Methods: Sixty two-week old Sprague-Dawley rats were injected intraperitoneally with BrdU twice daily for four consecutive days. The BrdU-labeled rats were sacrificed at 2 hrs, week 2, 4, 6, 8, 10, 12, 14 and 16 after the last BrdU injection. The tissues of cheek, tongue and palate were analyzed by techniques of fluorescence-activated cell sorting and immunohistochemistry .
Results: The number of BrdU-labeled cells quantified by fluorescence-activated cell sorting increased within 2 weeks after labeling, then, decreased gradually until week 10. After week 10, the BrdU-labeled cells were found to locate mainly in basal layer and their number kept consistent at 3-6% of total oral epithelial cells. The number of BrdU-labeled epithelial cells in palate was statistically higher than that in cheek or tongue at the same time point. More importantly, when paired serial sections of every sample harvested at week 10 were progressed for BrdU, CD34 and Integrin alpha6 staining, it was noted that CD34, Integrin alpha6 were not specific for LRCs in rat oral epithelia.
Conclusion: These BrdU-labeled cells after a 10-week chase were considered rat oral epithelial LRCs. The oral epithelial LRCs of rats did not express CD34 and Integrin alpha6.