The dynamics of precursor cells in the olfactory epithelium of juvenile and adult guinea pigs

The dynamics of precursor cells in the olfactory epithelium of juvenile and adult guinea pigs were examined by immunohistochemical double staining using bromodeoxyuridine (BrdU), the neural cell adhesion molecule (N-CAM) and the protein gene product 9.5 (PGP9.5). Expression of apoptotic cells in the olfactory epithelium with the use of the TdT-mediated dUTP biotin nick end labeling (TUNEL) method was also observed. BrdU was given to healthy guinea pigs at the ages of 2 weeks and 6 months old. Tissue specimens were serially collected 1 h to 28 days after administration. BrdU-labeled cells were seen above the basal cell layer after 1 h and migrated to the middle layer of the olfactory epithelium, after 1 day in juveniles and 5 days in adults with expression of N-CAM. PGP9.5 was observed in BrdU-labeled cells after 5 days in juvenile guinea pigs and 7 days in adult. At 14 days after administration, BrdU-labeled cells in the epithelium appeared to decrease. However, a few of these cells were recognized above the basal cell layer after 28 days. The number and location of TUNEL-positive cells did not significantly differ between the juvenile and adult olfactory epithelium. Therefore, we conclude that the division speed from stem cells in juveniles is faster than that in adults, and apoptosis is unaffected by aging in the normal olfactory epithelium.