Nitric Oxide(NO) is synthetized from L-arginine by nitric oxide synthetase(NOS), and a short lived free radical that play an important role in several biological process. An incresed expression of nitric oxide synthetase(NOS) has been observed in human colon cancer cell lines as well as in human gynecological, breast, and CNS tumors. This obseuation sugests a pathobiological role of tumer-assocaited NO production. Hence, we investigated the expression of NOS in Epithetial Odontogenic tumor, and in developing tooth germ of human embryos and fetuses. Expression was evaluated by immunohistochehucal staining for NOS₂, NOS₂, and NOS₃.
In early human tooth germ(cap/early bell stage) NOS protein was found in the epithelial dental lamina and enamel organ, and there was no difference among the NOS₁, NOS₂, and NOS₃. NOS expressions were seen in inner and outer dental epithelium during bell stage. During enamel and cementum appositioilal stage, NOS expression shifted from the presecretory ameloblast to the odonroblast.
NOS expressions in follicular and plexiform amelobalstoma are positive reaction in ectodermal tumor components and reveal strong reaction for NOS₁& NOS₃. In acanthomatous type, NOS was seen the strongest expression in stellate reticulum cell. NOS₃ expressions were noted mild or rare in granular ameloblastoms. In unicystic ameloblastoma, NOS expression was rare feature in cystic luminal epithelium.
In AOT, duct like cells and spindle epithelial tumor cells were positive for NOS, and more expressed for NOS₁. Epithelial tunors cells around calcification in AOT were strong positive reaction for NOS and expressed at NOS₁, NOS₃, NOS₂, desending order, respecRively.
Our comparative studies on the expression of NOS protein indicate that NOS play an important role in epithelial diffrrentiation during tooth development, tumorigenesis of epithelial odontogenic tumors and tumor calcifications.
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