The Impact Of CD146 +/- Serum Extracellular Vesicles On Recovery Of Skeletal Muscle Following Hindlimb Immobilization

Abstract

Our laboratory recently reported a significant decline in muscle-resident pericyte quantity following hindlimb immobilization, and subsequently demonstrated the capacity for pericyte transplantation to accelerate recovery of skeletal muscle mass during the rehabilitation period. PURPOSE: The purpose of this study was to determine the extent to which pericyte-derived extracellular vesicles (EVs) effectively recover skeletal muscle mass following hindlimb immobilization. METHODS: Two groups of donor mice (n=6/group) were used to isolate serum EVs before (“Pre”) and after (“Post”) an acute bout of contraction using a sciatic nerve stimulation procedure. Serum EVs were isolated using ultracentrifugation followed by magnetic bead sorting to isolate CD146+ EVs and CD146- EVs. Five groups of mice (n=4/group) underwent unilateral hindlimb immobilization for 14 days. At 14 days, the mice were intramuscularly (tibialis anterior) injected with 1) PBS, 2) CD146+Pre EVs 3) CD146+Post EVs, 4) CD146-Pre EVs, or 5) CD146-Post EVs (in 40 μL of PBS), then remobilized for 2 weeks to determine therapeutic capacity. RESULTS: A significant decrease in serum CD146+ EVs was observed following 14 days of hindlimb immobilization (p<0.05). CD146-Post EVs demonstrated significant recovery of myofiber cross-sectional area compared to PBS control (p<0.05). CD146+Pre and CD146+Post EVs significantly restored capillary density compared to PBS control (p<0.05). CD146-Pre EVs recovered capacity for collagen remodeling compared to PBS control (p<0.05). CONCLUSIONS: The results from this study suggest that CD146- serum EVs positively benefit regrowth of skeletal muscle following a period of disuse. Additionally, CD146+ serum EVs enhance skeletal muscle capillarization. Overall, a combination of both EV fractions may optimize recovery of skeletal muscle mass following disuse. Supported by NIH NIAMS R01 AR072735 (to MDB) and ACSM NASA Space Physiology Research Grant (to SD).