MMP1 and autosomal dominant polycystic kidney disease: qRT-PCR analyses of the vascular cells from all seven ADPKD-iPSCs were performed to examine the reproducibility of the microarray data and showed that only the MMP1 expression was significantly upregulated in the iPSC-derived endothelia from the four ADPKD patients with ICAs compared with the three patients without ICAs (P = 0.007; Figs 5a and S10).