Establishment Of An In Vivo Bone Loading Model For SD Rat And Its Application In A Study Of Mechanical Adaptation In The Rat Tibia

Mechanical loading is essential for maintaining bone structure and function.Bone has the capability to adapt to its surrounding mechanical environment.Bone loss and weakness of the mechanical properties occur following mechanical unloading.For instance,during long-term space mission or bed rest,the astronauts or patients generally experience osteopenia,in particular,in the weight-bearing bones.By contrast,bone quality improves normally with physiological overloading.Professional athletes experiencing intensive training have higher bone mass and strength,and more optimized bone structure.Numerous studies have suggested that mechanical loading plays a crucial role in maintaining bone structure and mechanical properties.However,how bone mass,structure and strength response to mechanical stimulation and the relationship among them during the adaption remain unknown.Bone matrix deformation engendered by mechanical loading is closely related to bone structure and mechanical properties.The relationship between bone matrix deformation and bone adaptation is to be further explored.Therefore,the present study,firstly,established an in vivo strain gauge approach to assess tibia deformation in vivo.Secondly,a non-invasive tibia axial loading device was developed to stimulate bone with precisely controlled mechanical loading.Furthermore,the tail-suspension model was adopted to investigate the response of bone mass,structure and mechanical properties to mechanical loading,the effect of the deformation produced by mechanical load is of great significance for bone structure and strength,and the effect of bone matrix strain on bone loss during disuse.Results could be acquired as follows: 1.The non-invasive bone loading device was capable of generating stably sin-wave mechanical loading with the frequency ranging from 0.25 to 2 Hz and the amplitude from 11 to 33 N;2.The mechanical load couldn't confront unload-related bone loss at day 7,14,21 and 28;3.Mechanical load that produced 800 ?? was not large enough to affect the BMD of rat tibia;the BMC of tail-suspension rat loaded tibia was higher than contralateral tibia at day 14,the BMD and BMC of the control group were higher than tail-suspension group at day 14 and day 21;4.The BMD and BMC of all rat tibias were at a range of 0.14-0.17 g/cm2 and 0.4-0.5 g,respectively.The following conclusion could be obtained from the study: 1.The loading device wascapable of generating stably sin-wave mechanical loading,which was available to experimental use.2.800 ?? was not enough as a countermeasure unload-related bone loss and strength decrease;3.On day 14 and 21,the bone mass,structure and strength of rat tibia changed,and the change of the three aspects was not consistent.In the ‘Discussion' section,the response process of bone structure and strength to unload-related bone loss was further discussed.Taking all the evidence together,this study suggested the process of bone structure and strength response to unload-related bone loss.Based on the previous discovery,the research uncovered the specific process of bone structure response to mechanical load,which will help for further study by providing basic data,and help develop new countermeasures of unload-induced bone loss.