口腔的上皮組織依據角化程度可以分為角化與非角化上皮，角化上皮表現K1、K10角化蛋白，而非角化上皮表現K4、K13角化蛋白。以前的研究已知上皮底下的結締組織會調控上皮的分化，而非角化上皮的結締組織富含elastin此種纖維蛋白，但在角化組織裡並沒有發現，因此推測結締組織裡的elastin可能會調控上皮的分化。另外在非角化黏膜中扁平苔癬的病變會表現出過度角化的表徵，推想其elastin的改變與過度角化可能有相關性。所以本論文以正常組織與細胞探討elastin對上皮角化機制的影響，另外以病變的組織去觀察是否可以得到相同的驗證。
利用免疫組織染色觀察elastin及K1、K4、K10、K13等角化蛋白表現情形以驗證手術取出的組織同時含有角化與非角化上皮及結締組織。接著以transwell方式培養含有角化上皮的組織，並外加elastin在培養溶液裡，培養兩週後發現表現出原先角化組織不表現的K4與 K13。從活體組織中分離出角化牙齦及非角化牙齦的纖維母細胞(KGF，NKGF)，並將其作免疫細胞染色及西方點墨法發現只有NKGF會表現與分泌elastin。之後利用organotypic culture來進行人類口腔上皮細胞(NOK)、KGF與NKGF的細胞多層培養，並在培養液裡外加elastin，由免疫組織染色發現實驗組表現出原先不表現的K4與K13。
利用免疫組織染色觀察扁平苔癬角化蛋白、elastin、neutrophil　elastase及matrix metalloproteinase-12 (macrophage elastase; MMP-12)表現情形，發現過度角化的病變黏膜裡存在大量的neutrophil elastase與MMP-12 positive cells，以及明顯變少的elastin，三者都具有統計學上的意義。證明在上皮過度角化的扁平苔癬中，elastin的確比正常組織少。結論:當elastin的存在會使上皮趨向表現非角化的上皮特徵，而在過度角化的扁平苔癬裡發現elastin有明顯變少的現象，證實elastin在上皮角化機制裡的確扮演相當重要的角色。

Epithelium in the oral cavity mainly has two forms: keratinized epithelium and non-keratinized epithelium. Histologically, keratinized epithelium exclusively expresses cytokeratin-1 and -10, while non-keratinized epithelium expresses cytokeratin-4 and -13. The phenotype of oral epithelium is determined by the underlying connective tissue. Previous studies showed that elastin is abundant in non-keratinized gingival connective tissue but scarce in the keratinized type. Whether elastin modulates the cytokeratin expression of oral epithelial cells is unknown. Lichen planus, which is an overkeratinized lesion in the oral cavity, occurs mainly on the non-keratinized mucosa. Therefore, it is a good model to investigate whether the reduction of elastin occurs in this lesion and changes the non-keratinized phenotype.
Gingival specimens containing both keratinized and non-keratinized portions were obtained from crown-lengthening procedures. IHC staining with elastin, cytokeratin-1,-4,-10 and-13 was applied to check if all specimens had both keratinized and non-keratinized portions. Keratinized gingiva was cultured in trans-well organ culture system with purified elastin for 14 days. The results indicated that cytokeratin-4 and -13, which are absent in the normal keratinized gingiva were expressed in the specimen treated with exogenous elastin. Then, cell cultures of keratinized and non-keratinized gingiva fibroblasts were established and tested, using immunocytochemistry and immunoblotting, for elastin expression. The results showed that only non-keratinized gingiva fibroblasts expressed and secreted elastin. Oral mucosa equivalents were engineered by embedding different fibroblasts in fibrin gels, and the oral epithelial cells were then cultured on the surfaces of the gels. The results revealed that the keratinocytes in elastin added group expressed cytokeratin-4 and -13. Finally, the expression of elastin, neutrophil elastase and matrix metalloproteinase-12 (macrophage elastase; MMP-12) was examined in six lichen planus cases. The lichen planus groups showed less elastin, more neutrophil elastase and MMP-12 positive cells compared to six normal specimens by IHC. All tested results were statistically significant. Conclusion: the oral epithelium expressed the non-keratinized epithelial phenotype when elastin was present. Little elastin, but large amounts of neutrophil elastase and MMP-12 positive cells, were found in the lichen planus specimens. We demonstrated that elastin plays an important role in the
mechanism of oral epithelial keratinization.

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