Animal models of mucositis: critical tools for advancing pathobiological understanding and identifying therapeutic targets

PURPOSE OF REVIEW:Mucositis remains a prevalent, yet poorly managed side effect of anticancer therapies. Mucositis affecting both the oral cavity and gastrointestinal tract predispose to infection and require extensive supportive management, contributing to the growing economic burden associated with cancer care. Animal models remain a critical aspect of mucositis research, providing novel insights into its pathogenesis and revealing therapeutic targets. The current review aims to provide a comprehensive overview of the current animal models used in mucositis research. RECENT FINDINGS:A wide variety of animal models of mucositis exist highlighting the highly heterogenous landscape of supportive oncology and the unique cytotoxic mechanisms of different anticancer agents. Golden Syrian hamsters remain the gold-standard species for investigation of oral mucositis induced by single dose and fractionated radiation as well as chemoradiation. There is no universally accepted gold-standard model for the study of gastrointestinal mucositis, with rats, mice, pigs and dogs all offering unique perspectives on its pathobiology. SUMMARY:Animal models are a critical aspect of mucositis research, providing unprecedent insight into the pathobiology of mucositis. Introduction of tumour-bearing models, cyclic dosing scheduled, concomitant agents and genetically modified animals have been integral in refining our understanding of mucositis.Hannah R. Wardill, Wim J.E. Tissing, Hannelouise Kissow and Andrea M. Stringe

Glucagon-like peptide 2 (GLP-2) accelerates the growth of colonic neoplasms in mice

Background: Glucagon-like peptide 2 (GLP-2) is an intestinotrophic mediator with therapeutic potential in conditions with compromised intestinal capacity. However, growth stimulation of the intestinal system may accelerate the growth of existing neoplasms in the intestine. Aims: In the present study, the effects of GLP-2 treatment on the growth of chemically induced colonic neoplasms were investigated. Methods: In 210 female C57bl mice, colonic tumours were initially induced with the methylating carcinogen 1,2-dimethylhydrazine (DMH) and mice were then treated with GLP-2. Two months after discontinuation of the carcinogen treatment, 135 of the mice were allocated to one of six groups which were treated twice daily with 25 μg GLP-2, 25 μg Gly2-GLP-2 (stable analogue), or phosphate buffered saline for a short (10 days) or long (one month) period. The remaining 75 mice had a treatment free period of three months and were then allocated to groups subjected to long term treatment, as above. Results: Colonic polyps developed in 100% of the mice, regardless of treatment. Survival data revealed no statistical significant differences among the different groups but histopathological analysis demonstrated a clear and significant increase in tumour load of mice treated with Gly2-GLP-2. The tumour promoting effect of native GLP-2 was less pronounced but the number of small sized polyps increased following long term treatment. Conclusions: The present results clearly indicate that GLP-2 promotes the growth of mucosal neoplasms. Our findings highlight the need for future investigations on the effects of GLP-2 in conditions needing long time treatment or with increased gastrointestinal cancer susceptibility

Rectal insulin instillation inhibits inflammation and tumor development in chemically-induced colitis

Background & Aims The epithelial expression of the insulin receptor in the colon is previously reported to correlate with the extent of colonic inflammation. However, the impact of insulin signaling in the intestinal mucosa is still unknown. Here, we investigated the effects of inactivating the epithelial insulin receptor in the intestinal tract, in an experimental model of inflammation-induced colorectal cancer. Methods The mice were generated by utilizing the intestinal- and epithelial-specific villin promoter and the Cre-Lox technology. All mice included in the cohorts were generated by crossing (vil-Cre-INSR+/-) x (INSRfl/fl) to obtain (vil-Cre-INSR-/-) and their floxed littermates (INSRfl/fl) serving as the control group. For the intervention study, phosphate-buffered saline with or without insulin was instilled rectally in anesthetized wild type mice with chemically-induced colitis. Results We report higher endoscopic colitis scores together with potentiated colonic tumorigenesis in the knockout mice. Furthermore, we show that topically administered insulin in inflamed colons of wildtype mice reduces inflammation-induced weight loss and improves remission in a dose-dependent manner. Mice receiving rectal insulin enemas exhibited lower colitis endoscopic scores, reduced cyclooxygenase 2 mRNA expression, and developed significantly fewer and smaller tumors compared with the control group receiving phosphate-buffered saline only. Conclusions Rectal insulin therapy can potentially be a novel treatment targeting the epithelial layer to enhance mucosal healing in the ulcerated areas. Our findings open up new possibilities for combination treatments to synergize with the existing anti-inflammatory therapies

Disruption of glucagon receptor signaling causes hyperaminoacidemia exposing a possible liver-alpha-cell axis.

Glucagon secreted from the pancreatic alpha-cells is essential for regulation of blood glucose levels. However, glucagon may play an equally important role in the regulation of amino acid metabolism by promoting ureagenesis. We hypothesized that disruption of glucagon receptor signaling would lead to an increased plasma concentration of amino acids, which in a feedback manner stimulates the secretion of glucagon, eventually associated with compensatory proliferation of the pancreatic alpha-cells. To address this, we performed plasma profiling of glucagon receptor knockout (Gcgr(-/-)) mice and wild-type (WT) littermates using liquid chromatography-mass spectrometry (LC-MS)based metabolomics, and tissue biopsies from the pancreas were analyzed for islet hormones and by histology. A principal component analysis of the plasma metabolome from Gcgr(-/-) and WT littermates indicated amino acids as the primary metabolic component distinguishing the two groups of mice. Apart from their hyperaminoacidemia, Gcgr(-/-) mice display hyperglucagonemia, increased pancreatic content of glucagon and somatostatin (but not insulin), and alpha-cell hyperplasia and hypertrophy compared with WT littermates. Incubating cultured alpha-TC1.9 cells with a mixture of amino acids (Vamin 1%) for 30 min and for up to 48 h led to increased glucagon concentrations (similar to 6-fold) in the media and cell proliferation (similar to 2-fold), respectively. In anesthetized mice, a glucagon receptor-specific antagonist (Novo Nordisk 25-2648, 100 mg/kg) reduced amino acid clearance. Our data support the notion that glucagon secretion and hepatic amino acid metabolism are linked in a close feedback loop, which operates independently of normal variations in glucose metabolism