Effects of PGC-1α overexpression on the myogenic response during skeletal muscle regeneration

Abstract

The ability of skeletal muscle to regenerate from injury is crucial for locomotion, metabolic health, and quality of life. Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC1A) is a transcriptional coactivator required for mitochondrial biogenesis. Increased mitochondrial biogenesis is associated with improved muscle cell differentiation, however PGC1A's role in skeletal muscle regeneration following damage requires further investigation. The purpose of this study was to investigate the role of skeletal muscle-specific PGC1A overexpression during regeneration following damage. 22 C57BL/6J (WT) and 26 PGC1A muscle transgenic (A1) mice were injected with either phosphate-buffered saline (PBS, uninjured control) or Bupivacaine (MAR, injured) into their tibialis anterior (TA) muscle to induce skeletal muscle damage. TA muscles were extracted 3- or 28-days post-injury and analyzed for markers of regenerative myogenesis and protein turnover. Pgc1a mRNA was ∼10-20 fold greater in A1 mice. Markers of protein synthesis, AKT and 4EBP1, displayed decreases in A1 mice compared to WT at both timepoints indicating a decreased protein synthetic response. Myod mRNA was ∼75% lower compared to WT 3 days post-injection. WT mice exhibited decreased cross-sectional area of the TA muscle at 28 days post-injection with bupivacaine compared to all other groups. PGC1A overexpression modifies the myogenic response during regeneration.

Keywords: Muscle regeneration; PGC-1α; Protein turnover; Satellite cells; Skeletal muscle; p38 MAPK.

Fig. 1

mRNA abundance of transgenic identifier PGC-1α and associated phenotypic, metabolic markers at 3 days (left) and 28 days (right) post-injection in wildtype (WT) or muscle specific PGC-1α transgenic (A1) mice. (A–B) PGC-1α mRNA abundance. (C–D) LDHA mRNA abundance. (E–F) LDHB mRNA abundance. (G–H) LDHA:LDHB ratio. (I–J) CD-147 mRNA abundance. The uninjured phosphate buffered saline (PBS) group is denoted UNINJ. The injured Marcaine (MAR) group is denoted INJ. Main effects (ME) of genotype and/or injury appear on each graph when relevant, # signifies difference from genetic counterpart, ∗ signifies difference between injections within the same genotype following an interaction. Values are means ​± ​SE. Statistical significance we set at an alpha of p ​≤ ​0.05.

Fig. 2

mRNA abundance and protein content of inflammatory signaling factors, TNF-α, NFκB, p38 MAPK, and IL-1β at 3 days (left) and 28 days (right) post-injection in wildtype (WT) or muscle specific PGC-1α transgenic (A1) mice. (A–B) TNF-α mRNA abundance. (C–D) NFκB protein content. (E–F) p38 MAPK protein content. (G–H) IL-1β mRNA abundance. The uninjured phosphate buffered saline (PBS) group is denoted UNINJ. The injured Marcaine (MAR) group is denoted INJ. Main effects (ME) of genotype and/or injury appear on each graph when relevant, # signifies difference from genetic counterpart, ∗ signifies difference between injections within the same genotype following an interaction. Values are means ​± ​SE. Statistical significance we set at an alpha of p ​≤ ​0.05.

Fig. 3

mRNA abundance and protein content of protein synthetic and catabolic factors, Akt, 4E-BP1, and the E3 ligases Atrogin-1 and MuRF-1 at 3 days (left) and 28 days (right) post-injection in wildtype (WT) or muscle specific PGC-1α transgenic (A1) mice. (A–B) Akt protein content. (C–D) 4E-BP1 protein content. (E–F) Atrogin-1 mRNA abundance. (G–H) MuRF-1 mRNA abundance. The uninjured phosphate buffered saline (PBS) group is denoted UNINJ. The injured Marcaine (MAR) group is denoted INJ. Main effects (ME) of genotype and/or injury appear on each graph when relevant, # signifies difference from genetic counterpart, ∗ signifies difference between injections within the same genotype following an interaction. Values are means ​± ​SE. Statistical significance we set at an alpha of p ​≤ ​0.05.

Fig. 4

Cross-sectional area and muscle fiber size distribution at 28 days post-injection, followed by mRNA abundance of satellite cell dynamics-associated factors at 3 days (left) and 28 days (right) post-injection in wildtype (WT) or muscle specific PGC-1α transgenic (A1) mice. (A) Cross-sectional area (CSA). (B) Representative images of H&E staining of tibialis anterior cross-sections 28 days post-injection. (C–F) Relative frequency of the muscle fiber sizes across each possible pairwise comparison. (G–H) mRNA abundance of Cyclin D1. (I–J) mRNA abundance of MyoD. (K–L) mRNA abundance of Myogenin. The uninjured phosphate buffered saline (PBS) group is denoted UNINJ. The injured Marcaine (MAR) group is denoted INJ. Main effects (ME) of genotype and/or injury appear on each graph when relevant, # signifies difference from genetic counterpart, ∗ signifies difference between injections within the same genotype following an interaction. Values are means ​± ​SE. Statistical significance we set at an alpha of p ​≤ ​0.05.

Fig. 5

mRNA abundance of CHOP and TRB3 at 3 days (left) and 28 days (right) post-injection in wildtype (WT) or muscle specific PGC-1α transgenic (A1) mice. (A–B) CHOP mRNA content. (C–D) TRB3 mRNA content. The uninjured phosphate buffered saline (PBS) group is denoted UNINJ. The injured Marcaine (MAR) group is denoted INJ. Values are means ​± ​SE. Statistical significance we set at an alpha of p ​≤ ​0.05.