利用倍頻顯微術對臉部曬斑之組織病理特徵分析及治療評估

Abstract

在日常生活中，暴露在紫外光的照射下會造成皮膚的病變與慢性傷害，而曬斑就是其中之一，曬斑在亞洲人以及白人有很高的普遍性，又因為其常常長在臉上，因此有很龐大的治療需求。然而，治療過後通常不會完全治好，因此，本論文利用非侵入式活體倍頻顯微術去即時觀察治療對病灶內部帶來的改變。此技術提供即時造影，擁有對細胞病理學診斷非常關鍵的次微米級的解析度。一位亞裔男性與二十四位亞裔女性志願者參與了本研究的臨床試驗，志願者們的年齡分布從四十六至七十八歲並滿足在臉上有曬斑且準備接受治療之條件。本論文進一步將取得的活體倍頻顯微虛擬切片影像進行分析與量化，共計有十種關於曬斑皮膚內黑色素含量或組織結構的參數被量化分析。 論文中揭示了在曬斑病灶區域中，角質層厚度、活表皮層厚度、基底細胞質黑色素濃度(MMD)、基底細胞質黑色素不均勻度、以及基底細胞高度等皆有增加。醫生使用紅寶石雷射以及皮秒雷射來治療曬斑，本文發現基底細胞高度在兩種雷射治療過後依舊偏高，而黑色素不均勻度則在皮秒雷射治療後依舊偏高，而在紅寶石雷射治療後變正常。特別的是，基底細胞的核質比以及黑色素細胞的活性在術後均顯著增加，而噬黑色素細胞數量與游離黑色素顆粒則是在紅寶石雷射治療後增加，但在皮秒雷射治療後維持正常。MMD是代表黑色素的絕對濃度，比起其他量測黑色素的技術，這是一個更精確、客觀的參數，本論文進一步的分析指出MMD與外觀是有關連性的，也發現治療效果較好者，其術前的MMD是比較高的。 最後，由於曬斑在治療過後通常不會完全治好，再加上術後基底細胞的高度依舊偏高的結果，因此我們認為基底細胞的高度反映出曬斑主要的病因，同時也適合做為是其重要的病理特徵，而此特徵可能是因為角質形成細胞的增值與分化平衡的破壞所造成。

Cumulative ultraviolet exposure can cause chronic damage of the skin. Solar lentigo (SL), also known as solar lentigine, is a major sign of skin photoaging. There is a serious cosmetic concern for SL in Asians. The main treatment option for SL is pigmented laser. However, the risk of post-laser hyperpigmentation and the possibility of recurrence still exist. Noninvasive harmonic generation microscopy (HGM) provides the merits of submicron resolution, enhanced third harmonic generation (THG) signals from melanin and high penetration, which are crucial for in vivo histopathological examination of solar lentigo. The aim of this study is to understand the pathogenesis of solar lentigo from its histopathological changes before and after pigmented laser treatment. One male and 24 female Asian volunteers, aged 46 to 78 years old, having at least 2 lentigines on the cheeks were recruited. We treated one lesion with Q-switched ruby laser (QSRL) and the other with Nd:YAG 532-nm picosecond laser (PL), respectively. HGM was utilized to assess the in vivo histopathological changes of SL before, 3 weeks and 6 weeks after laser treatment. Ten HGM parameters concerning the histopathological features in SL were quantified and analyzed. At baseline, the thickness of stratum corneum (SC), thickness of viable epidermis (VE), melanin mass density (MMD) of basal cells, inhomogeneity of MMD (IMMD) of basal cells, and height of basal cells (HBC) were increased in SL, comparing to the normal counterpart. After laser treatments, although the thickness of SC and VE resumed to the normal levels, the HBC remained significantly higher. The nuclear-cytoplasmic ratio (NCR) of basal cells also become increased after both laser treatments. Our study showed that MMD of basal cells, an objective parameter measuring absolute melanin amount, became normal after laser treatment and its levels had a positive correlation with the clinical improvement of SL. Furthermore, we found that SL with higher MMD had better therapeutic responses than SL bearing lower MMD. The IMMD of basal cells kept high after PL, but became normal after QSRL treatment. The melanocyte dendriticity score (MDS) and dermal melanophages/free melanin granules (DMM) became significantly higher after laser treatments and persisted till week 6, only the DMM in the PL group resumed to normal at week 6. Finally, because the HBC remains elevated after laser treatments, we propose that changes in basal keratinocytes are related to the development of SL. The increased HBC might reflect the impairment of the proliferation/differentiation program in keratinocytes and could contribute to the pathogenesis of SL.