Effects Of Whole-body Vibration On Bone Microstructures And Mechanical Properties In Female Rats At Different Periods

Osteoporosis is a progressive bone disease with decreased bone mass and deterioration of microstructures.As a non-drug and non-invasive therapy,whole-body vibration is more and more popular in treating osteoporosis.It is particularly important to study the mechanism and effect of whole-body vibration therapy.The purpose of this study is to investigate the effects of whole-body vibration therapy before or after osteoporosis on bone microstructures and mechanical properties,and to observe the effect of vibration maintenanceThe effects of high-frequency and low-magnitude whole-body vibration on bone properties in female rats were explored from the macro-micro-nano multi-level study A total of 180 female Wistar rats aged 10 weeks were randomly divided into four groups pre-ovariectomized vibration group(WBV),post-ovariectomized vibration group(OW),ovariectomized group(OVA)and control group(CON).After 2 weeks of adaptation,the WBV group was subjected to vertical whole-body vibration with a vibration frequency of 35Hz,a peak acceleration of 0.25 g,30 minutes/day,5 days/week,for 8 weeks,while the rest groups were free to move.At the end of the 8th week,15 rats were sacrificed in each group,whose serum and limb bones were collected.At the 9th week,all remained rats in the WBV,OW,and OVA groups were underwent bilateral ovariectomy then recovered for 2 weeks.At the 11th week,the OW group was subjected to whole-body vibration experiment with the same vibration parameters as the WBV group at 1-8 weeks,while the rest groups were free to move At the end of the 18th week,15 animals were sacrificed in each group to collect samples of the same parts as the 8th week.For eight weeks from week 19,all of four groups were free to move without any intervention.At the end of 26th week,all rats in each group were sacrificed to collect samples of the same parts as 8th week.After the whole-body vibration experiment,the left femurs and tibias were scanned by micro-computed tomography to evaluate the microstructures of the distal femur and proximal tibia cancellous bones,and the microstructures of the middle femur and middle tibia cortical bones.Three-point bending test was performed on the left femurs to evaluate mechanical parameters of femurs.Collagen tensile test was performed on the right ulnar and radial bones to evaluate the mechanical parameters of the ulnar and radial bones.The left ulnar and radial bones were quantitatively analyzed by Raman spectroscopy.The blood was centrifuged and serum was used to evaluate the activity of bone remodeling.The results of the five test methods were compared by one-way analysis of variance(ANOVA).The results showed that no significant change was found in the microstructures parameters of the WBV group at week 8.Compared with the OVA group and the CON group,the elastic modulus,femoral stiffness,and mechanical parameters of ulnar and radial bone collagen of the WBV group were significantly reduced(p<0.05).Serum level of Carboxy-terminal telopeptide of type I collagen(CTX-1)and tartrate resistant acid phosphatase 5b(TRACP-5b)in the WBV group were significantly increased(p<0.05).In this study,it was found that whole-body vibration before osteoporosis reduced the stiffness of cortical bones and the tensile mechanical properties of bone collagen,but had no positive effect on the bone microstructures.At week 18,compared with the OVA group and the CON group,BMD,BV/TV and Tb.N in the distal femurs and proximal tibias of the OW group all showed a tendency of OVA group<OW group<CON group(p<0.05),and mechanical parameters of ulnar and radial bone collagen in the OW group were significantly lower than those in the OVA group and the CON group(p<0.05).In this study,it was found that whole-body vibration after osteoporosis has a positive effect on the microstructures of cancellous bones,but it also reduced the mechanical properties of bone collagenAt week 26,the mechanical parameters of ulnar and radial bone collagen in the WBV group and the OW group were significantly lower than those in the OVA group and the CON group(p<0.05).No significant difference was observed in femoral mechanical parameters between the OVA group and the CON group.After the suspension of whole-body vibration,the positive effect of the whole-body vibration on the bone microstructures could not be maintained,and the bone collagen was damaged According to Raman spectroscopy analysis,this damage was not caused by changes in the bone chemical composition,and it was speculated that the collagen configuration was changed,which still needs further studyThe mechanical properties of bone were damaged by whole-body vibration before osteoporosis,so it is not recommended for clinical use.The whole-body vibration after osteoporosis can improve the microstructure and mechanical properties of bone,so it is not recommended for clinical use.This study provides a reference for the design of intervention time and scheme of whole-body vibration in the treatment of osteoporosis.