Fig. 3.

Principle of indirect cell labeling. Indirect cell labeling methods are methods that permanently detect the survival and proliferation of stem cells in vivo through genetic manipulation. There is a method in which the protein expressed by the reporter gene functions as an enzyme and emits a specific wavelength (GFP) and a method in which a contrast agent is additionally administered to the experimental animal (Fluc, D2R, NIS, HSV1-r39sTK). GFP: green fluorescent protein, Fluc: Photinus pyralis (firefly) luciferase, Tet: tetracycline, MRI: magnetic resonance imaging, D2R: dopa-mine 2 receptor, ¹⁸F-FESP: 3-(2’-[18F]fluoroethyl) spiperone, NIS: sodium iodide symporter, HSV1-r39sTK: herpes simplex virus 1 thymidine kinase, ¹⁸F-FHBG: 9-(4-(18)F-Fluoro-3-[hydroxymethyl]butyl) guanin.