Nuclear Factor I-C 결손 생쥐에서 상아모세포의 형태학적 특징 = MORPHOLOGICAL CHARACTERISTICS OF ODONTOBLAST IN NFC-C KNOCK/OUT MICE

국문 초록 (Abstract)

NFI-C K/O 생쥐에서는 상아모세포의 분화과정에 이상이 초래되어 상아질 형성에 이상이 생기고 치근 형성이 불완전하게 이루어지는 것으로 알려져 있으나 이에 대한 명확한 기전은 잘 알려져 있지 않다. 상아모세포가 분화하여 정상적으로 상아질을 형성하기 위해서 핵과 세포질이 극성을 띠고 잘 조직화되어야 하며, 이 과정에서 다양한 세포사이 결합장치들이 중요한 역할을 하는 것으로 알려져 있다.
본 연구에서는 NFI-C K/O 생쥐에서 상아질 형성에 이상이 생기는 것이 상아포세포의 형태학적 변화와 세포사이 결합장치들이 기능을 하지 못한 결과에서 기인한 것인지 알아보기 위하여, NFI-C K/O 생쥐에서 발생한 비정상적인 상아모세포들을 광학 및 투과 전자현미경을 이용하여 형태학적으로 관찰하고, Zo-1과 occludin의 발현을 면역조직화학적으로 관찰하여 세포사이 결합장치들의 분포를 확인하여 다음과 같은 결과를 얻었다.
1. 광학현미경 소견에서 NFI-C K/O 생쥐의 전치부 상아모세포는 세포 극성이 상실되고, 여러 층으로 배열되어 있었으며 상아질에 많은 세포들이 함입된 것과 같은 비정상적인 상아질의 소견을 나타냈다. 반면에 NFI-C K/O 생쥐의 구치부 상아모세포는 치관부에서는 잘 조직화된 소견을 보였으나 치근 형성 부위에서는 세포 배열이 불규칙해지고 세포 극성이 상실되었다.
2. 투과 전자현미경 소견에서 NFI-C K/O 생쥐 전치부의 비정상적인 상아모세포는 둥근 형태로 세포 사이 간격이 넓으며 폐쇄연접과 같은 세포사이 결합장치들이 전혀 관찰되지 않았다.
3. Zo-1의 면역조직화학적 염색에서 NFI-C K/O 생쥐의 전치부 법랑모세포의 근위부와 원위부에서 ZO-1이 강하게 발현되었으나 비정상적인 상아모세포에서는 ZO-1의 발현을 관찰할 수 없었다.
4. Occludin의 면역조직화학적 염색에서 정상 생쥐의 전치부 상아모세포에서는 occludin의 발현이 관찰되었으나 NFI-C K/O 생쥐의 비정상적인 상아모세포에서는 occludin의 발현이 관찰되지 않았다.
이상의 결과를 종합하여 볼 때 NFI-C의 결손은 상아모세포의 분화 이상을 초래하고 비정상적으로 상아질을 형성하는 과정에 세포사이 결합장치의 상실과 같은 형태학적인 변화의 중요한 요소로 작용하는 것으로 생각된다.

다국어 초록 (Multilingual Abstract)

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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