Transcutaneous Electrical Acupoint Stimulation Prevents Bone Loss and Muscle Atrophy Induced by Hindlimb Suspension in Rats

Background: Microgravity exposure significantly disrupts physiological systems, leading to conditions such as bone loss and muscle atrophy, thereby posing a threat to the sustainability of long-term space missions. Aims and Objectives: This research seeks an effective strategy to counteract bone loss and muscle atrophy caused by microgravity. Materials and Methods: We employed the hindlimb suspension (HS) rat model to assess the effects of transcutaneous electrical acupoint stimulation (TEAS) in preventing these conditions resulting from unloading, evaluated femoral morphological indices using three-dimensional reconstructed images from micro-computed tomography scanning and assessed the biomechanical properties of the femur through flexural strength testing. In addition, We quantified and compared changes in bone and muscle fibers among control, HS, TEAS, and sham stimulation groups. Results: The results revealed that the most significant changes associated with weightlessness-induced bone loss involved trabecular bone mineral density (BMD) and bone biomechanical properties, while TEAS increased BMD and improved bone microstructure. TEAS enhanced osteoblast differentiation, increased osteoblast count, and elevated serum bone formation markers (alkaline phosphatase , osteocalcin, and procollagen type I N-terminal propeptide) while reducing bone resorption markers (tartrate-resistant acid phosphatase and C-terminal telopeptide of type I collagen).Despite intact nerves, rats subjected to HS experienced a rapid weight loss within 1–2 weeks, accompanied by a significant reduction in muscle fiber cross-sectional area (CSA),but the CSA of soleus and gastrocnemius single muscle fibers was larger in the TEAS group than in the HS group. Furthermore, TEAS prevented the unloading-induced slow-to-fast fiber muscle shifts. However, sham stimulation did not demonstrate significant improvements in the bone and muscle tissues of rats subjected to HS. Conclusion: In conclusion, these findings suggest that TEAS is a promising and effective preventive measure for protecting against microgravity-induced bone loss and muscle atrophy.