Figure 8. Type I IFN cooperates with IL-22 in the induction of angiogenesis by promoting EC survival and proliferation.

(A) The indicated cathelicidin peptides, or saline, were injected intradermally 4 times over a 48-hour period as previously, followed by intraperitoneal injection with BrdU for 72 hours. EC numbers were defined as Cd31⁺Cd45^– cells from debris-excluded pregating, and they were determined per injection site. (B) Proliferation was determined by staining of Ki67 and BrdU from cells gated on ECs as in A, and defined as Ki67–single positive, Ki67-BrdU–double positive, and BrdU–single positive cells. (C) Mice intradermally injected with LL-37 or saline as in A and B were either pretreated with an anti-Ifnar blocking antibody or an IgG2a. EC numbers and proliferation were determined as in A and B. (D) HUVECs were plated (black bar at time of plating) and kept with or without growth factors (GFs) EGF, IGF1, FGF2, and VEGFA and with or without IL-22 or IL-17, in the presence or absence of IFN-α. Live cells were defined as CytoGreen⁺CytoXOrange^– cells and depicted as absolute counts. (E) HUVEC were stimulated for 8 hours in the indicated conditions, and gene expression was analyzed for the designated genes. Results are representative of 3 independent experiments. (F) Mice were treated as in C and pretreated with an anti–IL-22 blocking antibody or an IgG2a, and EC counts and proliferation were assessed as in C. (G) Mice were treated as in C, with either an IgG2a, anti-Ifnar, or anti–IL-22 antibody, and vessels were visualized by videocapillaroscopy and counted in and around the injection site. Scale bar: 250 μm. Multiplicity adjusted P values of 1-way ANOVA are depicted in A, B, D, and G. P values of 2-tailed Mann-Whitney nonparametric unpaired t test are depicted in C and F.