Loss of Endothelium-Derived Wnt5a Is Associated With Reduced Pericyte Recruitment and Small Vessel Loss in Pulmonary Arterial Hypertension

Abstract

Background: Pulmonary arterial hypertension (PAH) is a life-threatening disorder of the pulmonary circulation associated with loss and impaired regeneration of microvessels. Reduced pericyte coverage of pulmonary microvessels is a pathological feature of PAH and is caused partly by the inability of pericytes to respond to signaling cues from neighboring pulmonary microvascular endothelial cells (PMVECs). We have shown that activation of the Wnt/planar cell polarity pathway is required for pericyte recruitment, but whether production and release of specific Wnt ligands by PMVECs are responsible for Wnt/planar cell polarity activation in pericytes is unknown. Methods: Isolation of pericytes and PMVECs from healthy donor and PAH lungs was carried out with 3G5 or CD31 antibody–conjugated magnetic beads. Wnt expression profile of PMVECs was documented via quantitative polymerase chain reaction with a Wnt primer library. Exosome purification from PMVEC media was carried out with the ExoTIC device. Hemodynamic profile, right ventricular function, and pulmonary vascular morphometry were obtained in a conditional endothelium-specific Wnt5a knockout ( Wnt5a ECKO ) mouse model under normoxia, chronic hypoxia, and hypoxia recovery. Results: Quantification of Wnt ligand expression in healthy PMVECs cocultured with pericytes demonstrated a 35-fold increase in Wnt5a, a known Wnt/planar cell polarity ligand. This Wnt5a spike was not seen in PAH PMVECs, which correlated with an inability to recruit pericytes in Matrigel coculture assays. Exosomes purified from media demonstrated an increase in Wnt5a content when healthy PMVECs were cocultured with pericytes, a finding that was not observed in exosomes of PAH PMVECs. Furthermore, the addition of either recombinant Wnt5a or purified healthy PMVEC exosomes increased pericyte recruitment to PAH PMVECs in coculture studies. Although no differences were noted in normoxia and chronic hypoxia, Wnt5a ECKO mice demonstrated persistent pulmonary hypertension and right ventricular failure 4 weeks after recovery from chronic hypoxia, which correlated with significant reduction, muscularization, and decreased pericyte coverage of microvessels. Conclusions: We identify Wnt5a as a key mediator for the establishment of pulmonary endothelium-pericyte interactions, and its loss could contribute to PAH by reducing the viability of newly formed vessels. We speculate that therapies that mimic or restore Wnt5a production could help prevent loss of small vessels in PAH.

Noncanonical Wnt planar cell polarity signaling in lung development and disease

“…The expression of VANGL2 and its binding partner SCRIB are also down-regulated in emphysematous human lungs [13]. VANGL2 disruption leads to impaired directional migration and delayed wound repair via disrupted actin dynamics in a human alveolar epithelial cell line, a defect shared with PCP mutant airway [88] epithelial cells [12]. WNT5A was proposed as a noncanonical ligand upstream of PCP as exogenous WNT5A greatly accelerates wound closure in the same assay.…”

“…Wnt5a was also shown to regulate VEGF expression [47], a critical factor in vascular development. Wnt5a is also expressed and secreted in extracellular vesicles by endothelial cells [88]. Exosomal Wnt5a is critical for the recruitment, motility and polarity of pericytes, which interact with endothelial cells to promote pulmonary angiogenesis via a noncanonical program downstream of Fzd7 [88,89].…”

“…WNT5A, an important upstream regulator of the endothelial-pericyte interaction during angiogenesis is strongly reduced in human IPAH tissues [88]. Wnt5a mutant mice have pulmonary hypertension with fewer pulmonary microvessels with decreased muscularization and pericyte coverage [88]. Thus, Wnt5a driven PCP signaling is thought to contribute to IPAH by reducing the viability of newly formed vessels.…”

The protective effects of MSC-EXO against pulmonary arterial hypertension through inhibition of Wnt/BMP signaling pathway

“…Pulmonary arterial hypertension (PAH) is a life-threatening lung disease is associated with microvascular lost or regenerate damaged [1]. Pulmonary vascular endothelial cells and smooth muscle cells dysfunction caused by pulmonary vascular remodeling, and even the right ventricle hypertrophy and failure is important pathological features of PAH [2,3].…”

“…Wnt5a is one of a member of the Wingless (Wnt), activates non-canonical or canonical Wnt signaling pathways through specific coupling of different receptor. Down-regulation of Wnt5a could promote hypoxiainduced pulmonary vascular smooth muscle cells (PASMC) proliferation [7], loss of Wnt5a could lead to PH via reducing the formation of new vessels [1]. Thus, the production of Wnt5a is likely to become a new way to prevent the small vessel loss in PH.…”