Despite a reduction in cyst burden, pcy/pcy; Spp1−/− kidneys exhibited increased expression of genes involved in kidney fibrosis, including α‐smooth muscle actin (Acta2), collagen 1 α1‐subunit (Col1α1), and transforming growth factor‐β (TGFβ) (Figure 3a–c). This evidence concerns the gene COL1A1 and cyst.