Definition of human intestinal mesenchymal origins and of mesenchymal epithelial cross-talk in health and disease

成纤维细胞和平滑肌细胞等细胞在肠道等器官中提供关键的结构支持。在过去的10年里，很明显，这些细胞在胚胎发育和稳定的成人肠道中扮演着重要的和不同的细胞功能。除了它们的结构作用外，这些细胞还发送控制免疫细胞活动水平的信号。它们还向肠道表面的细胞--上皮细胞发出信号，以确保它们的生长，在肠道组织和肠道微生物之间提供健康的屏障。我们之前使用了最新的单细胞技术(单细胞RNA测序)来测量在健康或结肠炎期间从人或小鼠结肠间充质分离的单个间充质细胞中的基因表达。这揭示了在之前被认为是一个种群中的几种新细胞类型的令人惊讶的观察。我们继续探索这些新的间充质细胞状态，并展示了不同的功能和在结肠组织中的解剖位置。这项研究使我们能够确定间充质中的哪些细胞作为肠上皮干细胞的利基，产生它们分化和形成结肠上皮屏障层所需的因子。在结肠炎中，我们确定了单个间充质细胞的重要变化，包括高活性群体的出现，该群体表达吸引免疫细胞的因子和损害上皮功能的因子。这些疾病相关细胞的异常扩张有助于在炎症性肠病等疾病中观察到炎症。这些结构细胞在肠道纤维化中也发挥着重要作用，当它们产生过多的基质蛋白时，会使组织变得僵硬，并导致肠道狭窄，从而阻止食物通过，需要手术。此外，它们在癌症中发挥着重要作用，助长了结肠癌的侵袭和转移行为。尽管最近发现了它们在结肠生理和疾病中的重要作用，但人们对这些细胞是如何在人类发育或成年状态下产生的知之甚少。这些细胞如何分化成不同的类型，以及它们如何控制不同上皮细胞的解剖位置，如肠道内的干细胞，人们知之甚少。重要的是要鉴定间充质前体细胞，并确定控制致病群体出现的分子决定因素，以逆转他们在疾病中的异常行为。此外，更好地了解间充质祖细胞将使器官芯片系统的开发能够在药物开发期间模拟人类肠道，并使胃肠道疾病的再生医学方法成为可能。在这项工作中，我们将使用单细胞RNA测序和空间成像来描绘人类胚胎结肠间充质细胞和相关的结肠上皮层的发育，以期确定间充质前体细胞以及间充质和上皮细胞之间的分子串扰，从而决定健康屏障的形成。我们将使用同样的方法来定义这种关系是如何破坏的，从而推动IBD和结直肠癌的病理。我们将使用胎儿发育数据在成人组织中寻找结肠间充质干细胞，并从功能上确定是否存在这样的细胞类型。这项工作对于促进针对发育性和成人结肠疾病的屏障的治疗至关重要。

Cells such as fibroblasts and smooth muscle cells provide critical structural support in organs such as the gut. Over the last 10 years it has become apparent that these cells play important and diverse cellular functions during embryonic development and in the steady state adult intestine. In addition to their structural roles these cells send signals that control the level of immune cell activity. They also signal to the cells lining the surface of the gut, epithelial cells, to ensure they grow to provide a healthy barrier between the intestinal tissue and the gut microbes. We previously used new state of the art single cell technologies (single-cell RNA-sequencing) to measure genes expressed within single mesenchymal cells isolated from human or mouse colonic mesenchyme in health or during colitis. This revealed the surprising observation of several new cell types within what was previously thought to be one population. We went onto explore these new mesenchymal cell states and demonstrated differing functions and anatomical location within the colonic tissue. The study enabled us to identify which cells in the mesenchyme act as a niche for intestinal epithelial stem cells producing factors required for their differentiation and formation of the epithelial barrier layer of the colon. In colitis we identified important changes in single mesenchymal cells including in emergence of a highly activated population that expressed factors that attract immune cells and factors that impair epithelial function. Abnormal expansion of these disease-associated cells contributes to inflammation observed in diseases such as inflammatory bowel disease. These structural cells also play important roles in intestinal fibrosis, when they produce too much matrix protein that makes tissues stiff and leads to strictures in the intestine that prevent the passage of food and require surgery. Furthermore they play important roles in cancer, fuelling invasiveness and metastatic behaviour in colon cancer. Despite their newly identified and important roles in colon physiology and disease little is known of how these cells arise either in human development or adult state. Little is known about how these cells differentiate into different types and how they control anatomical location of different epithelial cells such as stem cells lining the gut. It is important to identify mesenchymal precursor cells and define the molecular determinants that control emergence of pathogenic populations to revert their aberrant behaviour in disease. Furthermore better understanding of mesenchymal progenitors would enable development of organ-on a chip systems to model human intestine during drug development and enable regenerative medicine approaches for gastrointestinal disease. In this work we will use both single-cell RNA-sequencing and spatial imaging to map human foetal development of colonic mesenchymal cells and the associated colonic epithelial layer with a view to defining a mesenchymal progenitor cell and the molecular cross-talk between mesenchymal and epithelia that dictates formation of healthy barrier. We will use the same approach to define how this relationship breaks down to drive pathology in IBD and colorectal cancer. We will use the foetal development data to inform a search for the colonic mesenchymal stem cell in adult tissue and define functionally if such a cell type exists. This work is critical for advancement of treatments targeting the barrier in both developmental and adult colonic diseases.