Development of Timd2 as a reporter gene for MRI

PURPOSE: To assess the potential of an MRI gene reporter based on the ferritin receptor Timd2 (T‐cell immunoglobulin and mucin domain containing protein 2), using T(1)‐ and T(2)‐weighted imaging. METHODS: Pellets of cells that had been modified to express the Timd2 transgene, and incubated with either iron‐loaded or manganese‐loaded ferritin, were imaged using T(1)‐ and T(2)‐weighted MRI. Mice were also implanted subcutaneously with Timd2‐expressing cells and the resulting xenograft tissue imaged following intravenous injection of ferritin using T(2)‐weighted imaging. RESULTS: Timd2‐expressing cells, but not control cells, showed a large increase in both R(2) and R(1) in vitro following incubation with iron‐loaded and manganese‐loaded ferritin, respectively. Expression of Timd2 had no effect on cell viability or proliferation; however, manganese‐loaded ferritin, but not iron‐loaded ferritin, was toxic to Timd2‐expressing cells. Timd2‐expressing xenografts in vivo showed much smaller changes in R(2) following injection of iron‐loaded ferritin than the same cells incubated in vitro with iron‐loaded ferritin. CONCLUSION: Timd2 has demonstrated potential as an MRI reporter gene, producing large increases in R(2) and R(1) with ferritin and manganese‐loaded ferritin respectively in vitro, although more modest changes in R(2) in vivo. Manganese‐loaded apoferritin was not used in vivo due to the toxicity observed in vitro. Magn Reson Med, 2015. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Magn Reson Med 75:1697–1707, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance.