| BackgroundsAs a systemic skeletal disease, osteoporosis (OP) is characterized by bone loss, degradation of bone tissue microstructure, and the resulting in increasing of bone brittleness and easy fracture. Bone remodeling is a self-renewal process, including absorbing bone by osteoclasts and forming new bone constantly by osteoblasts on the resorption bone. Osteoclasts play an important role in maintaining stable bone mass in the remodeling process after bones mature. More or osteoclast activity increased results in increased bone resorption and bone remodeling imbalance, and even leads to the occurrence of many bone diseases such as:OP. There had been more than90millions patients in China. Its incidence has leapt to the7th of common diseases. One of OP’S major complication is OP fractures, a common disease which is harmful to the health of the elderly, Especially in the postmenopausai women. Fracture of hip, which had obviously decreased activity and a High mortality, was thought as the most dangerous consequence in osteoporosis. With ageing and prolonging of life, the rate of osteoporotic fracture increased by1%each year in the world. To deal with the problem,we had to seek more effective and convenient non-pharmacal ways for osteoporosis prevention and treatment. At present, there are two aim of the treatment for osteoporosis. One is to relieve ache, the other is to prevent the happening of the pathological fracture. The clinical treatments ofosteoporosis include drug therapy, physical therapy and surgical treatment, etc. The drug treatment has been become as the main method. Clinical commonly used drugs for preventing osteoporosis include five categories, such as bone formation actived agent, bone resorption inhibited agent, uncoupler, bone mineralization agent and traditional Chinese medicine. Now more and more patients take bone resorption inhibited drug to prevent osteoporosis, such as bisphostates that is the main anti-osteoporosis drug. Bisphostates which can inhibit osteoclast activity to reduce bone resorption, to increase bone mineral density and bone turnover, can reduce the incidence of vertebral body and the vertebral fracture which has been confirmed in clinical researches. Alendronate, which is the third generation representative drug of bisphostates, is a drug widely used for preventing osteoporosis in the clinical. Alendronate (ALE) is one of the traditional medicines for the treatment of OP. ALE can inhibit bone absorption, improve the quality of the bone. At the same time, ALE also can relieve lower back pain and improve the quality of life of senile osteoporosis. But there are some side effects, especially the gastrointestinal tract reaction, limiting some osteoporosis patients using this drug. With the development of social economy and the transformation of medical model, more and more attention has turned to non-drug methods and measures.In recent years, the studies of prevention OP using physical therapy (mechanics, electromagnetism) have become hotspot. Wolff law shows that the bone remodels to adapt to the needs of function and the changes of the mechanical stress. So the mechanical stress loading on osteocytes within the bone is the original power for bone reconstruction. A certain frequency and intensity are required for vibration inducing osteoblastic bone formation. Two low intensity or frequency is hard to reach the stimulation for bone formation. While too high-intensity, vibration is harmful to human. Many researches confirmed that high frequency(>30Hz), low level(<l g)and short time(<30minutes)mechanical vibration could regulate bone metabolism, inhibit bone absorption and promote bone formation. On the other hand, it also could increase muscle mass, and improve muscle force and be helpful in balance control. Thus, the mechanical vibration signal that is lower than that leading to injury the bone tissue, has a strong osteogenic effect. It not only can prevent bone loss, but also improve the bone structure and mechanical properties of biology. So vibration is a non-invasive, non-pharmacological and safe treatment for osteoporosis. However, there have been no published studies investigating the effect of low-magnitude WBV combined with ALE in ovariectomized rats.Objectives1. To evaluate the preventive effects of high frequency and low level compound vibration on ovariectomized rats;2. To evaluate the preventive effects of alendronate on ovariectomized rats;3. To differentiate the effect in ovariectomized rats between conventionally alendronate drug and low-magnitude whole-body vibration.4. To investigate the effect of low-magnitude WBV combined with ALE in ovariectomized rats5. To determine whether low-magnitude WBV could enhance the effect of ALE on bone turnover and bone properties in ovariectomized rats.Methods1. To evaluate the preventive effects of high frequency and low level compound vibration on ovariectomized rats1.1Materials and methods:A total of80Sprague-Dawley rats were randomly divided into three groups (SHAM, OVX+VEH, OVX+WBV). The sham group not received ovariectomy and the other two treat groups received ovariectomy. The level of WBV was applied0.3g at45-55Hz for20min/day,5day/week, for12weeks. VEH was administered in dose of1mg/Kg, once a week.1.2Measurements:During the experimental period, the body weight of the rats in all groups was measured using electronic scale and was recorded every four weeks during the experimental period. The rats were sacrificed at four predetermined time points for the Sham group (0,4,8and12weeks) and three time points for the remaining four groups (4,8and12weeks). Every four weeks, eight rats from each group were sacrificed and their blood and both tibiae were harvested. At sacrifice, whole blood was collected with a cardiac puncture to determine the serum osteocalcin (OC) and CTX (C-terminal cross-linked telopeptides of type I collagen, CTX) using standard laboratory techniques. The bilateral tibiae were collected, with the soft tissues being thoroughly removed and wrapped in normal saline-soaked gauze and stored at-20℃until further use for biomechanical testing and micro-CT scanning.2. To investigate the effect of ALE on ovariectomized rats2.1Materials and methods:A total of80Sprague-Dawley rats were randomly divided into three groups (SHAM, OVX+VEH, OVX+ALE). The sham group not received ovariectomy and the other two treat groups received ovariectomy. VEH and ALE were administered in dose of1mg/Kg, once a week.2.2Measurements:During the experimental period, the body weight of the rats in all groups was measured using electronic scale and was recorded every four weeks during the experimental period. The rats were sacrificed at four predetermined time points for the Sham group (0,4,8and12weeks) and three time points for the remaining four groups (4,8and12weeks). Every four weeks, eight rats from each group were sacrificed and their blood and both tibiae were harvested. At sacrifice, whole blood was collected with a cardiac puncture to determine the serum osteocalcin (OC) and CTX (C-terminal cross-linked telopeptides of type I collagen, CTX) using standard laboratory techniques. The bilateral tibiae were collected, with the soft tissues being thoroughly removed and wrapped in normal saline-soaked gauze and stored at-20℃ until further use for biomechanical testing and micro-CT scanning.3. To investigate the effect of low-magnitude WBV combined with ALE in ovariectomized rats3.1Materials and methods:A total of128Sprague-Dawley rats were randomly divided into five groups (SHAM, OVX+VEH, OVX+WBV, OVX+ALE, OVX+WBV+ALE). The sham group not received ovariectomy and the other four treat groups received ovariectomy. The level of WBV was applied0.3g at45-55Hz for20min/day,5day/week, for12weeks. VEH and ALE were administered in dose of1mg/Kg, once a week.3.2Measurements:During the experimental period, the body weight of the rats in all groups was measured using electronic scale and was recorded every four weeks during the experimental period. The rats were sacrificed at four predetermined time points for the Sham group (0,4,8and12weeks) and three time points for the remaining four groups (4,8and12weeks). Every four weeks, eight rats from each group were sacrificed and their blood and both tibiae were harvested. At sacrifice, whole blood was collected with a cardiac puncture to determine the serum osteocalcin (OC) and CTX (C-terminal cross-linked telopeptides of type I collagen, CTX) using standard laboratory techniques. The bilateral tibiae were collected, with the soft tissues being thoroughly removed and wrapped in normal saline-soaked gauze and stored at-20℃until further use for biomechanical testing and micro-CT scanning.Results1. To evaluate the preventive effects of high frequency and low level compound vibration on ovariectomized rats1.1The change of experimental rats weight and uterus index:The rat weight increased significantly after the ovary removed (P<0.001), but the uterus weight reduced significantly (P<0.001).1.2The results of serum markers:Osteocalcin (OC) and CTX rose with ovariectomy. They were not appreciably changed by WBV. 1.3The bone microstructure results of the tibia measured by Micro-CT:Compared with the Sham group, nearly all tested indices were lower in the OVX+VEH group at week12, such as the BV/TV, Tb. N, Tb. T h, Tb. Sp and Conn. D. Moreover, compared with the OVX+VEH group, the BV/TV (+38.1%, P<0.001), Tb. N (+12.3%, P=0.015), Tb. Th (+33.7%, P=0.001), and Conn. D (+47.5%, P=0.029) were higher, and the SMI (-17.9%, P=0.003) was lower in the OVX+WBV group.1.4Three point bending experiment result of tibiae:All biomechanical parameters in various time points showed no significant difference between the OVX+VEH and OVX+WBV groups. All biomechanical parameters at week4also showed no significant difference between the OVX+VEH and Sham group. However, compared with the Sham group, all biomechanical parameters were lower in the OVX+VEH group at week8and week12.2. To investigate the effect of ALE in ovariectomized rats2.1The results of serum markers:Osteocalcin (OC) and CTX rose with ovariectomy. The level of OC was not appreciably changed by alendronate alone. Alendronate treatment significantly prevented an increase in this CTX serum marker.2.2The bone microstructure results of the tibia measured by Micro-CT:Compared with the Sham group, nearly all tested indices were lower in the OVX+VEH group at week12, such as the BV/TV, Tb. N, Tb. T h, Tb. Sp and Conn. D. Moreover, compared with the OVX+VEH group, nearly all tested indices were higher in the OVX+ALE group at week12, such as the BV/TV (+73%, P<0.001), TV apparent (+89.9%, P<0.001), Tb. N (+29.9%, P<0.001), Tb. T h (+56.3%, P<0.001), and Conn. D (+53.6%, P=0.012), and the SMI (-31.3%, P<0.001) and Tb. Sp (-38.7%, P=0.027) were lower in the OVX+ALE group.2.3Three point bending experiment result of tibiae:All biomechanical parameters at week4also showed no significant difference between the OVX+VEH and Sham group. However, compared with the Sham group, all biomechanical parameters were lower in the OVX+VEH group at week8and week12. Compared with the OVX+VEH (69.80±9.23N) group, the F max were higher in the OVX+ALE group (+27.6%, P=0.009) at week12. At week12, compared with the OVX+VEH group (52.03±1.58N), bone energy absorption were higher in the OVX+ALE group (66.27±2.64N,+27.4%, P=0.040). However, there were no significant differences for stiffness at any point in the two study groups examined.3. To investigate the effect of low-magnitude WBV combined with ALE in ovariectomized rats3.1The results of serum markers:Osteocalcin (OC) and CTX rose with ovariectomy. The level of OC was not appreciably changed by WBV combined ALE. WBV+ALE treatment significantly prevented an increase in this CTX serum marker.3.2The bone microstructure results of the tibia measured by Micro-CT:Compared with the Sham group, nearly all tested indices were lower in the OVX+VEH group at week12, such as the BV/TV, Tb. N, Tb. T h, Tb. Sp and Conn. D. Compared with the OVX+WBV group, the BV/TV (+25.3%, p=0.004), TV apparent (+60.3%, P<0.001), BV material (+28.4%, P=0.044), Tb. N (+15.6%, P=0.001), and Tb. T h (+16.9%, p=0.037) were higher, and the SMI (-16.4%, p=0.013) was lower in the OVX+ALE group at week12. At week12, significant differences were found for some tested indices between the OVX+ALE and OVX+WBV+ALE groups. Compared with the OVX+ALE group, the BV/TV (+25%, p=0.001), TV apparent (+30.4%, P=0.032), Tb. N (+10%, P=0.015), and Con. D (+44.5%, p=0.042) were higher, and the SMI (-18.4%, p=0.042) was lower in the OVX+WBV+ALE group.3.3Three point bending experiment result of tibiae:All biomechanical parameters at week4also showed no significant difference between the OVX+VEH and Sham group. However, compared with the Sham group, all biomechanical parameters were lower in the OVX+VEH group at week8and week12. Compared with the OVX+VEH (69.80+-9.23N) group, the F M were higher in the OVX+WBV+ALE group (89.86±6.21N,+28.7%, P=0.008) at week12. At week12, compared with the OVX+VEH group (52.03±1.58N), bone energy absorption were higher in the OVX+WBV+ALE group (76.81±3.23N,+47.6%, P=0.003). However, there were no significant differences for stiffness at any point in the four study groups examined.Conclusions1. Low-magnitude, high-frequency whole body vibration can increase bone formation and improve bone microstructure.2. Alendronate can inhibit osteoclaste activity, reduce bone resorption, inhibit bone transformation. Alendronate also can improve the microstructure and biomechanical properties of cancellous bone.3. Compared with the WBV, ALE was more effective at preventing bone loss and improved the trabecular architecture. Moreover, WBV enhance the effect of alendronate in ovariectomized rats by inducing further improvements in trabecular architecture. |
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