Electrical stimulation prevents condyle and subchondral degeneration following the masseter atrophy.

Abstract

There is a strong relationship between masticatory muscle atrophy and condyle degeneration. Although electrical stimulation (ES) is an effective treatment for muscle atrophy, its influence on the underlying condyle is unclear. This study aimed to investigate whether ES can prevent condyle degradation during the stage of masseter muscle atrophy. Six-week-old rats were randomly divided into the control, botulinum toxin (BTX), or BTX + ES group. BTX was injected into the bilateral masseters of rats to induce masseter atrophy. The left-side masseters without ES treatment were served as BTX group, and the right-side masseters received ES with different parameters (5 mA/10 Hz, 5 mA/50 Hz, 6 mA/10 Hz, 6 mA/50 Hz, 7 mA/10 Hz, and 7 mA/50 Hz) were served as BTX + ES groups. After 4 weeks, micro-CT and qualitative or quantitative analysis of osteogenesis, chondrogenesis, and angiogenesis-related genes in condyles were conducted. ES, especially at 7 mA/50 Hz, significantly attenuated masseter atrophy, condyle degeneration, and subchondral bone loss. Moreover, the upregulation of related proteins, including collagen 1, osteocalcin, bone morphogenetic protein 2, collagen 2a, and vascular endothelial growth factor were observed. ES partly rescued condylar degeneration and subchondral bone loss following masseter atrophy.