Efficient In Vitro Labeling Of Human Neural Precursor Cells With Superparamagnetic Iron Oxide Particles: Relevance For In Vivo Cell Tracking

¹ Stem Cell Research Institute (SCRI), Via Olgettina 58, 20132 Milano, Italy
² Neuroradiology Department, San Raffaele Scientific Institute, Via Olgettina 58, 20132 Milano, Italy
³ Department of Morphology and Biomedical Sciences, Section of Anatomy, University of Verona, Italy.
⁴ Stem Cell Research Institute (SCRI), Via Olgettina 58, 20132 Milano, Italy; University of Milano-Bicocca, Dept. Biotechnology and Biosciences, Piazza della Scienza 2, 20126 Milano, Italy.

^* To whom correspondence should be addressed. E-mail: gritti.angela{at}hsr.it.

Correspondence may also be addressed to Angelo Vescovi at vescovi@tin.it

	Abstract

Recent studies have raised appealing possibilities of replacing damaged or lost neural cells by transplantating in vitro-expanded neural precursor cells (NPCs) and/or their progeny. Magnetic resonance (MR) tracking of superparamagnetic iron oxide (SPIO)-labeled cells is a non-invasive technique to track transplanted cells in longitudinal studies on living animals. Murine NPCs and human mesenchymal or hematopoietic stem cells can be efficiently labeled by SPIOs. However, the validation of SPIO-based protocols to label human (h) NPCs has not been extensively addressed. Here we report the development ad validation of optimized protocols using two SPIOs (Sinerem® and Endorem®) to label human hNPCs that display bona fide stem cell features in vitro. A careful titration of both SPIOs was required to set the conditions resulting in efficient cell labeling without impairment of cell survival, proliferation, self-renewal and multipotency. In vivo MR imaging (MRI) combined with histology and confocal microscopy indicated that low numbers (5x10³-1x10⁴) of viable SPIO-labeled hNPCs could be efficiently detected short-term after transplantation in the adult murine brain and could be tracked for at least one month in longitudinal studies. By using this approach we also clarified the impact of donor cell death to the MR signal. This study describes a simple protocol to label NPCs of human origin using SPIOs at optimized low dosages and demonstrates the feasibility of non-invasive imaging of labeled cells after transplantation in the brain; it also evidentiates potential limitations of the technique that have to be considered, particularly in the perspective of neural cell-based clinical applications.