MFN1 and pulmonary fibrosis: Collectively, the marked upregulation of purine metabolism in Mfn1/2−/− AEC2 cells and in bleomycin-treated Mfn1- or Mfn2-deficient AEC2 cells may play a direct role in promoting lung fibrosis, and the pathogenic role of AEC2-specific purine metabolism warrants future investigation.