干酪乳杆菌通过调控肠干细胞再生对辐射肠损伤的改善作用及机制研究

Radiation-induced intestinal injury is a common complication in patients receiving abdominal and pelvic radiotherapy. Radiation can cause a dramatic decrease in the number and function of intestinal epithelial cells and intestinal stem cells (ISCs) ,damage to the intestinal mucosa with a result of severe clinical symptoms. Probiotics supplementation can repair the damaged intestinal mucosa caused by irradiation and effectively improve intestinal adverse reactions in radiotherapy patients, but the effect of lactobacillus casei on irradiation-induced intestinal injury have rarely been reported. Our previous work found that lactobacillus casei could increase the number of Lgr5+ intestinal stem cells in the crypt of rats with acute radiation injury, maintain the integrity of intestinal structure, and protect the function of intestinal mucosal barrier. It is important to maintain intestinal epithelial homeostasis for ISCs regeneration. We hypothesized that lactobacillus casei could improve and protect the irradiation-induced intestinal injury by regulating ISCs regeneration. This project intends to establish a rat model of acute radiation-induced intestinal injury, with control group, model group and the low, medium and high dose lactobacillus casei intervention groups. The effect and dose-response relationship of lactobacillus casei on irradiation-induced intestinal injury will be explored. The effects of lactobacillus casei on intestinal flora, intestinal immunity and IL-22 secretion will be studied, thus illustrating the mechanism that lactobacillus casei promote ISCs regeneration. This study is expected to provide a theoretical basis for nutritional prevention and treatment of patients with radiotherapy.

辐射肠损伤是腹盆腔放疗的常见并发症，辐射会引起肠上皮细胞及肠干细胞（ISCs）数量急剧减少和功能减退，损伤肠黏膜，导致严重临床症状。益生菌补充能够修复辐射损伤肠黏膜，有效改善放疗患者的肠道不良反应，但干酪乳杆菌对辐射诱导的肠损伤作用效果及机制鲜有报道。申请人前期研究发现干酪乳杆菌干预能够增加急性辐射损伤大鼠小肠肠腺隐窝内Lgr5+肠干细胞，维持小肠结构的完整性，保护肠黏膜屏障功能。ISCs再生对维持肠上皮稳态非常重要，我们假设干酪乳杆菌可通过调控ISCs再生，改善和保护辐射导致的肠损伤。本项目拟建立急性辐射肠损伤大鼠模型，设立正常对照组、模型组和低、中、高剂量干酪乳杆菌干预组，探索其对急性辐射肠损伤黏膜的改善效果及量效反应关系；并研究干酪乳杆菌对肠道菌群、肠道免疫、IL-22分泌的影响，阐明其在ISCs再生中的作用机制。本项目可为改善放射肿瘤患者肠道不良反应、开展营养防治提供理论依据。

辐射肠损伤是腹盆腔放疗的常见并发症，辐射会引起肠上皮细胞及肠干细胞（ISCs）数量急剧减少和功能减退，损伤肠黏膜，导致严重临床症状。益生菌补充能够修复辐射损伤肠黏膜，有效改善放疗患者的肠道不良反应，但不同益生菌补充结果存在争议，相关机制尚不明确。本项目通过单剂量的9Gy X射线全腹照射建立急性辐射肠损伤大鼠模型，设立正常对照组、模型组和提前持续7天给予低、中、高剂量干酪乳杆菌灌胃L. casei ATCC334干预组，探索其对急性辐射肠损伤黏膜的改善效果及机制。结果显示干酪乳杆菌补充能有效改善辐射诱导的体重减轻，与辐射模型组相比中、高剂量干预组IL-6水平较低，IL-10和IL-22水平较高。干酪乳杆菌干预能促进肠道干细胞（ISCs）的增殖，增加肠黏膜上皮紧密连接蛋白的表达，降低肠道渗透性，保护肠道屏障的完整性。此外，16S rRNA测序显示，中剂量和高剂量的L. casei ATCC334重塑肠道微生物组的多样性、菌群结构，抑制埃希氏菌/志贺氏菌的生长，有利于阿克曼菌的增殖。粪便代谢组学结果显示L. casei ATCC334可能上调α-亚麻酸代谢通路，下调亚精胺和精胺的生物合成途径，从而降低炎性水平，促进肠干细胞的再生，预防/减轻肠黏膜屏障损伤。