The mammalian organism is continuously exposed to various biological and chemical threats from its surroundings. In order to provide protection against these threats, mammals have developed a specialized defense system at the interface with their environment. This system, known as the epidermis, is mainly composed of stratified keratinocytes organized in a complex self-renewing structure providing a mechanical and chemical barrier at the skin surface. However, numerous skin-related pathologies can interfere with the proper formation and function of the epidermal barrier. The pathogenesis of these alterations is often very complex. Understanding the changes induced in epidermal tissues by these pathologies at a molecular level is key for their treatment and prevention. In this context, this work aims at developing a thorough and reproducible characterization methodology of the human epidermis by applying ToF-SIMS to the study of an in vitro epidermal model known as reconstructed human epidermis (RHE). Indeed, although the potential of ToF-SIMS for the characterization of the mammalian skin has already been demonstrated, very few studies focus their efforts on the human epidermis itself. Here, we performed static ToF-SIMS characterizations of RHE cryosections, combining both high mass and high lateral resolution acquisitions. In addition, principal components analysis was used as a multivariate analysis tool. This contributed to the decorrelation of the complex datasets obtained from these biological systems and allowed capturing of their most statistically representative spectral features. Remarkably, this tool proved to be successful in extracting meaningful biological information from the datasets by yielding principal components distinguishing the cornified layers from the metabolically active epidermal cells. Finally, on the basis of multiple ToF-SIMS acquisitions, we showed that this methodology allows for the convenient production of experimental replicates, a key feature often difficult to achieve in ex vivo approaches.

中文翻译：

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通过结合 ToF-SIMS 和多变量分析探测人体表皮

哺乳动物有机体不断暴露于来自周围环境的各种生物和化学威胁。为了提供针对这些威胁的保护，哺乳动物在与其环境的接口处开发了专门的防御系统。该系统称为表皮，主要由分层角质形成细胞组成，这些角质形成细胞组织成复杂的自我更新结构，在皮肤表面提供机械和化学屏障。然而，许多与皮肤相关的病症会干扰表皮屏障的正常形成和功能。这些改变的发病机制通常非常复杂。在分子水平上了解这些病理学在表皮组织中引起的变化是治疗和预防的关键。在这种情况下，体外表皮模型称为重建人表皮 (RHE)。事实上，尽管已经证明了 ToF-SIMS 在表征哺乳动物皮肤方面的潜力，但很少有研究将他们的努力集中在人类表皮本身上。在这里，我们对 RHE 冷冻切片进行了静态 ToF-SIMS 表征，结合了高质量和高横向分辨率采集。此外，主成分分析被用作多变量分析工具。这有助于从这些生物系统中获得的复杂数据集的去相关性，并允许捕获它们最具统计代表性的光谱特征。值得注意的是，该工具通过产生主要成分来区分角化层和代谢活跃的表皮细胞，证明可以成功地从数据集中提取有意义的生物信息。最后，在多次 ToF-SIMS 采集的基础上，我们证明了这种方法可以方便地生产实验复制品，这是一个通常难以实现的关键特征离体方法。