The Establishment Of A New Mechanobiology Model Of Rat Bone And Functional Adaptation Studies In Vivo

Objectives To establish a mechanobiology model of rat bone, study the functional adaptation in response to artifical loading in vivo, and to explore the better compressi-ve loading condition that promote bone development.Methods A single element strain gauge of<2 mm×3mm in size was attached in longitudinal alignment to the medial surface of the ulnar midshaft, in vivo recordings of ulnar strains during locomotion were obtained. The ulnae of matural female rats were subjected to dynamic axial loading in vivo simulate strains during locomotion using Instron materials-testing machine. The left ulna of adult female rats were subjected to applied loading at frequencies of 5Hz,10Hz,15Hz for 10 min/d with a haversine, low-magnitude(1mm peak to peak) waveform for a two weeks period, the peak strains at the left ulnar midshaft is 2000μεand 3000με. To measure bone mineral density at the ulnar; test mechanical characteristic. Immhistochemistry as an effect of elevated strain in the bone matrix. The ulna's response to loading was traced by subcutaneously injecting each rat twice with calcein and Tetracycline Hcl, and analyzed by histomorphometry with image analysis software.Results A new mechanobiology model of the axial ulna loading technique had be established successfully in rat. At frequencies of 10Hz,15Hz groups, loading promoted obviously secreted of osteocalcin(OCN) and collagen I compared to the control groups and 5Hz groups; fluorescence label showed there are yellow and green bands; a relative benefit in BMD was found compare to the control (P<0.05) followed the decline of material mechanical properties (modulus of elasticity, ultimate stress) (P<0.01) .Conclusion These data show that bone adaptation to mechanical loading to increase with increasing loading frequency which correlate with position and characters of bone, a short daily period of low-magnitude, high-frequency mechanical stimuli results in an osteogenic response related to peak strain magnitude, especially in 10Hz and 15Hz groups,which do not result in significant differences in mechanical properties between the groups.