F2RL1 and inflammatory bowel disease: Mucosal mast cells produce tryptase, which contributes to the progression of IBD caused by intestinal fibrosis by activating the major fibroblast PAR-2/Akt/mTOR (protease-activated receptor-2 (PAR-2)/protein kinase B (PKB, Akt)/mammalian target of rapamycin (mTOR)) pathway [60].