Radiolabeling Rhesus Monkey CD34 Hematopoietic and Mesenchymal Stem Cells with Cu-Pyruvaldehyde-Bis(N4-Methylthiosemicarbazone) for MicroPET Imaging

Abstract

Noninvasive positron emission tomography (PET) provides a potential method for in vivo tracking of radiolabeled cells. The goal of this study was to assess the potential toxicity of 64 Cu-pyruvaldehyde-bis(N4-methylthiosemicarbazone) (PTSM) on rhesus monkey CD34 + hematopoietic and mesenchymal stem cells in vitro in preparation for developing imaging protocols posttransplantation. CD34 + hematopoietic cells were radiolabeled with 0 to 40 μCi/mL 64 Cu-PTSM and viability and colony formation were assessed. Rhesus monkey mesenchymal stem cells (rhMSCs) were placed in culture postradiolabeling for assessments of growth and differentiation toward adipogenic, osteogenic, and chondrogenic lineages. The results indicated that CD34 + cells radiolabeled with 20 μCi/mL and rhMSCs radiolabeled with 10 μCi/mL 64 Cu-PTSM did not result in adverse effects on growth or differentiation. Nonradioactive copper was also evaluated and showed that the presence of copper was not harmful to the cells. CD34 + cells and rhMSCs radiolabeled with the optimized concentrations of 20 and 10 μCi/mL, respectively, were also assessed using the microPET scanner. Studies showed that a minimum of 2.50 × 10 4 CD34 + cells (1.1 pCi/cell) and 6.25 × 10 3 rhMSCs (4.4 pCi/cell) could be detected. These studies indicate that CD34 + hematopoietic cells and rhMSCs can be safely radiolabeled with 64 Cu-PTSM without adverse cellular effects.