We investigated whether the angiogenic capacity shown by PF exosomes in vitro may translate into improvement of angiogenesis and blood flow recovery in vivo. The therapeutic potential of PF exosomes was studied in a mouse model of ischemia, in which local stimulation of angiogenesis represents a possibility to improve tissue perfusion. As controls, we used PBS and plasma exosomes, which we had proved unable to induce in vitro angiogenesis (Figures S6B–S6G). Mice with surgically induced unilateral limb ischemia were injected with either PBS or exosomes (100 μg/mouse) directly into their ischemic adductor muscles. Compared with PBS, at 7 days from delivery, the PF-derived exosomes improved post-ischemic blood flow recovery (Figures 8A and 8B), reduced the incidence of ischemia-induced toe necrosis (Figure 8C), and improved capillary density in ischemic muscles (Figures 8D and 8E). The positive impact of PF exosomes on blood flow recovery was not sustained over time (data not shown). Plasma exosomes were not able to reproduce any of the above therapeutic benefits (Figures 8A–8E). Importantly, after transfer of PF exosomes into ischemic limb muscles, there was a trend toward increased let-7b-5p expression (p = 0.18; Figure 8F) and a significant decrease in Tgfbr1 expression (p < 0.05; Figure 8G), which could be explained by an amplified functional response at the target gene level of the PF exosome-mediated delivery of active let-7b-5p.Figure 8PF-Derived Exosomes Promote Reparative Angiogenesis and Blood Flow Recovery in a Mouse Limb Ischemia ModelUnilateral limb ischemia was surgically induced in CD1 mice. Next, mice were injected in their ischemic adductor muscle with 100 μg of exosomes from either the PF or plasma. A control group received PBS. (A) Representative color laser Doppler images of lower limb perfusion at baseline and at day 7 post-ischemia. (B) The blood flow recovery to the ischemic foot was calculated as percentage versus the contralateral foot (n = 20 mice/group). (C) Percentage of necrotic toes in animals treated with PBS, PF, or plasma-derived exosomes. **p < 0.01 versus PBS. (D) Representative immunofluorescent images of ischemic adductor muscle sections after staining with green fluorescent isolectin-B4. (E) Capillary densities in the ischemic adductors at 7 days post-ischemia induction (n = 8 per group). Average capillary density was determined from eight randomly selected high-power fields (magnification 20×). ##p < 0.01 versus PBS. (F and G) Let-7b-5p (F) and Tgfbr1 (G) expression in ischemic mouse adductors injected with PF exosomes or PBS (control); n = 5. *p ≤ 0.05 versus PBS. All values are mean + SEM.