Fig. 2

Reduced incorporation of endothelial progenitor cells (EPCs) into endothelial capillary network and cluster formation on Matrigel in children with systemic vasculitis. a Representative image of EPC cluster formation on Matrigel. The inset shows an example of a sprouting EPC. b and c Representative images of the incorporation of EPCs from a healthy child (b), and a child with active granulomatosis with polyangiitis (c) into an endothelial capillary network on Matrigel. d Comparison of the number of EPC clusters with active and inactive systemic vasculitis and child healthy controls. The number of EPC clusters was reduced for 15 children with active disease compared with healthy control children (p = 0.01); cells clusters in the inactive vasculitis group did not differ significantly from healthy controls. e EPC incorporation into HUVEC capillary networks on Matrigel in children with active and inactive systematic vasculitis and child healthy controls. Compared to five healthy control children, the number of EPC incorporated into HUVEC vascular networks on Matrigel was decreased for 15 children with active vasculitis (p = 0.003) and five children with inactive vasculitis (p = 0.04). The Kruskal-Wallis test was used to examine overall differences between the study groups followed by the Mann–Whitney U test. P values <0.05 were considered significant. HUVEC human umbilical vein endothelial cell