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(Circulation. 2008;117:e307.)
© 2008 American Heart Association, Inc.

Correspondence

Response to Letter Regarding Article, "Iron-Oxide Labeling and Outcome of Transplanted Mesenchymal Stem Cells in the Infarcted Myocardium"

Yoram Amsalem, MD; Micha S. Feinberg, MD; Natalie Landa, BSc; Liron Miller, MSc; Radka Holbova; Orna Shaharabani-Yosef, PhD; Israel M. Barbash, MD; Jonathan Leor, MD

Neufeld Cardiac Research Institute, Tel-Aviv University, Sheba Medical Center, Tel-Hashomer, Israel

Yael Mardor, PhD; Dianne Daniels, MSc; Aharon Ocherashvilli, PhD

The Advanced Technology Center, Sheba Medical Center, Tel-Hashomer, Israel

We appreciate the comments of Drs Sadek and Garry on our study.¹ We agree that ‘the competent immune system of the rat may have recognized the mesenchymal cells as foreign and eliminated those cells via cellular rejection.‘ We also agree that studies with autologous stem cells or delivery of allogeneic stem cells into an immunocompromised host could improve the chance of cell survival and the probability of generating a true positive magnetic resonance imaging signal from the implanted cells. However, we disagree that the design of our study created ‘misleading‘ conclusions. Our study was not designed to confirm or refute the immunoprivileged properties of mesenchymal stem cells. We describe a scenario in which the magnetic resonance image continue to provide a positive signal from the superparamagnetic iron oxide marker despite the disappearance of the implanted, labeled cells. We showed that the reason for this finding emerged from the superparamagnetic iron oxide marker that was engulfed by resident macrophages. This may also occur after autologous stem cell transplantation, especially after long-time ex vivo expansion, as the cells may change their phenotype² and may be rejected after transplantation. In addition, even autologous cells could die from other causes such as trauma, ischemia, or apoptosis. We believe that our model is suitable to demonstrate a clinically relevant scenario in which the implanted superparamagnetic iron oxide–labeled cells died and the magnetic resonance imaging signal arose from cardiac macrophages that engulfed the superparamagnetic iron oxide nanoparticles.¹

	Acknowledgments

 
Disclosure

None.

	References

Top References

 
1. Amsalem Y, Mardor Y, Feinberg MS, Landa N, Miller L, Daniels D, Ocherashvilli A, Holbova R, Yosef O, Barbash IM, Leor J. Iron-oxide labeling and outcome of transplanted mesenchymal stem cells in the infarcted myocardium. Circulation. 2007; 116 (suppl I): I-38–I-45.[Medline] [Order article via Infotrieve]

2. Zhang CC, Lodish HF. Murine hematopoietic stem cells change their surface phenotype during ex vivo expansion. Blood. 2005; 105: 4314–4320.[Abstract/Free Full Text]

This Article Extract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Amsalem, Y. Articles by Ocherashvilli, A. Search for Related Content PubMed Articles by Amsalem, Y. Articles by Ocherashvilli, A. Related Collections Animal models of human disease Myogenesis Acute myocardial infarction Computerized tomography and Magnetic Resonance Imaging