Effects of ultrasound stimuli on mechanical and biological properties of ligament fibroblasts
Research hypothesis: Ultrasound stimulation on ligament fibroblasts will increase their elastic modulus, harmonic vibration, cell proliferation, migration, synthesis of extracellular matrix (ECM) (Collagen type I, type III and Fibronectin), and β-actin expression. Data shows the elastic modulus (Pa); Harmonic of the natural frequency of vibration (Hz); cell proliferation (Cell number/mL) on 2nd, 4th, and 6th day of culture; cell migration length (um); synthesis of proteins: collagen type I (ng/mL), type III (ng/mL) and Fibronectin (ng/mL); β-actin area (cm2) for treated cells and the control group. Following ultrasound stimulation (at either 1.0 W/cm2 (Group A-low dose) or 2.0 W/cm2 (Group B-high dose) for five days every 24 hours, Control cells (Group C) were manipulated identically with ultrasound off) the elastic modulus of ligament fibroblasts decreased (Group A, 22%; Group B, 31%) (p<0.05). The harmonic of the natural frequency of vibration of ligament fibroblasts decreased (Group A, 13%; Group B, 17%). Cell proliferation and migration increased by 10% and 4%, (Group A), and decreased by 13% and 11%, (Group B) (p<0.05). Synthesis of type I collagen was increased 100% following the high dose, but no type III collagen synthesis was detected in cells stimulated for the low dose or in control cells. Fibronectin production was significantly increased following ultrasound stimulation (79%, Group A; 61%, Group B). Most cells were viable (85%, Group A; 77%, Group B; 86%, Group C). The low dose of ultrasound decreased the β-actin area by 74%, and the high dose decreased the β-actin area by 31%.