MSC-induced ROS production in matrigel. (A) Images show phase contrast (Ph) and DCF fluorescence (DCF) of MSC capillaries after indicated days of culture under nontreated (CT) and NAC-treated (NAC) conditions. NAC was added simultaneous with MSC seeding. Fluorescence was background corrected. Bar = 500 μm. (B) Plot shows time course of MSC ROS production in nontreated (CT) or NAC-treated (NAC) MSC capillaries. Mean plus or minus SD n = 3 (each group). *P < .05 versus NAC. (C) Images show phase contrast (Ph) and DCF fluorescence (DCF) of EC capillaries after indicated days of culture under untreated conditions (CT), or after addition of MSCs to day-old capillaries at 1:1 ratio (MSC). Bar = 500 μm. (D) Plots show time dependent effects of adding MSCs or CHO cells to day-old EC capillaries at 1:1 ratio. Mean plus or minus SD. *P < .05 relative to control (CT) at same time point. (E) Exponential regression of mean capillary density against mean EC fluorescence (R2 = 0.9887; P < .05). (F) Images show mitochondria-stained MSCs (red) juxtaposed with day-old EC-GFP capillaries (green) that were treated NAC or PEG-catalase (PC). Days of capillary culture are indicated. Bar = 500 μm. Group data are mean plus or minus SD. *P < .05 relative to untreated group.