Research Paper Volume 16, Issue 5 pp 4609—4630

Figure 6. MPC-Exo and MPC-Exo¹⁴⁰⁻ activate muscle satellite cells to promote repair of gastrocnemius muscle injury. (A–C) and (D) show the mRNA expression changes (fold change) of miR-140-5p and muscle regeneration-related factors Pax7, MyoD, and myogenin after two interventions with MPC-EVs on the injured muscle. (E) presents changes in protein expression. (F) displays the impact of MPC-EVs on muscle satellite cells postinjury: activated SCs are characterized by the coexpression of Pax7⁺/MyoD⁺ (Figure 4F). The marked locations in the figure show that in the injury group, SCs enter an activated state stimulated by stress signals and move from the cell pool to between damaged muscle fibers. In the injected myogenic extracellular vesicle group, there was a significant increase in activated SCs around the muscle fibers. In the injected MPC-Exo¹⁴⁰⁺ group, miR-140-5p mimics antagonize the activation effect of MPC-Exo on SCs, resulting in a significant decrease in the number of Pax7⁺/MyoD⁺ cells. In the injected MPC-Exo¹⁴⁰⁻ group and the AAV-KO-140 group, there was a significant increase in activated SCs. This suggests that under the intervention of miR-140-5p inhibitors, Pax7 and its downstream gene MyoD are activated in SCs, promoting SC proliferation (Scale bar in 100 μm). Different letters between bars mean P ≤ 0.05 analyses followed by non-paired Student’s t-test. ^nsp > 0.05, ^*p < 0.05, ^**p < 0.01 and ^***p < 0.001 vs. CON.