維生素D藉由抑制乙型轉化生長因子多方面訊息傳遞以減弱口腔肌纖維母細胞所致纖維化之研究

Abstract

口腔黏膜下纖維化症(oral submucous fibrosis;OSF)是一種慢性的發炎疾病，特徵在於膠原蛋白過量累積或分解速度下降，導致口腔黏膜的透明硬化。OSF患者的臨床症狀為口腔黏膜灼熱及張口困難。嚼食檳榔被認為是主要的致病因子。嚼食過程檳榔不斷的與口腔黏膜摩擦，引起發炎症狀並產生細胞激素及生長因子，使纖維母細胞分化為肌纖維母細胞(myofibroblasts)，導致膠原蛋白的過度增加。目前研究中，尚無OSF可逆性的治療方式。近年來，在肝其其他器官纖維化的研究中發現，維生素D可以透過抑制TGF-β訊息傳遞路徑的Smad 2/3蛋白和α-smooth muscle actin（α-SMA）基因表現，抑制纖維化蛋白表現。因此， 我們從健康受試者與OSF患者口腔黏膜取得的纖維母細胞，進行一系列口腔黏膜細胞纖維化致病機轉的探究。首先，我們檢測了維生素D對OSF纖維母細胞的作用，該作用抑制了pro-collagen 1A1和α-SMA的表達。其次，使用正常口腔黏膜纖維母細胞經TGF-β誘導處理，模擬OSF致病機轉中纖維化的變化。在維生素D作用之後，結果發現維生素D可以有效抑制TGF-β誘導之Smad訊息傳遞路徑中之Smad3蛋白。同時，我們發現維生素D可以抑制p38和JNK的表現(但不能抑制ERK表現)，且明顯抑制Pro-collagen1A1及α-SMA的表現。最後，我們在OSF之纖維母細胞中也發現，維生素D亦可透過抑制TGF-β誘導的Smad和Non-Smad路徑中之訊息傳遞蛋白，Smad3、p38 及JNK，抑制纖維化蛋白Pro-collagen1A1及α-SMA的表現。總而言之，不論正常口腔黏膜纖維母細胞經TGF-β誘導所產生之纖維化蛋白表現，或是OSF纖維母細胞纖維化蛋白的表現，都可以被維生素D抑制。因此，維生素D可以預防和緩解OSF的進程。

Oral subucous fibrosis (OSF) is a chronic inflammatory oral disease characterized by the overproduction of collagen or reduced collagen degradation, which results in the hyalinization of the oral mucosa. Patients with OSF present burning sensation and difficulty in mouth opening. Betel quid chewing is often recognized as the causative factor for this disease that induces inflammation from micro-abrasions, which generated cytokine and growth factors by the constant friction of the course fibers of the areca nut to the oral mucosa. Meanwhile, fibroblasts were activated to be myofiborblasts, which is highly produce over expression of collagen. Up to now, there is no treatment strategy to reverse OSF to be normal. However, recent studies showed that vitamin D could inhibit the TGF-β-mediated fibrosis development through the suppression of Smad2/3 proteins and α-SMA gene expression. This mechanism consequently resulted in decrease pro-collagen expression. Therefore, vitamin D may provide a promising new treatment modality for reversing OSF. In this study, we obtained primary cultures of fibroblasts from healthy volunteers and OSF patients. First, we detected the effect vitamin D on OSF fibroblasts, which suppressed the expression of pro-collagen 1A1 and α-smooth muscle actin (α-SMA). Then, we used normal oral mucosa fibroblasts (OMF) to be treated by TGF-β cytokine induction on the normal fibroblast to simulately induce the fibrotic change as mimicking the pathogenesis of OSF. Upon exposure to vitamin D, we observed that it was able to block the TGF-β-mediated classic Smad and non-Smad signaling pathway through inhibition of the Smad3, p38 and JNK protein, but not ERK protein, which eventually decreased pro-collagen 1A1 and α-SMA production. Finally, we also found that there was similar suppression of Smad3, p38 and JNK expression in OSF fibroblasts treated by vitamin D. In conclusion, no matter how the fibrogenesis of OMF induced by TGF-β or OSF fibroblasts could be suppressed by vitamin D. Therefore, vitamin D is possibly able to prevent and alleviate OSF progression.