PS224. Porcine Mesenchymal Stem Cell Labeling with MRI Contrast Agent Ferex

Mesenchymal stem cell (MSC) transplantation is currently being investigated in porcine abdominal aortic aneurysm (AAA) models for its potential as regenerative treatment. Reliable methods of labeling and tracking MSCs are necessary to evaluate their effects. This study aims to evaluate in vitro performance of Ferex, a superparamagnectic iron oxide that can be tracked by magnetic resonance imaging (MRI) and potentially be used for in vivo labeling of porcine MSCs. MSCs were isolated from pig bone marrow aspirates via Ficoll Paque separation and expanded in culture. MSCs were incubated with varying concentration of Ferex and 2 cationic transfecting agents protamine sulfate and Poly-L-Lysine (PLL). MSCs were then analyzed for cellular viability, phenotypic preservation and Ferex uptake. To confirm intracellular Ferex uptake, transmission electron microscopy (TEM) was performed. An MRI phantom was conducted by imaging known numbers of Ferex-labeled cells and examining the correlation between resulting MR signals and cell number. Ferex uptake was greatest with PLL and 200 ug/ml Ferex (2.7 ± 1.4 pg Fe/cell), with 87.1% cell viability. Flow cytometry analysis demonstrated that Ferex-labeled cells maintained phenotypic expression consistent with MSCs, with positive CD90 signals and negative CD45 and CD117 signals. TEM confirmed that Ferex particles localized to lysosomes of labeled cells. Phantom studies demonstrated a strong correlation (R2=0.9771) between cell number and in vitro MR signaling values. As a result, these findings indicate that Ferex may be used as labeling agent for in vivo tracking of transplanted MSCs in porcine AAA models.