The results from the CKD-FCF experiment are contrary to previous studies utilising rat and human renal fibroblast cell lines, where extracellular phosphate concentrations in the range of 2.5–5 mM have been reported to increase collagen, fibronectin and α-SMA gene expression (Chen et al., 2012, Tan et al., 2016). Here, ACTA1 is linked to chronic kidney disease.