Mitochondrial Pathway Dysregulation Defines Regenerative Failure in Volumetric Muscle Loss
Daniel F. Gibbard, Rebecca E. Schmitt, Andrew J. Hennigan, Aneesha Dasgupta, Jessica Z. Schneider, Jason D. DolesABSTRACT
Background
Volumetric muscle loss (VML) is a major muscle injury that significantly impacts quality of life in affected individuals. This substantial loss of muscle tissue leads to various complications including reduced force output, impaired muscle regeneration and long‐term mobility issues. Although skeletal muscle is typically a highly regenerative tissue, damage beyond a critical threshold prevents full recovery. To better understand this limitation, we investigated the differences between more regenerative (healing) and less regenerative (nonhealing) muscle in a murine model of VML.
Methods
We used longitudinal strength measurements, transcriptomic analyses and bioinformatics to assess differences between injury (defect) sizes. These approaches were used to assess functional recovery and to identify molecular and metabolic features associated with healing versus nonhealing injuries.
Results
Our results showed that 2‐mm VML defects led to reduced force outputs at 7 and 14 days of postinjury but recovered to baseline levels by 28 days—indicating healing. In contrast, mice with 4‐mm VML injuries failed to recover force output by 28 days—representing a nonhealing response. Transcriptomic and bioinformatic analyses revealed that nonhealing injuries exhibited prolonged activation of healing‐associated pathways. Mitochondria‐related transcript signatures were most strongly correlated with both strength loss and defect size. Additionally, we observed metabolic alterations at the whole muscle level via a shift in myofiber isotype composition—specifically a reduction in fast, glycolytic type IIB myofibers and an increase in oxidative type IIA myofibers.
Conclusions
These findings highlight the critical role of mitochondrial function and metabolic rewiring in determining regenerative outcomes following VML injury. Differences in mitochondrial activity, protein expression and myofiber composition distinguish healing from nonhealing defects and may explain why larger injuries fail to fully recover.