Electrical stimulation at the dorsal root ganglion preserves trabecular bone mass and microarchitecture of the tibia in hindlimb-unloaded rats

Summary: This study seeks to investigate the effect of electrical stimulation (ES) at dorsal root ganglion (DRG) on disuse bone loss in a rat model. Hindlimb unloading for 14 days resulted in significant bone loss in rat tibia while rats with ES at DRG showed a significant reduced bone loss.Introduction: Mechanical unloading induces osteoporosis in both human and animals. Previous studies demonstrated that electrical stimulation (ES) to dorsal root ganglion (DRG) could trigger secretion of calcitonin gene-related peptide (CGRP) which plays an important role in bone modeling and remodeling. This study seeks to investigate the effect of ES to DRG on disuse bone loss in a rat model.Methods: Twenty-four rats were randomly assigned in three experimental groups: cage control (CC), hindlimb unloading (HU), and hindlimb unloading with ES (HUES). ES was applied via implantable micro-electrical stimulators (IMES) to right DRGs at vertebral levels L4–L6 in HUES group.Results: Hindlimb unloading for 14 days resulted in 25.9 % decrease in total bone mineral content (BMC), 29.2 % decrease in trabecular BMD and trabecular microarchitecture and connectivity were significantly deteriorated in the proximal tibia metaphysis in HU group, while rats with ES at DRG showed significant reduced bone loss that there was 3.8 % increase in total BMC, 2.3 % decrease in trabecular BMD, and significant improvement in trabecular microarchitecture. There was a concurrent enhancement of expression of CGRP in stimulated DRGs.Conclusions: The results confirm the effect of ES at DRG on enhancing CGRP expression and suggest potential applications of IMES for the prevention and treatment of disuse bone loss.