Abstract
Cell sheet therapy has emerged as a potential therapeutic option for reparation and reconstruction of damaged tissues and organs. However, an effective means to assess the fate and distribution of transplanted cell sheets in a serial and noninvasive manner is still lacking. To investigate the feasibility of tracking Adipose derived stem cells (ADSCs) sheet in vivo using ultrasmall super-paramagnetic Fe3O4 nanoparticles (USPIO), canine ADSCs were cultured and incubated with USPIO and 0.75 μg/ml Poly-L-Lysine (PLL) for 12 h. Labeling efficiency, cell viability, apoptotic cell rate were assessed to screen the optimum concentrations of USPIO for best labeling ADSCs. The results showed ADSCs were labeled by USPIO at an iron dose of 50 μg/ml for a 12 h incubation time, which can most efficiently mark cells and did not impair the cell survival, self-renewal, and proliferation capacity. USPIO-labeled ADSCs sheets can be easily and clearly detected in vivo and have persisted for at least 12 weeks. Our experiment confirmed USPIO was feasible for in vivo labeling of the ADSCs sheets with the optimal concentration of 50 μg Fe/ml and the tracing time is no less than 12 weeks.
Highlights
To track cell sheet survival and migration in vivo, it is important to be able to provide serial images from weeks to months after transplantation
Transmission electron microscopy (TEM) images showed the monodisperse ultrasmall SPIO (USPIO) nanoparticles were approximately spherical with an average diameter of 10 ± 2 nm (Fig. 1A)
The ADSCs sheet can be effectively labeled with 50 μg Fe/ml USPIO and 0.75 μg/mL PLL
Summary
The primary cultured ADSCs in our study were negative for hematopoietic markers CD34 and CD45, and were strongly positive for MSC-related markers CD44, CD90 and CD105, which confirmed the stem cell origin of ADSCs (Supplementary Data 1). The data indicate, compared with unlabeled cells, no cellular cytotoxicity due to USPIO was found in the iron concentration range of 5–50 μg/ml and cells incubated with PLL alone, p > 0.05. Compared with unlabeled cells (0 μg/ml), incubation of ADSCs with PLL alone did not affect the rate of apoptotic cells, *p = 0.892, and no significant difference was observed at an iron concentration of 5–50 μg/ml, **p > 0.05. Gray difference can be identified by the naked eye at concentrations greater than or equal to 25 μg Fe/ml These results indicated that MRI can efficiently detect USPIO-labeled ADSCs and that the intensity of the signal is proportional to the concentrations of USPIO. Our study certified the feasibility of tracking ADSCs sheet with USPIO in vivo for a long time (12 weeks), due to the xenoplastic transplantation of ADSCs sheet, it is hard to detect the cell migration in this study, and further studies may focus on the cell sheet migration towards deep anatomical sites in homoplastic transplantation
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