Objective: The ductus arteriosus (DA) is a fetal artery connecting the aorta and pulmonary arteries. Progressive matrix remodeling, that is, intimal thickening (IT), occurs in the subendothelial region of DA to bring anatomic DA closure. IT is comprised of multiple ECMs (extracellular matrices) and migrated smooth muscle cells (SMCs). Because glycoprotein fibulin-1 binds to multiple ECMs and regulates morphogenesis during development, we investigated the role of fibulin-1 in DA closure. Approach and Results: Fibulin-1–deficient ( Fbln1 −/− ) mice exhibited patent DA with hypoplastic IT. An unbiased transcriptome analysis revealed that EP4 (prostaglandin E receptor 4) stimulation markedly increased fibulin-1 in DA-SMCs via phospholipase C-NFκB (nuclear factor κB) signaling pathways. Fluorescence-activated cell sorting (FACS) analysis demonstrated that fibulin-1 binding protein versican was derived from DA-endothelial cells (ECs). We examined the effect of fibulin-1 on directional migration toward ECs in association with versican by using cocultured DA-SMCs and ECs. EP4 stimulation promoted directional DA-SMC migration toward ECs, which was attenuated by either silencing fibulin-1 or versican. Immunofluorescence demonstrated that fibulin-1 and versican V0/V1 were coexpressed at the IT of wild-type DA, whereas 30% of versican-deleted mice lacking a hyaluronan binding site displayed patent DA. Fibulin-1 expression was attenuated in the EP4-deficient mouse ( Ptger4 −/− ) DA, which exhibits patent DA with hypoplastic IT, and fibulin-1 protein administration restored IT formation. In human DA, fibulin-1 and versican were abundantly expressed in SMCs and ECs, respectively. Conclusions: Fibulin-1 contributes to DA closure by forming an environment favoring directional SMC migration toward the subendothelial region, at least, in part, in combination with EC-derived versican and its binding partner hyaluronan.

Objective: COX inhibitors targeting smooth muscle cell (SMC) contraction represent the only pharmacological treatment for patent ductus arteriosus (PDA), but >30% patients are resistant to the current therapies. Intimal thickening (IT), occurs in the subendothelial region of DA to bring anatomical DA closure. We investigated the role of fibulin-1 in DA anatomical closure to seek a new IT-inducing pharmacological therapy. Approaches and results: Microarray analysis demonstrated that fibulin-1 was the most up-regulated gene by stimulation of EP4 in DA-SMCs. EP4-induced fibulin-1 expression was mediated through the phospholipase Cprotein kinase C-noncanonical nuclear factor-kappa B pathway. We performed FACS analysis and found that fibulin -1 binding protein versican was derived from DA-endothelial cells. Immunofluorescence demonstrated that fibulin-1 and versican V0/V1 were co-expressed at the IT of wild-type DA. In the DA of EP4-deficient mouse (Ptger4 -/-), fibulin-1was largely attenuated and showed PDA. All of fibulin-1-deficient mice exhibited PDA with hypoplastic IT, and fibulin-1 protein administration restored IT formation of Ptger4 -/-. Furthermore, 30% of versican deleted mice lacking a hyaluronan binding site displayed PDA. Conclusions: Fibulin-1 contributes to DA closure by forming an environment favoring directional SMC migration toward the subendothelial region in combination with versican and hyaluronan. Targeting fibulin-1 upregulation may provide the basis for therapeutic strategies for inducing anatomical DA closure.