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Labeling and Imaging Mesenchymal Stem Cells with Quantum Dots
Citation:
Collins, M., P. Gunst, W. Cascio, A. Kypson, AND B. Muller-Borer. Labeling and Imaging Mesenchymal Stem Cells with Quantum Dots. Chapter 15, Soloviev, Mikhail (ed.), Nanoparticles in Biology and Medicine: Methods and Protocols, Methods in Molecular Biology. Humana Press Incorporated, Totowa, NJ, 906:199-210, (2012).
Impact/Purpose:
Quantum dots are fluorescent semiconductor nanoparticles, with unique optical and chemical features which make them useful as fluorescent tags for long term in vitro and in vivo cell imaging applications. Quantum dots have narrow band emission spectra and broad excitation spectra, are photostable and resistance to chemical and metabolic degradation [1-3]. In addition, QDs demonstrate a direct relationship between size and emitted fluorescence. Quantum. dots emit light in the visible region of the spectra with the smallest QDs about the size of green fluorescent protein and largest about the size of red fluorescent protein [4]. These properties make QDs amenable to multicolor imaging applications and the tracking of live cells in vitro and in vivo [5-7]. Here we describe a technique for labeling MSCs with QDs. Once labeled the MSCs can be grown with other cells and tracked in vitro or introduced and tracked in an in vivo environment using laser scanning confocal fluorescent microscopy. We have successfully tracked QD labeled MSCs in cardiomyocyte co-cultures for up to seven days, while others have demonstrated in vivo tracking in rat hearts at 8 weeks post transplantation [6, 7]. For the purpose of evaluating QD location and distribution in MSCs we describe additional protocols using a second fluorescent label in fixed and live cell cultures. While additional fluorescent cell markers are not necessary for tracking QD labeled MSCs in vitro or in vivo, the technique of labeling cell membranes or organelles is effective in differentiating cell boundaries or for co-localization studies.
Description:
Mesenchymal stem cells (MSCs) are multipotent cells with the potential to differentiate into bone, cartilage, adipose and muscle cells. Adult derived MSCs are being actively investigated because of their potential to be utilized for therapeutic cell-based transplantation. Methods to track MSCs in vivo are limited, preventing long-term functional studies of transplanted cells. Quantum Dots (QDs) offer an alternative to organic dyes and fluorescent proteins to label and track cells in vitro and in vivo. Nanoparticles are resistant to chemical and metabolic degradation, demonstrating long term photostability. Here, we describe the technique to label MSCs with QDs and demonstrate intracellular QD distribution in the labeled MSCs with laser scanning confocal fluorescent microscopy.