Glycan Epitope and Integrin Expression Dynamics Characterize Neural Crest Epithelial-to-Mesenchymal Transition (EMT) in Human Pluripotent Stem Cell Differentiation

The neural crest gives rise to progeny as diverse as peripheral neurons, myelinating cells, cranial muscle, bone and cartilage tissues, and melanocytes. Neural crest derivation encompasses complex morphological change, including epithelial-to-mesenchymal transition (EMT) and migration to the eventual target locations throughout the body. Neural crest cultures derived from stem cells provide an attractive source for developmental studies in human model systems, of immediate biomedical relevance for neurocristopathies, neural cancer biology and regenerative medicine, if only appropriate markers for lineage and cell type definition and quality control criteria were available. Implementing a defined, scalable protocol to generate neural crest cells from embryonic stem cells, we identify stage-defining cluster-of-differentiation (CD) surface markers during human neural crest development in vitro. Acquisition of increasingly mesenchymal phenotype was characterized by absence of neuroepithelial stemness markers (CD15, CD133, CD49f) and by decrease of CD57 and CD24. Increased per-cell-expression of CD29, CD44 and CD73 correlated with established EMT markers as determined by immunofluorescence and immunoblot analysis. The further development towards migratory neural crest was associated with decreased CD24, CD49f (ITGA6) and CD57 (HNK1) versus an enhanced CD49d (ITGA4), CD49e (ITGA5) and CD51/CD61 (ITGAV/ITGB3) expression. Notably, a shift from CD57 to CD51/CD61 was identified as a sensitive surrogate surface indicator of EMT in neural crest in vitro development. The reported changes in glycan epitope and integrin surface expression may prove useful for elucidating neural crest stemness, EMT progression and malignancies.

Novel Concepts: Langerhans Cells in the Tumour Microenvironment

Langerhans cells (LCs) are immune cells that reside in the stratified epithelium of the skin and mucosal membranes. They play a range of roles in the skin, including antigen presentation and maintenance of peripheral tolerance. Reports of LC numbers have been variable in different cancer types, with the majority of studies indicating a reduction in their number. Changes in the cytokine profile and other secreted molecules, downregulation of surface molecules on cells and hypoxia all contribute to the regulation of LCs in the tumour microenvironment. Functionally, LCs have been reported to regulate immunity and carcinogenesis in different cancer types. An improved understanding of the function and biology of LCs in tumours is essential knowledge that underpins the development of new cancer immunotherapies.

Perturbations of mucosal homeostasis through interactions of intestinal microbes with myeloid cells

Mucosal surfaces represent the largest areas of interactions of the host with its environment. Subsequently, the mucosal immune system has evolved complex strategies to maintain the integrity of the host by inducing protective immune responses against pathogenic and tolerance against dietary and commensal microbial antigens within the broad range of molecules the intestinal epithelium is exposed to. Among many other specialized cell subsets, myeloid cell populations - due to their strategic location in the subepithelial lamina propria - are the first ones to scavenge and process these intestinal antigens and to send consecutive signals to other immune and non-immune cell subsets. Thus, myeloid cell populations represent attractive targets for clinical intervention in chronic inflammatory bowel diseases (IBDs) such as ulcerative colitis (UC) and Crohn's disease (CD) as they initiate and modulate inflammatory or regulatory immune response and shape the intestinal T cell pool. Here, we discuss the interactions of the intestinal microbiota with dendritic cell and macrophage populations and review in this context the literature on four promising candidate molecules that are critical for the induction and maintenance of intestinal homeostasis on the one hand, but also for the initiation and propagation of chronic intestinal inflammation on the other.