The Role of PGC-1a Overexperssion in Skeletal Muscle Exosome Biogenesis and Secretion

Skeletal muscle functions as an endocrine organ. Exosomes, small vesicles containing mRNAs, miRNAs, and proteins, are secreted from muscle cells and facilitate cell-to-cell communication. Our recent work found greater exosome release from oxidative compared to glycolytic muscle. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) is a key driver of mitochondrial biogenesis, a characteristic of oxidative muscle. It was hypothesized that PGC1α regulates exosome biogenesis and secretion in skeletal muscle. The purpose of this study is to determine if PGC-1α regulates skeletal muscle exosome biogenesis and secretion. On day 4 of differentiation, human primary myotubes from vastus lateralis biopsies from lean donors (BMI < 25.0 kg/m2) were exposed to adenovirus encoding human PGC-1α or GFP control. On day 6 of differentiation, culture media was replaced with exosome-free media. On day 8, cells were collected for mRNA and protein analysis, and culture media was collected for exosome isolation. Overexpression of PGC-1α increases regulators of exosome biogenesis in the endosomal sorting complexes required for transport (ESCRT) pathway: Alix (CON: 1.0 ± 0.2 vs. PGC-1α: 7.6 ± 3.8), TSG-101 (CON: 1.0 ± 0.1 vs. PGC-1α: 7.3 ± 2.1), CD63 (CON: 1.0 ± 0.17 vs. PGC-1α: 3.7 ± 0.4), Clathrin (CON: 1.0 ± 0.2 vs. PGC-1α: 11.6 ± 2.5), and the secretion pathway: Rab27b (CON: 1.0 ± 0.3 vs. PGC-1α: 3.2 ± 0.3), STAM (CON: 1.0 ± 0.3 vs. PGC-1α: 7.3 ± 0.6), and VTA1 (CON: 1.0 ± 0.1 vs. PGC-1α: 7.3 ± 2.4). Exosome count and total extracellular vesicle count were not significantly different from control. Overexpression of PGC-1α increases gene 9 expression of regulators of exosome biogenesis and secretion in human primary myotubes. In the future, in vitro studies assessing exosomal content from PGC-1 OE cells as well as in vivo effects of PGC-1 OE on exosome production and release should be investigated to further understand the role PGC-1 plays in exosome secretion.