Low-magnitude, high-frequency vibration(LMHFV) with rest days(particularly seven rest days) was considerably effective in improving the morphological and mechanical properties of rat proximal femur. However, current knowledge is limited regarding the possible benefit of this mechanical regimen to other bone sites and whether the optimal rest days are the same. This study followed our previous experiment on LMHFV loading with rest days for three-month-old male Wistar rats. The experiment involved seven groups, namely, vibrational loading for X day followed with X day rest(X=1, 3, 5, 7), daily vibrational loading,tail suspension and baseline control. Micro-computed tomography(micro-CT) scanning was used to evaluate the microarchitecture of the distal femoral trabecular bone. Micro-CT image-based microfinite element analysis was performed for each distal femoral metaphysis. LMHFV with rest days substantially changed the trabecular arrangement from remarkably plate-like to rod-like. Vibrational loading with 1 day rest was substantially effective in improving the architecture and apparent-and tissuelevel mechanical properties of the rat distal femoral metaphysis. This study may provide an improved understanding of the sitespecific responses of bone tissue to LMHFV with rest days for a substantially effective therapy of a targeted bone site.
He GongRui ZhangJiazi GaoMeng ZhangBei LiuMin ZhangDong Zhu
Tissue-engineered bone scaffolds provide temporary mechanical support for bone tissue growth. Mechanical stimuli are transferred to seeded cells through the scaffold structure to promote cell proliferation and differentiation. This paper presents a numerical investigation specifically on bone and cartilage tissue differentiation with the aim to provide a theoretical basis for scaffold design and bone defect repair in clinics. In this study, the scaffold structures were established on the basis of cancellous bone microarchitectures. For finite element simulations, inlet velocity and compressive strain were applied under in vitro culture conditions. The influences of this scaffold mor- phology and macro-level culture conditions on micro-mechanical stimuli at scaffold surfaces were investigated. Correlations between the microarchitectural parameters and the mechanical parameters, as well as the cell differentiation parameters were analyzed. Highly het- erogeneous stress distributions were observed on the scaffolds with irregular morphology. Cell differentiation on the scaffold was more sensitive to the inlet velocity than the axial strain. In addition, cartilage differentiation on the scaffolds with structures comprising more plate-like trabeculae was more pronounced than on those with more rod-like trabeculae. This paper is helpful to gain more insight into the mechanical environments under in vitro culture conditions that approximate the in vivo mechanical environments of Bone Marrow Stromal Ceils （BMSCs）.
