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Objective To investigate the role and influence of physiological loading and overloading on microgravity-induced osteoporosis, so as to find a reliable way to prevent or treat related-orthopedic disorders in astronauts induced by long-time space activity. Methods The microgravity environment in space was simulated by tail-suspension experiment, then the osteoporosis models of mice were built. A total of 32 C57BL/6J mice were randomly and evenly separated into four groups: normal group (normal), tail-suspension group (TS), physiological loading group (loading) and overloading group (overloading). Periodic dynamic mechanical load was applied on the left tibia in loading group and overloading group during tail-suspension test. After four weeks, tibial mechanical properties, micro-parameters of bone trabecular, biochemical indices and osteogenesis-related gene expression in each group were compared and analyzed. Results A great loss of tibial cancellous bone, significantly lower tibial biomechanical expression, serious damage of microstructure and weaker osteogenic activity were found in tail-suspended mice as compared with those of normal group. Physiological loading could clearly improve mechanical properties of bones, microstructure of bone trabecular, osteogenic activity and relative gene expression (P＜0.05). Overloading could also improve the condition of microgravity-induced osteoporosis, but the effect was not obvious (P＞0.05). Conclusions Tail-suspension can successfully simulate microgravity environment and duplicate osteoporosis model. Physiological loading can effectively prevent the emergence and development of microgravity-induced osteoporosis, while overloading can also counter microgravity-induced osteoporosis, but the results have no significant differences.
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Objective To construct a three-dimensional (3D) solid model of the cortical bone including osteons, verify the stress concentration effect of osteons, simulate and predict the stress concentration location under fatigue using finite element analysis (FEA). Methods The 3D solid model of the cortical bone including osteons was constructed in Pro/E wildfire 5.0, and local stress and strain distributions in the cortical bone under different axial compression were calculated and analyzed in ANSYS 12.0. Fatigue simulation on the selected locations was conducted to evaluate fatigue status of the model subjected to different fatigue loading intensities. Results Obvious stress concentration at the junction of osteon and the interstitical bone appeared under axial compressive loads, and the percentage of pathological local strain in the cortical bone increased with the axial compression increasing. Fatigue simulation on the selected locations demonstrated that bone fatigue risk during physiological or daily activities was very low, while a high fatigue or fracture risk might occur during high-intensity exercises or training. Conclusions The 3D solid model of the cortical bone including osteons is successfully established, the stress concentration effect of osteons is verified, and the location of bone fatigue damage under strenuous exercise and its risk are predicted. These experimental results can provide references for training management and athletic fatigue damage prevention in military recruits and long distance running athletes.
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Objective To explore the effect of hypergravity on morphology and osteogenesis function of preosteoblast MC3T3-E1 cells. Methods The cultured MC3T3-E1 cells under hypergravity by different loading forces were divided into five groups, including control group, 5 g group, 10 g group, 15 g group and 20 g group. The experimental groups were loaded for 30 min each time in the three successive days, and the control group was synchronously exposed to the same surrounding except for difference in g-value. The morphology of cytoskeletal protein was observed by phalloidin staining, The alkaline phosphatase (ALP) content was examined by ALP activity assay kit, the gene expression of ALP, collagen Ⅰ(ColⅠ), osteocalcin (OC), runt-related transcription factors (Runx2) was measured by real-time quantitative PCR, and the protein expression of ColⅠ and OC was tested by Western blot. Results Under the condition of hypergravity, cell body of osteoblast became thinner, but its surface area increased significantly; with the structure of skeletal arrangement becoming loose, actin microfilament structure reduced so that arrangement of actin-like dispersion orderly lowered. The gene expressions of related indicators of osteogenic differentiation including ALP, ColⅠ, OC, Runx2 loaded by hypergravity were significantly up-regulated, which was the same as ColⅠ protein and OC protein after hypergravity loading. There was only a very minute quantity of small red-orange nodules in the control group, while the cells after hypergravity loading in experimental groups obviously formed various sizes of red-orange nodules. Conclusions Under hypergravity, changes in osteoblast morphology can be triggered by rearrangements of skeletal structure. Furthermore, osteoblast maturation and differentiation can be stimulated effectively by up-regulating differentiation-related gene and protein expressions.
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Objective To study the effect of the icariin on apoptosis and cytoskeleton of osteoblasts in response to overload damage. Methods The four-point bending loading device was used to simulate the mechanical environment of overload damage and establish the cell overload damage model. According to whether the drugs were added before or after mechanical loading, the experiment was divided into blank control group, icariin group, damage group, damage prevention group and damage treatment group. Cell apoptosis was detected by flow cytometry. The specific fluorescent dyes were used to label the actin filament and the nucleus, and the changes of cytoskeleton were observed under laser scanning confocal microscope. Results Compared with control group, the apoptosis rate of damage group was the highest, and the icariin group was the lowest (P<0.05). Compared with damage group, the apoptosis rate of the damage prevention group was the lowest (P<0.05). The damage group showed cell shrinkage deformation, microfilaments disorganization, loosely arranged skeleton with vague outline, even broken skeleton. The morphological changes of cytoskeleton in damage prevention group were not significant, and there was no obvious change in cell nucleus. Conclusions Icariin can inhibit the apoptosis of osteoblasts after overload injury and maintain the stability of cytoskeleton to some extent.
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Objective To construct a three-dimensional (3D) solid model of the cortical bone including osteons,verify the stress concentration effect of osteons,simulate and predict the stress concentration location under fatigue using finite element analysis (FEA).Methods The 3D solid model of the cortical bone including osteons was constructed in Pro/E wildfire 5.0,and local stress and strain distributions in the cortical bone under different axial compression were calculated and analyzed in ANSYS 12.0.Fatigue simulation on the selected locations was conducted to evaluate fatigue status of the model subjected to different fatigue loading intensities.Results Obvious stress concentration at the junction of osteon and the interstitical bone appeared under axial compressive loads,and the percentage of pathological local strain in the cortical bone increased with the axial compression increasing.Fatigue simulation on the selected locations demonstrated that bone fatigue risk during physiological or daily activities was very low,while a high fatigue or fracture risk might occur during high-intensity exercises or training.Conclusions The 3 D solid model of the cortical bone including osteons is successfully established,the stress concentration effect of osteons is verified,and the location of bone fatigue damage under strenuous exercise and its risk are predicted.These experimental results can provide references for training management and athletic fatigue damage prevention in military recruits and long distance running athletes.
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Objective To investigate the role and influence of physiological loading and overloading on microgravity-induced osteoporosis,so as to find a reliable way to prevent or treat related-orthopedic disorders in astronauts induced by long-time space activity.Metbods The microgravity environment in space was simulated by tail-suspension experiment,then the osteoporosis models of mice were built.A total of 32 C57BL/6J mice were randomly and evenly separated into four groups:normal group (normal),tail-suspension group (TS),physiological loading group (loading) and overloading group (overloading).Periodic dynamic mechanical load was applied on the left tibia in loading group and overloading group during tail-suspension test.After four weeks,tibial mechanical properties,micro-parameters of bone trabecular,biochemical indices and osteogenesis-related gene expression in each group were compared and analyzed.Results A great loss of tibial cancellous bone,significantly lower tibial biomechanical expression,serious damage of microstructure and weaker osteogenic activity were found in tail-suspended mice as compared with those of normal group.Physiological loading could clearly improve mechanical properties of bones,microstructure of bone trabecular,osteogenic activity and relative gene expression (P ＜ 0.05).Overloading could also improve the condition of microgravity-induced osteoporosis,but the effect was not obvious (P ＞ 0.05).Conclusions Tail-suspension can successfully simulate microgravity environment and duplicate osteoporosis model.Physiological loading can effectively prevent the emergence and development of microgravity-induced osteoporosis,while overloading can also counter microgravity-induced osteoporosis,but the results have no significant differences.
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Objective To explore the effect of hypergravity on morphology and osteogenesis function of preosteoblast MC3T3-E1 ceils.Methods The cultured MC3T3-E1 cells under hypergravity by different loading forces were divided into five groups,including control group,5 g group,10 g group,15 g group and 20 g group.The experimental groups were loaded for 30 min each time in 3 successive days,and the control group with no g-value was synchronously exposed to the same surrounding.The morphology of cytoskeletal protein was observed by phalIoidin staining,The alkaline phosphatase (ALP) content was examined by ALP activity assay kit,the gene expression of ALP,collagen Ⅰ (Col Ⅰ),osteocalcin (OC),runt-related transcription factors (Runx2) was measured by real-time quantitative PCR,and the protein expression of Col Ⅰ and OC was tested by Western blotting.Results Under the condition of hypergravity,cell body of osteoblast became thinner,but its surface area increased significantly;with the structure of skeletal arrangement becoming loose,actin microfilament structure reduced so that the orderly arrangement of actin-like dispersion lowered.The gene expressions of related indicators of osteogenic differentiation including ALP,Col][,OC,Runx2 were significantly up-regulated,which was the same as Col Ⅰ protein and OC protein after hypergravity loading.A very minute quantity of small red-orange nodules was found in the control group,while the cells in experimental groups after hypergravity loading obviously formed various sizes of red-orange nodules.Conclusions Under hypergravity,changes in osteoblast morphology can be triggered by rearrangements of skeletal structure.Furthermore,osteoblast maturation and differentiation can be stimulated effectively by up-regulating differentiation-related gene and protein expressions.
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Objective To investigate the role and influence of physiological loading and overloading on microgravity-induced osteoporosis,so as to find a reliable way to prevent or treat related-orthopedic disorders in astronauts induced by long-time space activity.Metbods The microgravity environment in space was simulated by tail-suspension experiment,then the osteoporosis models of mice were built.A total of 32 C57BL/6J mice were randomly and evenly separated into four groups:normal group (normal),tail-suspension group (TS),physiological loading group (loading) and overloading group (overloading).Periodic dynamic mechanical load was applied on the left tibia in loading group and overloading group during tail-suspension test.After four weeks,tibial mechanical properties,micro-parameters of bone trabecular,biochemical indices and osteogenesis-related gene expression in each group were compared and analyzed.Results A great loss of tibial cancellous bone,significantly lower tibial biomechanical expression,serious damage of microstructure and weaker osteogenic activity were found in tail-suspended mice as compared with those of normal group.Physiological loading could clearly improve mechanical properties of bones,microstructure of bone trabecular,osteogenic activity and relative gene expression (P ＜ 0.05).Overloading could also improve the condition of microgravity-induced osteoporosis,but the effect was not obvious (P ＞ 0.05).Conclusions Tail-suspension can successfully simulate microgravity environment and duplicate osteoporosis model.Physiological loading can effectively prevent the emergence and development of microgravity-induced osteoporosis,while overloading can also counter microgravity-induced osteoporosis,but the results have no significant differences.
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Objective To explore the effect of hypergravity on morphology and osteogenesis function of preosteoblast MC3T3-E1 ceils.Methods The cultured MC3T3-E1 cells under hypergravity by different loading forces were divided into five groups,including control group,5 g group,10 g group,15 g group and 20 g group.The experimental groups were loaded for 30 min each time in 3 successive days,and the control group with no g-value was synchronously exposed to the same surrounding.The morphology of cytoskeletal protein was observed by phalIoidin staining,The alkaline phosphatase (ALP) content was examined by ALP activity assay kit,the gene expression of ALP,collagen Ⅰ (Col Ⅰ),osteocalcin (OC),runt-related transcription factors (Runx2) was measured by real-time quantitative PCR,and the protein expression of Col Ⅰ and OC was tested by Western blotting.Results Under the condition of hypergravity,cell body of osteoblast became thinner,but its surface area increased significantly;with the structure of skeletal arrangement becoming loose,actin microfilament structure reduced so that the orderly arrangement of actin-like dispersion lowered.The gene expressions of related indicators of osteogenic differentiation including ALP,Col][,OC,Runx2 were significantly up-regulated,which was the same as Col Ⅰ protein and OC protein after hypergravity loading.A very minute quantity of small red-orange nodules was found in the control group,while the cells in experimental groups after hypergravity loading obviously formed various sizes of red-orange nodules.Conclusions Under hypergravity,changes in osteoblast morphology can be triggered by rearrangements of skeletal structure.Furthermore,osteoblast maturation and differentiation can be stimulated effectively by up-regulating differentiation-related gene and protein expressions.
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In the environment of adaptive mechanics, osteoblasts, which are the main functional cells of bone formation, are one of the main cells in response to the mechanical loading. With the development of technology, more and more astronauts, pilots and other are exposed to the hypergravity environment. In order to better understand the mechanobiology response of osteoblasts under hypergravity, this paper reviews the mechanobiological research progress in morphology, gene expression, cytokine secretion and signal transduction pathways of ostoblasts, so as to thoughts and preparations for mechanobiology research of bone tissues in hypergravity environment.
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The growth and metabolism of bone are controlled by osteogenesis of osteoblasts and absorption of osteoclasts, and osteoblasts play a main role in the process of osteogenesis. Overload will affect proliferation and differentiation of osteoblasts, while the loading mode, intensity, duration and other factors can change the biological properties of osteoblasts and further affect the functional activity of osteoblasts. However, the mechanism of osteoblast response to overload is still at the exploratory stage and needs in-depth study. Numerous studies have demonstrated that icariin, a kind of Chinese herbal medicine, can promote proliferation and differentiation of osteoblasts, and icariin with a certain concentration plays an important role in the repair of osteoblast injuries. In this paper, the response of osteoblasts to overload stimulation and repair of osteoblast injuries by icariin were summarized.
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Bone growth, development and maintenance, which become multidisciplinary with the rapid development of biomechanics, tissue engineering and cell biology, are intimately linked with bone remodeling. Mechanobiology has become an important method to study bone remodeling. This article summarizes related skeletal mechanobiology researches in recent years to provide theoretical basis for bone remodeling, bone tissue engineering and clinical treatments of related orthopedic disorders.
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Bone, acting as the main load-bearing organ in human body, is of mechanical adaptability. It is prevalent but perilous that under fatigue loading, bone suffers from fatigue damage characterized as the initiation, propagation of micro-cracks, deterioration of bone mechanical properties or even stress fracture, which is commonly seen in long distance running of athletes, fitness training of military recruits and daily activities of the elderly. Bone fatigue damages exist in multi-levels of ultra-micro structure, microstructure and macrostructure. The anti-fatigue units in cortical bone (osteons) and cellular components (osteocytes) inside have been proved to play important roles in fatigue damage prevention, micro-cracks recognition and bone-targeted remodeling activation. Therefore, a general review and summing-up of relative research findings can help to provide a systematic understanding of fatigue behavior and corresponding repair process, and to give some useful references and insights for subsequent clinical researches aiming at prevention and treatment for bone fatigue damage.
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Objective To investigate the effect of 1,25-(OH)2-vitamin D3 (VD3) or mechanical strain alone and their combined treatment on proliferation and differentiation of pre-osteoblast MC3T3-E1 cells in vitro, as well as gene and protein expression of osteoprotegerin (OPG) and receptor activator of nuclear factor-кB ligand (RANKL) in those cells. Methods MC3T3-E1 cells were treated with 10 nmol/L VD3, intermitted mechanical strain or with a combination of these two factors. Cell proliferation was assessed with flow cytometry, and alkaline phosphatase (ALP) activity was measured using a fluorometric detection kit. The mRNA expression of ALP, runt-related transcriptional factor 2 (Runx2), OPG, and RANKL genes was determined by real-time PCR. The proteins expression of Runx2, OPG, and RANKL was determined by Western blotting. ResultsVD3 inhibited the proliferation of MC3T3-E1 cells, but the mechanical strain had no effect on cell proliferation. Mechanical strain, VD3, and the combined treatment enhanced the ALP activity of MC3T3-E1 cells as well as the protein expression of Runx2. The effect of combined treatment was less pronounced than the effect of VD3 or mechanical strain alone. Mechanical strain promoted the gene and protein expression of osteoprotegerin (OPG) and increased the ratio of OPG/RANKL. However, the combination of VD3 and mechanical strain led to a decrease in ratio of OPG/RANKL. Conclusions Mechanical strain might be effective in inducing osteogenic differentiation and increasing bone formation. A joint stimulation with VD3 and strain can decrease proliferation and osteogenic differentiation and increase RANKL expression, which might affect bone remodeling. This study supplies some new data, which might be important in theoretical and clinical research of osteoporosis (OP) and other related bone diseases.
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Objective To investigate the loading rate-dependent property of different layers for articular cartilage by unconfined compression testing on articular cartilage at different loading rates. Methods The non-contact digital image correlation (DIC) technique was applied to investigate the mechanical properties of different layers for fresh pig articular cartilage at different loading rates. Results At constant loading rate, the compressive strain of superficial layer and deep layer was the largest, while that of middle layer was in between under the same compressive stress. The Poisson’s ratio increased from superficial layer to deep layer along with cartilage depth increasing. The stress-strain curves of cartilage were different at different loading rates, indicating that the mechanical properties of cartilage were dependent on the loading rate. The elastic modulus of cartilage increased with loading rates increasing, and the compressive strains of different layers decreased under the same compressive stress with loading rates increasing. Conclusions The compressive strain decreased while the Poisson’s ratio increased from superficial layer to deep layer along the cartilage depth. The mechanical properties of different layers for cartilage were dependent on the loading rate. This study can provide the basis for clinical cartilage disease prevention and treatment, and is important for mechanical function evaluation of artificial cartilage as well.
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<p><b>OBJECTIVES</b>To construct the cancellous bone explant model and a method of culturing these bone tissues in vitro, and to investigate the effect of mechanical load on growth of cancellous bone tissue in vitro.</p><p><b>METHODS</b>Cancellous bone were extracted from rabbit femoral head and cut into 1-mm-thick and 8-mm-diameter slices under sterile conditions. HE staining and scanning electron microscopy were employed to identify the histomorphology of the model after being cultured with a new dynamic load and circulating perfusion bioreactor system for 0, 3, 5, and 7 days, respectively. We built a three-dimensional model using microCT and analyzed the loading effects using finite element analysis. The model was subjected to mechanical load of 1000, 2000, 3000, and 4000 με respectively for 30 minutes per day. After 5 days of continuous stimuli, the activities of alkaline phosphatase (AKP) and tartrate-resistant acid phosphatase (TRAP) were detected. Apoptosis was analyzed by DNA ladder detection and caspase-3/8/9 activity detection.</p><p><b>RESULTS</b>After being cultured for 3, 5, and 7 days, the bone explant model grew well. HE staining showed the apparent nucleus in cells at the each indicated time, and electron microscope revealed the living cells in the bone tissue. The activities of AKP and TRAP in the bone explant model under mechanical load of 3000 and 4000 με were significantly lower than those in the unstressed bone tissues (all P<0.05). DNA ladders were seen in the bone tissue under 3000 and 4000 με mechanical load. Moreover, there was significant enhancement in the activities of caspase-3/8/9 in the mechanical stress group of 3000 and 4000 με(all P<0.05).</p><p><b>CONCLUSIONS</b>The cancellous bone explant model extracted from the rabbit femoral head could be alive at least for 7 days in the dynamic load and circulating perfusion bioreactor system, however, pathological mechanical load could affect the bone tissue growth by apoptosis in vitro. The differentiation of osteoblasts and osteoclasts might be inhibited after the model is stimulated by mechanical load of 3000 and 4000 με.</p>
Sujet(s)
Animaux , Mâle , Lapins , Acid phosphatase , Métabolisme , Phosphatase alcaline , Métabolisme , Apoptose , Développement osseux , Caspases , Métabolisme , Analyse des éléments finis , Isoenzymes , Métabolisme , Contrainte mécanique , Tartrate-resistant acid phosphatase , Microtomographie aux rayons XRÉSUMÉ
Objective To study mechanical properties of the medical water-jet scalpel when cutting parenchyma such as liver and verify its tissue-selective cutting characteristic. Methods The tension mechanical properties of porcine liver parenchyma and its vessels with different sizes were determined. Porcine and Wistar rat liver tissues were cut with arteriovenous vessels well reserved, and pathological section of the rats were analyzed by HE staining to explain the experimental phenomena. Results When the working pressure was set at 3 MPa, the incising and separating on the right lobe of porcine liver by medical water-jet scalpel in this experiment were done with minimal vessels of 0.8 mm in diameter left. Pathological sections from ordinary scalpel and medical water-jet scalpel showed that the medical water-jet scalpel caused smaller tissue damage. Conclusions The medical water-jet scalpel could cut heterogeneity soft tissue with highly-selective characteristics, which may effectively avoid the existing “one size fits all” phenomenon caused by ordinary scalpel.
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Objective To investigate the effect of mechanical loading with different magnitudes on the proliferation, differentiation and activity of preosteoclasts and osteoclasts. Methods One group of RAW264.7 preosteoclastic cells cultured in osteoclast inductive medium were subjected to the cyclic tensile strain for three days, and then cultured for four days; the other group of RAW264.7 cells were induced in osteoclast inductive medium for four days to be osteoclasts, then subjected to the cyclic tensile strain for three days. Results Under the tensile strain at different magnitudes, the proliferation variations in two groups of RAW264.7 cells were approximately identical, but changes in the activities of tartrate-resistant acid phosphatage (TRAP) and numbers of TRAP-positive multinucleated cells (osteoclasts) in the two groups were significantly different. Under the moderate tensile strain (2 500 με), the reduction of TRAP activity and osteoclasts number were both the highest in the first group, and both the lowest in the second group. Conclusions The influence of different tensile strain on osteoclast differentiation and osteoclastic activity of preosteoclasts in early differentiation is different to that of the preosteoclasts already differentiated into osteoclasts.
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Objective To investigate the effects of different vibration durations on expression level of osteogenesis-related proteins by loading low intensity mechanical vibration in the ovariectomized (OVX) rats. Methods Twenty-four 6-month old female Wistar rats were ovariectomized and then randomly divided into 8-week-control group (C8), 12-week-control group (C12), 8-week-vibration group (V8), and 12-week-vibration group (V12). Vibration treatment was started one week after all the rats were ovariectomized. Rats in both V8 and V12 groups were loaded with 35 Hz, 0.25 g low intensity mechanical vibration for 15 minutes per day. C8 and C12 groups served as control without any treatment. Rats were executed in batch at 8th and 12th week, respectively, to analyze expression level of osteogenesis-related proteins, including BMP-2, p-ERK, Runx2 and OCN. Results Low-intensity mechanical vibration enhanced the osteogenesis related protein expression in OVX rats (P<0.01). With the extension of vibration duration, the osteogenesis related proteins BMP-2、p-ERK、Runx2 and OCN in V12 group were increased by 22.61% (P<0.05), 27.96% (P<0.01), 25.85% (P<0.01), 27.05% (P<0.01), respectively, as compared with V8 group. But for the control groups, no significant differences were found in expression level of osteogenesis-related proteins. Conclusions The low intensity mechanical vibration could elevate expression level of osteogenesis-related proteins, and the osteogenesis was enhanced with the extension of vibration duration.
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Objective To simulate the internal structure of proximal tibia in both normal and valgus knees. Methods The internal structure of proximal tibia under normal mechanical environment was simulated using quantitative bone remodeling theory combined with finite element method. Based on this structure as the initial model and the changing pattern of pressure distributions on tibial plateau in valgus knee, the internal structure of proximal tibia in valgus knee was simulated with the action point of resultant force on the lateral tibial plateau. Results The simulated distributions of bone mineral density (BMD) were compared with the real tibia, and found the simulated results highly consistent with the actual ones both under normal mechanical environment and in valgus cases. Conclusions The method and the load distributions adopted in this study can accurately simulate and predict the internal structure of proximal tibia, thus could be served as the basis for further study on periprosthetic bone remodeling behavior after the total knee arthroplasty.