Abstract 14770: Long Non-Coding RNA NEAT1 Modulates Angiogenic and Proliferative Capacity of Endothelial Cells

Non-coding RNAs are increasingly recognized as regulators of various biological functions. Specifically, long non-coding RNAs (lncRNAs) are known to control epigenetic, transcriptional and post-transcriptional processes. NEAT1 is among the most highly expressed lncRNAs and is known to be an architectural lncRNA that is indispensable for the formation of specialized cellular compartments, so called nuclear paraspeckles. However, the role of NEAT1 and its isoforms NEAT1_1 and NEAT1_2 in endothelial cell (EC) function and angiogenesis is unknown.ResultsNEAT1 is well conserved in human ECs. The isoforms NEAT1_1 and NEAT1_2 exhibit different expression patterns as NEAT1_2 displays higher expression levels than NEAT1_1. Under hypoxic conditions, NEAT1_1 expression was found to be abolished, whereas NEAT1_2 levels remained unchanged. Moreover, NEAT1 expression was found to be induced in endothelial cells exposed to shear-stress. To investigate the role of NEAT1 and its isoforms in controlling EC activities we employed loss-of-function experiments. Efficient LNA-GapmeRs-mediated silencing of NEAT1 in HUVECs (reduction to 18%+/- 1.3%, p < 0.05) induced in vitro sprouting activity (to 157%+/- 11.8, p 0.04), but insufficient tube formation indicated by calculation of total tube segment length (reduction of 44.24%+/- 14.14, p 0.01) and total mesh area (reduction of 89.76%+/- 20.86, p 0.002). Accordingly, NEAT1 knockdown inhibited EC proliferation (reduction from 18.5 to 6.97% +/- 1.3 in S-phase, p < 0.05) and modulated the expression of cell cycle proteins. NEAT1 silencing reduced EC viability (by 20.3%+/- 5.72, p 0.01) and induced EC death (increase of 135%+/- 39.1, p 0.02). Specific effects of the short isoform NEAT1_1 were determined by using GapmeRs targeting exon-exon junction, which did not affect the long isoform NEAT1_2 expression. Specific silencing of NEAT1_1 isoform resulted in a reduction of EC viability (of 25.44%+/- 5.7, p 0.002) and EC proliferation (from 18.5% to 9.24% +/- 1.1 in S-phase, p < 0.05), whereas silencing of NEAT1_2 isoform had no effect on the aforementioned EC functions. In conclusion, the highly expressed and well-conserved lncRNA NEAT1 has a complex effect on endothelial cell angiogenic functions by inducing insufficient sprouting, while inhibiting appropriate tube formation and EC proliferation by blocking cell cycle progression. Isoform NEAT1_1 plays a different functional role than NEAT1_2 in ECs. The consequence of the effects on ve