Figure 6.

Delivery of macrophages from aged donors after hindlimb unloading/reloading to aged recipients following hindlimb unloading. Ex vivo force production of soleus muscles from aged mice during early recovery following hindlimb unloading that received intramuscular injections of macrophages from 4-day reloaded aged mice (Mac) or PBS (Vehicle) into contralateral hindlimbs. A–D: muscles were subjected to a single pulse stimulation to induce a twitch contraction for the measurement of specific force (A), rate of contraction (B), or rate of relaxation (C). D: raw force tracings from a single-pulse stimulation that induced a twitch contraction. E: specific force was measured across a range of stimulation frequencies from 10 to 200 Hz. F: raw force tracings from a 100 Hz stimulation. A–C: individual data points are shown and connected with respective contralateral limbs and the mean is represented as a bar. E: data points are shown as means ± SE. Paired t tests (A–C) or a two-way ANOVA with Sidak’s multiple-comparisons test (E) was used. n = 9/group.