Figure 2.

Exogenous IL-15 therapy rescues wound healing in aged, sedentary mice. A, experimental design of intravenous pre-treatments and wound surgery with key experimental days denoted on a timeline. B, representative photographs of wound healing progress in young control (Young PBS), old control (Old PBS) and old IL-15 (Old rmIL-15)–treated mice on the indicated days post-wounding. Wound margins are delineated by the dotted white line. Scale bar = 5 mm. C, quantification of wound areas from B. D, final wound closure at time of sacrifice on day 9 expressed as a proportion of the original wound area. E, wound closure rate per day determined by average slope of best fit lines. F, projected time for full wound closure based on wound closure rate calculated in E. n = 4–8 mice per group for A–E data. G, quantification of Keratin 14-stained proliferative hub thickness in young PBS, old PBS, and old rmIL-15–treated mice. n = 3–5 mice per group. H, stitched panoramic immunofluorescence images of Keratin 14-stained stem cells and EdU labeling in day 9 post-wounded skin showing the wound bed (WB) and proliferative hub (PH) region of each side. White arrow (original wound edge) to and the yellow arrow (300 μm inwards) indicates the proliferative hub region. Scale bar = 100 μm. Data are mean ± S.E. *, significantly different (p < 0.05) relative to Young PBS mice. #, significantly different (p < 0.05) relative to Old PBS mice.