In vitro and in vivo tracking of bioorthogonally labeled mesenchymal stem cells based on fluorescence imaging platforms

Abstract

Noninvasive and precise stem cell tracking after transplantation in living subjects is very important to monitor in vivo fate of stem cells, which is closely related to therapeutic effects. However, labeling of stem cells often has faced limitations, due to (i) diluted or lost imaging probes by the stem cell proliferation, (ii) heterogeneous labeling of the stem cells with lower labeling efficiency, (iii) impracticability of cell proliferation, and cell death, (iv) signal distortion by phagocytosis, (v) potential side effects by hindering stem cell differentiation, etc. In this study, we developed near-infrared fluorescent dye (Cy5.5) and superparamagnetic iron oxide nanoparticle-incorporated bicyclo[6.1.0]nonyne-modified glycol chitosan nanoparticles (BCN-dual-NPs) as a dual-fluorescence and magnetic resonance imaging probe for tracking human adipose-derived mesenchymal stem cells (hMSCs). Based on the metabolic glycoengineering and bioorthogonal click chemistry, BCN-dual-NPs were rapidly bound to the stem cell surface and effectively taken up by the cell membrane turn-over mechanism without any cytotoxicity and harmful effect on stem cells. After transplantation of BCN-dual-NPs-labeled hMSCs into the brain stroke mice model, we confirmed that migration of BCN-dual-NPs-labeled hMSCs in the brain could be effectively tracked using fluorescence imaging for up to 14 days, and the fluorescence signals were correlated with anatomical images from T2-weighted magnetic resonance (MR) imaging. Our observation would provide potential applications for hMSCs labeling strategy in regenerative medicine by providing safety and high labeling efficiency for labeling and tracking of hMSCs in vitro and in vivo.