Intravenous ferumoxytol allows noninvasive MR imaging monitoring of macrophage migration into stem cell transplants.

Evidence from laboratory and animal studies provides groundwork for understanding mechanisms and potential before human studies continue.

• Level A · Stronger Clinical Evidence
• Level B · Emerging clinical evidence with positive signals
• Level C · Early human research exploring benefits
• Level D · Scientific groundwork from lab and animal studies
• Emerging · Emerging topic under active research

Abstract (original English)

Purpose To develop a clinically applicable imaging technique for monitoring differential migration of macrophages into viable and apoptotic matrix-associated stem cell implants (MASIs) in arthritic knee joints. Materials and methods With institutional animal care and use committee approval, six athymic rats were injected with intravenous ferumoxytol (0.5 mmol iron per kilogram of body weight) to preload macrophages of the reticuloendothelial system with iron oxide nanoparticles. Forty-eight hours later, all animals received MASIs of viable adipose-derived stem cells (ADSCs) in an osteochondral defect of the right femur and mitomycin-pretreated apoptotic ADSCs in an osteochondral defect of the left femur. One additional control animal each received intravenous ferumoxytol and bilateral scaffold-only implants (without cells) or bilateral MASIs without prior ferumoxytol injection. All knees were imaged with a 7.0-T magnetic resonance (MR) imaging unit with T2-weighted fast spin-echo sequences immediately after, as well as 2 and 4 weeks after, matrix-associated stem cell implantation. Signal-to-noise ratios (SNRs) of viable and apoptotic MASIs were compared by using a linear mixed-effects model. MR imaging data were correlated with histopathologic findings. Results All ADSC implants showed a slowly decreasing T2 signal over 4 weeks after matrix-associated stem cell implantation. SN

Evidence level

Evidence from laboratory and animal studies provides groundwork for understanding mechanisms and potential before human studies continue.

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