The effects of frequency-dependent dynamic muscle stimulation on inhibition of trabecular bone loss in a disuse model

Abstract

Clinical electrical muscle stimulation has been shown to alleviate muscle atrophy resulting from functional disuse, yet little is known about its effect on the skeleton. The objective of this study is to evaluate the potential of dynamic muscle stimulation on disused trabecular bone, and to investigate the importance of optimized stimulation frequency in the loading regimen. Fifty-six skeletally mature Sprague-Dawley rats were divided into seven groups for the 4-week experiment: baseline control, age-matched control, hindlimb suspended (HLS), and HLS with muscle stimulation at 1 Hz, 20 Hz, 50 Hz, and 100 Hz. Muscle stimulation was carried out for 10 minutes per day for 5 days per week, total of 4 weeks. The metaphyseal and epiphyseal trabecular regions of the distal femurs were analyzed with microcomputed tomography and histomorphometry methods. HLS alone for 4-week resulted in a significant amount of trabecular bone loss and structural deterioration. Muscle contraction at 1 Hz was not sufficient to inhibit trabecular bone loss and resulted in similar amount of loss to that of HLS alone. Bone quantity and structure were significantly improved by applying muscle stimulation at mid-frequency (20 Hz & 50 Hz). Dynamic stimulation at 50 Hz demonstrated the greatest preventive effect on the skeleton against functional disused alone animals (up to +147% in bone volume fraction, +38% in trabecular number and -36% in trabecular separation). Histomorphometric analysis showed that the stimulation, regardless of its frequency, did not have an effect on the bone formation indices, such as mineral apposition rate and bone formation rate. Overall, the data demonstrated the potentials of frequency-dependent dynamic muscle contraction in regulating skeletal adaptive responses under disuse conditions. Dynamic muscle stimulation, with a specific regimen, may be beneficial to future orthopedic research in developing a countermeasure for disuse osteopenia and osteoporosis.

Ultrasound Evaluation of Site-Specific Effect of Simulated Microgravity on Articular Cartilage

“…These results might suggest adverse effects of microgravity on articular cartilage, although it is mild compared with acute bone loss. It has been reported that bone mineral density reduces during one day of human space flight (Williams et al 2009), and in the 14-day TS young rat model (Kodama et al 1997) and the four-week TS mature rat model (Allen and Bloomfield 2003;Sakata et al 1999;Lam and Qin 2008). The alterations in mechanical forces have a great influence on the development and integrity of articular cartilage (Arokoski et al 2000;Moriyama et al 2008;O'Connor 1997).…”

“…Significant bone loss and reductions in bone formation resulted from four-week TS (Allen and Bloomfield 2003;Sakata et al 1999;Lam and Qin 2008). To compare with bone loss, this study used the four-week TS rat model to evaluate changes in articular cartilage.…”

Dynamic Fluid Flow Mechanical Stimulation Modulates Bone Marrow Mesenchymal Stem Cells

“…Animals were randomly divided into 12 groups: 1) age-matched -day 3 (n=8), 2) HLS -day 3 (n=8), 3) HLS+DHS -day 3 (n=8), 4) age-matched -day 7 (n=8), 5) HLS -day 7 (n=8), 6) HLS+DHS -day 7 (n=8), 7) age-matched -day 14 (n=8), 8) HLS -day 14 (n=6), 9) HLS+DHS -day 14 (n=8), 10) age-matched -day 21 (n=8), 11) HLS -day 21 (n=8), 12) HLS+DHS -day 21 (n=7). The HLS procedure, similar to the setup from Lam's study (30), introduced functional disuse to the rat hindlimbs. Briefly, after cleaning with 70% alcohol, the animal's tail was lightly coated with tincture of benzoin.…”

Alteration of contraction-to-rest ratio to optimize trabecular bone adaptation induced by dynamic muscle stimulation

“…[7, 8] Many in vivo studies have determined parameters, such as frequency, strain magnitude, strain history, and fluid pressure, within stimulation regimens to be influential to bone adaptation. [9–12] The concept of inserting rest period has recently shown to enhance osteogenesis. Short rest duration, e.g., 10 seconds, inserted into a low frequency loading regime augmented anabolic response on the periosteal surfaces of isolated avian ulnae.…”

“…[9, 16] In particular, the level of osteopenic attenuation is depended on the stimulation frequency. Whether inserting rest period into MS regimen, with a specific frequency, can optimize bone’s adaptive response remains uncertain.…”