BACKGROUND:Parkinson's disease has the main pathological changes in the midbrain,especially in the dense substantia nigra,leading to impaired motor and non-motor function in patients.At present,research is limited by cellular heterogeneity,and its pathogenesis still needs to be further elucidated.In recent years,single-cell RNA sequencing(scRNA-seq)has gradually been applied in neurodegenerative diseases,which is of great significance for understanding intercellular heterogeneity,disease development mechanisms,and treatment strategies. OBJECTIVE:To review the research progress of scRNA-seq technology applied to Parkinson's disease in recent years,providing a theoretical basis for the application of scRNA-seq in the treatment and diagnosis of Parkinson's disease. METHODS:The first author used a computer system to search for relevant literature in the CNKI,WanFang,PubMed,and Web of Science databases,with the Chinese search terms"single-cell RNA sequencing,Parkinson's disease,cell heterogeneity,cell subtypes,dopaminergic neurons,glial cells"and English search terms"single-cell RNA seq,Parkinson disease,heterogenicity,subtypes,dopaminergic neurons,glial cells."71 articles were ultimately included for review and analysis. RESULTS AND CONCLUSION:(1)scRNA-seq is a high-throughput experimental technique that utilizes RNA sequencing at the single-cell level to quantify gene expression profiles in specific cell populations,revealing cellular mysteries at the molecular level.Compared with traditional sequencing techniques,scRNA-seq technology is used to reveal the diversity of cell types and changes in specific gene expression in complex tissues under various physiological and pathological conditions through automatic clustering analysis of cell transcriptome.(2)By using scRNA-seq,the development process of dopaminergic neurons and the unique functional characteristics of various cell subtypes are elucidated,in order to better understand potential therapeutic molecular targets.(3)The use of scRNA-seq analysis has improved our understanding of the response of Parkinson's disease glial cells,enabling us to comprehensively map and characterize different cell type populations,identify specific glial cell subpopulations related to neurodegeneration,and draw valuable single cell maps as reference data for future research.(4)The application of scRNA-seq to detect embryonic mice and stem cells will help improve the in vitro differentiation protocol and quality control of cell therapy,as well as evaluate the overall cell quality and developmental stage of dopaminergic neurons derived from stem cells.

BACKGROUND:3D organoids have characteristics that resemble physiological tissues and to some extent mimic organ function,making them excellent models for applications ranging from basic development/stem cell research to personalized medicine. OBJECTIVE:To review and discuss the types of diseases and application areas such as tumor modeling that organoids can be applied to,as well as their regulatory status and challenges. METHODS:With"organoid,stem cell,disease model,3D printing technology,medical field"as Chinese and English search terms,we searched PubMed,Elsevier,WanFang,and CNKI databases to summarize and analyze organoid products at home and abroad,summarize the application of organoid technology in the medical field,and prospect the future development of organoid products in the medical field. RESULTS AND CONCLUSION:Organoids can break the limitations of traditional cell and animal models,avoid the ethical problems existing in clinical research,and have a high similarity to the source organ,a more similar performance to the physiology and pathology of human systems,and genetic stability,which has great advantages in current research.Organoids have been applied in the following fields:efficacy evaluation studies(preclinical models),including intestinal organoids,kidney organoids,liver organoids,gallbladder organoids,lung organoids,brain organoids,heart organoids,skin organoids,and reproductive system organoids;research on infectious diseases;cancer research and precision therapy;regenerative medicine;immune organoids.Although the United States,the European Union and China do not have perfect regulatory provisions,they are trying to promote the formulation of organoid regulatory laws and regulations.In China,although no organoid medical device products have been listed for the time being,its related regenerative medicine products have made breakthroughs.

BACKGROUND:Acute myocardial infarction can cause cardiac remodeling and heart failure,as well as skeletal myopathy,affecting patients'quality of life.Exercise therapy is an important rehabilitation method for patients with heart failure;however,the optimal exercise prescription has not been clarified. OBJECTIVE:To compare the effects of different exercise modes(aerobic exercise,resistance exercise)on skeletal muscle remodeling in rats with acute myocardial infarction induced heart failure and to explore the possible mechanism,so as to provide a basis for optimizing the exercise rehabilitation program. METHODS:Forty-eight Sprague-Dawley rats were randomly divided into sham operation group,myocardial infarction group,aerobic exercise group and resistance exercise group.Coronary artery ligation was used to create model of heart failure.After 3 months,animals in the aerobic exercise group and resistance exercise group underwent 12 weeks of corresponding exercise mode interventions,while those in the sham operation group and myocardial infarction group were kept quietly in mouse cages.After the experiment,maximal running speed and maximal weight-bearing load were measured by graded treadmill exercise test and ladder-climbing test respectively,and heart structure and function were evaluated by echocardiography.The heart was isolated,and hematoxylin-eosin staining and Sirius red staining were performed to detect cardiac remodeling.For the gstrocnemius muscle,ATPase staining was performed to observe changes in muscle fiber type and cell cross-sectional area,dihydroethidium method was used to evaluate reactive oxygen species levels,enzyme-linked immunosorbent method was used to determine malondialdehyde content and antioxidant enzyme activity,western blot was used to determine the expression of ubiquitin-proteasome system proteins,and the number of activated satellite cells(Pax7+/MyoD+)were detected by double immunofluorescence staining. RESULTS AND CONCLUSION:(1)Exercise performance:Compared with the sham operation group,maximal running speed and maximal weight-bearing load in the myocardial infarction group decreased(P<0.05);compared with the myocardial infarction group,the maximal running speed of the aerobic exercise group and the maximal weight-bearing load of the resistance exercise group increased(P<0.05).(2)Cardiac remodeling:Compared with the sham operation group,infarction area,myocardial cell cross-sectional area,and collagen content in the myocardial infarction group increased(P<0.05),while leftventricular ejection fraction and shortening fraction decreased(P<0.05);compared with the myocardial infarction group,there was no statistical difference in the above parameters in both aerobic exercise resistance exercise groups(P>0.05).(3)Skeletal muscle remodeling:Compared with the sham operation group,gastrocnemius muscle mass,gastrocnemius muscle mass index,cell cross-sectional area,superoxide dismutase activity,glutathione peroxidase activity,and the number of activated satellite cells decreased in myocardial infarction group(P<0.05),while reactive oxygen species content,malondialdehyde content,and the protein expression of ubiquitin,MuRF1 and MAFbx increased(P<0.05);compared with the myocardial infarction group,gastrocnemius muscle mass index,superoxide dismutase activity,the number of activated satellite cells increased in both aerobic exercise and resistance exercise groups(P<0.05),while reactive oxygen species content and the protein expression of ubiquitin,MuRF1,and MAFbx decreased(P<0.05);compared with the aerobic exercise group,gastrocnemius muscle mass,gastrocnemius muscle mass index,cell cross-sectional area,reactive oxygen species content,malondialdehyde content,the number of activated satellite cells increased in resistance exercise group(P<0.05),while superoxide dismutase activity,glutathione peroxidase activity down-regulated(P<0.05).To conclude,aerobic exercise and resistance exercise can both improve exercise performance of rats with heart failure,and the mechanism is related to reducing oxidative stress,inhibiting ubiquitin-proteasome system activity and activating satellite cells to improve skeletal muscle remodeling.Aerobic exercise has a better effect on improving skeletal muscle oxidative stress,while resistance exercise has a more significant effect on promoting skeletal muscle regeneration.

BACKGROUND:Bone defects can directly affect the success rate and long-term stability of dental implants.Studies have shown that salidroside has the ability to promote the proliferation and differentiation of osteoblasts,but less is reported on its pathways related to osteogenic differentiation. OBJECTIVE:To investigate the effects of salidroside on the proliferation and differentiation of MC3T3-E1 cells and the expression of related genes and proteins through in vitro cell experiments. METHODS:Cell counting kit-8 test and alkaline phosphatase test were used to determine the optimal concentration of salidroside(0.5,1,5,10,and 50 μmol/L)in promoting the proliferation and differentiation of MC3T3-E1 cells.There were four groups in the experiment:control group,salidroside group,salidroside+LY294002 group,and LY294002 group,which were cultured with osteogenic induction solution,osteogenic induction solution containing 10 μmol/L salidroside,osteogenic induction solution containing 10 μmol/L salidroside+10 μmol/L LY294002,and osteogenic induction solution containing 10 μmol/L LY294002,respectively.The effects of salidroside and LY294002,an inhibitor of the PI3K/Akt signaling pathway,on the expressions of genes and proteins related to osteogenesis were observed. RESULTS AND CONCLUSION:Cell counting kit-8 assay and alkaline phosphatase assay showed that salidroside promoted the proliferation of MC3T3-E1 cells most significantly at 10 μmol/L.Compared with the control group,salidroside could promote mineralization,promote cell adhesion,reduce cell death,increase mRNA expression of Runx-2,osteocalcin and osteopontin(P<0.01),and increase protein expression of Runx-2 and p-Akt(P<0.01).However,the addition of LY294002 reversed the above results.These findings indicate that salidroside can promote the mineralization of MC3T3-E1 cells and the expression of osteogenesis-related genes and proteins,which may be related to the activation of PI3K/Akt signaling pathway.

BACKGROUND:Prolyl hydroxylase domain 2(PHD2)inhibitors can regulate bone metabolism and relieve osteoporosis in ovariectomized rats.cpd17 is a small molecule oral PHD2 inhibitor newly developed by China Pharmaceutical University.It is effective in the treatment of renal anemia with few side effects,but its effect on bone formation and bone resorption is still unclear. OBJECTIVE:To investigate the effects of cpd17 on mouse osteogenic precursor cells. METHODS:Osteogenic precursor cells were treated with cpd17.Alkaline phosphatase activity and extracellular matrix mineralization were measured,and the expression levels of osteogenesis-and osteoclastogenesis-related markers,as well as PHD2 and hypoxia-inducible factor 1α,were detected.After inhibition of the hypoxia-inducible factor 1α pathway using LW6(a hypoxia-inducible factor 1α pathway inhibitor),alkaline phosphatase activity and extracellular matrix mineralization were detected again,as well as the expression levels of osteogenesis-and osteoclastogenesis-related markers,PHD2 and hypoxia-inducible factor 1α. RESULTS AND CONCLUSION:cpd17 significantly enhanced alkaline phosphatase activity and extracellular matrix mineralization,up-regulated the expression of osteogenesis-related markers,down-regulated the expression of osteoclastogenesis-related markers,up-regulated the expression of hypoxia-inducible factor 1α,down-regulate the expression of PHD2.However,cpd17's effects were significantly attenuated by LW6.To conclude,the PHD2 inhibitor cpd17 promotes osteogenic differentiation and inhibits osteoclastic differentiation through activation of the hypoxia-inducible factor 1α signaling pathway.

BACKGROUND:Carnosic acid,a bioactive compound found in rosemary,has been shown to reduce inflammation and reactive oxygen species(ROS).However,its mechanism of action in osteoclast differentiation remains unclear. OBJECTIVE:To investigate the effects of carnosic acid on osteoclast activation,ROS production,and mitochondrial function. METHODS:Primary bone marrow-derived macrophages from mice were extracted and cultured in vitro.Different concentrations of carnosic acid(0,10,15,20,25 and 30 μmol/L)were tested for their effects on bone marrow-derived macrophage proliferation and toxicity using the cell counting kit-8 cell viability assay to determine a safe concentration.Bone marrow-derived macrophages were cultured in graded concentrations and induced by receptor activator of nuclear factor-κB ligand for osteoclast differentiation for 5-7 days.The effects of carnosic acid on osteoclast differentiation and function were then observed through tartrate-resistant acid phosphatase staining,F-actin staining,H2DCFDA probe and mitochondrial ROS,and Mito-Tracker fluorescence detection.Western blot and RT-PCR assays were subsequently conducted to examine the effects of carnosic acid on the upstream and downstream proteins of the receptor activator of nuclear factor-κB ligand-induced MAPK signaling pathway. RESULTS AND CONCLUSION:Tartrate-resistant acid phosphatase staining and F-actin staining showed that carnosic acid dose-dependently inhibited in vitro osteoclast differentiation and actin ring formation in the cell cytoskeleton,with the highest inhibitory effect observed in the high concentration group(30 μmol/L).Carnosic acid exhibited the most significant inhibitory effect during the early stages(days 1-3)of osteoclast differentiation compared to other intervention periods.Fluorescence imaging using the H2DCFDA probe,mitochondrial ROS,and Mito-Tracker demonstrated that carnosic acid inhibited cellular and mitochondrial ROS production while reducing mitochondrial membrane potential,thereby influencing mitochondrial function.The results of western blot and RT-PCR revealed that carnosic acid could suppress the expression of NFATc1,CTSK,MMP9,and C-fos proteins associated with osteoclast differentiation,and downregulate the expression of NFATc1,Atp6vod2,ACP5,CTSK,and C-fos genes related to osteoclast differentiation.Furthermore,carnosic acid enhanced the expression of antioxidant enzyme proteins and reduced the generation of ROS during the process of osteoclast differentiation.Overall,carnosic acid exerts its inhibitory effects on osteoclast differentiation by inhibiting the phosphorylation modification of the P38/ERK/JNK protein and activating the MAPK signaling pathway in bone marrow-derived macrophages.

BACKGROUND:Ca2+expression in astrocytes has been found to be closely related to cognitive function,and the Ca2+signaling pathway regulated by inositol 1,4,5-trisphosphate receptors(IP3R2)and ryanodine receptor(RYR)2 receptors has become a hot spot in the study of cognitive disorder-related diseases. OBJECTIVE:To investigate the expression of Ca2+signals mediated by IP3R2 and RYR2 in hippocampal astrocytes in animal models of delayed encephalopathy after acute carbon monoxide poisoning,and to explore the possible pathogenesis of delayed encephalopathy after acute carbon monoxide poisoning. METHODS:C57BL mice with qualified cognitive function were selected by Morris water maze experiment and randomly divided into control group and experimental group.An animal model of delayed encephalopathy after acute carbon monoxide poisoning was established by static carbon monoxide inhalation in the experimental group,and the same amount of air was inhaled in the control group.Behavioral and neuronal changes,astrocyte specific marker glial fibrillary acidic protein,IP3R2,RYR2 receptor and Ca2+concentration in astrocytes of the two groups were detected using Morris water maze,hematoxylin-eosin staining,western blot,immunofluorescence double labeling and Ca2+fluorescence probe at 21 days after modeling. RESULTS AND CONCLUSION:In the Morris water maze,the escape latency of the experimental group was significantly longer than that of the control group(P<0.05).Hematoxylin-eosin staining results showed that in the experimental group,the number of hippocampal pyramidal cells decreased,the cell structure was disordered,and the nucleus was broken and dissolved.Immunofluorescence results showed that IP3R2 and RYR2 were co-expressed with glial fibrillary acidic protein in the hippocampus,and the expressions of IP3R2,RYR2 and glial fibrillary acidic protein were up-regulated in the hippocampus of the experimental group(P<0.05).Western blot analysis showed that the expressions of IP3R2,RYR2,and glial fibrillary acidic protein in the hippocampus of the experimental group were increased(P<0.05).Ca2+concentration in hippocampal astrocytes increased significantly in the experimental group(P<0.05).To conclude,astrocytes may affect Ca2+signals by mediating IP3R2 and RYR2 receptors,then impair the cognitive function of mice with carbon monoxide poisoning,and eventually lead to delayed encephalopathy after acute carbon monoxide poisoning.

BACKGROUND:Early exercise treatment is the main prevention way for traumatic joint contracture and is also a research focus.Swimming may be a potential intervention for joint contracture due to the special physical properties of water. OBJECTIVE:To explore the effects of swimming on the development of joint contracture in a rat model and study its mechanisms. METHODS:Twenty-four Sprague-Dawley rats were randomly divided into a blank control group(n=8)and a joint contracture group(n=16).After the surgical operation of knee joint contracture rat models,the joint contracture group was randomly subdivided into a surgical control group(n=8)and a swimming treatment group(n=8).Swimming started in the swimming treatment group in the second week after surgery and lasted for a total of 5 weeks.At the 6th week after surgery,the body mass,knee joint range of motion,and quadriceps diameter were tested,and the diameter/body mass index was calculated.Hematoxylin-eosin staining was performed to detect the pathological changes in the knee joint capsule and quadriceps muscle,and Masson staining was used to observe fibrotic changes in the knee joint capsule.Furthermore,the protein expression of transforming growth factor β1 and type I collagen in the knee joint capsule was quantified by immunohistochemical assay and western blot was performed to detect the protein expression of MuRF1 in the quadriceps femoris. RESULTS AND CONCLUSION:Compared with the blank control group,the knee range of motion decreased in the surgical control and swimming treatment groups(P<0.01),and knee extension deficit and arthrogenic extension deficit were significantly increased(P<0.01),the diameter of the quadriceps muscle was decreased(P<0.01),the joint capsule showed significant fibrosis,the quadriceps muscle was atrophied,and the diameter/body mass index was decreased(P<0.01).Compared with the surgical control group,the swimming treatment group showed a significant increase in knee joint range of motion and quadriceps diameter(P<0.01),and significant improvement in joint capsule fibrosis and quadriceps atrophy.Compared with the blank control group,collagen fiber content and expression of transforming growth factor β1 and type I collagen were increased in the joint capsule of rats in both the surgical control group and the swimming treatment group(P<0.01).Compared with the surgical control group,collagen fiber content and expression of transforming growth factor β1 and type I collagen protein in the joint capsule were decreased in the swimming treatment group.Compared with the blank control group,the expression of MuRF1 protein in the quadriceps muscle of rats in the surgical control group and the swimming treatment group was increased(P<0.05).Compared with the surgical control group,the expression of MuRF1 protein in the quadriceps muscle of rats in the swimming treatment group was decreased(P<0.05).To conclude,early swimming intervention reduces transforming growth factor β1 and type I collagen expression in the joint capsule of traumatic joint contracture rats,decreases MuRF1 expression in the quadriceps muscle,and increases joint range of motion and quadriceps diameter,thereby inhibiting the development of joint contracture.

BACKGROUND:Carboxylesterase 1 and inflammatory factors play a crucial role in regulating lipid metabolism and glucose homeostasis.However,the effects of different exercise intensity interventions on carboxylesterase 1 and inflammatory factors in skeletal muscle of type 2 diabetic rats remain to be revealed. OBJECTIVE:To investigate the effects of different exercise intensity interventions on carboxylesterase 1 and inflammatory factors in skeletal muscle of type 2 diabetic rats. METHODS:Thirty-two 8-week-old male Sprague-Dawley rats were randomly divided into normal control group(n=12)and modeling group(n=20)after 1 week of adaptive feeding.Rat models of type 2 diabetes mellitus were prepared by high-fat diet and single injection of streptozotocin.After successful modeling,the rats were randomly divided into diabetic control group(n=6),moderate-intensity exercise group(n=6)and high-intensity intermittent exercise group(n=6).The latter two groups were subjected to treadmill training at corresponding intensities,once a day,50 minutes each,and 5 days per week.Exercise intervention in each group was carried out for 6 weeks.After the intervention,ELISA was used to detect blood glucose and blood lipids of rats.The morphological changes of skeletal muscle were observed by hematoxylin-eosin staining.The mRNA expression levels of carboxylesterase 1 and inflammatory cytokines were detected by real-time quantitative PCR.The protein expression levels of carboxylesterase 1 and inflammatory cytokines were detected by western blot and immunofluorescence. RESULTS AND CONCLUSION:Compared with the normal control group,fasting blood glucose,triglyceride,low-density lipoprotein cholesterol,insulin resistance index in the diabetic control group were significantly increased(P<0.01),insulin activity was decreased(P<0.05),and the mRNA and protein levels of carboxylesterase 1,never in mitosis gene A related kinase 7(NEK7)and interleukin 18 in skeletal muscle tissue were upregulated(P<0.05).Compared with the diabetic control group,fasting blood glucose,triglyceride,low-density lipoprotein cholesterol,and insulin resistance index in the moderate-intensity exercise group and high-intensity intermittent exercise group were down-regulated(P<0.05),and insulin activity was increased(P<0.05).Moreover,compared with the diabetic control group,the mRNA level of NEK7 and the protein levels of carboxylesterase 1,NEK7 and interleukin 18 in skeletal muscle were decreased in the moderate-intensity exercise group(P<0.05),while the mRNA levels of carboxylesterase 1,NEK7,NOD-like receptor heat protein domain associated protein 3 and interleukin 18 and the protein levels of carboxylesterase 1 and interleukin 18 in skeletal muscle were downregulated in the high-intensity intermittent exercise group(P<0.05).Hematoxylin-eosin staining showed that compared with the diabetic control group,the cavities of myofibers in the moderate-intensity exercise group became smaller,the number of internal cavities was reduced,and the cellular structure tended to be more intact;the myocytes of rats in the high-intensity intermittent exercise group were loosely arranged,with irregular tissue shape and increased cavities in myofibers.To conclude,both moderate-intensity exercise and high-intensity intermittent exercise can reduce blood glucose,lipid,insulin resistance and carboxylesterase 1 levels in type 2 diabetic rats.Moderate-intensity exercise can significantly reduce the expression level of NEK7 protein in skeletal muscle,while high-intensity intermittent exercise can significantly reduce the expression level of interleukin 18 protein in skeletal muscle.In addition,the level of carboxylesterase 1 is closely related to the levels of NEK7 and interleukin 18.

BACKGROUND:It has been shown that Gushukang affects bone metabolism by regulating nucleotide and amino acid metabolism and immune mechanisms.Current research on the mechanism of Gushukang in the treatment of osteoporosis primarily focuses on osteoblast regulation and requires further improvement from the perspective of osteoclasts. OBJECTIVE:To investigate the mechanism by which Gushukang interferes with osteoclasts in the treatment of osteoporosis using RAW264.7 cells as the research model. METHODS:Twenty-four 8-week-old female Sprague-Dawley rats were randomly divided into four groups(n=6 per group):the three experimental groups were given 1,2 and 4 g/kg osteoporosis solution by gavage(2 times per day),and the control group was given an equal amount of distilled water by gavage(2 times per day).After 7 days of intragastric administration,aortic blood samples were extracted to collect serum samples using centrifugation,and serum samples from the same groups were combined to obtain the low-,medium-,and high-concentration Gushukang-containing and normal sera for the subsequent experiments.(1)RAW264.7 cells were cultured in six groups:normal serum was added to the control group;low,medium,and high concentration groups were added with low,medium,and high concentrations of Gushukang-containing serum,respectively;ML385,a nuclear factor erythroid 2-related factor 2(Nrf2)inhibitor was given in the Nrf2 inhibitor group;and t-BHQ,a Nrf2 activator,was added in the Nrf2 activator group.Cell viability was detected using the cell counting kit-8 assay.(2)The 3rd generation RAW 264.7 cells were cultured and divided into five groups:the blank control group was added with normal serum,the osteoclast group was added with receptor activator of nuclear factor κB ligand(RANKL),and the low-,medium-,and high-concentration groups were added with low-,medium-,and high-concentration Gushukang-containing serum based on the addition of RANKL.Tartrate-resistant acid phosphate staining was performed after 5 days of culture.(3)RAW264.7 cells were cultured and divided into five groups:blank control group was cultured with normal serum,osteoclast group cultured with normal serum and RANKL,high concentration+osteoclast group cultured with RANKL+high concentration Gushukang-containing serum,osteoclast+Nrf2 agonist group cultured with RANKL+t-BHQ,and high concentration+osteoclast+Nrf2 inhibitor group cultured with RANKL+high concentration Gushukang-containing serum+ML385.Western blot assay and determination of reactive oxygen content were performed after 5 days of culture. RESULTS AND CONCLUSION:The cell counting kit-8 results indicated that Gushukang-containing serum,NRF2 inhibitor or agonist had no significant effect on RAW264.7 cell viability.Tartrate-resistant acid phosphate staining results demonstrated that Gushukang-containing serum exhibited a concentration-dependent inhibitory effect on osteoclast differentiation.Western blot analysis and determination of reactive oxygen species revealed that compared with the blank control group,Nrf2 protein expression was decreased in the osteoclast group(P<0.05),while c-Fos and NFATc1 protein expression and reactive oxygen species content were elevated(P<0.05);compared with the osteoclast group,Nrf2 protein expression was elevated and reactive oxygen species content was decreased in the high-concentration+osteoclast group,osteoclast+Nrf2 agonist group,and high-concentration+osteoclast+Nrf2 inhibitor group(P<0.05),while c-Fos and NFATc1 protein expression was decreased in the high concentration+osteoclast group and osteoclast+Nrf2 agonist group(P<0.05);compared with the high concentration+osteoclast group,Nrf2 protein expression was decreased(P<0.05)and reactive oxygen species content was elevated(P<0.05)in the high concentration+osteoclast+Nrf2 inhibitor group.To conclude,Gushukang reduces reactive oxygen species production by activating Nrf2,thereby inhibiting downstream of the c-Fos/NFATc1 pathway and suppressing osteoclast differentiation.