Overcoming pitfalls
Until recently, thymidine analogs were used to label stem cells for experimental implantation into the rodent brain. Results suggested extraordinary abilities of adult stem cells. However, a high percentage of cells typically die shortly after transplantation. Dr. Burns and colleagues found that thymidine analog (red) from dead cells can be recycled and incorporated into the DNA of live proliferating cells in the recipient brain, making them appear as transplanted cells. As such, this technique is now known to be unreliable.