Gastrointestinal mucositis (GM) is a dose-limiting toxicity of chemotherapy, characterised by epithelial damage and loss of intestinal barrier integrity. Vitamin D (VitD) deficiency, common in cancer patients, may worsen mucosal injury. This study investigated the impact of vitD status and vitD–based therapies on 5-fluorouracil (5-FU)–induced GM in both the duodenum and colon.
Male C57BL/6 mice were maintained on either a vitD–replete (1000 IU/kg) or vitD–deficient (0 IU/kg) diet for five weeks. Mice received daily subcutaneous injections of 25-hydroxyvitamin D (25(OH)D; 6.25 mg/kg), VD1-6 (500 ng/kg), both agents, or vehicle. On day five, 5-FU (300 mg/kg) or saline was administered intraperitoneally. Tissues were collected 48 hours post-chemotherapy for histological and molecular analysis.
VitD deficiency significantly reduced epithelial proliferation (p < 0.01) and crypt architecture (p < 0.05) in both the duodenum and colon. In the duodenum, 5-FU induced villus atrophy and crypt loss (p < 0.001), which were more pronounced in vitD–deficient mice. Treatment with 25(OH)D and/or VD1-6 significantly preserved crypt depth (p < 0.01) and enhanced epithelial regeneration (p < 0.01), though villus height remained significantly reduced across all 5-FU–treated groups (p > 0.05). In the colon, vitD deficiency worsened 5-FU-induced crypt damage, goblet cell cavitation, and reduced proliferation (p < 0.01). Treatment with 25(OH)D and/or VD1-6 preserved crypt structure (p < 0.01), maintained Ki-67+ cell counts (p < 0.01), and normalised tight junction gene expression (ZO-1, claudin-3; p < 0.05). Downregulation of TLR4, NF-κB, and VDR by 5-FU was significantly prevented by vitD therapies (p < 0.05–0.01), with combination therapy showing additive benefit.
VitD deficiency exacerbates chemotherapy-induced GM in both the duodenum and colon. While villus height was not restored, vitD–based treatments preserved crypt structure, epithelial proliferation, and molecular markers of barrier integrity. These findings support further evaluation of vitD pathway interventions to mitigate chemotherapy-associated intestinal toxicity.