Inhibition of Fgf signaling in short bowel syndrome increases weight loss and epithelial proliferation

Thyroid Hormones Regulate Goblet Cell Differentiation and Fgf19-Fgfr4 Signaling

Hypothyroidism is a common pathological condition characterized by insufficient activity of the thyroid hormones (THs), thyroxine (T4), and 3,5,3'-triiodothyronine (T3), in the whole body or in specific tissues. Hypothyroidism is associated with inadequate development of the intestine as well as gastrointestinal diseases. We used a zebrafish model of hypothyroidism to identify and characterize TH-modulated genes and cellular pathways controlling intestine development. In the intestine of hypothyroid juveniles and adults, the number of mucus-secreting goblet cells was reduced, and this phenotype could be rescued by T3 treatment. Transcriptome profiling revealed dozens of differentially expressed genes in the intestine of hypothyroid adults compared to controls. Notably, the expression of genes encoding to Fgf19 and its receptor Fgfr4 was markedly increased in the intestine of hypothyroid adults, and treatment with T3 normalized it. Blocking fibroblast growth factor (FGF) signaling, using an inducible dominant-negative Fgfr transgenic line, rescued the number of goblet cells in hypothyroid adults. These results show that THs inhibit the Fgf19-Fgfr4 signaling pathway, which is associated with inhibition of goblet cell differentiation in hypothyroidism. Both the TH and Fgf19-Fgfr4 signaling pathways can be pharmaceutical targets for the treatment of TH-related gastrointestinal diseases.

R-Spondin1 enhances wnt signaling and decreases weight loss in short bowel syndrome zebrafish

Background

R-spondins, including R-spondin 1 (RSPO1), are a family of Wnt ligands that help to activate the canonical Wnt/β-catenin pathway, which is critical for intestinal epithelial cell proliferation and maintenance of intestinal stem cells. This proliferation underpins the epithelial expansion, or intestinal adaptation (IA), that occurs following massive bowel resection and short bowel syndrome (SBS). The purpose of this study was to identify if recombinant human RSPO1 (rhRSPO1) could be serially administered to SBS zebrafish to enhance cellular proliferation and IA.

Methods

Adult male zebrafish were assigned to four groups: sham + PBS, SBS + PBS, sham + rhRSPO1, and SBS + rhRSPO1. Sham fish had a laparotomy alone. SBS fish had a laparotomy with distal intestinal ligation and creation of a proximal stoma. Fish were weighed at initial surgery and then weekly. rhRSPO1 was administered post-operatively following either a one- or two-week dosing schedule with either 3 or 5 intraperitoneal injections, respectively. Fish were harvested at 7 or 14 days with intestinal segments collected for analysis.

Results

Repeated intraperitoneal injection of rhRSPO1 was feasible and well tolerated. At 7 days, intestinal epithelial proliferation was increased by rhRSPO1. At 14 days, SBS + rhRSPO1 fish lost significantly less weight than SBS + PBS fish. Measurements of intestinal surface area were not increased by rhRSPO1 administration but immunofluorescent staining for β-catenin and gene expression for cyclin D1 was increased.

Conclusions

Intraperitoneal injection of rhRSPO1 decreased weight loss in SBS zebrafish with increased β-catenin + cells and cyclin D1 expression at 14 days, indicating improved weight maintenance might result from increased activation of the canonical Wnt pathway.

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rhRSPO1 decreased weight loss in SBS zebrafish.

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rhRSPO1 increased intestinal cell epithelial proliferation at 7 days.

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rhRSPO1 increased β-catenin + cells at 14 days in the intestine of SBS zebrafish.

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rhRSPO1 increased cyclin D1 expression at 14 days in the intestine of SBS zebrafish.

Broad-spectrum antibiotics alter the microbiome, increase intestinal fxr, and decrease hepatic steatosis in zebrafish short bowel syndrome

Short bowel syndrome (SBS) is associated with changes in the intestinal microbiome and marked local and systemic inflammation. There is also a late complication of SBS, intestinal failure associated liver disease (IFALD) in which hepatic steatosis progresses to cirrhosis. Most patients with SBS arrive at massive intestinal resection after a contaminating intraabdominal catastrophe and have a history of exposure to broad-spectrum antibiotics. We therefore investigated whether the administration of broad-spectrum antibiotics in conjunction with SBS in zebrafish (ZF) would replicate these systemic effects observed in humans to identify potentially druggable targets to aid in the management of SBS and resulting IFALD. In zebrafish with SBS, broad-spectrum antibiotics altered the microbiome, decreased inflammation, and reduced the development of hepatic steatosis. After two weeks of broad-spectrum antibiotics, these fish exhibited decreased alpha diversity, with less variation in microbial community composition between SBS and sham fish. Additionally, administration of broad-spectrum antibiotics was associated with decreased expression of intestinal toll-like receptor 4 (tlr4), increased expression of the intestinal gene encoding the Farnesoid X receptor (fxr), decreased expression of downstream hepatic cyp7a1, and decreased development of hepatic steatosis. SBS in zebrafish reproducibly results in increased epithelial surface area as occurs in human patients who demonstrate intestinal adaptation, but antibiotic administration in zebrafish with SBS reduced these gains with increased cell death in the intervillus pocket that contains stem/progenitor cells. These alternate states in SBS zebrafish might direct the development of future human therapies.NEW & NOTEWORTHY In a zebrafish model that replicates a common clinical scenario, systemic effects of the administration of broad-spectrum antibiotics in a zebrafish model of SBS identified two alternate states that led to the establishment of fat accumulation in the liver or its absence. Broad-spectrum antibiotics given to zebrafish with SBS over 2 wk altered the intestinal microbiome, decreased intestinal and hepatic inflammation, and decreased hepatic steatosis.

Wnt signaling inhibition by monensin results in a period of Hippo pathway activation during intestinal adaptation in zebrafish

Intestinal adaptation (IA) is a critical response to increase epithelial surface area after intestinal loss. Short bowel syndrome (SBS) may follow massive intestinal resection in human patients, particularly without adequate IA. We previously validated a model in zebrafish (ZF) that recapitulates key SBS pathophysiological features. Previous RNA sequencing in this model identified upregulation of genes in the Wnt and Hippo pathways. We therefore sought to identify the timeline of increasing cell proliferation and considered the signaling that might underpin the epithelial remodeling of IA in SBS. SBS was created in a ZF model as previously reported and compared with sham fish with and without exposure to monensin, an ionophore known to inhibit canonical Wnt signaling. Rescue of the monensin effects was attempted with a glycogen synthase kinase 3 inhibitor that activates wnt signaling, CHIR-99021. A timeline was constructed to identify peak cellular proliferation, and the Wnt and Hippo pathways were evaluated. Peak stem cell proliferation and morphological changes of adaptation were identified at 7 days. Wnt inhibition diminished IA at 2 wk and resulted in activation of genes of the Wnt/β-catenin and Yes-associated protein (YAP)/Hippo pathway. Increased cytoplasmic YAP was observed in monensin-treated SBS fish. Genes of the WASP-interacting protein (WIP) pathway were elevated during Wnt blockade. In conclusion, cellular proliferation and morphological changes accompany SBS even in attempted Wnt blockade. Wnt/β-catenin, YAP/Hippo pathway, and WIP pathway genes increase during early Wnt blockade. Further understanding of the effects of Wnt and YAP pathway signaling in proliferating stem cells might enrich our knowledge of targets to assist IA. NEW & NOTEWORTHY Intestinal adaptation is a critical response to increase epithelial surface area after large intestinal losses. Inhibition of Wnt/β-catenin signaling impairs intestinal adaptation in a zebrafish model of short bowel syndrome. There is a subsequent upregulation in genes of the Yes-associated protein/Hippo and WIP pathway. These may be targets for future human therapies, as patients are salvaged by the compensation of increased intestinal epithelial surface area through successful intestinal adaptation.

Prolonged Absence of Mechanoluminal Stimulation in Human Intestine Alters the Transcriptome and Intestinal Stem Cell Niche

BACKGROUND & AIMS

For patients with short-bowel syndrome, intestinal adaptation is required to achieve enteral independence. Although adaptation has been studied extensively in animal models, little is known about this process in human intestine. We hypothesized that analysis of matched specimens with and without luminal flow could identify new potential therapeutic pathways.

METHODS

Fifteen paired human ileum samples were collected from children aged 2-20 months during ileostomy-reversal surgery after short-segment intestinal resection and diversion. The segment exposed to enteral feeding was denoted as fed, and the diverted segment was labeled as unfed. Morphometrics and cell differentiation were compared histologically. RNA Sequencing and Gene Ontology Enrichment Analysis identified over-represented and under-represented pathways. Immunofluorescence staining and Western blot evaluated proteins of interest. Paired data were compared with 1-tailed Wilcoxon rank-sum tests with a P value less than .05 considered significant.

RESULTS

Unfed ileum contained shorter villi, shallower crypts, and fewer Paneth cells. Genes up-regulated by the absence of mechanoluminal stimulation were involved in digestion, metabolism, and transport. Messenger RNA expression of LGR5 was significantly higher in unfed intestine, accompanied by increased levels of phosphorylated signal transducer and activator of transcription 3 protein, and CCND1 and C-MYC messenger RNA. However, decreased proliferation and fewer LGR5+, OLFM4+, and SOX9+ intestinal stem cells (ISCs) were observed in unfed ileum.

CONCLUSIONS

Even with sufficient systemic caloric intake, human ileum responds to the chronic absence of mechanoluminal stimulation by up-regulating brush-border enzymes, transporters, structural genes, and ISC genes LGR5 and ASCL2. These data suggest that unfed intestine is primed to replenish the ISC population upon re-introduction of enteral feeding. Therefore, the elucidation of pathways involved in these processes may provide therapeutic targets for patients with intestinal failure. RNA sequencing data are available at Gene Expression Omnibus series GSE82147.