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KMID : 0358920060330020181
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Journal of the Korean Academy of Pedodontics
2006 Volume.33 No. 2 p.181 ~ p.191
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MORPHOLOGICAL CHARACTERISTICS OF ODONTOBLAST IN NFC-C KNOCK/OUT MICE
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Ko Seung-Bak
Lee Chang-Seep
Lee Nan-Young
Lee Sang-Ho
Kim Heung-Joong
Park Ju-Cheol
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Abstract
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NFO-C null mice demonstrated aberrant odntoblast differentiation and thus abnormal dentin formation while other tissues/organs in the body, including ameloblasts, appear to be unaffected and normal. However, little is known about the mechanism of NFI-C function in odontoblast differentiation and dentin formation.
Odontoblasts are tall, highly polarized cells that are responsible for formation and maintenance of the predentin and dentin. An indication of their polarity is the acquisition of specialized intercellular junctions. As predontoblasts differentiate into odontoblasts, they are joined and attached at the apical end by well developed terminal webs of cytoskeletal actins, and associated tight as well as adherent njunctions.
In this study, in order to investigate if disruption of the NFI-C gene interferes with formation of a specific or other structural proteins of the intercellular junctions, we examined morphological charcteristic of the aberrant odontoblast in NFI-C null mice using light and electron microscope. In addition, we determined the expression of major structural proteins of intercellular junctions, ZO-1 and occludin, during the differentiation of odontoblasts using immunohitochemistry.
The results were as follows:
1. In light microscopy, abnormal odontoblasts of incisors of the NFI-C null mice were round in shape, lost their polarity, and trapped in osteodentin-like mineralized tissue. Mutant molars have relatively normal crowns, but short and abnormal differentiating adontoblasts in root formation area.
2. Electron microscopy of abnormal odontoblasts revealed the dissociation of the round osteoblast-like cells, the loss of their cellular polarity, and the absence of an intercellular junctional complex known as the tight junctions.
3. A mutant incisor showed labeling for ZO-1 at the proximal and distal ends of secreting ameloblasts, while staining for ZO-1 was not observed in the abnormal odontoblasts.
4. A normal incisor showed immunoreactivity for occludin in the differentiating odontoblasts. However, staining for occludin was not observed in the abnormal odntoblasts of mutant incisor.
These results suggest that NFI-C gene causes dissociation of odontoblast and thus abberant odontoblast differentiation and abnormal dentin formation by interfering with the formation of intercellular junctions.
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KEYWORD
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NFI-C, Odontoblast differentiation, Root formation
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