Chronic activation of the prostaglandin receptor EP4 promotes hyaluronan-mediated neointimal formation in the ductus arteriosus

Abstract

PGE, a potent vasodilator, plays a primary role in maintaining the patency of the ductus arteriosus (DA). Genetic disruption of the PGE-specific receptor EP4, however, paradoxically results in fatal patent DA (PDA) in mice. Here we demonstrate that EP4-mediated signals promote DA closure by hyaluronic acid-mediated (HA-mediated) intimal cushion formation (ICF). Chronic EP4 stimulation by ONO-AE1-329, a selective EP4 agonist, significantly enhanced migration and HA production in rat DA smooth muscle cells. When HA production was inhibited, EP4-mediated migration was negated. Activation of EP4, adenylyl cyclase, and PKA all increased HA production and the level of HA synthase 2 (HAS2) transcripts. In immature rat DA explants, ICF was promoted by EP4/PKA stimuli. Furthermore, adenovirus-mediated Has2 gene transfer was sufficient to induce ICF in EP4-disrupted DA explants in which the intimal cushion had not formed. Accordingly, signals through EP4 have 2 essential roles in DA development, namely, vascular dilation and ICF. The latter would lead to luminal narrowing, helping adhesive occlusion and permanent closure of the vascular lumen. Our results imply that HA induction serves as an alternative therapeutic strategy for the treatment of PDA to the current one, i.e., inhibition of PGE signaling by cyclooxygenase inhibitors, which might delay PGE-mediated ICF in immature infants.

BMP9 and BMP10 are necessary for proper closure of the ductus arteriosus

“…This process is initiated prenatally or at birth, depending on the size of the animal, with the development of intimal cushions, and is completed postnatally by humoral and mechanical stimuli (3,4). PGE 2 elicits the deposition of HA within the intimal tissue and stimulates the inward migration of VSMCs (10). The present data further support that wall thickening, in mice, starts within the first hour after birth (1).…”

“…3C). Hyaluronan (HA) production under the control of prostaglandins has been recently described to play a key role in DA closure (10). We therefore tested whether hyaluronan synthases (HAS) and cyclooxygenases (COX1 and -2), which were described as being the key enzymes for prostaglandin production in the DA (11), could be targets of BMP9 or BMP10 in endothelial cells [human pulmonary arterial endothelial cells (HPAECs)].…”

Regulation of vascular tone and remodeling of the ductus arteriosus

“…Intimal thickening, a characteristic developmental remodeling process in the DA, is required for postnatal DA closure (Rabinovitch, 1996;Mason et al, 1999;Yokoyama et al, 2006b). Intimal thickening starts with lifting of the endothelial cells (Gittenberger-de Groot et al, 1985) and accumulations of hyaluronan in the subendothelial region, creating a space that is suitable for migration of smooth muscle cells through the fragmented elastic lamina into the subentothelial region (De Reeder et al, 1988).…”

“…Closure of the human DA is believed to occur in two phases: (1) functional closure of the lumen within the first hours after birth by smooth muscle constriction, and (2) anatomic occlusion of the lumen over the next several days due to extensive neointimal thickening and loss of smooth muscle cells from the inner muscle media (Smith, 1998;Clyman, 2006;Yokoyama et al, 2006b). Although its process is similar in mammalian DA, the time course of two phases is variable among species.…”

“…Anatomical closure of the DA is associated with the formation of intimal thickening, which are characterized by (a) an area of subendothelial deposition of extracellular matrix, (b) the disassembly of the internal elastic lamina and loss of elastic fiber in the medial layer, and (c) migration into the subendothelial space of undifferentiated medial smooth muscle cells (Smith, 1998). Some of these changes begin about halfway through gestation and some occur after functional closure of the DA in the neonate (Slomp et al, 1997;Yokoyama et al, 2006b). This cascade of events is thought to orchestrate the subsequent luminal DA reorganization, leading finally to complete obliteration of the DA.…”