Pulmonary Artery Endothelial Cell Phenotypic Alterations in a Large Animal Model of Pulmonary Arteriovenous Malformations After the Glenn Shunt

Abstract

Background: Longevity of the superior cavopulmonary connection (SCPC) is limited by the development of pulmonary arteriovenous malformations (PAVM). The goal of this study was to determine whether phenotypic changes in pulmonary artery endothelial cells (PAEC) that favor angiogenesis occur with PAVM formation. Methods: A superior vena cava to right pulmonary artery connection was constructed in 5 pigs. Pulmonary arteries were harvested at 6-8 weeks following surgery to establish cultures of PAEC and smooth muscle cells, to determine cell proliferation, gene expression, and tubule formation. Abundance of proteins related to angiogenesis was measured in lung tissue. Results: Contrast echocardiography revealed right-to-left shunting, consistent with PAVM formation. While the proliferation of smooth muscle cells from the right pulmonary artery (RPA) (shunted side) and left pulmonary artery (LPA) (non- shunted side) were similar, right PAEC proliferation was significantly higher. Expression profiles of genes encoding cellular signaling proteins were higher in PAECs from the RPA vs. LPA. Protein abundance of angiopoietin-1, and Tie-2 (angiopoietin receptor) were increased in the right lung (both p<0.05). Tubule formation was increased in endothelial cells from the RPA compared to the LPA (404±16 vs. 199±71 tubules/mm2, respectively p<0.05). Conclusions: These findings demonstrate that PAVMs developed in a clinically relevant animal model of SCPC. This study found that PAVM development occurred concomitantly with differential changes in PAEC proliferative ability and phenotype. Moreover, there was a significant increase in the angiopoietin/Tie-2 complex in the right lung, which may provide novel therapeutic targets to attenuate PAVM formation following a SCPC.

Hepatic Vein Blood Increases Lung Microvascular Angiogenesis and Endothelial Cell Survival—Toward an Understanding of Univentricular Circulation

“…One of the initial studies investigating hepatic factor and CHDassociated PAVMs reported that hepatocyte-conditioned media inhibited pulmonary artery EC proliferation. 16 This finding is consistent with the data reported by Kavarana et al 14 Kavarana et al reported that exclusive SVC blood flow in their pig model of SCPC physiology increased pulmonary artery EC proliferation compared to control ECs. 14 These results are in contrast to our finding that HV serum increases HPMEC proliferation compared to SVC serum.…”

Pulmonary arteriovenous malformations after the superior cavopulmonary shunt: mechanisms and clinical implications

“…[74] This study demonstrated that the pulmonary artery endothelial cells (PAEC) converted to a “proangiogenic” phenotype with PAVM formation (Figure 4B). These phenotypic differences in the PAECs from lungs with PAVMs included increased proliferation, tubule formation, and gene expression of proangiogenic factors such as angiopoietin-1 and TIE2 pathway.…”

“…These phenotypic differences in the PAECs from lungs with PAVMs included increased proliferation, tubule formation, and gene expression of proangiogenic factors such as angiopoietin-1 and TIE2 pathway. [74] Another group developed a porcine model of a bidirectional SCPC in which the RPA was ligated or banded. [75] They demonstrated that residual antegrade pulsatile flow following a SCPC prevented PAVM formation.…”

“…However, there were no differences in gene expression of these markers demonstrated in a porcine model of PAVMs. [74] While hypoxia may indeed play a role in PAVM development in true single ventricle physiology clinically, this may not be demonstrable in the currently established SCPC animal models, which do not have significant hypoxemia in the post-SCPC setting. A potential explanation for these findings is that all animal models studied to date use SCPC within the context of two-ventricle physiology where normal cellular and tissue oxygenation may be maintained,.…”

“…[64] The promotion of angiogenesis through the well established angiopoietin-1/TIE2 pathway and its association with PAVM development following SCPC creation provides another mechanism through which medical therapies for PAVMs may be investigated. [74]…”