OBJECTIVETo trace the embryonic stem (ES) cells transplanted into rat brain by labeling the cells with green fluorescent protein (GFP) and by mouse neuronal specific antibody Thy-1 and compare their features.

METHODSFor GFP labeling,transfect pEGFP-N1 plasmid containing GFP and anti-neomycin sequences into embryonic stem cell and add neomycin for more than 10 passages. To test the GFP expression in vivo, the GFP-ES was transplanted into healthy rat brain, and the frozen sectioned slides were observed under fluorescence microscope and laser con-focal microscope 21 days later. For the antibody labeling,embryonic stem cells were directly transplanted into the rat brain. The specific mouse thy-1 antibody was used in immunostaining of transplanted cells. For both of the two labeling method, the slides were also examined by double labeling with the antibodies,neuronal nuclei (NeuN) or glial fibrillary acidic protein (GFAP) to identify the differentiation of transplanted cells.

RESULTSBoth single ES cell and cell pellets expressed bright green fluorescence the day after plasmid transfection, and more than 30% ES cells were labeled. The GFP-labeled cells could still be found gathered around the infusion channel at least 21 days later, but the GFP fluorescent could not be overlapped with NeuN or GFAP staining. On the contrary, Thy-1 antibody overlapped well with NeuN or GFAP staining.

CONCLUSIONSLiposome-helped plasmid GPF transfection is effective in labeling mouse embryonic stem cell in vivo,but is not effective in showing the differentiated cells. On the contrary, Thy-1 antibody can not only show the transplanted cells, but also trace the transplanted cells after their differentiation.