular matrix (dECM) scaffolds intended for regenerating 3D tissues.

Methods: A small molecule manganese porphyrin, MnPNH₂ , was synthesized and used to label dECM scaffolds made from porcine bladder and trachea and murine whole lungs. The labeling protocol was optimized on bladder dECM, and imaging on a 3T clinical scanner was performed to assess reductions in T₁ and T₂ relaxation times. In vivo MRI was performed on dECM injected in the rat dorsum to verify sensitivity of detection. Toxicity assays for cell viability, metabolism, and proliferation were performed on human umbilical vein endothelial cells. The incorporation of MnPNH₂ and its long-term retention in dECM were assessed on transmission electron microscopy and ultraviolet absorbance of eluted MnPNH₂ over time.

Results: All tissues, including thick whole 3D organs, were uniformly labeled and demonstrated high signal-to-noise on MRI. A nearly 10-fold reduction in T₁ was consistently obtained at a labeling dose of 0.4 mM, and even 0.2 mM provided sufficient contrast in vivo and ex vivo. No toxicity was observed up to 0.4 mM, the maximum tested. Binding studies suggested nonspecific association, and retention studies in the labeled whole decellularized lungs revealed less than 20% MnPNH₂ loss over 30 days, the majority occurring in the first 3 days after labeling.

Conclusion: The proposed labeling method is the first report for visualizing dECM on MRI and has the potential for long-term monitoring and optimization of dECM-based organ tissue engineering.

Keywords: biomaterial; decellularized extracellular matrix; regenerative medicine; scaffold; tissue engineering.