MTHFD2 and pulmonary fibrosis: To gain further insights into the involvement of mitochondrial folate pathway in silicosis, mice were intratracheally instilled with silica suspension for four weeks to induce pulmonary fibrosis, and the expression levels of Slc25a32 and Mthfd2 in fibrotic lung tissue were indeed elevated comparing to the control (Fig. 1J, K).