By contrast, expression of the major collagen fibrillogenesis gene COL1A1 did not significantly correlate with their expression (Figure 1—figure supplement 1e), suggesting that, in lung fibrosis, distinct pathways might promote pyridinoline cross-linking to dysregulate collagen fibril nano-structure independently of pathways regulating major fibrillar collagen synthesis. Here, COL1A1 is linked to pulmonary fibrosis.