Mouse Model Of Postmenopausal Osteoporosis Research Articles

CDK14 is regulated by IGF2BP2 and involved in osteogenic differentiation via Wnt/β-catenin signaling pathway in vitro

AimsCyclin-dependent kinase (CDK) family proteins involve in various cellular processes via regulating the cell cycle; however, their expression during osteogenic differentiation and postmenopausal osteoporosis remains poorly understood. Main methodsUsing bioinformatics, we screened for CDK14 bound to Insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2) and explored its expression in vitro with time-gradient model and in a mouse model of postmenopausal osteoporosis, building on prior research. Subsequently, we investigated its effect on osteoblast proliferation, cell cycle dynamics, and osteogenic differentiation by administering CDK14 siRNA and the covalent inhibitor FMF-04-159-2. Furthermore, we examined the interaction between IGF2BP2 and CDK14. Finally, we validated the regulatory role of CDK14 on the Wnt/β-catenin pathway. Key findingsOur findings demonstrate a time-dependent CDK14 expression patterns during osteogenic differentiation of MC3T3-E1 cell line, with an initial increase followed by gradual decline over time. Notably, CDK14 expression exhibited significant reduction in bone tissue of postmenopausal osteoporosis mouse model. CDK14 inhibition altered osteoblast cell cycle dynamics, significantly reduced cellular proliferation capacity, and impaired osteogenic differentiation ability. IGF2BP2 interacted with CDK14 mRNA, and stabilizing mRNA's structure and inhibiting its degradation. Additionally, CDK14 facilitated Low-density lipoprotein receptor-related protein 6 (LRP6) and Glycogen synthase kinase 3β (GSK3β) phosphorylation, thus regulating β-catenin levels. SignificanceThese findings provide further insight into the molecular mechanisms governing osteoblast proliferation, differentiation and osteoporosis.

Bone protective effects of the polysaccharides from Grifola frondosa on ovariectomy-induced osteoporosis in mice via inhibiting PINK1/Parkin signaling, oxidative stress and inflammation

BackgroundPolysaccharides from Grifola frondosa(GFP) have gained worldwide attention owing to their promising biological activities and potential health benefits. PurposeThis study aimed to investigate the effects of GFP on alleviation of osteoporosis in ovariectomized (OVX) mice and examine the underlying mechanism. MethodA mouse model of postmenopausal osteoporosis was established by OVX method, Forty eight C57BL/6 female mice were randomly divided into Normal group, OVX alone (Model group, n = 8), OVX + 10 mg/kg GFP (GFP-L group, n = 8), OVX + 20 mg/kg GFP (GFP-M group, n = 8), OVX + 40 mg/kg GFP (GFP-H group, n = 8), OVX + 10 mg/kg Estradiol valerate (Positive group, n = 8). ResultsThe results showed that compared with Model group, the concentrations of interleukin (IL)-1β, interleukin (IL)-6 and Tumor necrosis factor-α (TNF-α) were significantly reduced, the activity of superoxide dismutase (SOD) and glutathione (GSH) were significantly increased, the content of myeloperoxidase (MPO) and malondialdehyde (MDA) were significantly reduced, and the proteins levels of PINK1, Parkin, Beclin-1 and LC3-II were significantly decreased in the GFP groups. ConclusionThis study demonstrates that GFP alleviates ovariectomy-induced osteoporosis via reduced secretion of inflammatory cytokines, improvement in the oxidative stress status in the body, and inhibition of the PINK1/Parkin signaling pathway.

Lipidomics analysis of bone marrow in a mouse model of postmenopausal osteoporosis

Postmenopausal osteoporosis (PMOP) is a major public health problem worldwide, afflicting many postmenopausal women. Although many studies have focused on the biological role of individual lipids in osteoporosis, no studies have systematically elucidated the lipid profile of osteoporosis. In this study, liquid chromatography-tandem mass spectrometry (LC-MS/MS) technology based on multiple reaction monitoring (MRM) method was used to compare the levels of lipid molecules in bone marrow cells of osteoporotic mice (OVX) group and sham-operation (Sham) group. Principal component analysis (PCA) was used for multivariate statistics. Differential lipids were obtained by bar graph, heatmap and volcano map. A total of 400 lipid molecules were identified. A total of 199 lipid molecules were identified to be associated with PMOP, including 6 phospholipids and 3 sphingolipids. These differential lipid molecules provide a systematic lipid profile for osteoporosis, which helps to discover new candidate osteoporosis biomarkers, and their changes at the molecular level can be used as new targets for diagnosis or prevention.

Conditioned medium of human mesenchymal stem cells affects stem cell senescence in osteoporosis

Systemic transplantation of mesenchymal stem cells (MSCs) and conditioned medium derived from MSCs have been reported to recover bone loss in animal models of osteoporosis; however, the underlying mechanisms remain unclear. We recently reported that extracellular vesicles released from human mesenchymal stem cells (hMSCs) prevent senescence of stem cells in bisphosphonate-related osteonecrosis of the jaw model. In this study, we aimed to compare the effects of conditioned medium (hMSCs-CM) from early and late passage hMSCs on cellular senescence and to verify the benefits of CM from early passage hMSCs in mitigating the progression of osteoporosis through the prevention of cellular senescence. We investigated the distinct endocrine effects of early (P5) and late (P17) passage hMSCs in vitro, as well as the preventive benefits of early passage hMSCs-CM in osteoporosis model triggered by ovariectomy. Our results indicate that long-term cultured hMSCs contributed to the progression of inflammatory transcriptional programs in P5 hMSCs, ultimately impairing their functionality and enhancing senescence-related characteristics. Conversely, early passage hMSCs reversed these alterations. Moreover, early passage hMSCs-CM infused intravenously in a postmenopausal osteoporosis mouse model suppressed bone degeneration and prevented osteoporosis by reducing ovariectomy-induced senescence in bone marrow MSCs and reducing the expression of senescence-associated secretory phenotype-related cytokines. Our findings highlight the high translational value of early passage hMSCs-CM in antiaging intervention and osteoporosis prevention.

Early changes of bone metabolites and lymphocyte subsets may participate in osteoporosis onset: a preliminary study of a postmenopausal osteoporosis mouse model.

Metabolic and immune changes in the early stages of osteoporosis are not well understood. This study aimed to explore the changes in bone metabolites and bone marrow lymphocyte subsets and their relationship during the osteoporosis onset. We established OVX and Sham mouse models. After 5, 15, and 40 days, five mice in each group were sacrificed. Humeri were analyzed by microCT. The bone marrow cells of the left femur and tibia were collected for flow cytometry analysis. The right femur and tibia were analyzed by LC-MS/MS for metabolomics analysis. Bone microarchitecture was significantly deteriorated 15 days after OVX surgery. Analysis of bone metabolomics showed that obvious metabolite changes had happened since 5 days after surgery. Lipid metabolism was significant at the early stage of the osteoporosis. The proportion of immature B cells was increased, whereas the proportion of mature B cells was decreased in the OVX group. Metabolites were significantly correlated with the proportion of lymphocyte subsets at the early stage of the osteoporosis. Lipid metabolism was significant at the early stage of the osteoporosis. Bone metabolites may influence bone formation by interfering with bone marrow lymphocyte subsets.

XianLingGuBao protects against osteoporosis through activating STAT3 in vitro and vivo

BackgroundXianLingGuBao (XLGB) is a potent traditional Chinese patent medicine used to treat osteoporosis (OP), osteoarthritis, aseptic bone necrosis, and other musculoskeletal disorders. The current study aims to identify the active ingredients of XLGB and further elucidate its mechanism on OP treatment. MethodsExperimental pharmacology coupled with network pharmacology methods were used, and the effects of XLGB on mouse osteoblast MC3T3-E1 and ovariectomized (OVX) postmenopausal OP mouse model were detected. Furthermore, ultra performance liquid chromatography tandem quadrupole time of flight mass spectrometry (UPLC Q/TOF MS) was used to identify the active ingredients in XLGB for protecting osteoporosis. ResultsXLGB was shown to significantly promote the growth of MC3T3-E1 cells. It could promote the cell proliferation and enhance the formation of mineralized nodule of MC3T3-E1 cells. The efficacy of XLGB in preventing osteoporosis in OVX mice was also demonstrated. The network pharmacological analysis indicated that the top 5 active components of XLGB anti-OP were HX-14, 3-hydroxypsoralen, kaempferol, palmitic acid, and terpene ether. Both KEGG and GO analysis indicated that XLGB may inhibit bone loss through activating the STAT3. Results from the Western blot analysis confirmed that the expression and activity of STAT3 were affected by XLGB. ConclusionThis study clearly demonstrates that the activation of STAT3 plays an crucial role in the protective effect of XLGB against OP. These findings provide a solid experimental foundation on the extensive use of XLGB in the clinical treatment of OP.

Melatonin induces RAW264.7 cell apoptosis via the BMAL1/ROS/MAPK-p38 pathway to improve postmenopausal osteoporosis.

Currently, the effect of drug treatment for osteoporosis is relatively poor, and the side effects are numerous and serious. Melatonin is a potential drug to improve bone mass in postmenopausal women. Unfortunately, the mechanism by which melatonin improves bone metabolism remains unclear. The aim of this study was to further investigate the potential mechanism of melatonin in the treatment of osteoporosis. The effects of melatonin on mitochondrial apoptosis protein, bmal1 gene, and related pathway proteins of RAW264.7 (mouse mononuclear macrophage leukaemia cells) were analyzed by western blot. Cell Counting Kit-8 was used to evaluate the effect of melatonin on cell viability. Flow cytometry was used to evaluate the effect of melatonin on the apoptosis of RAW264.7 cells and mitochondrial membrane potential. A reactive oxygen species (ROS) detection kit was used to evaluate the level of ROS in osteoclast precursors. We used bmal1-small interfering RNAs (siRNAs) to downregulate the Bmal1 gene. We established a postmenopausal mouse model and verified the effect of melatonin on the bone mass of postmenopausal osteoporosis in mice via micro-CT. Bmal1 lentiviral activation particles were used to establish an in vitro model of overexpression of the bmal1 gene. Melatonin promoted apoptosis of RAW264.7 cells and increased the expression of BMAL1 to inhibit the activation of ROS and phosphorylation of mitogen-activated protein kinase (MAPK)-p38. Silencing the bmal1 gene weakened the above effects of melatonin. After that, we used dehydrocorydaline (DHC) to enhance the activation of MAPK-p38, and the effects of melatonin on reducing ROS levels and promoting apoptosis of RAW264.7 cells were also blocked. Then, we constructed a mouse model of postmenopausal osteoporosis and administered melatonin. The results showed that melatonin improves bone loss in ovariectomized mice. Finally, we established a model of overexpression of the bmal1 gene, and these results suggest that the bmal1 gene can regulate ROS activity and change the level of the MAPK-p38 signalling pathway. Our study confirmed that melatonin promotes the apoptosis of RAW264.7 cells through BMAL1/ROS/MAPK-p38, and revealed the therapeutic effect and mechanism of melatonin in postmenopausal osteoporosis. This finding enriches BMAL1 as a potential target for the treatment of osteoporosis and the pathogenesis of postmenopausal osteoporosis.

Suppression of IRF9 Promotes Osteoclast Differentiation by Decreased Ferroptosis via STAT3 Activation.

Osteoporosis is a chronic disease that endangers the health of the elderly. Inhibiting osteoclast hyperactivity is a key aspect of osteoporosis prevention and treatment. Several studies have shown that interferon regulatory factor 9 (IRF9) not only regulates innate and adaptive immune responses but also plays an important role in inflammation, antiviral response, and cell development. However, the exact role of IRF9 in osteoclasts has not been reported. To elucidate the role of IRF9 in osteoclast differentiation, we established the ovariectomized mouse model of postmenopausal osteoporosis and found that IRF9 expression was reduced in ovariectomized mice with overactive osteoclasts. Furthermore, knockdown of IRF9 expression enhanced osteoclast differentiation in vitro. Using RNA sequencing, we identified that the differentially expressed genes enriched by IRF9 knockdown were related to ferroptosis. We observed that IRF9 knockdown promoted osteoclast differentiation via decreased ferroptosis in vitro and further verified that IRF9 knockdown reduced ferroptosis by activating signal transducer and activator of transcription 3 (STAT3) to promote osteoclastogenesis. In conclusion, we identified an essential role of IRF9 in the regulation of osteoclastogenesis in osteoporosis and its underlying mechanism.

Estrogen-regulated miRs in bone enhance osteoblast differentiation and matrix mineralization

Estrogen signaling is critical for the development and maintenance of healthy bone, and age-related decline in estrogen levels contributes to the development of post-menopausal osteoporosis. Most bones consist of a dense cortical shell and an internalmesh-like network of trabecular bone that respond differently to internal and external cues such as hormonal signaling. To date, no study has assessed the transcriptomic differences that occur specifically in cortical and trabecular bone compartments in response to hormonal changes. To investigate this, we employed a mouse model of post-menopausal osteoporosis (ovariectomy, OVX) and estrogen replacement therapy (ERT). mRNA and miR sequencing revealed distinct transcriptomic profiles between cortical and trabecular bone in the setting of OVX and ERT. Seven miRs were identified as likely contributors to the observed estrogen-mediated mRNA expression changes. Of these, four miRs were prioritized for further study and decreased predicted target gene expression in bone cells, enhanced the expression of osteoblast differentiation markers, and altered the mineralization capacity of primary osteoblasts. As such, candidate miRs and miR mimics may have therapeutic relevance for bone loss resulting from estrogen depletion without the unwanted side effects of hormone replacement therapy and therefore represent novel therapeutic approaches to combat diseases of bone loss.

Coupling induction of osteogenesis and type H vessels by pulsed electromagnetic fields in ovariectomy-induced osteoporosis in mice.

The growth of blood vessels and osteogenesis are coupled in bone tissue. A specialized subset of CD31hiEndomucinhi (CD31hiEmcnhi) vascular endothelium in bone has been identified to positively regulate bone formation. Pulsed electromagnetic field (PEMF) can promote the facture healing and reverse the loss of bone mass. However, the underlying mechanisms mediating in the positive effects of PEMF on bone mass accrual remain unclear. In the ovariectomized (OVX) osteoporotic mouse model, PEMF with specific parameters was administrated after 12weeks of surgery and continued for 8weeks. μCT analysis, quantitative PCR and Elisa assays were used to assess the PEMF-induced the osteogenesis, while immunostaining and flow cytometry were used to evaluate the abundance of CD31hiEmcnhi endothelium in the metaphysis near the growth plate. Administration of PEMF substantially countered OVX-induced bone loss as shown by greater trabecular bone, higher expression of Osterix, PDGFB and Col-1a1 transcripts, and modulation of bone anabolic and catabolic activity. The PEMF-induced osteogenesis was coupled by the expansion of CD31hiEmcnhi endothelium as demonstrated by CD31 and Endomucin double-positive immunostaining and flow cytometry. Concurrently, the higher level of HIF-α was found in PEMF-treated mice than in vehicle controls. Notably, inhibition of HIF-1α considerably reduced PEMF-induced osteogenesis, and led to a remarkable decrease of CD31hiEmcnhi vessels in the PEMF-treated OVX mice. The present study demonstrated the PEMF-induced coupling promotion of osteogenesis and CD31hiEmcnhi endothelial cells in a mouse model of postmenopausal osteoporosis. This coupling effect might be mediated in HIF-1α signaling in CD31hiEmcnhi endothelium. These findings open up new directions of al that might enable therapeutic improvement of osteogenesis in patients with osteoporosis.

Osteal macrophages support osteoclast-mediated resorption and contribute to bone pathology in a postmenopausal osteoporosis mouse model.

Osteal macrophages (osteomacs) support osteoblast function and promote bone anabolism, but their contribution to osteoporosis has not been explored. Although mouse ovariectomy (OVX) models have been repeatedly used, variation in strain, experimental design and assessment modalities have contributed to no single model being confirmed as comprehensively replicating the full gamut of osteoporosis pathological manifestations. We validated an OVX model in adult C3H/HeJ mice and demonstrated that it presents with human postmenopausal osteoporosis features with reduced bone volume in axial and appendicular bone and bone loss in both trabecular and cortical bone including increased cortical porosity. Bone loss was associated with increased osteoclasts on trabecular and endocortical bone and decreased osteoblasts on trabecular bone. Importantly, this OVX model was characterized by delayed fracture healing. Using this validated model, we demonstrated that osteomacs are increased post-OVX on both trabecular and endocortical bone. Dual F4/80 (pan-macrophage marker) and tartrate-resistant acid phosphatase (TRAP) staining revealed osteomacs frequently located near TRAP+ osteoclasts and contained TRAP+ intracellular vesicles. Using an in vivo inducible macrophage depletion model that does not simultaneously deplete osteoclasts, we observed that osteomac loss was associated with elevated extracellular TRAP in bone marrow interstitium and increased serum TRAP. Using in vitro high-resolution confocal imaging of mixed osteoclast-macrophage cultures on bone substrate, we observed macrophages juxtaposed to osteoclast basolateral functional secretory domains scavenging degraded bone byproducts. These data demonstrate a role for osteomacs in supporting osteoclastic bone resorption through phagocytosis and sequestration of resorption byproducts. Overall, our data expose a novel role for osteomacs in supporting osteoclast function and provide the first evidence of their involvement in osteoporosis pathogenesis. © 2021 American Society for Bone and Mineral Research (ASBMR).

Fecal and Serum Metabolomic Signatures and Microbial Community Profiling of Postmenopausal Osteoporosis Mice Model.

BackgroundMultiple studies have shown that an imbalance in the intestinal microbiota is related to bone metabolism, but the role of the intestinal microbiota in postmenopausal osteoporosis remains to be elucidated. We explored the effect of the intestinal microbiota on osteoporosis.MethodsWe constructed a postmenopausal osteoporosis mouse model, and Micro CT was used to observe changes in bone structure. Then, we identified the abundance of intestinal microbiota by 16S RNA sequencing and found that the ratio of Firmicutes and Bacteroidetes increased significantly. UHPLC-MS analysis was further used to analyze changes in metabolites in feces and serum.ResultsWe identified 53 upregulated and 61 downregulated metabolites in feces and 2 upregulated and 22 downregulated metabolites in serum under OP conditions, and interestedly, one group of bile acids showed significant differences in the OP and control groups. Network analysis also found that these bile acids had a strong relationship with the same family, Eggerthellaceae. Random forest analysis confirmed the effectiveness of the serum and fecal models in distinguishing the OP group from the control group.ConclusionsThese results indicated that changes in the gut microbiota and metabolites in feces and serum were responsible for the occurrence and development of postmenopausal osteoporosis. The gut microbiota is a vital inducer of osteoporosis and could regulate the pathogenesis process through the “microbiota-gut-metabolite-bone” axis, and some components of this axis are potential biomarkers, providing a new entry point for the future study on the pathogenesis of postmenopausal osteoporosis.

Poria Cocos Ameliorates Bone Loss in Ovariectomized Mice and Inhibits Osteoclastogenesis In Vitro.

Estrogen deprivation in postmenopausal women causes disruption of bone homeostasis, resulting in bone loss and osteoporosis. Conventional therapies can exert adverse effects. The sclerotum of Poria cocos has been used in traditional medicine and as a nutritional supplement and to treat various diseases. However, the effects of P. cocos on the bone remain largely undetermined. In this study, we examined the effects of P. cocos hydroethanolic extract (PC) on osteoclast differentiation and estrogen-deprivation-induced bone loss in an ovariectomized mouse model of postmenopausal osteoporosis. PC-mediated inhibition of receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation and resorption activity suppressed RANKL-induced expression of nuclear factor of activated T cells cytoplasmic 1 (NFATc1), which is a crucial transcription factor for osteoclast differentiation. In ovariectomized mice, PC markedly alleviated trabecular bone loss and reduced the accumulation of lipid droplets in the bone marrow. We additionally identified ten triterpenoid constituents of PC using UPLC-MS/MS analysis. Our results indicate that PC negatively regulated osteoclast differentiation and function, and can potentially be used to manage postmenopausal osteoporosis.

The combined effects of teriparatide and anti-RANKL monoclonal antibody on bone defect regeneration in ovariectomized mice.

The purpose of this study was to investigate the combined effects of teriparatide (TPTD) and anti-murine receptor activator of nuclear factor-κB ligand monoclonal antibody (anti-RANKL Ab) on both cancellous and cortical bone healing in ovariectomized mice. Thirteen-week-old mice were divided into the sham-operated group (n=11) or the ovariectomized group (n=44). At 1 month post-operation, all mice underwent bone defect surgery on the left femoral metaphysis (cancellous bone healing model) and right femoral mid-diaphysis (cortical bone healing model). After creating the bone defects, all ovariectomized mice were assigned to one of four groups to receive 1) saline (5 times a week; CNT group), 2) TPTD (40μg/kg 5 times a week; TPTD group), 3) anti-RANKL Ab (5mg/kg once; Ab group), or 4) a combination of TPTD and anti-RANKL Ab (COMB group). The following analyses were performed: Time-course microstructural analysis of healing in both cancellous and cortical bone in the bone defect, measuring the volumetric bone mineral density and the cortical bone thickness of the tibia as a representative of whole body bone with the use of micro-computed tomography, and histological analysis. Regeneration of cancellous bone volume in the COMB group was the highest among the four groups, and combined treatment accelerated the formation of medullary callus during the early phase of bone regeneration. On the other hand, there were no significant differences in the regeneration of cortical bone volume during the early phase of bone regeneration among the four groups. Furthermore, lamellar bone was not well identified in the all four groups. Volumetric bone mineral density in the tibia in the COMB group was significantly higher compared with that in the CNT and TPTD groups and tended to be higher compared with that in the Ab group. The mean values of cortical bone thickness in the TPTD and COMB groups were significantly higher than that in the CNT group. In a mouse model of postmenopausal osteoporosis, combination therapy of TPTD and anti-RANKL Ab accelerates regeneration of cancellous bone more effectively than either agent alone during the early phase of bone regeneration.

MicroRNA-218-5p relieves postmenopausal osteoporosis through promoting the osteoblast differentiation of bone marrow mesenchymal stem cells.

MicroRNAs (miRs) are short noncoding RNAs that play key regulatory roles in osteoblast differentiation. In this study, the specific regulatory roles of miR-218-5p on postmenopausal osteoporosis (PMOP) were investigated. The mouse model of PMOP was established by bilateral ovariectomy, and the injection of miR-218-5p mimics significantly relieved PMOP degree. Then, bone marrow mesenchymal stem cells (BMMSCs) isolated from PMOP mice were induced into osteoblasts. When compared with normal BMMSCs, PMOP BMMSCs exhibited significantly lower alkaline phosphatase (ALP) activity and less mineralized nodules, as well as downregulated miR-218-5p, Runx2, Osterix, COL1A1, and OCN after induction (P < .05). The transfection of miR-218-5p mimics, and inhibitor significantly promoted, inhibited the osteoblast differentiation of PMOP BMMSCs, respectively. In addition, COL1A1 was a target of miR-218-5p. The transfection of miR-218-5p mimics into PMOP BMMSCs significantly upregulated COL1A1 at 14th and 21st day post-induction, but not at 7th day. Our findings suggest miR-218-5p may relieve PMOP through promoting the osteoblast differentiation of BMMSCs.

Human Enriched Serum Following Hydrolysed Collagen Absorption Modulates Bone Cell Activity: from Bedside to Bench and Vice Versa.

Collagen proteins are crucial components of the bone matrix. Since collagen-derived products are widely used in the food and supplement industry, one may raise the question whether collagen-enriched diets can provide benefits for the skeleton. In this study, we designed an innovative approach to investigate this question taking into account the metabolites that are formed by the digestive tract and appear in the circulation after ingestion of hydrolysed collagen. Blood samples collected in clinical and pre-clinical trials following ingestion and absorption of hydrolysed collagen were processed and applied on bone-related primary cell cultures. This original ex vivo methodology revealed that hydrolysed collagen-enriched serum had a direct impact on the behaviour of cells from both human and mouse origin that was not observed with controls (bovine serum albumin or hydrolysed casein-enriched serum). These ex vivo findings were fully in line with in vivo results obtained from a mouse model of post-menopausal osteoporosis. A significant reduction of bone loss was observed in mice supplemented with hydrolysed collagen compared to a control protein. Both the modulation of osteoblast and osteoclast activity observed upon incubation with human or mouse serum ex vivo and the attenuation of bone loss in vivo, clearly indicates that the benefits of hydrolysed collagen for osteoporosis prevention go beyond the effect of a simple protein supplementation.

Wnt3a involved in the mechanical loading on improvement of bone remodeling and angiogenesis in a postmenopausal osteoporosis mouse model.

Osteoporosis is a major health problem, making bones fragile and susceptible to fracture. Previous works showed that mechanical loading stimulated bone formation and accelerated fracture healing. Focusing on the role of Wnt3a (wingless/integrated 3a), this study was aimed to assess effects of mechanical loading to the spine, using ovariectomized (OVX) mice as a model of osteoporosis. Two-week daily application of this novel loading (4 N, 10 Hz, 5 min/d) altered bone remodeling with an increase in Wnt3a. Spinal loading promoted osteoblast differentiation, endothelial progenitor cell migration, and tube formation and inhibited osteoclast formation, migration, and adhesion. A transient silencing of Wnt3a altered the observed loading effects. Spinal loading significantly increased bone mineral density, bone mineral content, and bone area per tissue area. The loaded OVX group showed a significant increase in the number of osteoblasts and reduction in osteoclast surface/bone surface. Though expression of osteoblastic genes was increased, the levels of osteoclastic genes were decreased by loading. Spinal loading elevated a microvascular volume as well as VEGF expression. Collectively, this study supports the notion that Wnt3a-mediated signaling involves in the effect of spinal loading on stimulating bone formation, inhibiting bone resorption, and promoting angiogenesis in OVX mice. It also suggests that Wnt3a might be a potential therapeutic target for osteoporosis treatment.-Li, X., Liu, D., Li, J., Yang, S., Xu, J., Yokota, H., Zhang, P. Wnt3a involved in the mechanical loading on improvement of bone remodeling and angiogenesis in a postmenopausal osteoporosis mouse model.

Daily intake of polyamine-rich Saccharomyces cerevisiae S631 prevents osteoclastic activation and bone loss in ovariectomized mice.

An imbalance in the sophisticated regulation between bone-resorbing osteoclasts and bone-forming osteoblasts leads to the pathogenesis and etiology of certain metabolic bone diseases including osteoporosis. Certain polyamines are related to the pathophysiology of some disorders, including Alzheimer's disease, infectious disease, cancer, and aging. Recently, we demonstrated that oral intake of polyamines (spermidine and spermine) prevented bone loss through preferential disturbance of osteoclastic activation in ovariectomy-induced mouse model of postmenopausal osteoporosis. Here, we showed that daily oral supplementation of a diet containing polyamine-rich Saccharomyces cerevisiae S631 significantly inhibited osteoclastic activation as well as reduction of bone volume in the cancellous bone without affecting uterine weight in ovariectomized mice. Our findings recommend that daily oral supplementation with polyamine-rich yeast diet would be beneficial for prophylaxis of metabolic bone diseases associated with abnormal osteoclast activation.

WY 1048, a 17-methyl 19-nor D-ring analog of vitamin D3, in combination with risedronate restores bone mass in a mouse model of postmenopausal osteoporosis

Bisphosphonates like risedronate inhibit osteoclast-mediated bone resorption and are therefore used in the prevention and treatment of osteoporosis. Also vitamin D3 and calcium supplementation is commonly used in the prevention or treatment of osteoporosis. Combined therapy of risedronate with 1,25(OH)2D3, the active metabolite of vitamin D3, may be advantageous over the use of either monotherapy, but bears a risk of causing hypercalcemia thereby decreasing the therapeutic window for osteoporosis treatment. In this study, we evaluated the effect on bone mass of the combination of risedronate with the 17-methyl 19-nor five-membered D-ring vitamin D3 analog WY 1048 in a mouse ovariectomy model for postmenopausal osteoporosis. Ovariectomy-induced bone loss was restored by administration of risedronate or a combination of risedronate with 1,25(OH)2D3. However, the combination of WY 1048 with risedronate induced an even higher increase on total body and spine bone mineral density and on trabecular and cortical bone mass. Our data indicate that combination therapy of risedronate with WY 1048 was superior in restoring and improving bone mass over a combination of risedronate with 1,25(OH)2D3 with minimal calcemic side effects.

Aptamer-functionalized exosomes from bone marrow stromal cells target bone to promote bone regeneration.

In elderly people particularly in postmenopausal women, inadequate bone formation by osteoblasts originating from bone marrow mesenchymal stem cells (BMSCs) for compensation of bone resorption by osteoclasts is a major reason for osteoporosis. Enhancing osteoblastic differentiation of BMSCs is a feasible therapeutic strategy for osteoporosis. Here, bone marrow stromal cell (ST)-derived exosomes (STExos) are found to remarkably enhance osteoblastic differentiation of BMSCs in vitro. However, intravenous injection of STExos is inefficient in ameliorating osteoporotic phenotypes in an ovariectomy (OVX)-induced postmenopausal osteoporosis mouse model, which may be because STExos are predominantly accumulated in the liver and lungs, but not in bone. Hereby, the STExo surface is conjugated with a BMSC-specific aptamer, which delivers STExos into BMSCs within bone marrow. Intravenous injection of the STExo-Aptamer complex enhances bone mass in OVX mice and accelerates bone healing in a femur fracture mouse model. These results demonstrate the efficiency of BMSC-specific aptamer-functionalized STExos in targeting bone to promote bone regeneration, providing a novel promising approach for the treatment of osteoporosis and fracture.