Adult stem cells in the small intestine are intrinsically programmed with their location-specific function

Differentiation and specialisation of epithelial cells in the small intestine is regulated in two ways. First, there is differentiation along the crypt-villus axis of the intestinal stem cells into absorptive enterocytes, Paneth, goblet, tuft, enteroendocrine or M-cells, which is mainly regulated by WNT. Second, there is specialization along the cephalocaudal axis with different absorptive and digestive functions in duodenum, jejunum and ileum that is controlled by several transcription factors such as GATA4. However, so far it is unknown whether location-specific functional properties are intrinsically programmed within stem cells or if continuous signalling from mesenchymal cells is necessary to maintain the location-specific identity of the small intestine. By using the pure epithelial organoid technique, we show that region-specific gene expression profiles are conserved throughout long-term cultures of both mouse and human intestinal stem cells and correlated with differential Gata4 expression. Furthermore, the human organoid culture system demonstrates that Gata4-regulated gene expression is only allowed in absence of WNT signalling. These data show that location-specific function is intrinsically programmed in the adult stem cells of the small intestine and that their differentiation fate is independent of location-specific extracellular signals. In light of the potential future clinical application of small intestine-derived organoids, our data imply that it is important to generate GATA4-positive and GATA4-negative cultures to regenerate all essential functions of the small intestine.

小肠上皮细胞的分化与特化受两种机制调控。其一，肠干细胞（intestinal stem cells）沿隐窝-绒毛轴（crypt-villus axis）分化为吸收性肠上皮细胞、潘氏细胞（Paneth）、杯状细胞、簇细胞、肠内分泌细胞或M细胞（M-cells），该过程主要受WNT信号通路（WNT）调控。其二，沿头尾轴（cephalocaudal axis）存在特化：十二指肠、空肠与回肠具备不同的吸收与消化功能，该特化过程受GATA4转录因子（GATA4）等多种转录因子调控。然而目前尚不清楚，位置特异性的功能特性是干细胞内在编程的结果，还是需要间质细胞持续传递信号以维持小肠的位置特异性身份。本研究通过纯上皮类器官技术（pure epithelial organoid technique）证实，在小鼠与人类肠干细胞的长期培养过程中，区域特异性基因表达谱始终保持保守，且与Gata4的差异表达相关。此外，人类类器官培养系统显示，Gata4调控的基因表达仅在WNT信号通路缺失的情况下得以激活。上述数据表明，小肠成体干细胞的位置特异性功能是内在编程的，其分化命运不受位置特异性细胞外信号的影响。鉴于小肠来源的类器官未来具备潜在临床应用价值，本研究数据提示，为重建小肠的所有核心功能，构建GATA4阳性与GATA4阴性的类器官培养体系至关重要。