Mesenchymal stem cell labeling and in vitro MR characterization at 1.5 T of new SPIO contrast agent: Molday ION Rhodamine‐B™

Abstract

In vivo detection of transplanted stem cells is requisite for improving stem cell-based treatments by developing a thorough understanding of their therapeutic mechanisms. MRI tracking of magnetically labeled cells is non-invasive and is suitable for longitudinal studies. Molday ION Rhodamine-B™ (MIRB) is a new superparamagnetic iron oxide (SPIO) contrast agent specifically formulated for cell labeling and is readily internalized by non-phagocytic cells. This investigation characterizes mesenchymal stem cell (MSC) labeling and MR imaging properties of this new SPIO agent. Effects of MIRB on MSC viability and differentiation as well as cellular loading properties were assessed for MSC labeled with MIRB at concentrations from 5 to 100 μg Fe/ml. Labeled MSC were evaluated, in vitro, on a clinical 1.5 T MRI. Optimal scanning sequences and imaging parameters were determined based on contrast-to-noise ratio and contrast modulation. Relaxation rates (1/T2*) for gradient-echo sequences were approximated and an idealized limit of detection was established. MIRB labeling did not affect MSC viability or the ability to differentiate into either bone or fat. Labeling efficiency was found to be approximately 95% for labeling concentrations at or above 20 μg Fe/ml. Average MIRB per MSC ranged from 0.7 pg Fe for labeling MIRB concentration of 5 μg Fe/ml and asymptotically approached a value of 20–25 pg Fe/MSC as labeling concentration increased to 100 μg Fe/ml. MRI analysis of MIRB MSC revealed long echo time, gradient echo sequences to provide the most sensitivity. Limit of detection for gradient echo sequences was determined to be less than 1000 MSC, with approximately 15 pg Fe/MSC (labeled at 20μg Fe/ml). These investigations have laid the groundwork and established feasibility for the use of this contrast agent for in vivo MRI detection of MSC. Properties evaluated in this study will be used as a reference for tracking labeled MSC for in vivo studies.

Umbilical cord mesenchymal stem cells labeled with multimodal iron oxide nanoparticles with fluorescent and magnetic properties: application for in vivo cell tracking

“…Therefore, polycationic transfection agents should be used to enhance membrane permeability. 34 However, MION-Rh does not require a polycationic transfection agent to be internalized efficiently by UC-MSC, 19 and does not affect the viability or proliferative capacity of UC-MSC, as shown in Figure 3. The colloidal behavior of SPION in different types of culture medium is almost never considered to be related to particle-cell interactions.…”

“…[16][17][18] Nanoparticles labeled with Rhodamine-B (Rh-B), a fluorescent dye that can be visualized by both MRI and fluorescent imaging, is an example of multimodal iron oxide nanoparticles (MION) with magnetic and fluorescent properties. 11,19,20 Multimodal imaging may be a powerful tool for in vivo studies of stem cell homing and injured tissue regeneration by fluorescence techniques. 11,19 This is because MIONs are not only nontoxic, but they also do not cause cell cycle arrest or changes in morphology or phenotype, and are visible by MRI and optical imaging without the requirement for invasive methods.…”

“…11,19,20 Multimodal imaging may be a powerful tool for in vivo studies of stem cell homing and injured tissue regeneration by fluorescence techniques. 11,19 This is because MIONs are not only nontoxic, but they also do not cause cell cycle arrest or changes in morphology or phenotype, and are visible by MRI and optical imaging without the requirement for invasive methods. 11,19 In this study, we report the development and validation of an efficient in vitro protocol for labeling of UC-MSC with MION conjugated to Rh-B (MION-Rh).…”

“…11,19 This is because MIONs are not only nontoxic, but they also do not cause cell cycle arrest or changes in morphology or phenotype, and are visible by MRI and optical imaging without the requirement for invasive methods. 11,19 In this study, we report the development and validation of an efficient in vitro protocol for labeling of UC-MSC with MION conjugated to Rh-B (MION-Rh). We optimized the best concentration of MION-Rh and UC-MSC, achieving robust labeling of these cells in vitro without impairing their functional properties.…”

Pre- and postmortem imaging of transplanted cells

“…48 A similar approach was employed in bone marrow-derived stem progenitor cells, where cells were labeled with the T2 contrast agent ferumoxide and a fluorescent tissue marker. 49 Ferumoxide has also been successfully used in intraventricular delivery in the pediatric patient with global ischemia (Figure 1), and long-term observation did not reveal negative consequences. 50 Microsized paramagnetic iron oxide nanoparticles are another type of MRI contrast agent, in which the diameter of nanoparticles is …”