To enable the visualization of hUCBSCs after their transplantation into the spinal cord, their nuclei were labeled with 5-bromo-2′-deoxyuridine (BrdU). BrdU (Merck, Germany) at the final concentration of 10 mg/ml was added to the culture of the hUCBSCs 24 hr before transplantation. The excess tracer was washed out with PBS and cells were suspended in fresh culture medium to obtain approximately 300,000 cells in 10 μl.