Human WARS2 adenoviral particles

Coronary flow (CF) measured ex vivo is primarily determined by capillary density, which reflects angiogenesis in the heart in vivo. Here, researchers exploit this relationship and show that CF in rats is influenced by a locus on rat chromosome 2 that is also associated with cardiac capillary density. By integrating genomic datasets, the mitochondrial tryptophanyl-tRNA synthetase (Wars2), encoding the L53F protein variant within the ATP-binding motif, was prioritized as a candidate for this locus. WARS2(L53F) has low enzymatic activity, and inhibition of WARS2 in endothelial cells reduces angiogenesis. In zebrafish, inhibition of wars2 results in defects in trunk vessels, disrupted endocardial-myocardial contacts, and impaired cardiac function. Inhibition of Wars2 in rats results in defects in cardiac angiogenesis and reduced cardiac capillary density. These data suggest that Wars2 has pro-angiogenic functions both within and outside the heart, which may have translational relevance given WARS2's association with common human diseases.

After 48 hours of siRNA transfection or 48 hours of WARS2 adenovirus and GFP adenovirus transduction, HUVECs were harvested and seeded in 96-well plates pre-coated with 50 μl of Matrigel at a density of 8,000 cells per well. After 8 hours of culture in complete EGM-2 medium, images of each well (center position) were acquired under a ×5 objective. Confocal and super-resolution microscopy showed that WARS2 silencing led to a significant reduction in EC spreading, abnormal membrane ruffles, and EC actin fibers, which are essential for EC motility, division, and polarity (Figure 1d). The researchers tested the effects of WARS2 in an established in vitro angiogenesis model: WARS2 loss of function resulted in impaired angiogenesis (Figure 1e-g), while WARS2 gain of function enhanced angiogenesis (Figure 1h-j).

Figure 1. WARS2 regulates endothelial cell morphology and angiogenic potential. (Wang M, et al., 2016)