SummaryHuman intestinal organoids (HIOs) are a tissue culture model in which small intestine-like tissue is generated from pluripotent stem cells. By carrying out unsupervised hierarchical clustering of RNA-sequencing data, we demonstrate that HIOs most closely resemble human fetal intestine. We observed that genes involved in digestive tract development are enriched in both fetal intestine and HIOs compared to adult tissue, whereas genes related to digestive function and Paneth cell host defense are expressed at higher levels in adult intestine. Our study also revealed that the intestinal stem cell marker OLFM4 is expressed at very low levels in fetal intestine and in HIOs, but is robust in adult crypts. We validated our findings using in vivo transplantation to show that HIOs become more adult-like after transplantation. Our study emphasizes important maturation events that occur in the intestine during human development and demonstrates that HIOs can be used to model fetal-to-adult maturation.

Background & Aims Iron deficiency and iron overload affect over a billion people, worldwide. Dietary iron absorption in the small intestine is required for systemic iron homeostasis. Ferroportin (FPN) is the only characterized, mammalian, basolateral iron exporter. Despite the importance of FPN in maintaining iron homeostasis, its in vivo mechanisms of regulation are unclear. Methods Systemic iron homeostasis was assessed in mice with intestine-specific disruption of genes encoding the von Hippel-Lindau tumor suppressor protein (Vhl), hypoxia-inducible factor (HIF)-1α, HIF-2α, and aryl hydrocarbon nuclear translocator (ARNT). Results We observed biphasic regulation of Fpn during iron deficiency. Fpn was rapidly induced under conditions of low iron, which required the transcription factor HIF-2α. Targeted disruption of HIF-2α in the intestine inhibited Fpn induction in mice with low iron, through loss of transcriptional activation. Analysis of the Fpn promoter and in vivo chromatin immunoprecipitation assays demonstrated that HIF-2α directly binds to the Fpn promoter and induces its expression, indicating a mechanism of transcriptional regulation of Fpn following changes in systemic levels of iron. During chronic iron deficiency, FPN protein levels also increased, via increased stability through a HIF-2α-independent pathway. Conclusion In mice, expression of the gene that encodes Fpn and its protein levels are regulated by distinct pathways to provide a rapid and sustained response to acute and chronic iron deficiency. Therapies that target FPN might be developed for patients with iron-related disorders..

Background & Aims Hypoxic inflammation (decreased oxygen tension at sites of inflammation) is a feature of inflammatory bowel disease (IBD). The hypoxia response is mediated by the transcription factors hypoxia-inducible factor (HIF)1α and endothelial PAS domain protein 1 (EPAS1 or HIF2α), which are induced in intestinal tissues of patients with IBD. HIF1α limits intestinal barrier dysfunction, but the role of EPAS1 has not been assessed under conditions of hypoxic inflammation or in models of IBD. Methods Acute colitis was induced by administration of Citrobacter rodentium ordextran sulfate sodium (DSS) to transgenic hypoxia reporter mice (ODD-Luc), mice with conditional overexpression of Epas1 (Epas1LSL/LSL), mice with intestinal epithelium-specific deletion of Epas1 (Epas1ΔIE), or wild-type littermates (controls). Colon tissues from these mice and from patients with ulcerative colitis (UC) or Crohn's disease (CD) were assessed by histologic and immunoblot analyses, immunohistochemistry, and quantitative PCR. Results Levels of hypoxia and EPAS1 were increased in colon tissues of mice following induction of colitis and patients with UC or CD, compared with controls. Epas1ΔIE mice had attenuated colonic inflammation and were protected from DSS-induced colitis. Intestine-specific overexpression of EPAS1, but not HIF-1α, led to spontaneous colitis, increased susceptibility to induction of colitis by C rodentium or DSS, and reduced survival times compared with controls. Disruption of intestinal epithelial EPAS1 attenuated the inflammatory response following administration of DSS or C rodentium, whereas intestine-specific overexpression of EPAS1 increased this response. We found EPAS1 to be a positive regulator of tumor necrosis factor (TNF)α production by the intestinal epithelium. Blocking TNFα completely reduced hypoxia-induced intestinal inflammation. We found EPAS1 to be a positive regulator of tumor necrosis factor (TNF)α production by the intestinal epithelium. Blocking TNFα completely reduced hypoxia-induced intestinal inflammation. Conclusions EPAS1 is a transcription factor that activates mediators of inflammation, such as TNFα, in the intestinal epithelium and promotes development of colitis in mice.

Oxygen dynamics in the liver is a central signaling mediator controlling hepatic homeostasis, and dysregulation of cellular oxygen is associated with liver injury. Moreover, the transcription factor relaying changes in cellular oxygen levels, hypoxia-inducible factor (HIF), is critical in liver metabolism and sustained increase in HIF signaling can lead to spontaneous steatosis, inflammation, and liver tumorigenesis. However, the direct responses and genetic networks regulated by HIFs in the liver are unclear. To help define the HIF signal transduction pathway, an animal model of HIF overexpression was generated and characterized. In this model, overexpression was achieved by Von Hippel-Lindau (Vhl) disruption in a liver-specific temporal fashion. Acute disruption of Vhl induced hepatic lipid accumulation in a HIF-2α-dependent manner. In addition, HIF-2α activation rapidly increased liver inflammation and fibrosis demonstrating that steatosis and inflammation are primary responses of the liver to hypoxia. To identify downstream effectors, a global microarray expression analysis was performed using livers lacking Vhl for 24-hours and 2-weeks, revealing a time-dependent effect of HIF on gene expression. Increase in genes involved in fatty acid synthesis were followed by an increase in fatty acid uptake-associated genes, and an inhibition of fatty acid β-oxidation. A rapid increase in pro-inflammatory cytokines and fibrogenic gene expression was also observed. In vivo chromatin immunoprecipitation assays revealed novel direct targets of HIF signaling that may contribute to hypoxia-mediated steatosis and inflammation. These data suggest that HIF-2α is a critical mediator in progression from clinically manageable steatosis to more severe steatohepatitis and liver cancer, and may be a potential therapeutic target.

Conservative treatment should be reserved for cerebrospinal fluid otorrhea or otorhinorrhea resulting from head injury. Postoperative and nontraumatic cerebrospinal fluid otorrhea or otorhinorrhea should have early operative intervention. A multilayer technique combining allogenic materials with free autologous grafts is recommended.