IL1B and fibrosis: Compared with MSCs under normoxia, hypoxia-preconditioned BM-MSCs demonstrated increased expression of cytoprotective and regenerative factors, leading to greater reduction of interleukin (IL)-1β and IL-6 levels, airway constriction, lung edema, and fibrosis in experimental bleomycin-induced lung fibrosis (Lan et al., 2015).