Gene expression profile of keratinocyte stem cells. Homo sapiens

Background: Human interfollicular epidermis is sustained by the proliferation of stem cells and their progeny, transient amplifying cells. Molecular characterization of these two cell populations is essential for better understanding of self renewal, differentiation and mechanisms of skin pathogenesis. The purpose of this study was to obtain gene expression profiles of alpha 6+/MHCI+, transient amplifying cells and alpha 6+/MHCI- , putative stem cells, and to compare them with existing data bases of gene expression profiles for mouse hair follicle stem cells. The expression of Major Histocompatibility Complex (MHC) class I, previously shown to be absent in stem cells in several tissues, and alpha 6 integrin were used to isolate MHCI positive basal cells , and MHCI low/negative basal cells. Results: Transcriptional profiles of the two cell populations were determined and comparisons made with published data for hair follicle stem cell gene expression profiles. We demonstrate that presumptive interfollicular stem cells, alpha 6+/MHCI- cells, are enriched in messenger RNAs encoding surface receptors, cell adhesion molecules, extracellular matrix proteins, transcripts encoding members of IFN-alpha family proteins and components of IFN signaling, but contain lower levels of transcripts encoding proteins which take part in energy metabolism, cell cycle, ribosome biosynthesis, splicing, protein translation, degradation, DNA replication, repair, and chromosome remodeling. Furthermore, our data indicate that the cell signaling pathways Notch1 and NF-κB are downregulated/inhibited in MHC negative basal cells. Conclusion: This study demonstrates that alpha 6+/MHCI- cells have additional characteristics attributed to stem cells. In addition, the transcription profile of alpha 6+/MHCI- cells shows similarities to transcription profiles of mouse hair follicle bulge cells known to be enriched for stem cells. Collectively, our data suggests that alpha 6+/MHCI- cells may be enriched for stem cells. This study is the first comprehensive gene expression profile of putative human epithelial cells and their progeny that were isolated directly from neonatal foreskin tissue. Our study is important for understanding self renewal and differentiation of epidermal stem cells, and for elucidating signaling pathways involved in those processes. The generated data base may serve those working with other human epithelial tissue progenitors. Keywords: Comparison of stem and TA cells Overall design: In the present work we employ microarray technology, to report global transcriptional profiles of two cell populations: the basal cells that express MHCI, α6+/MHCI+ (transient amplifying cells) and the basal cells that have low/negative MHCI expression, α6+/MHCI- cells, (putative stem cells). Cells were isolated using fluorescence-activated cell sorter (FACS) directly from human epidermis. Further comparisons were made with published data of hair follicle stem cell gene expression profiles.

研究背景：人体毛囊间表皮（interfollicular epidermis）由干细胞及其子代——瞬时扩增细胞（transient amplifying cells）的增殖维持。对这两种细胞群进行分子表征，对于深入理解自我更新、分化以及皮肤致病机制至关重要。本研究旨在获取α6+/MHCI+瞬时扩增细胞与α6+/MHCI- 假定干细胞（putative stem cells）的基因表达谱，并将其与已公开的小鼠毛囊干细胞基因表达谱数据库进行对比。主要组织相容性复合体（Major Histocompatibility Complex, MHC）I类分子此前被证实在多种组织的干细胞中不表达，结合α6整联蛋白（alpha 6 integrin），我们成功分离得到MHCI阳性基底细胞与MHCI低表达/阴性基底细胞。
研究结果：本研究明确了两种细胞群的转录谱，并与已发表的毛囊干细胞基因表达谱数据进行对比。我们发现，推定的毛囊间表皮干细胞（α6+/MHCI-细胞）富集编码表面受体、细胞黏附分子、细胞外基质蛋白的信使RNA，以及I型干扰素（IFN-α）家族蛋白成员与干扰素信号通路组分的转录本；但其编码参与能量代谢、细胞周期、核糖体生物合成、RNA剪接、蛋白质翻译、降解、DNA复制、修复以及染色质重塑的蛋白的转录本水平较低。此外，我们的数据显示，细胞信号通路Notch1与NF-κB在MHCI阴性基底细胞中被下调/抑制。
研究结论：本研究证实，α6+/MHCI-细胞具备干细胞的多项额外特征。此外，α6+/MHCI-细胞的转录谱与已知富集干细胞的小鼠毛囊隆突细胞（hair follicle bulge cells）的转录谱具有相似性。综上，我们的数据提示α6+/MHCI-细胞可能富集干细胞。本研究是首个直接从新生儿包皮组织中分离得到的假定人上皮细胞及其子代的全面基因表达谱分析。本研究对于理解表皮干细胞的自我更新与分化，以及阐明参与这些过程的信号通路具有重要意义。本研究生成的数据库可为其他从事人类上皮组织祖细胞研究的科研人员提供参考。
关键词：干细胞与瞬时扩增细胞的对比
整体实验设计：本研究采用微阵列技术，报道两种细胞群的全局转录谱：表达MHC I类分子的基底细胞α6+/MHCI+（瞬时扩增细胞），以及MHC I类分子表达水平低/阴性的基底细胞α6+/MHCI-（假定干细胞）。研究人员通过荧光激活细胞分选术（fluorescence-activated cell sorter, FACS）直接从人表皮中分离得到上述细胞。后续将其与已公开的毛囊干细胞基因表达谱数据进行对比分析。