Figure 4.

MRI tracer preserves differentiation and self-renewal of human CD34⁺ cells in vitro. (A) Human bone marrow CD34⁺ HSCs were incubated with or without increasing amounts of the MRI tracer for 4 h prior to seeding in methocellulose in triplicate for colony-forming unit (CFU) assays. Results show the average CFU per 1,000 progenitor cells/dish, and error bars indicate standard deviations. One of two independent studies with identical findings is depicted. (B) Limiting dilution of human bone marrow CD34⁺ HSCs (unlabeled and MRI tracer-labeled, 10 mg/ml), 20 replicate wells per condition, were cultured with stromal cells in the presence of serum, interleukin (IL)-3, and granulocyte macrophage-colony-stimulating factor (GM-CSF) for 5 weeks and then observed for the formation of cobblestone areas (cobblestone area forming cell, CAFC, assay). The frequency of negative wells plotted against the number of cells added per culture provides a graphical depiction of the Poisson equation to calculate precursor frequency in the treated and untreated cells. CFU-E, CFU-erythroid; BFU-E, blast forming unit-erythroid; CFU-GM, CFU-granulocyte, macrophage; CFU-GEMM, CFU-granulocyte, erythroid, macrophage, megakaryocyte.