In Vitro Model of BrdU or Iron Oxide Nanoparticle Uptake by Activated Macrophages from Labeled Stem Cells: Implications for Cellular Therapy

¹ Experimental Neuroimaging Section Laboratory of Diagnostic Radiology Research, Clinical Center, Bethesda, Maryland 20892
² Department of Radiology, Henry Ford Health System, Detroit Michigan, Bethesda, Maryland 20892
³ Experimental Neuroimaging Section Laboratory of Diagnostic Radiology Research, Clinical Center, Detroit Michigan, Bethesda, Maryland 20892
⁴ National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland 20892

^* To whom correspondence should be addressed. E-mail: pawelczyke{at}cc.nih.gov.

	Abstract

There is increasing interest in using exogenous labels such as bromodeoxyuridine (BrdU) or superparamagnetic iron oxide nanoparticles (SPION) to label cells to identify transplanted cells and monitor their migration by fluorescent microscopy or in vivo magnetic resonance imaging (MRI), respectively. Direct implantation of cells into target tissue can result in >80% cell death due to trauma or apoptosis. Bystander uptake of labeled cells by activated macrophages (AM) can confound the interpretation of results. This study investigated the frequency of BrdU or SPION uptake by AM using Boyden chamber model of inflammation. SPION/BrdU labeled bone marrow stromal cells (BMSCs) or HeLa (HC), AM and mouse (MF) or human fibroblasts (HF) were mixed in various ratios in Matrigel^TM, in the upper chamber and incubated for up to 96 hours. The AM were chemotactically induced to migrate to the lower chamber. FACS analysis of AM from lower and upper chambers, in the presence of either MF or HF using anti-CD68, anti-BrdU, anti-dextran antibodies, revealed 10 to 20% dextran or 10% BrdU positive AM after 96 hours of incubation. Transfer of iron to AM was < 10% of the total iron in labeled cells. The uptake of BrdU and SPION was dependent on the density of labeled cells to inflammatory cells and microenvironmental conditions. Direct implantation of BrdU/SPION labeled cells into target tissue can result in uptake of label by AM, therefore care should be taken to validate by histology transplanted cells by staining for bystander cell markers and correlation with MRI results.

This article has been cited by other articles:

				A. S. Arbab, B. Janic, R. A. Knight, S. A. Anderson, E. Pawelczyk, A. M. Rad, E. J. Read, S. D. Pandit, and J. A. Frank Detection of migration of locally implanted AC133+ stem cells by cellular magnetic resonance imaging with histological findings FASEB J, September 1, 2008; 22(9): 3234 - 3246. [Abstract] [Full Text] [PDF]