Activation of the Wnt/Planar Cell Polarity Pathway Is Required for Pericyte Recruitment during Pulmonary Angiogenesis

Abstract

Pericytes are perivascular cells localized to capillaries that promote vessel maturation, and their absence can contribute to vessel loss. Whether impaired endothelial-pericyte interaction contributes to small vessel loss in pulmonary arterial hypertension (PAH) is unclear. Using 3G5-specific, immunoglobulin G-coated magnetic beads, we isolated pericytes from the lungs of healthy subjects and PAH patients, followed by lineage validation. PAH pericytes seeded with healthy pulmonary microvascular endothelial cells failed to associate with endothelial tubes, resulting in smaller vascular networks compared to those with healthy pericytes. After the demonstration of abnormal polarization toward endothelium via live-imaging and wound-healing studies, we screened PAH pericytes for abnormalities in the Wnt/planar cell polarity (PCP) pathway, which has been shown to regulate cell motility and polarity in the pulmonary vasculature. PAH pericytes had reduced expression of frizzled 7 (Fzd7) and cdc42, genes crucial for Wnt/PCP activation. With simultaneous knockdown of Fzd7 and cdc42 in healthy pericytes in vitro and in a murine model of angiogenesis, motility and polarization toward pulmonary microvascular endothelial cells were reduced, whereas with restoration of both genes in PAH pericytes, endothelial-pericyte association was improved, with larger vascular networks. These studies suggest that the motility and polarity of pericytes during pulmonary angiogenesis are regulated by Wnt/PCP activation, which can be targeted to prevent vessel loss in PAH.

Novel Signaling Pathways in Pulmonary Arterial Hypertension (2015 Grover Conference Series)

“…Knockdown of both Fzd7 and CDC42 in healthy lung pericytes reproduced the abnormal PAH pericyte phenotype both in vitro and in an in-vivo matrigel plug assay, whereas restoring their expression in PAH pericytes resulted in increased association with endothelial cells and larger tube networks. 87 Taken together, these studies suggest a model in which both Wnt/βC and Wnt/PCP participate in regeneration of pulmonary microvessels by promoting angiogenesis in response to injury (Fig. 4).…”

Vascular Smooth Muscle LRP6 Limits Arteriosclerotic Calcification in Diabetic LDLR −/− Mice by Restraining Noncanonical Wnt Signals

“…Similar responses occur with Fzd9 (Figure 3B, and data not shown), the Fzd member most closely related to Fzd10. ML141 – an inhibitor of cdc42/Rac1 signaling 38 in the noncanonical Wnt planar cell polarity pathway 39 – inhibited Fzd10 and Fzd9 activation of NFAT-LUC (Figure 3B). Conversely, constitutively active Cdc42(Q61L) activated NFAT-LUC, and was inhibited by LRP6 (Figure 3C).…”

Disruption of lineage specification in adult pulmonary mesenchymal progenitor cells promotes microvascular dysfunction

“…In WT SMCs, BMP signaling activates both β-catenin and noncanonical Wnt pathways, which regulate SMC proliferation and motility in response to stimuli (20). Primary pericytes derived from IPAH or WT lung explants demonstrate a decreased association with microvessels in vitro that is attributed to abnormal noncanonical Wnt signaling (93). In contrast, increased noncanonical Wnt signaling in endothelial cells increases their survival and decreases vascular pruning in vivo and in vitro (94).…”