By contrast, when BMDMs and PDA cells were co-cultured in a transwell system separated by an 8-μm pore membrane (contact co-culture), allowing migration of PDA cells toward macrophages, methylation of both Nqo-1 and Aldh1a3 was observed after 1 day of co-culture (Fig. 2a, b). This evidence concerns the gene ALDH1A3 and Patent ductus arteriosus.