S1PR3 and idiopathic pulmonary fibrosis: TGF-β, a key profibrogenic cytokine that is upregulated in the lungs of patients with IPF as well as bleomycin- and asbestos-challenged murine fibrotic lungs [1,3,7,41], can promote lung fibroblast SPHK1 expression and S1P levels as well as trans-differentiation of myoblasts to myofibroblasts via the upregulation of the SPHK1/S1P3 axis [3,15,39,40,42,43,44,45].