CD34 marks angiogenic tip cells in human vascular endothelial cell cultures.

"Conflict of interest The authors declare no competing financial interests."

"We thank Berend Hooibrink for assisting with the FACS experiments; Maaike van Berkel for assisting with the HUVEC spheroid angiogenesis model; and Jan Stap for help with the live cell imaging. This work was partially funded by the Dutch Association for the Prevention of Visually Impairment and Blindness, the Blindenpenning Foundation, the Dr. F. P. Fisher foundation, the Dutch National Foundation for the Visually Impaired and Blind, the Dutch Oogfonds Foundation, the Dutch Macular Degeneration Fund, and the Dutch Retina Foundation, combined in the Uitzicht grant 2009-18. The helpful editorial suggestions of Drs. Kelly McNagny and Michael Hughes (The Biomedical Research Center, University of British Columbia, Vancouver, BC, Canada) with respect to the manuscript are gratefully acknowledged as well as the assistance in the preparation of the final version of the manuscript by Monique Arendse."