The vast osteocytic network is believed to orchestrate bone metabolic activity in response to mechanical stimuli through production of sclerostin, RANKL, and osteoprotegerin(OPG). However, the mechanisms of osteocyte ...The vast osteocytic network is believed to orchestrate bone metabolic activity in response to mechanical stimuli through production of sclerostin, RANKL, and osteoprotegerin(OPG). However, the mechanisms of osteocyte mechanotransduction remain poorly understood. We've previously shown that osteocyte mechanosensitivity is encoded through unique intracellular calcium (Ca^(2+) ) dynamics. Here, by simultaneously monitoring Ca^(2+) and actin dynamics in single cells exposed to fluid shear flow, we detected actin network contractions immediately upon onset of flow-induced Ca^(2+) transients, which were facilitated by smooth muscle myosin and further confirmed in native osteocytes ex vivo. Actomyosin contractions have been linked to the secretion of extracellular vesicles(EVs), and our studies demonstrate that mechanical stimulation upregulates EV production in osteocytes through immunostaining for the secretory vesicle marker Lysosomal-associated membrane protein 1(LAMP1) and quantifying EV release in conditioned medium, both of which are blunted when Ca^(2+) signaling was inhibited by neomycin. Axial tibia compression was used to induce anabolic bone formation responses in mice, revealing upregulated LAMP1 and expected downregulation of sclerostin in vivo. This load-related increase in LAMP1 expression was inhibited in neomycin-injected mice compared to vehicle.Micro-computed tomography revealed significant load-related increases in both trabecular bone volume fraction and cortical thickness after two weeks of loading, which were blunted by neomycin treatment. In summary, we found mechanical stimulation of osteocytes activates Ca^(2+) -dependent contractions and enhances the production and release of EVs containing bone regulatory proteins. Further, blocking Ca^(2+) signaling significantly attenuates adaptation to mechanical loading in vivo, suggesting a critical role for Ca^(2+) -mediated signaling in bone adaptation.展开更多
Osteoporotic hip fracture is associated with significant trabecular bone loss, which is typically characterized as low bone density by dual-energy X-ray absorptiometry （DXA） and altered microstructure by micro-compu...Osteoporotic hip fracture is associated with significant trabecular bone loss, which is typically characterized as low bone density by dual-energy X-ray absorptiometry （DXA） and altered microstructure by micro-computed tomography （pCT）. Emerging morphological analysis techniques, e.g. individual trabecula segmentation （ITS）, can provide additional insights into changes in plate-like and rod-like trabeculae, two major micro- structural types serving different roles in determining bone strength. Using ITS, we evaluated trabecular microstructure of intertrochanteric bone cores obtained from 23 patients undergoing hip replacement surgery for intertrochanteric fracture and 22 cadaveric controls. Micro-finite element （~FE） analyses were performed to further understand how the abnormalities seen by ITS might translate into effects on bone strength. ITS analyses revealed that, near fracture site, plate-like trabeculae were seriously depleted in fracture patients, but trabecular rod volume was maintained. Besides, decreased plate area and rod length were observed in fracture patients. Fracture patients also showed decreased elastic moduli and shear moduli of trabecular bone. These results provided evidence that in intertrochanteric hip fracture, preferential loss of plate-like trabeculae led to more rod-like microstructure and deteriorated mechanical competence adjacent to the fracture site, which increased our understanding of the biomechanical pathogenesis of hip fracture in osteoporosis.展开更多
Type 2 diabetes （T2D） is associated with systemic abnormal bone remodeling and bone loss. Meanwhile, abnormal subchondral bone remodeling induces cartilage degradation, resulting in osteoarthritis （OA）. Accordingl...Type 2 diabetes （T2D） is associated with systemic abnormal bone remodeling and bone loss. Meanwhile, abnormal subchondral bone remodeling induces cartilage degradation, resulting in osteoarthritis （OA）. Accordingly, we investigated alterations in subchondral bone remodeling, microstructure and strength in knees from T2D patients and their association with cartilage degradation. Tibial plateaus were collected from knee OA patients undergoing total knee arthroplasty and divided into non-diabetic （n---70） and diabetes （n = 51） groups. Tibial plateaus were also collected from cadaver donors （n = 20） and used as controls. Subchondral bone microstructure was assessed using micro-computed tomography. Bone strength was evaluated by micro-finite-element analysis. Cartilage degradation was estimated using histology. The expression of tartrate-resistant acidic phosphatase （TRAP）, osterix, and osteocalcin were calculated using immunohistochemistry. Osteoarthritis Research Society International （OARSI） scores of lateral tibial plateau did not differ between non-diabetic and diabetes groups, while higher OARSI scores on medial side were detected in diabetes group. Lower bone volume fraction and trabecular number and higher structure model index were found on both sides in diabetes group. These microstructural alterations translated into lower elastic modulus in diabetes group. Moreover, diabetes group had a larger number of TRAP~ osteoclasts and lower number of Osterix~ osteoprogenitors and Osteocalcin~ osteoblasts. T2D knees are characterized by abnormal subchondral bone remodeling and microstructural and mechanical impairments, which were associated with exacerbated cartilage degradation. In regions with intact cartilage the underlying bone still had abnormal remodeling in diabetes group, suggesting that abnormal bone remodeling may contribute to the early pathogenesis of T2D-associated knee OA.展开更多
Bone modeling and remodeling are governed by distinct biochemical processes that may hold unique opportunities for optimizing bone mass[1,2].Remodeling refers to the coupled resorption and subsequent formation on the ...Bone modeling and remodeling are governed by distinct biochemical processes that may hold unique opportunities for optimizing bone mass[1,2].Remodeling refers to the coupled resorption and subsequent formation on the bone surface,while modeling represents uncoupled formation or resorption.Mechanical loading is known to improve bone mass,though whether this occurs through modeling or remodeling(or by some combination)is unclear.Dynamic in vivo morphometry utilizing high resolution micro-CT and image registration has only recently become feasible and thus holds an untapped and expanding potential for understanding bone metabolism by quantifying and localizing formation/resorption and modeling/remodeling events.16-week-old mice were given 2 baseline weekly micro-CT scans of both tibiae prior to the initiation of daily unilateral loading(contralateral limb for nonloaded control).Weekly scanning and daily loading continued for 5 weeks.Registered images for each mouse in a global coordinate system revealed the time course of each voxel,and changes in bone mass were quantified as modeling or remodeling starting at the onset of loading.In cortical bone,after an initial response to loading in both regimes,modeling emerged as the dominant response.Loading effects were largest in areas of mechanical significance.For example,anabolic modeling on the periosteal surface of the half of the tibia in compression under axial load presented a strong effect of loading,whereas the same measure on the endosteal surface in the area in tension showed no difference.Similarly,in trabecular bone anabolic modeling was significantly increased with loading on trabecular plates but not rods(plates have been shown to be the major contributor to overall bone strength).The catabolic modeling response on the endosteal surface showed an interesting transition over time.Loading initially led to a significant suppression of catabolic modeling,but over time increased it to levels significantly beyond that of nonloaded controls.展开更多
Hispanic Americans of Caribbean origin are a fast-growing subset of the US population, but there are no studies on bone density, microstructure and biomechanical integrity in this minority group. In this study, we aim...Hispanic Americans of Caribbean origin are a fast-growing subset of the US population, but there are no studies on bone density, microstructure and biomechanical integrity in this minority group. In this study, we aimed to compare Caucasian and Caribbean Hispanic postmenopausal American women with respect to these characteristics. Thirty-three Caribbean Hispanics were age-matched to thirty-three Caucasian postmenopausal women. At the lumbar spine, the Hispanic women had significantly lower areal bone mineral density （aBMD）. At the radius by high-resolution peripheral quantitative computed tomography （HR-pQCT）, there were minimal differences between Hispanic and Caucasian women. At the tibia, Hispanic women had lower trabecular volumetric bone density and trabecular number, and higher trabecular separation. Individual trabecula segmentation （ITS） analyses indicated that at the tibia, Hispanic women not only had significantly lower bone volume fraction, but also had significantly lower rod bone volume fraction, plate trabecular number, rod trabecular number and lower plate-plate, plate-rod and rod-rod junction densities compared to Caucasian women. The differences in bone quantity and quality contributed to lower whole bone stiffness at the radius, and both whole bone and trabecular bone stiffness at the tibia in Hispanic women. In conclusion, Hispanic women had poorer bone mechanical and microarchitectural properties than Caucasian women, especially at the load-bearing distal tibia.展开更多
Osteocytes in vivo are embedded in the mineralized extracellular bone matrix,where their cell bodies reside in the lacunae and are interconnected to neighboring osteocytes through numerous intercellular processes.The ...Osteocytes in vivo are embedded in the mineralized extracellular bone matrix,where their cell bodies reside in the lacunae and are interconnected to neighboring osteocytes through numerous intercellular processes.The 3-dimensional（3D）osteocyte network positioning and ability to communicate with other bone cells make osteocytes ideal mechanosensors of bone.Thus the role of osteocyte network and intercellular communication between osteocytes in response to mechanical stimulation may clarify the mechanisms behind normal bone adaptation to mechanical loading.We have been using intracellular calcium([Ca<sup>2+</sup>]<sub>i</sub>)as a ubiquitous real-time signaling indicator for studying mechanotransduction in osteocytic network展开更多
Introduction Osteocytes are interconnected through numerous intercellular processes,forming extensive cell networks throughout the bone tissue[1]. It has been shown that osteocyte density is an important physiological...Introduction Osteocytes are interconnected through numerous intercellular processes,forming extensive cell networks throughout the bone tissue[1]. It has been shown that osteocyte density is an important physiological parameter,which decreases展开更多
A recent study published in Nature Communications demonstrated that restoring SERCA2 pump deficiency can enhance bone mechano-responsiveness in type 2 diabetes(T2D)by modulating osteocyte calcium dynamics.The findings...A recent study published in Nature Communications demonstrated that restoring SERCA2 pump deficiency can enhance bone mechano-responsiveness in type 2 diabetes(T2D)by modulating osteocyte calcium dynamics.The findings revealed that in T2D mice,the ability of the bone to respond to mechanical stress is compromised,primarily due to attenuated calcium oscillatory dynamics within osteocytes rather than in osteoblasts or osteoclasts.The underlying mechanism of this reduction in bone mechano-responsiveness in T2D was identified as a specific decrease in osteocytic SERCA2 expression mediated by PPARα.Additionally,mice overexpressing SERCA2 in osteocytes exhibited reduced deterioration of bone mechano-responsiveness induced by T2D.Collectively,this study provides mechanistic insights into T2D-induced deterioration in bone mechanoresponsiveness and identifies a promising therapeutic approach to counteract T2D-associated fragility fractures.展开更多
A recent study published in Cell Metabolism entitled“Gut microbial alterations in arginine metabolism determine bone mechanical adaptation”demonstrated that administration of L-arginine enhanced bone mechanical adap...A recent study published in Cell Metabolism entitled“Gut microbial alterations in arginine metabolism determine bone mechanical adaptation”demonstrated that administration of L-arginine enhanced bone mechanical adaptation by activating a nitric oxide-calcium feedback loop in osteocytes.The findings revealed that mechanical regulation of bone adaptation is associated with gut microbiota.The underlying cause of heterogeneity of bone mechanoresponsiveness was the significant difference in the composition of the gut microbiota,in which the family Lachnospiraceae contributed to the inter-individual high variability in bone mechanical adaptation.Additionally,administration of Lachnospiraceae exhibited increased expression levels of L-citrulline and L-arginine and enhanced bone mechanoresponsiveness in recipients.Collectively,this study provides mechanistic insights into inter-individual variability of the gut microbial,which is related to the heterogeneity of bone mechanical adaptation and provides a novel preventive and therapeutic strategy to anti-osteoporotic for maximizing bone mechanoresponsiveness via the microbiota-metabolite axis.展开更多
Bone adapts to mechanical loading by changing its shape and mass.Osteocytes,as major mechanosensors,are critical for bone modeling/remodeling in response to mechanical stimuli.Intracellular calcium oscillation is one ...Bone adapts to mechanical loading by changing its shape and mass.Osteocytes,as major mechanosensors,are critical for bone modeling/remodeling in response to mechanical stimuli.Intracellular calcium oscillation is one of the early responses in osteocytes,and this further facilitates bone cell communication through released biochemical signals.Our previous study has found that mechanically induced calcium oscillations in osteocytes enhance the release of extracellular vesicles(EVs),and those released EVs can elevate bone formation activity.However,the mechanism of mechanically stimulated EVs’regulation of bone formation and resorption is still unclear.Here,using in vitro studies,we exposed OCY454 cells,with relatively high sclerostin expression,to steady fluid flow(SFF)and characterized the functions of rapidly released EVs in osteoblast and osteoclast regulation.Our study demonstrates that SFF stimulates intracellular calcium response in OCY454 cells and further induces sclerostin,osteoprotegerin(OPG),receptor activator of NF-κB ligand(RANKL)inside or outside EVs to regulate osteoblast and osteoclast activities.This load-induced protein and EVs release is load-duration dependent.Moreover,stimulated osteocytes rapidly regulate osteoclast maturation through EVs capsulated RANKL.In contrast,other regulating proteins,OPG,and sclerostin,are mainly released directly into the medium without EV capsulation.展开更多
基金supported by NIH R01 AR052461 and NIH R01 AR069148supported by a NSF Graduate Research Fellowship. A. E. M.supported by training grant T32 AR059038
文摘The vast osteocytic network is believed to orchestrate bone metabolic activity in response to mechanical stimuli through production of sclerostin, RANKL, and osteoprotegerin(OPG). However, the mechanisms of osteocyte mechanotransduction remain poorly understood. We've previously shown that osteocyte mechanosensitivity is encoded through unique intracellular calcium (Ca^(2+) ) dynamics. Here, by simultaneously monitoring Ca^(2+) and actin dynamics in single cells exposed to fluid shear flow, we detected actin network contractions immediately upon onset of flow-induced Ca^(2+) transients, which were facilitated by smooth muscle myosin and further confirmed in native osteocytes ex vivo. Actomyosin contractions have been linked to the secretion of extracellular vesicles(EVs), and our studies demonstrate that mechanical stimulation upregulates EV production in osteocytes through immunostaining for the secretory vesicle marker Lysosomal-associated membrane protein 1(LAMP1) and quantifying EV release in conditioned medium, both of which are blunted when Ca^(2+) signaling was inhibited by neomycin. Axial tibia compression was used to induce anabolic bone formation responses in mice, revealing upregulated LAMP1 and expected downregulation of sclerostin in vivo. This load-related increase in LAMP1 expression was inhibited in neomycin-injected mice compared to vehicle.Micro-computed tomography revealed significant load-related increases in both trabecular bone volume fraction and cortical thickness after two weeks of loading, which were blunted by neomycin treatment. In summary, we found mechanical stimulation of osteocytes activates Ca^(2+) -dependent contractions and enhances the production and release of EVs containing bone regulatory proteins. Further, blocking Ca^(2+) signaling significantly attenuates adaptation to mechanical loading in vivo, suggesting a critical role for Ca^(2+) -mediated signaling in bone adaptation.
基金This work was partially supported by grants from National Institutes of Health(AR051376,AR058004)
文摘Osteoporotic hip fracture is associated with significant trabecular bone loss, which is typically characterized as low bone density by dual-energy X-ray absorptiometry （DXA） and altered microstructure by micro-computed tomography （pCT）. Emerging morphological analysis techniques, e.g. individual trabecula segmentation （ITS）, can provide additional insights into changes in plate-like and rod-like trabeculae, two major micro- structural types serving different roles in determining bone strength. Using ITS, we evaluated trabecular microstructure of intertrochanteric bone cores obtained from 23 patients undergoing hip replacement surgery for intertrochanteric fracture and 22 cadaveric controls. Micro-finite element （~FE） analyses were performed to further understand how the abnormalities seen by ITS might translate into effects on bone strength. ITS analyses revealed that, near fracture site, plate-like trabeculae were seriously depleted in fracture patients, but trabecular rod volume was maintained. Besides, decreased plate area and rod length were observed in fracture patients. Fracture patients also showed decreased elastic moduli and shear moduli of trabecular bone. These results provided evidence that in intertrochanteric hip fracture, preferential loss of plate-like trabeculae led to more rod-like microstructure and deteriorated mechanical competence adjacent to the fracture site, which increased our understanding of the biomechanical pathogenesis of hip fracture in osteoporosis.
基金supported by National Natural Science Foundation of China(NSFC Nos.81601930 and U1613224)Natural Science Foundation of Guangxi(2016JJB140050)+1 种基金Research Grant Council of Hong Kong(HKU715213 and 17206916)Shenzhen Peacock Project
文摘Type 2 diabetes （T2D） is associated with systemic abnormal bone remodeling and bone loss. Meanwhile, abnormal subchondral bone remodeling induces cartilage degradation, resulting in osteoarthritis （OA）. Accordingly, we investigated alterations in subchondral bone remodeling, microstructure and strength in knees from T2D patients and their association with cartilage degradation. Tibial plateaus were collected from knee OA patients undergoing total knee arthroplasty and divided into non-diabetic （n---70） and diabetes （n = 51） groups. Tibial plateaus were also collected from cadaver donors （n = 20） and used as controls. Subchondral bone microstructure was assessed using micro-computed tomography. Bone strength was evaluated by micro-finite-element analysis. Cartilage degradation was estimated using histology. The expression of tartrate-resistant acidic phosphatase （TRAP）, osterix, and osteocalcin were calculated using immunohistochemistry. Osteoarthritis Research Society International （OARSI） scores of lateral tibial plateau did not differ between non-diabetic and diabetes groups, while higher OARSI scores on medial side were detected in diabetes group. Lower bone volume fraction and trabecular number and higher structure model index were found on both sides in diabetes group. These microstructural alterations translated into lower elastic modulus in diabetes group. Moreover, diabetes group had a larger number of TRAP~ osteoclasts and lower number of Osterix~ osteoprogenitors and Osteocalcin~ osteoblasts. T2D knees are characterized by abnormal subchondral bone remodeling and microstructural and mechanical impairments, which were associated with exacerbated cartilage degradation. In regions with intact cartilage the underlying bone still had abnormal remodeling in diabetes group, suggesting that abnormal bone remodeling may contribute to the early pathogenesis of T2D-associated knee OA.
基金supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases ( R01 AR069148)
文摘Bone modeling and remodeling are governed by distinct biochemical processes that may hold unique opportunities for optimizing bone mass[1,2].Remodeling refers to the coupled resorption and subsequent formation on the bone surface,while modeling represents uncoupled formation or resorption.Mechanical loading is known to improve bone mass,though whether this occurs through modeling or remodeling(or by some combination)is unclear.Dynamic in vivo morphometry utilizing high resolution micro-CT and image registration has only recently become feasible and thus holds an untapped and expanding potential for understanding bone metabolism by quantifying and localizing formation/resorption and modeling/remodeling events.16-week-old mice were given 2 baseline weekly micro-CT scans of both tibiae prior to the initiation of daily unilateral loading(contralateral limb for nonloaded control).Weekly scanning and daily loading continued for 5 weeks.Registered images for each mouse in a global coordinate system revealed the time course of each voxel,and changes in bone mass were quantified as modeling or remodeling starting at the onset of loading.In cortical bone,after an initial response to loading in both regimes,modeling emerged as the dominant response.Loading effects were largest in areas of mechanical significance.For example,anabolic modeling on the periosteal surface of the half of the tibia in compression under axial load presented a strong effect of loading,whereas the same measure on the endosteal surface in the area in tension showed no difference.Similarly,in trabecular bone anabolic modeling was significantly increased with loading on trabecular plates but not rods(plates have been shown to be the major contributor to overall bone strength).The catabolic modeling response on the endosteal surface showed an interesting transition over time.Loading initially led to a significant suppression of catabolic modeling,but over time increased it to levels significantly beyond that of nonloaded controls.
基金supported by NIH Grants R01 AR051376 (XEG), NIH R01 AR058004 (XEG, ES), NIH U01 AR055968 (ES)the Thomas L.Kempner and Katheryn C.Patterson Foundation
文摘Hispanic Americans of Caribbean origin are a fast-growing subset of the US population, but there are no studies on bone density, microstructure and biomechanical integrity in this minority group. In this study, we aimed to compare Caucasian and Caribbean Hispanic postmenopausal American women with respect to these characteristics. Thirty-three Caribbean Hispanics were age-matched to thirty-three Caucasian postmenopausal women. At the lumbar spine, the Hispanic women had significantly lower areal bone mineral density （aBMD）. At the radius by high-resolution peripheral quantitative computed tomography （HR-pQCT）, there were minimal differences between Hispanic and Caucasian women. At the tibia, Hispanic women had lower trabecular volumetric bone density and trabecular number, and higher trabecular separation. Individual trabecula segmentation （ITS） analyses indicated that at the tibia, Hispanic women not only had significantly lower bone volume fraction, but also had significantly lower rod bone volume fraction, plate trabecular number, rod trabecular number and lower plate-plate, plate-rod and rod-rod junction densities compared to Caucasian women. The differences in bone quantity and quality contributed to lower whole bone stiffness at the radius, and both whole bone and trabecular bone stiffness at the tibia in Hispanic women. In conclusion, Hispanic women had poorer bone mechanical and microarchitectural properties than Caucasian women, especially at the load-bearing distal tibia.
基金supported by the US National Institutes of Health grants R21 AR052417,R01 AR052461,RC1 AR058453(XEG),and R01 AR054385(LW)
文摘Osteocytes in vivo are embedded in the mineralized extracellular bone matrix,where their cell bodies reside in the lacunae and are interconnected to neighboring osteocytes through numerous intercellular processes.The 3-dimensional（3D）osteocyte network positioning and ability to communicate with other bone cells make osteocytes ideal mechanosensors of bone.Thus the role of osteocyte network and intercellular communication between osteocytes in response to mechanical stimulation may clarify the mechanisms behind normal bone adaptation to mechanical loading.We have been using intracellular calcium([Ca<sup>2+</sup>]<sub>i</sub>)as a ubiquitous real-time signaling indicator for studying mechanotransduction in osteocytic network
基金supported by US National Institute of Health grants (National Institute of Arthritis and Musculoskeletal and Skin Diseases) R21 AR052417,R01 AR1R052461,and RC1 AR058453
文摘Introduction Osteocytes are interconnected through numerous intercellular processes,forming extensive cell networks throughout the bone tissue[1]. It has been shown that osteocyte density is an important physiological parameter,which decreases
文摘A recent study published in Nature Communications demonstrated that restoring SERCA2 pump deficiency can enhance bone mechano-responsiveness in type 2 diabetes(T2D)by modulating osteocyte calcium dynamics.The findings revealed that in T2D mice,the ability of the bone to respond to mechanical stress is compromised,primarily due to attenuated calcium oscillatory dynamics within osteocytes rather than in osteoblasts or osteoclasts.The underlying mechanism of this reduction in bone mechano-responsiveness in T2D was identified as a specific decrease in osteocytic SERCA2 expression mediated by PPARα.Additionally,mice overexpressing SERCA2 in osteocytes exhibited reduced deterioration of bone mechano-responsiveness induced by T2D.Collectively,this study provides mechanistic insights into T2D-induced deterioration in bone mechanoresponsiveness and identifies a promising therapeutic approach to counteract T2D-associated fragility fractures.
文摘A recent study published in Cell Metabolism entitled“Gut microbial alterations in arginine metabolism determine bone mechanical adaptation”demonstrated that administration of L-arginine enhanced bone mechanical adaptation by activating a nitric oxide-calcium feedback loop in osteocytes.The findings revealed that mechanical regulation of bone adaptation is associated with gut microbiota.The underlying cause of heterogeneity of bone mechanoresponsiveness was the significant difference in the composition of the gut microbiota,in which the family Lachnospiraceae contributed to the inter-individual high variability in bone mechanical adaptation.Additionally,administration of Lachnospiraceae exhibited increased expression levels of L-citrulline and L-arginine and enhanced bone mechanoresponsiveness in recipients.Collectively,this study provides mechanistic insights into inter-individual variability of the gut microbial,which is related to the heterogeneity of bone mechanical adaptation and provides a novel preventive and therapeutic strategy to anti-osteoporotic for maximizing bone mechanoresponsiveness via the microbiota-metabolite axis.
文摘Bone adapts to mechanical loading by changing its shape and mass.Osteocytes,as major mechanosensors,are critical for bone modeling/remodeling in response to mechanical stimuli.Intracellular calcium oscillation is one of the early responses in osteocytes,and this further facilitates bone cell communication through released biochemical signals.Our previous study has found that mechanically induced calcium oscillations in osteocytes enhance the release of extracellular vesicles(EVs),and those released EVs can elevate bone formation activity.However,the mechanism of mechanically stimulated EVs’regulation of bone formation and resorption is still unclear.Here,using in vitro studies,we exposed OCY454 cells,with relatively high sclerostin expression,to steady fluid flow(SFF)and characterized the functions of rapidly released EVs in osteoblast and osteoclast regulation.Our study demonstrates that SFF stimulates intracellular calcium response in OCY454 cells and further induces sclerostin,osteoprotegerin(OPG),receptor activator of NF-κB ligand(RANKL)inside or outside EVs to regulate osteoblast and osteoclast activities.This load-induced protein and EVs release is load-duration dependent.Moreover,stimulated osteocytes rapidly regulate osteoclast maturation through EVs capsulated RANKL.In contrast,other regulating proteins,OPG,and sclerostin,are mainly released directly into the medium without EV capsulation.
