ACTA1 and pulmonary fibrosis: In a previous in vivo study, 1,25(OH)2D3 was administered to mice with bleomycin-induced pulmonary fibrosis, and immunostaining of lung tissues showed a decrease of αSMA-positive cells probably because suppression of osteopontin expression by 1,25(OH)2D3 reduced the accumulation of activated fibroblasts.(12) The in vitro experiment performed in this study showed little suppression of inflammatory markers by 1,25(OH)2D3 administration, probably due to the influence of the time lag from addition of 1,25(OH)2D3 to addition of bleomycin (overnight) and the short half-life of 1,25(OH)2D3.