Tracking neural progenitor cells transplanted into rabbit spinal cord by detection of dopamine receptor 2 with positron emission computed tomography

Abstract

To explore the effect of in vivo positron emission computed tomography (PET) in tracking the stem cells transplanted into spinal cord. Telomerase-immortalized human neural progenitor cells of the line hNPC-TERT were cultured. HeLa cells were used as control cells. RT-PCR was used to detect the mRNA expression of dopamine receptor 2 (D(2)) in both cell lines. (3)H-raclopride was added into the suspensions of these 2 cell lines. RT-PCR was used to detect the mRNA expression of D(2), and immunofluorescent staining was conducted on the cells to detect the protein expression of D(2). Twenty-two New Zealand rabbits were randomly divided into 4 groups to undergo transplantation of hNPC-TERT cell suspension into the spinal cord at the segment T10, or transplantation of HeLa cells. Two day after the transplantation some rabbits were killed to take out the spinal cord at the segment T10 to undergo immunofluorescent staining to examine the radioactivity in the spinal cord. Some rabbits were injected with (11)C-raclopride intravenously and then underwent PET imaging. RT-PCR showed that mRNA expression was positive in the hNPC-TERT cells but negative in the HeLa cells, and immunofluorescent staining showed protein expression of D(2) in the in the hNPC-TERT cells and not in the HeLa cells. The spinal cords specimens taken 2 days after transplantation had human-specific nuclear (HN) antigen positive and D(2) positive cells. Fluorescent microscopy showed that the hNPC-TERT cells in the injection site did not migrate remarkably; and showed that the D(2) staining was negative and HN antigen was positive in the HeLa cells. (11)C-raclopride PET imaging of the live rabbits showed accumulation of radioactivity at the hNPC-TERT cell injection site with a standard uptake value significantly higher than that of the HeLa cell transplantation group (P < 0.01). (11)C-raclopride PET imaging of the isolated spinal cords showed rounded focal image of increased radioactivity in the hNPC-TERT cell transplantation group and linear image of radioactivity without clear border in the HeLa cell transplantation group. PET imaging with as radiotracer targeting at specific cellular marker is effective in tracking cells into the body and in vivo visual evaluation of stem cell transplantation.