Effects of high frequency vibration on the expression of osteogenic genes in SAOS-2 and BMSCs.

Introduction Mechanical stresses are important to the development of musculoskeletal system (1), but biological mechanisms that are involved by these stimuli remain largely unknown. On the other hand, muscle vibration is used in clinical therapy and sports training to enhance strength and improve motor control (2), (3). Positive therapeutic effects of muscle vibration have been reported in different experimental conditions, for example in the treatment of sportsmen after an accident (3). So, the aim of this work is to understand this phenomena at cellular level and, for this reason, we have designed and realized a system to produce vibration with all the adaptations for “in vivo” studies. Materials and Methods The device to produce vibrating stimuli is composed by an eccentric motor controlled with voltage working with frequency of 30 Hz and imposing a displacement with 3 m/s2 of acceleration and by a 3D accelerometer to record this amplitude (Fig.1). We have taken 30 newborn mice CD1 wild type, divided in two groups, one as control and one treated group. Fifteen mice of treated group were stimulated with a vibration of 30 Hz for 5 weeks 5 days/week for 1h/day. Every week we collected for controls and treated mice tibials and quadriceps anterior muscles and we analyzed on criosections perimeter and surface of muscle fibers with a morfometric analysis software (Image J system). Moreover with molecular biology analysis we investigated genes involved in terminal differentiation, such as MyOD (myogenic differentiation) and MCK (myosin creatin-kinase). Results and Discussion Results of morphometric analysis of muscle fibers (Fig.2) demonstrate that whole-body vibration increases the rate of proliferation of muscle fibers in the first weeks of treatment (increase of fibers number and reduction of surface), while at the end of the experiment (at five weeks of treatment) treated and control fibers tend to balance and probably, tend to fuse to form mature muscle. Molecular biology analysis (Real-Time PCR) was performed only at the second and at the third week on treated and control muscles. Results seem to reveal that high frequency vibrations promote better differentiation of treated muscle tissue with respect to the control ones. This experiment represent a preliminary investigation of the effect of high frequency vibrations at cellular level and at tissue level. Moreover it can establish the starting point for further studies on muscle development and muscle regeneration after injury and treatment with a vibrating system.