The researchers then bypassed exercise entirely, injecting recombinant PEDF into mice for 4 weeks. While the effects were not as profound as in the 8-week exercise experiment, PEDF was found to decrease some senescence markers in lung tissues.
It isn't clear to me in which way the PEDF is working here, as the article points to many of the benefits of exercise in general: reduction of reactive oxygen species (ROS), inflammation reduction, and reduction of senescence-related factors. Still, seems to be doing something.