Alternative splicing of vasohibin-1 generates an inhibitor of endothelial cell proliferation, migration, and capillary tube formation

Objective - In this study, the alternative splicing product of vasohibin 1 (VASH1B) was analyzed in direct comparison to the major isoform (VASH1A) for antiangiogenic effects on endothelial colony forming cells (ECFCs) from peripheral blood and on human umbilical vein endothelial cells (HUVECs). Methods and Results - Expression studies in primary human endothelial cells revealed that both vasohibin proteins, hVASH1A and hVASH1B, localized in the nucleus and cytoplasm. Adenoviruses carrying the cDNA for VASH1A/B and purified recombinant proteins were used to study the function of both molecules in ECFCs and HUVECs. Recombinant VASH1A protein did not inhibit cell proliferation, tube formation, or vessel growth in vivo in the chick chorioallantoic membrane ( CAM) assay, but promoted endothelial cell migration in vitro. The VASH1B protein had an inhibitory effect on cell proliferation, migration, tube formation, and inhibited blood vessel formation in the CAM assay. Adenoviral overexpression of VASH1B, but not of VASH1A, resulted in inhibition of endothelial cell growth, migration, and capillary formation. Interestingly, overexpression of VASH1A and B induced apoptosis in proliferating human fibroblasts, but did not affect cell growth of keratinocytes. Conclusion - Our data point out that alternative splicing of the VASH1 pre-mRNA transcript generates a potent antiangiogenic protein.