Project description:The morphogen Indian Hedgehog plays a very important role during intestinal embryogenesis, but also maintains homeostasis of the adult gut. Intestinal Indian Hedgehog is expressed by the intestinal epithelium and signals in paracrine manner to fibroblasts in the stromal compartment. Unresolved deletion of Ihh from the intestinal epithelium leads to a severe enterocolitis. We studied the short term changes in the colon upon deletion of Ihh from the epithelial layer.
Project description:In chronic kidney disease (CKD) and with ageing, individuals lose regenerative capacity after renal injury and are predisposed to progressive fibrosis and cardiovascular disease. With ageing and CKD increased numbers of activated leukocytes are present in the circulation and within the kidney where they correlate with progressive fibrosis. The potential role of activated leukocytes in mediating progressive renal and systemic fibrosis remains incompletely understood. Here, we show that tumour necrosis factor alpha (TNFa) released with injury and aging promotes renal and cardiac fibrosis. We identify a Ubiquitin D expressing population of TNFa induced inflammatory proximal tubular epithelia (iPT) responsible for Indian Hedgehog release in aged and fibrotic kidneys. Indian Hedgehog production by iPT cells activates canonical Hedgehog signalling in Gli1+ stromal cells leading to activation, proliferation and fibrosis deposition. Our data links the immune activation seen in aging and chronic kidney disease to cardio-renal fibrosis. This provides multiple targets for antifibrotic therapies which we validate in murine models of aging and kidney disease.
Project description:Upon intestinal epithelial damage a complex wound healing response is initiated to restore epithelial integrity and defend against pathogenic invasion. Epithelium-derived Indian Hedgehog (Ihh) functions as a critical sensor in this process. Signaling occurs in a paracrine manner because the receptor for Ihh is expressed only in the mesenchyme, but the exact Hedgehog target cell has remained elusive. The aim of this study was to elucidate further the nature of this target cell in the context of intestinal inflammation.Hedgehog activity was modulated genetically in both cell type-specific and body-wide models and the resulting animals were analyzed for gene expression profiles and sensitivity for dextran sodium sulfate (DSS) colitis. To characterize the Hedgehog target cell, Gli1-CreERT2-Rosa26-ZsGreen animals were generated, which express ZsGreen in all Hedgehog-responsive cells. These cells were characterized using flow cytometry and immunofluorescence.Loss of Indian Hedgehog from the intestinal epithelium resulted in a rapid increase in expression of inflammation-related genes, accompanied by increased influx of immune cells. Animals with epithelium-specific deletion of Ihh or lacking the Hedgehog receptor Smoothened from Hedgehog target cells were more sensitive to DSS colitis. In contrast, specific deletion of Smoothened in the myeloid compartment did not alter the response to DSS. This suggests that Hedgehog signaling does not repress intestinal immunity through an effect on myeloid cells. Indeed, we found that Hedgehog-responsive cells expressed gp38, smooth muscle actin, and desmin, indicating a fibroblastic nature. Ihh signaling inhibited expression of C-X-C motif chemokine ligand 12 (CXCL12) in fibroblasts in vitro and in vivo, thereby impairing the recruitment of immune cells.We show that epithelium-derived Indian Hedgehog signals exclusively to fibroblasts in the intestine. Loss of Ihh leads to a rapid immune response with up-regulation of fibroblast-derived CXCL12, and migration of immune cells into the lamina propria.
Project description:The morphogen Indian Hedgehog plays a very important role during intestinal embryogenesis, but also maintains homeostasis in the adult gut. Intestinal Hedgehog is expressed by the intestinal epithelium and signals in paracrine manner to fibroblasts in the stromal compartment. We studied the stromal changes upon simultaneous homozygous deletion of Ihh and the tumor-suppressor gene Apc in the colon.
Project description:The morphogen Indian Hedgehog plays a very important role during intestinal embryogenesis, but also maintains homeostasis in the adult gut. Intestinal Hedgehog is expressed by the intestinal epithelium and signals in paracrine manner to fibroblasts in the stromal compartment. We studied the colonic changes upon activation of the Hedgehog pathway by deleting the Hedgehog receptor Patched1 in order to alleviate its repressive function.
Project description:Epithelial Hedgehog (Hh) ligands regulate several aspects of fetal intestinal organogenesis and emerging data implicate the Hh pathway in inflammatory signaling in adult colon. We investigated the effects of chronic Hh inhibition in vivo and profiled molecular pathways acutely modulated by Hh signaling in the intestinal mesenchyme. Experiment Overall Design: E18.5 intestinal mesenchyme was isolated and cultured. Mesenchyme was treated with Sonic (Shh) or Indian (Ihh) hedgehog ligand or Vehicle (control) acutely to identify targets regulated by Hh signaling in intestinal mesenchyme.