IMMUNOHISTOCHEMICAL DETECTION OF CELLS LABELED WITH BROMODEOXYURIDINEAFTER NEURAL TRANSPLANTATION

Pregnant rats were treated with 5-bromo-2'-deoxyuridine (BrdU) from em bryonic d 12 (ED12) to ED14. BrdU administration allowed timed labelin g of dividing embryonic cells in utero, since the drug is incorporated into the DNA in place of thymidine during the S-phase of the cell cyc le. ED14 rat cerebral cortex or placenta was grafted into the brain of adult rats. Anti-bromodeoxyuridine immunohistochemistry was used for identifying labeled transplanted cells after different survival period s in paraffin-embedded sections. BrdU labeled cells were observed in b oth intraventricular and intraparenchymal cortical grafts, even after a 3-mo survival. Although the percentage of positive cells decreased i n comparison with ED14 cortex, the level of BrdU (i.e., the intensity of anti-BrdU immunohistochemistry) in labeled nuclei was probably the same. BrdU pretreatment of ED14 cells prior to grafting did not affect the proliferative ability of the grafted tissue. In ED14 placental gr afts, all trophoblastic cells were labeled distinctly. This precise la beling technique enabled an examination of individual migrating tropho blastic cells. However, migration of these cells into the host brain w as very limited.