Rat Model of Quadriceps Contracture by Joint Immobilization

Effect of Combining Exercise with Adipose-Derived Mesenchymal Stem Cells in Muscle Atrophy Model of Sarcopenia

Deterioration in muscle mass, strength, and physical performance due to conditions such as sarcopenia can affect daily activities and quality of life in the elderly. Exercise and mesenchymal stem cells (MSCs) are potential therapies for sarcopenia. This study evaluates the combined effects of exercise and adipose-derived MSCs (ADMSCs) in aged rats with sarcopenia. Eighteen-month-old rats were randomly divided into four groups: control, exercise (Ex), ADMSCs injection (MSC), and ADMSCs injection with exercise (MSC + Ex). Gastrocnemius (GCM) muscle mass increased in the Ex, MSC, and MSC + Ex groups compared to the control group. Although the mean CSA did not differ significantly between the groups, the size distribution of myofibers shifted toward larger sizes in the Ex and MSC + Ex groups. The MSC + Ex group performed best in functional tests, including the rotarod and hot plate tests. The protein expression levels of tumor necrosis factor (TNF) and the p-AMP-activated protein kinase (AMPK)/AMPK ratio in the GCM muscle were the lowest in the MSC + Ex group. This study demonstrates that combining exercise and ADMSC interventions was the most effective treatment for aged sarcopenic rats, suggesting a potential synergistic approach for sarcopenia treatment.

Validity of Elastic Imaging Evaluation of Hamstring Muscles With Knee Contracture Using Ultrasound Shear Wave Elastography

PURPOSE

This study used ultrasound shear wave elastography (SWE) to evaluate the mechanical properties of hamstring muscles from cadaveric specimens with knee flexion contractures.

METHODS

Hamstring muscles for tensile testing were harvested from Thiel soft-embalmed cadavers with and without knee flexion contracture. Muscle specimens were mounted on a testing machine. The initial load detected when a tensile load was applied to the distal end was used as the slack length. The cross-sectional areas of the muscle at slack length were measured at the proximal and distal sites using B-mode ultrasonography. Subsequently, the muscle specimen was elongated from the slack length to 8% strain, with the shear modulus measured using SWE. Young's modulus (stress/strain) was calculated based on the displacement and tensile force obtained from the tensile test.

RESULTS

Regression analysis showed a significant positive linear relationship between the Young's and shear moduli for all specimens at all the sites (P < 0.01 and coefficient of determination: 0.95-0.99). The Young's and average shear moduli at the proximal and distal sites were higher in all hamstring muscles with contractures than in those without contractures.

CONCLUSIONS

SWE can be used to estimate Young's moduli of hamstring muscles with contractures. Muscle specimens with contractures exhibited higher resistance to elongation, thereby indicating that their mechanical properties differed from those of muscles without contractures.

Effects of Neuromuscular Electrical Stimulation and Therapeutic Ultrasound on Quadriceps Contracture of Immobilized Rats

Quadriceps contracture is a condition where the muscle-tendon unit is abnormally shortened. The treatment prognosis is guarded to poor depending on the progress of the disease. To improve the prognosis, we investigated the effectiveness of therapeutic ultrasound and NMES in treating quadriceps contracture in an immobilized rat model. Thirty-six Wistar rats were randomized into control, immobilization alone, immobilization and spontaneous recovery, immobilization and therapeutic ultrasound, immobilization and NMES, and immobilization and therapeutic ultrasound and NMES combination groups. The continuous therapeutic ultrasound (frequency, 3 MHz, intensity 1 W/cm2) and NMES (TENS mode, frequency 50 Hz; intensity 5.0 ± 0.8 mA) were performed on the quadriceps muscle. On Day 15, immobilization-induced quadriceps contracture resulted in a decreased ROM of the stifle joint, reduction in the sarcomere length, muscle atrophy, and muscle fibrosis. On Day 43, therapeutic ultrasound, NMES, and combining both methods improved muscle atrophy and shortening and decreased collagen type I and III and α-SMA protein. The combination of therapeutic ultrasound and NMES significantly reduced the mRNA expression of IL-1β, TGF-β1, and HIF-1α and increased TGF-β3. Therefore, the combination of therapeutic ultrasound and NMES is the most potent rehabilitation program for treating quadriceps contracture.

Usefulness of Ultrasound Shear Wave Elastography for Detection of Quadriceps Contracture in Immobilized Rats

Quadriceps contracture is an abnormal pathological shortening of the muscle-tendon unit. To improve the prognosis of quadriceps contracture, improvement of its diagnostic method is needed. In this study, we evaluated the diagnostic utility of ultrasound shear wave elastography in a rat model of quadriceps contracture induced by immobilization. Fifty Wistar rats were randomly divided into control and immobilization groups. During up to 4 weeks of joint immobilization, the quadriceps elastic modulus, muscle hardness, creatinine phosphokinase levels, joint range of motion, histopathologic parameters, and levels of fibrosis-associated mRNA expression were measured every week in the immobilization and control groups and compared. In the immobilization group, the elastic modulus gradually but significantly increased (p < 0.05) throughout the immobilization period. However, muscle hardness and serum creatinine phosphokinase levels only increased at 1 and 2 weeks after the start of immobilization, respectively. Muscle atrophy and shortening progressed throughout the immobilization group. Collagen type I and III, α-SMA protein, and mRNA expression of IL-1β and TGF-β1 significantly increased (p < 0.05) throughout in the immobilization group. Ultrasound shear wave elastography is the most useful method for clinical assessment of muscle contracture.