Cell tracking using iron oxide fails to distinguish dead from living transplanted cells in the infarcted heart
E M Winter1, B Hogers, L M van der Graaf
1Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, The Netherlands.
Abstract:
Recently, debate has arisen about the usefulness of cell tracking using iron oxide-labeled cells. Two important issues in determining the usefulness of cell tracking with MRI are generally overlooked; first, the effect of graft rejection in immunocompetent models, and second, the necessity for careful histological confirmation of the fate of the labeled cells in the presence of iron oxide. Therefore, both iron oxide-labeled living as well as dead epicardium-derived cells (EPDCs) were investigated in ischemic myocardium of immunodeficient non-obese diabetic (NOD)/acid: non-obese diabetic severe combined immunodeficient (NOD/scid) mice with 9.4T MRI until 6 weeks after surgery, at which time immunohistochemical analysis was performed. In both groups, voids on MRI scans were observed that did not change in number, size, or localization over time. Based on MRI, no distinction could be made between living and dead injected cells. Prussian blue staining confirmed that the hypointense spots on MRI corresponded to iron-loaded cells. However, in the dead-EPDC recipients, all iron-positive cells appeared to be macrophages, while the living-EPDC recipients also contained engrafted iron-loaded EPDCs. Iron labeling is inadequate for determining the fate of transplanted cells in the immunodeficient host, since dead cells produce an MRI signal indistinguishable from incorporated living cells.
Insights
Iron oxide labeling is unreliable for tracking transplanted cells with MRI. Both living and dead cells produce indistinguishable signals, hindering accurate assessment of cell fate in vivo.
Area of Science:
- Regenerative Medicine
- Biomedical Imaging
- Cell Biology
Background:
- Cell tracking using iron oxide nanoparticles and MRI is a promising technique for monitoring transplanted cells.
- However, the accuracy of this method is debated, particularly concerning graft survival and histological confirmation.
Purpose of the Study:
- To evaluate the reliability of iron oxide labeling for tracking living and dead epicardium-derived cells (EPDCs) in vivo using MRI.
- To investigate the influence of graft rejection and the necessity of histological confirmation in cell tracking studies.
Main Methods:
- Iron oxide-labeled living and dead EPDCs were transplanted into the ischemic myocardium of immunodeficient NOD/scid mice.
- High-field MRI (9.4T) was used for longitudinal tracking up to 6 weeks post-transplantation.
- Immunohistochemical analysis, including Prussian blue staining, was performed for histological confirmation.
Main Results:
- MRI scans showed voids (hypointense spots) in both living and dead cell groups, with no change in number, size, or location over time.
- MRI could not differentiate between living and dead injected cells.
- Histology confirmed that voids corresponded to iron-loaded cells, but in dead cell recipients, these were primarily macrophages, while living cell recipients showed engrafted iron-loaded EPDCs.
Conclusions:
- Iron oxide labeling is insufficient for determining the fate of transplanted cells, especially in immunodeficient hosts.
- Dead cells generate MRI signals indistinguishable from living cells, complicating interpretation of cell tracking studies.
- Accurate assessment requires complementary histological analysis to differentiate between cell types and states.
