Methods: Postnatal day 1-10(1, 3, 5, 7, 9, and 10) mice were used. Under deep anesthesia, the animals were perfused, and the upper second molar(M2) was removed. Cryosections were immunostained using antibodies against DCC and Netrin-1. And TUNEL staining was performed on the same section using In Situ Cell Death Detection Kit. The immunostaining and TUNEL staining of M2 were observed using fluorescence microscopy.
Results: Dental lamina: postnatal day 1(P1); DCC(+), Netrin-1(+) and TUNEL(-). P9; DCC(+), Netrin-1(-) and TUNEL(+). While, under the resorbing bone around M2 at P10(just before tooth eruption): DCC(+), Netrin-1(+) and TUNEL(+).
Conclusion: These results in dental lamina suggested that apoptosis, which induced by DCC, involved in reduction of dental lamina, and that apoptosis was inhibited when DCC was occupied by Netrin-1. While the results in under the resorbing bone around M2 suggested that apoptosis, which regulated by DCC/Netrin-1 interaction was not involved in the mechanism of bone resorption.