The urothelium is a specialized epithelium that lines the urinary tract. It consists of three different cell types, namely, basal, intermediate and superficial cells arranged in relatively distinct cell layers. Normally, quiescent, it regenerates fast upon injury, but the regeneration process is not fully understood. Although several reports have indicated the existence of progenitors, their identity and exact topology, as well as their role in key processes such as tissue regeneration and carcinogenesis have not been clarified. Here we show that a minor subpopulation of basal cells, characterized by the expression of keratin 14, possesses self-renewal capacity and also gives rise to all cell types of the urothelium during natural and injury-induced regeneration. Moreover, these cells represent cells of origin of urothelial cancer. Our findings support the hypothesis of basally located progenitors with profound roles in urothelial homoeostasis.

Genome-wide association studies of complex immune-mediated diseases have indicated that many genetic factors, each with individual low risk, contribute to overall disease. It is therefore timely and important to characterize how immune responses may be subtly modified by tissue context. In this article, we explore the role of tissue-derived molecules in influencing the function of T cells, which, owing to their migratory nature, come into contact with many different microenvironments through their lifespan. Hedgehog (Hh) proteins act as secreted morphogens, providing concentration-dependent positional and temporal cell-fate specification in solid tissues. Hh signaling is required for embryogenesis and is important in postnatal tissue renewal and in malignancy. However, the function of Hh in dynamic, fluid systems, such as in mammalian immunity, is largely unknown. In this article, we show that Hh-dependent transcription in T cells promoted Th2 transcriptional programs and differentiation, exacerbating allergic disease. Of interest, expression of Sonic Hh increased in lung epithelial cells following the induction of allergic disease, and lung T cells upregulated Hh target gene expression, indicating that T cells respond to locally secreted Hh ligands in vivo. We show that Il4, the key Th2 cytokine, is a novel transcriptional target of Hh signals in T cells, providing one mechanism for the role of Hh in Th differentiation. We propose that Hh, secreted from inflamed, remodeling, or malignant tissue, can modulate local T cell function. Our data present an unexpected and novel role for tissue-derived morphogens in the regulation of fluid immune responses, with implications for allergy and tumor responses, suggesting new uses for anti-Hh therapeutics.

Significance: Dendritic cells (DCs) are important for the development of intestinal inflammation in humans with inflammatory bowel disease (IBD) and in mice with experimental colitis. We demonstrate that a subset of DCs, CD103⁻DCs, isolated from murine mesenteric lymph nodes, is highly pathogenic for murine intestinal inflammation and expresses high levels of the cytokine osteopontin (Opn). This Opn expression by CD103⁻DCs is crucial for their pathogenicity. We define a specific domain of Opn protein significant for inducing pathogenic properties in CD103⁻DCs. Blockade of the interaction of this Opn domain with integrin α9 expressed on CD103⁻DCs abrogated their harmful effects. These findings may open new paths in IBD treatment.

Annexin‐1 is a well‐known endogenous anti‐inflammatory protein that modulates the activation of cells of the innate immune system such as neutrophils and macrophages. We have recently reported a positive role for the exogenous protein on T cell differentiation, however, whether such a role holds true for the endogenous protein has yet to be determined. This aspect has been investigated here finding that Annexin‐1‐deficient T cells display an impaired activation and proliferation in response to anti‐CD3 plus anti‐CD28 stimulation. Furthermore, differentiation of T cells from Annexin‐1‐deficient mice in Th0/Th1/Th2 or Th17 skewing conditions demonstrated an increased Th2 phenotype compared to cells from control littermates. Similar results were obtained when we analyzed the Th1/Th2 profile of lymph node cells obtained from mice immunized with keyhole limpet hemocyanin or the inflammatory infiltrate in mouse model of allergic inflammation. These results demonstrate a novel modulatory role of endogenous Annexin‐1 in TCR signaling and T cell differentiation and suggest this protein might play a dual and complementary role in the innate and adaptive immune response.

Background: Autoimmune diseases, like multiple sclerosis, are triggered by uncontrolled activation of cells of the immune system against self-antigen present, for instance, in the central nervous system. We have reported novel biological functions for Annexin A1, an effector of endogenous anti-inflammation, to produce positive actions on the adaptive immune system by reducing the threshold of T cell activation. In this study, we investigated the potential modulatory role of Annexin A1 in the development of experimental autoimmune encephalomyelitis, a model of multiple sclerosis.Methods: Male control C57/BL6 and AnxA1 null mice were immunized subcutaneously with an emulsion consisting of 300 μg of MOG_35-55in PBS combined with an equal volume of CFA. Lymph node cells obtained from mice immunized with MOG_33-55for 14 days were re-stimulatedin vitrowith MOG_33-55(100 μg/ml) for 4 days and the Th1/Th17 cytokine profile measured by ELISA. Spinal cords were processed either to isolate the infiltrated T cells or fixed and stained with haematoxylin and eosin. Statistical analyses were performed using two-tailed, unpaired Student's t tests or ANOVA.Results: Our results show a direct correlation between Annexin A1 expression and severity of EAE. Analysis of MOG_35-55-induced EAE development in Annexin A1 null mice showed decreased signs of the disease compared to wild type mice. This defect was significant at the peak of the disease and accompanied by reduced infiltration of T cells in the spinal cord. Finally, analysis of the T cell recall responsein vitrofollowing stimulation with MOG_35-55showed a decrease proliferation of Annexin A1 null T cells, with a significantly reduced Th1/Th17 phenotype, compared to wild type cells.Conclusion: Together these findings suggest that Annexin A1 null mice have an impaired capacity to develop EAE. Furthermore strategies aiming at reducing Annexin A1 functions or expression in T cells might represent a novel therapeutic approach for multiple sclerosis.