COL4A1 and idiopathic pulmonary fibrosis: Furthermore, consistent with our findings in lung fibroblasts, the expression of profibrotic genes, particularly collagen-associated genes, such as COL1A1, COL3A1, COL4A1, COL5A1, and COL5A3, was strongly associated with WISP1 in IPF-diseased fibroblasts but not in dermal fibroblasts, suggesting tissue-specific differences and heterogeneity in primary human fibroblasts (Table S5).