Impaired H19 lncRNA expression contributes to the compromised developmental angiogenesis in EVL-deficient mice

Abstract

Endothelial tip cells are essential for VEGF-induced angiogenesis, but underlying mechanisms are elusive. Endothelial-specific deletion of EVL, a member of the mammalian Ena/VASP protein family, reduced the expression of the tip cell marker protein endothelial cell specific molecule-1 (Esm1) and compromised the radial sprouting of the vascular plexus in the postnatal mouse retina. The latter effects could at least partly be attributed to reduced VEGF receptor 2 (VEGFR2) internalization and signaling but the underlying mechanisms(s) are not fully understood. In the present study, we revealed that the expression of the long non-coding RNA H19 was significantly reduced in endothelial cells from postnatal EVL-/- mice and in siRNA-transfected human endothelial cells under hypoxic conditions. H19 was recently shown to promote VEGF expression and bioavailability via Esm1 and hypoxia inducible factor 1α (HIF-1α). Similar to EVL-/- mice, the radial outgrowth of the vascular plexus was significantly delayed in the postnatal retina of H19-/- mice. In summary, our data suggests that loss of EVL not only impairs VEGFR2 internalization and downstream signaling, but also impairs VEGF expression and bioavailability in the hypoxic retina via downregulation of lncRNA H19.

Cardiovascular Functions of Ena/VASP Proteins: Past, Present and Beyond

“…In addition to altered internalization of growth factor receptors, the Ena/VASP proteins may alter angiogenesis by other mechanisms. For example, a recent study reported that the expression of the long non-coding RNA H19 was significantly reduced in retinal endothelial cells from postnatal EVL −/− mice and in siRNA-transfected human endothelial cells under hypoxic conditions [220] (Figure 10B). Similar to EVL −/− mice, H19-deficient animals [224] displayed a significantly impaired radial sprouting of the vascular plexus on postnatal day 5 (Figure 10C,D), indicating that down-regulation of the lncRNA in EVL-deficient mice may contribute to the impaired angiogenic sprouting [220].…”

“…For example, a recent study reported that the expression of the long non-coding RNA H19 was significantly reduced in retinal endothelial cells from postnatal EVL −/− mice and in siRNA-transfected human endothelial cells under hypoxic conditions [ 220 ] ( Figure 10 B). Similar to EVL −/− mice, H19-deficient animals [ 224 ] displayed a significantly impaired radial sprouting of the vascular plexus on postnatal day 5 ( Figure 10 C,D), indicating that down-regulation of the lncRNA in EVL-deficient mice may contribute to the impaired angiogenic sprouting [ 220 ]. Consistent with this finding, knockdown of H19 in glioma-associated endothelial cells suppressed glioma induced angiogenesis [ 225 ].…”

“…( D ) Statistical analysis of the radial outgrowth of wild-type and global H19-deficient animals normalized to the retinal radius as well as littermate controls; radial outgrowth of EVL-deficient mice is shown for comparison; *** p < 0.001. Figure modified from [ 220 ].…”