Experimental Chemotherapy-Induced Mucositis: A Scoping Review Guiding the Design of Suitable Preclinical Models

Mucositis is a common and most debilitating complication associated with the cytotoxicity of chemotherapy. The condition affects the entire alimentary canal from the mouth to the anus and has a significant clinical and economic impact. Although oral and intestinal mucositis can occur concurrently in the same individual, these conditions are often studied independently using organ-specific models that do not mimic human disease. Hence, the purpose of this scoping review was to provide a comprehensive yet systematic overview of the animal models that are utilised in the study of chemotherapy-induced mucositis. A search of PubMed/MEDLINE and Scopus databases was conducted to identify all relevant studies. Multiple phases of filtering were conducted, including deduplication, title/abstract screening, full-text screening, and data extraction. Studies were reported according to the updated Preferred Reporting Items for Systematic reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) guidelines. An inter-rater reliability test was conducted using Cohen's Kappa score. After title, abstract, and full-text screening, 251 articles met the inclusion criteria. Seven articles investigated both chemotherapy-induced intestinal and oral mucositis, 198 articles investigated chemotherapy-induced intestinal mucositis, and 46 studies investigated chemotherapy-induced oral mucositis. Among a total of 205 articles on chemotherapy-induced intestinal mucositis, 103 utilised 5-fluorouracil, 34 irinotecan, 16 platinum-based drugs, 33 methotrexate, and 32 other chemotherapeutic agents. Thirteen articles reported the use of a combination of 5-fluorouracil, irinotecan, platinum-based drugs, or methotrexate to induce intestinal mucositis. Among a total of 53 articles on chemotherapy-induced oral mucositis, 50 utilised 5-fluorouracil, 2 irinotecan, 2 methotrexate, 1 topotecan and 1 with other chemotherapeutic drugs. Three articles used a combination of these drugs to induce oral mucositis. Various animal models such as mice, rats, hamsters, piglets, rabbits, and zebrafish were used. The chemotherapeutic agents were introduced at various dosages via three routes of administration. Animals were mainly mice and rats. Unlike intestinal mucositis, most oral mucositis models combined mechanical or chemical irritation with chemotherapy. In conclusion, this extensive assessment of the literature revealed that there was a large variation among studies that reproduce oral and intestinal mucositis in animals. To assist with the design of a suitable preclinical model of chemotherapy-induced alimentary tract mucositis, animal types, routes of administration, dosages, and types of drugs were reported in this study. Further research is required to define an optimal protocol that improves the translatability of findings to humans.

Methotrexate mediates the integrity of intestinal stem cells partly through nitric oxide-dependent Wnt/β-catenin signaling in methotrexate-induced rat ileal mucositis

This study aimed to elucidate the role of nitric oxide (NO) in intestinal stem cells in methotrexate-induced ileal mucositis in rats. Methotrexate induced the mRNA expressions of the Wnt/β-catenin target genes Wnt3a, Sox9, and Lgr5 and the Wnt-antagonist gene sFRP-1 and the protein expressions of Lgr5 and sFRP-1. Methotrexate also induced Lgr5+ cells and lysozyme+ cells. A non-selective NO inhibitor inhibited the methotrexate induction of Wnt/β-catenin target genes and Lgr5+ cells but enhanced that of sFRP-1 expression. Thus, methotrexate mediates the integrity of intestinal stem cells partly through NO-dependent Wnt/β-catenin signaling and may enhance tolerability to methotrexate-induced injury.

The role of nitric oxide in small intestine differs between a single and a consecutive administration of methotrexate to rats

The role of nitric oxide (NO) on intestinal mucosal injury induced by single or consecutive administration of methotrexate was investigated in a rodent model. Rats received methotrexate intraperitoneally either as a single administration (50 mg/kg) or as a consecutive administration (12.5 mg/kg/day) for 4 days. N^G-nitro-l-arginine methyl ester (L-NAME) was given subcutaneously to inhibit NO synthase (NOS). Ninety-six hours after the first administration of methotrexate, ileal tissues were collected for analysis. Consecutive administration of methotrexate led to decreased body weight and reduced intake of food and water, which were further worsened by L-NAME. Although a slight mucosal injury resulted from single administration of methotrexate, L-NAME had almost no effect. Consecutive administration of methotrexate caused a significant mucosal injury, which was further worsened by L-NAME. Consecutive, but not single, administration of methotrexate induced mRNA expression of inflammatory cytokines in ileal tissue. Consecutive administration of methotrexate significantly induced constitutive NOS expression in ileal tissue. These results suggest that consecutive administration, rather than single administration, of methotrexate aggravates mucosal injury. Potentiation of constitutive NOS expression by consecutive administration might be one of the main reason to antagonize the intestinal mucosal injury as well as lead to a reduction in rat quality of life.