Abstract 1107: Labeling With a Novel Magnetofluorescent Molecular Imaging Probe Does Not Affect the Proliferation and Cardiomyogenic Potential of Cardiac Side Population Progenitor Cells
Non-invasive, in-vivo molecular imaging techniques are essential to track the cellular fate and function of implanted stem cells. However, the biological impact of cell labeling with magnetofluorescent nanoparticles (MNP) is poorly understood. We recently generated a novel poly-arginine derivatized MNP, CLIO-VT680-protamine, and investigated the effects of cellular labeling on cell function in HELA cells and cardiac side population (CSP) cells, which we have previously shown to differentiate in vitro into functional cardiomyocytes. CSP cells were loaded with 30 micrograms Fe/ml of CLIO-VT680-protamine for 90 minutes and HELA cells with CLIO-VT680-(protamine-rhodamine). Fluorescence microscopy of HELA cells revealed that the CLIO-VT680 moiety of the MNP had a perinuclear distribution, while protamine accumulated within the nucleus (Fig A⇓). Labeling of CSP cells did not alter cell proliferation (as determined by cell number 9 days following culture in vitro), and cardiomyogenic differentiation (as determined by GATA4 and alpha-actinin immunohistochemical staining and stimulated fura-2 calcium transients) (Fig B⇓).
Conclusion: The distribution of CLIO-VT680-protamine suggests that protamine is cleaved by intracellular proteases after translocation of the MNP into the cell; however, neither the perinuclear accumulation of CLIO-VT680 nor the nuclear localization of protamine had an adverse effect on the proliferation or cardiomyogenic differentiation of the CSP cells. Thus, CLIO-VT680-protamine MNP may prove to be an ideal label for non-invasive in-vivo molecular imaging and tracking of implanted stem cells.