Author(s): WEI, S., KUO, C., Institution: UNIVERSITY OF TAIPEI, Country: TAIWAN, Abstract-ID: 496

INTRODUCTION:
Blood-flow-restriction (BFR) combined with resistance training is known to elicit pronounced inflammatory responses in skeletal muscle. While often viewed as deleterious, inflammation is a necessary prerequisite for effective muscle regeneration.In this study, we aimed to identify the cellular localization and expression of peroxisome proliferator–activated receptor-γ coactivator-1α (PGC-1α) protein in mitochondria-rich activated stem/progenitor cells and myofibers at injured sites of human skeletal muscle following BFR resistance exercise.
METHODS:
Eleven healthy male participants were recruited. On the experimental day, participants completed three bouts of 5-min arterial occlusion at 180 mmHg, followed by four sets of barbell squats at 70% of one-repetition maximum, with 90 s of rest between sets. Muscle biopsies of the quadriceps were obtained at baseline (0 h) and 24 h post-exercise.
RESULTS:
BFR resistance exercise induced focal necrotic cell infiltration in skeletal muscle immediately after exercise. At injured sites, PGC-1α was highly expressed in Nestin⁺ cells (neural stem/progenitor cells), whereas expression in neighboring myofibers was minimal. Nestin⁺ cells were mitotically active and exhibited substantially higher mitochondrial density compared with myofibers. These mitochondria-rich STRO-1⁺ and Nestin⁺ cells selectively homed to disrupted muscle fibers characterized by neutrophil infiltration. Notably, a subset of these cells fused with adjacent myofibers, suggesting direct mitochondrial delivery.
CONCLUSION:
PGC-1α–expressing cells involved in human muscle repair following BFR resistance exercise are predominantly mitochondria-rich neural stem/progenitor cells rather than myofibers. These cells contribute to post-injury muscle regeneration by replenishing mitochondrial content under inflammatory conditions.