Fig. 1.

Difference between direct cell labeling and indirect cell labeling. (A) Direct cell labeling methods are non-permanent imaging methods that identify direct labeling agents such as fluorescent dyes, superparamagnetic iron oxide nanoparticles, and isotopes labeled on cells in vivo. Direct labeling agent after labeled stem cells can be detected for several hours to several days depending on the characteristics of the labeled material. (B) Indirect cell labeling methods are strategies for imaging stem cells by inserting a reporter gene into cells through genetic manipulation. The protein expressed by the reporter gene inserted into the stem cell functions as a cell receptor, transporter, enzyme, etc., and has the advantage of being able to image the stem cell permanently and repeatedly in vivo. In addition, since the reporter gene is also replicated during the cell division process, the degree of proliferation after stem cell transplantation in vivo can be analyzed.