CXCL12 and Patent ductus arteriosus: ERW1041E had no effect on the recovery of a preformed ∼52-kDa CXCL12–KRT19 heterodimer from PDA cells (SI Appendix, Fig. S5F), in contrast to its capacity to inhibit the formation of the CXCL12–KRT19 heterodimer in vitro (Fig. 2D).