Department of General Surgery, Shanghai Tenth People's Hospital of Tongji University, Tongji University, Shanghai, China.
Department of General Surgery, Shanghai Clinical Medical College, Anhui Medical University, Anhui, China.
Inflamm Bowel Dis. 2021 Jan 19;27(2):242-255. doi: 10.1093/ibd/izaa125.
Intestinal fibrosis is the final pathological outcome of chronic intestinal inflammation without specific therapeutic drugs, which leads to ileus and surgical intervention. Intestinal fibrosis is characterized by excessive deposition of extracellular matrix (ECM). The role of mast cells (MCs), which are members of the sentinel immune cell population, is unknown in intestinal fibrosis.
In this study, we analyzed changes in MCs, tryptase proteins, and ECM components in human fibrotic and control patient intestines. We constructed dextran sodium sulfate-induced intestinal fibrosis models using wild-type mice, MC-reconstituted mice, and MC-deficient mice to explore the role of MCs and tryptase in intestinal fibrosis. The roles and mechanisms of MCs and tryptase on fibroblasts were evaluated using human MCs (HMC-1 and LAD-2), commercial tryptase proteins, human colon fibroblasts (CCD-18Co fibroblasts), the tryptase inhibitor APC366, and the protease-activated receptor-2 (PAR-2) antagonist ENMD-1068.
Regardless of whether the colon was a human colon or a mouse colon, the fibrotic intestinal tissue had increased MC infiltration and a higher expression of ECM proteins or genes than that of the control group. The dextran sodium sulfate-induced intestinal fibrosis in MC-deficient mice was alleviated compared with that in wild-type mice. After MC reconstruction in MC-deficient mice, the alleviating effect disappeared. Tryptase, as a content stored in MC granules, was released into fibrotic intestinal tissues in the form of degranulation, resulting in an increased expression of tryptase. Compared with the control group, the tryptase inhibition group (the APC366 group) had reduced intestinal fibrosis. The CCD-18Co fibroblasts, when cocultured with MCs or treated with tryptase proteins, were activated to differentiate into myofibroblasts and secrete more ECM proteins (such as collagen and fibronectin). The underlying mechanism of fibroblast activation by tryptase was the activation of the PAR-2/Akt/mTOR pathway.
We found that MC tryptase promotes inflammatory bowel disease-induced intestinal fibrosis. The underlying mechanism is that tryptase promotes the differentiation of fibroblasts into fibrotic-phenotype myofibroblasts by activating the PAR-2/Akt/ mTOR pathway of fibroblasts.
肠道纤维化是慢性肠道炎症的最终病理结果，目前尚无特异性治疗药物，可导致肠梗阻和手术干预。肠道纤维化的特征是细胞外基质（ECM）过度沉积。肠道纤维化中肥大细胞（MCs）的作用尚不清楚，MCs 是哨兵免疫细胞群的成员之一。
本研究分析了人类纤维化和对照患者肠道中 MCs、类胰蛋白酶蛋白和 ECM 成分的变化。我们构建了葡聚糖硫酸钠诱导的野生型小鼠、MC 重建小鼠和 MC 缺陷小鼠的肠道纤维化模型，以探讨 MCs 和类胰蛋白酶在肠道纤维化中的作用。使用人 MCs（HMC-1 和 LAD-2）、商业类胰蛋白酶蛋白、人结肠成纤维细胞（CCD-18Co 成纤维细胞）、类胰蛋白酶抑制剂 APC366 和蛋白酶激活受体-2（PAR-2）拮抗剂 ENMD-1068 评估 MCs 和类胰蛋白酶对成纤维细胞的作用和机制。
无论结肠是人类结肠还是小鼠结肠，纤维化肠道组织中 MC 浸润增加，ECM 蛋白或基因的表达高于对照组。与野生型小鼠相比，MC 缺陷型小鼠的葡聚糖硫酸钠诱导的肠道纤维化减轻。在 MC 缺陷型小鼠中重建 MC 后，缓解作用消失。类胰蛋白酶作为 MC 颗粒中储存的内容物，以脱颗粒的形式释放到纤维化的肠道组织中，导致类胰蛋白酶表达增加。与对照组相比，类胰蛋白酶抑制组（APC366 组）的肠道纤维化减少。当与 MC 共培养或用类胰蛋白酶蛋白处理时，CCD-18Co 成纤维细胞被激活分化为肌成纤维细胞并分泌更多的 ECM 蛋白（如胶原和纤维连接蛋白）。类胰蛋白酶激活成纤维细胞的潜在机制是激活成纤维细胞的 PAR-2/Akt/mTOR 途径。
我们发现 MC 类胰蛋白酶促进炎症性肠病诱导的肠道纤维化。其潜在机制是类胰蛋白酶通过激活成纤维细胞的 PAR-2/Akt/mTOR 途径促进成纤维细胞分化为纤维化表型肌成纤维细胞。
