Our previous study on rat skin showed that cumulative oxidative pressure induces profound structural and ultrastructural alterations in both rat skin epidermis and dermis during aging. Here, we aimed to investigate the biophotonic properties of collagen as a main dermal component in the function of chronological aging. We used second harmonic generation (SHG) and two‐photon excited fluorescence (TPEF) on 5 μm thick skin paraffin sections from 15‐day‐, 1‐month‐ and 21‐month‐old rats, respectively, to analyze collagen alterations, in comparison to conventional light and electron microscopy methods. Obtained results show that polarization‐resolved SHG (PSHG) images can detect collagen fiber alterations in line with chronological aging and that this method is consistent with light and electron microscopy. Moreover, the β coefficient calculated from PSHG images points out that delicate alterations lead to a more ordered structure of collagen molecules due to oxidative damage. The results of this study also open the possibility of successfully applying this fast and label‐free method to previously fixed samples.

中文翻译：

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偏振分辨SHG成像作为老化过程中胶原蛋白变化的快速筛选方法：与光学和电子显微镜的比较

我们先前对大鼠皮肤的研究表明，在衰老过程中，累积的氧化压力会在大鼠皮肤表皮和真皮中引起深刻的结构和超微结构改变。在这里，我们旨在调查胶原蛋白的生物光子特性，作为按时间顺序衰老的主要皮肤成分。我们分别在15天，1个月和21个月大的大鼠的5μm厚的石蜡切片上使用了二次谐波（SHG）和双光子激发荧光（TPEF）来分析胶原蛋白的变化。与常规光学和电子显微镜方法的比较。获得的结果表明，偏振分辨的SHG（PSHG）图像可以检测到按时间顺序老化的胶原纤维变化，并且该方法与光镜和电子显微镜一致。而且，β从PSHG图像计算得出的系数指出，由于氧化损伤，微妙的变化导致胶原分子的结构更加有序。这项研究的结果也为成功地将这种快速且无标签的方法应用于先前固定的样品提供了可能性。