Transplantation of embryonic retinal donor cells labelled with BrdU or carrying a genetic marker to adult retina.

After transplantation of embryonic retinal cells to injured adult retina, it is often difficult to distinguish donor from host cells. To overcome this problem, two methods were applied: labelling donor cells with the nuclear marker bromodeoxyuridine (BrdU) and use of transgenic donor tissue. BrdU was injected into timed-pregnant rats on 2 or 3 consecutive days. The donor embryos were taken 1-4 days later for transplantation. The BrdU-labelled donor tissue was examined in transplants sampled up to 1 year after grafting. Labelled donor cells were specifically identified in the transplants and in the interface with the adjacent host retina. The varying intensities of cell labelling indicated differences in the initial uptake of BrdU in the S-phase, or the dilution of the label by cell divisions after BrdU injection. The best labelled cells were presumably the ones that stopped dividing shortly after injection of BrdU. As controls, the normal development of BrdU-labelled retinas from the offspring of females that had been BrdU-injected at E16 and E17 and not used for transplantation was studied. Near the time of birth, clones of labelled cells were radially distributed. In the mature retina, labelled cells were seen in all retinal layers. Embryonic retina derived from transgenic (NSE-lacZ) mice was transplanted to 'nude', immunodeficient rats (xenografts). These transgenic mice contain the Escherichia coli beta-galactosidase gene, coupled to the promoter for neuron-specific enolase (NSE). Thus, all retinal donor cells that contain NSE could be identified by histochemistry or immunohistochemistry. The donor cells expressing the transgene could be detected several months after transplantation.