The Effect Of Low-magnitude And High-frequency Vibraion On Human Skin Fibroblast: In Vitro Study

Objective: Low-Magnitude and High-Frequency (LMHF) vibration has becomeincreasingly popular over the last several years as a method of exercise or clinical treatment.However, the efficiency of LMHF applied on the cutaneous wound healing has not beenreported. The authors developed a novel in vitro model to investigate the effects of lowmagnitude and high frequency vibration on the migration, proliferation, differentiation andextracellular matrix of human cutaneous fibroblasts in order to understand the potentialapplication of mechanical vibration on wound healing.Methods: The authors tested a vibration bioreactor customized by company to figure outthe suitable parameters of mechanical vibration for human fibroblasts in vitro study. Thevibration bioreactor could stimulate sinusoid mechanical vibration waves with lowmagnitude (a<1g) and high frequency (f=30-100Hz). Based on the previously study, humancutaneous fibroblasts were subjected to vibration treatment (f=30,50,65,100Hz; a=0.4×g;t=15minutes). The effect of low magnitude and high frequency on fibroblasts migrationwas investigated via in-vitro scratch assay which means a wound gap was created on themonolayer and healing percentage was measured after vibration. Cells proliferationchanging after vibration treatment was analyzed using CellQuanti-Blue Assay and BrdUassay. The mRNA level of α-SMA and several vital extracellular matrix protein weredetected by real-time polymerase chain reaction (PCR) after mechanical vibration.Results: After exposure to sinusoid mechanical vibration for longer time (30min), part offibroblasts would be detached from bottom under microscope. Cellular morphologychanged from long spindle to short and round with the number of dendrites decreased. While, there were no significant difference of fibroblasts morphology and cellular viabilitybetween15min vibration group and control. Migration of human cutaneous fibroblast in allexperimental groups significantly (p<0.01) decreased compared with control group. Themigration speed tended to decrease with the frequency increasing but have no relationshipwith the direction of sinusoid vibration. The proliferation of fibroblasts stimulated afterexposure to low-magnitude and high frequency vibration (f=30Hz,50Hz,65Hz, a=0.4×g,t=15minutes) has no significant difference with control group, whereas f=100Hz vibrationconsiderably decreased cell proliferation (p<0.01). The mRNA expression of α-SMA hadbeen increased by3-5days vibration, which means mechanical vibration might bias thefibroblasts to differentiate into myofibroblasts. However, no significant differences ofextracellular matrix protein mRNA was observed between any experimental groups andcontrol.Conclusions: We reported the effect of the LMHF vibration-wound healing in-vitro modelfor the first time. The present results showed that horizontal low magnitude and highfrequency vibration (f=30Hz,50Hz,65Hz, a=0.4×g, t=15min) could slow down the humancutaneous fibroblasts migration but haven’t significant effect on the cells proliferation.Long-term low magnitude and high frequency vibration tend to bias cutaneous fibroblastsdifferentiate into myofibroblasts while could not change the extracellular matrixarrangement. This study has certain limitation because the effects of mechanical vibrationon the biology field are so complicated and confusing. Further investigations should beperformed to discover the mechanism of the biological application of mechanical forces.