S1P-S1PR1 Signaling: the "Sphinx" in Osteoimmunology.

The fundamental interaction between the immune and skeletal systems, termed as osteoimmunology, has been demonstrated to play indispensable roles in the maintenance of balance between bone resorption and formation. The pleiotropic sphingolipid metabolite, sphingosine 1-phosphate (S1P), together with its cognate receptor, sphingosine-1-phosphate receptor-1 (S1PR1), are known as key players in osteoimmunology due to the regulation on both immune system and bone remodeling. The role of S1P-S1PR1 signaling in bone remodeling can be directly targeting both osteoclastogenesis and osteogenesis. Meanwhile, inflammatory cell function and polarization in both adaptive immune (T cell subsets) and innate immune cells (macrophages) are also regulated by this signaling axis, suggesting that S1P-S1PR1 signaling could aslo indirectly regulate bone remodeling via modulating the immune system. Therefore, it could be likely that S1P-S1PR1 signaling might take part in the maintenance of continuous bone turnover under physiological conditions, while lead to the pathogenesis of bone deformities during inflammation. In this review, we summarized the immunological regulation of S1P-S1PR1 signal axis during bone remodeling with an emphasis on how osteo-immune regulators are affected by inflammation, an issue with relevance to chronical bone disorders such as rheumatoid arthritis, spondyloarthritis and periodontitis.

Saturated fatty acids promote chondrocyte matrix remodeling through reprogramming of autophagy pathways.

OBJECTIVES: Obesity is a known strong risk factor for the onset of knee osteoarthritis and is often accompanied by dysregulated lipid metabolism with elevated levels of free fatty acids such as saturated fatty acids (SFAs). The purpose of this study was to determine how autophagy varies in chondrocytes in response to predominant SFAs such as lauric, myristic, palmitic, and stearic acids. METHODS: Normal human articular cartilage chondrocytes and C28/I2 chondrocyte cell lines were stimulated with different SFAs in both the absence and presence of interleukin-1ß to study the effects of SFA and inflammatory cytokines in mediating the activation of autophagy. The effects of rapamycin and LY290042 on autophagy in response to different SFAs were also assessed. RESULTS: Palmitic and stearic acid stimulation of chondrocytes resulted in increased activation of both autophagy and the canonical NFκB pathway as evidenced by increased expressions of the key autophagy markers microtubule-associated protein-1 light chain 3, autophagy-related 5, beclin-1, and NFκB p65. In contrast, lauric acid stimulation resulted in decreased autophagy activation as shown by decreased expressions of microtubule-associated protein-1 light chain 3, autophagy-related 5, and beclin-1, which suggests decreased cellular stress. CONCLUSIONS: These results represent a novel mechanism by which various SFAs activate autophagy and simultaneously modulate NFκB signaling pathways and the expression of chondrocyte regulatory genes.

Humanization of bone and bone marrow in an orthotopic site reveals new potential therapeutic targets in osteosarcoma.

BACKGROUND: Existing preclinical murine models often fail to predict effects of anti-cancer drugs. In order to minimize interspecies-differences between murine hosts and human bone tumors of in vivo xenograft platforms, we tissue-engineered a novel orthotopic humanized bone model. METHODS: Orthotopic humanized tissue engineered bone constructs (ohTEBC) were fabricated by 3D printing of medical-grade polycaprolactone scaffolds, which were seeded with human osteoblasts and embedded within polyethylene glycol-based hydrogels containing human umbilical vein endothelial cells (HUVECs). Constructs were then implanted at the femur of NOD-scid and NSG mice. NSG mice were then bone marrow transplanted with human CD34 + cells. Human osteosarcoma (OS) growth was induced within the ohTEBCs by direct injection of Luc-SAOS-2 cells. Tissues were harvested for bone matrix and marrow morphology analysis as well as tumor biology investigations. Tumor marker expression was analyzed in the humanized OS and correlated with the expression in 68 OS patients utilizing tissue micro arrays (TMA). RESULTS: After harvesting the femurs micro computed tomography and immunohistochemical staining showed an organ, which had all features of human bone. Around the original mouse femur new bone trabeculae have formed surrounded by a bone cortex. Staining for human specific (hs) collagen type-I (hs Col-I) showed human extracellular bone matrix production. The presence of nuclei staining positive for human nuclear mitotic apparatus protein 1 (hs NuMa) proved the osteocytes residing within the bone matrix were of human origin. Flow cytometry verified the presence of human hematopoietic cells. After injection of Luc-SAOS-2 cells a primary tumor and lung metastasis developed. After euthanization histological analysis showed pathognomic features of osteoblastic OS. Furthermore, the tumor utilized the previously implanted HUVECS for angiogenesis. Tumor marker expression was similar to human patients. Moreover, the recently discovered musculoskeletal gene C12orf29 was expressed in the most common subtypes of OS patient samples. CONCLUSION: OhTEBCs represent a suitable orthotopic microenvironment for humanized OS growth and offers a new translational direction, as the femur is the most common location of OS. The newly developed and validated preclinical model allows controlled and predictive marker studies of primary bone tumors and other bone malignancies.

Notch expressed by osteocytes plays a critical role in mineralisation.

Notch is actively involved in various life processes including osteogenesis; however, the role of Notch signalling in the terminal mineralisation of bone is largely unknown. In this study, it was noted that Hey1, a downstream target of Notch signalling was highly expressed in mature osteocytes compared to osteoblasts, indicating a potential role of Notch in osteocytes. Using a recently developed thermosensitive cell line (IDG-SW3), we demonstrated that dentin matrix acidic phosphoprotein 1 (DMP1) expression was inhibited and mineralisation process was significantly altered when Notch pathway was inactivated via administration of N-[N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT), an inhibitor of Notch. Dysregulation of Notch in osteocyte differentiation can result in spontaneous deposition of calcium phosphate on collagen fibrils, disturbed transportation of intracellular mineral vesicles, alteration of mineral crystal structure, decreased bonding force between minerals and organic matrix, and suppression of dendrite development coupled with decreased expression of E11. In conclusion, the evidence presented here suggests that Notch plays a critical role in osteocyte differentiation and biomineralisation process. KEY MESSAGES: Notch plays a regulatory role in osteocyte phenotype. Notch modulates the mineralisation mediated by osteocytes. Notch activity influences the ultrastructural properties of bone mineralisation.

Alteration of clot architecture using bone substitute biomaterials (beta-tricalcium phosphate) significantly delays the early bone healing process.

When a bone substitute biomaterial is implanted into the body, the material's surface comes into contact with circulating blood, which results in the formation of a peri-implant hematoma or blood clot. Although hematoma formation is vital for the early bone healing process, knowledge concerning the biomaterial-induced structural properties of blood clots is limited. Here, we report that implantation of beta-tricalcium phosphate (ß-TCP) in a bone defect healing model in rats resulted in significantly delayed early bone healing compared to empty controls (natural healing). In vitro studies showed that ß-TCP had a profound effect on the overall structure of hematomas, as was observed by fibrin turbidity, scanning electron microscopy (SEM), compaction assays, and fibrinolysis. Under the influence of ß-TCP, clot formation had a significantly shortened lag time and there was enhanced lateral fibrin aggregation during the clot polymerization, which resulted in clots composed of thinner fibers. Furthermore, fibrin clots that formed around ß-TCP exhibited reduced compaction and increased resistance to fibrinolysis. Together, these results provide a plausible mechanism for how implanted bone-substitute materials may impact the structural properties of the hematoma, thereby altering the early bone healing processes, such as cell infiltration, growth factor release and angiogenesis.

Percutaneous Full-Endoscopic Anterior Transcorporeal Procedure for Cervical Disc Herniation: A Novel Procedure and Early Follow-Up Study.

OBJECTIVE: To describe the surgical technique of percutaneous full-endoscopic anterior transcorporeal cervical discectomy (PEATCD) in detail and report the clinical outcomes and radiologic changes in patients with cervical intervertebral disc herniation (CIVDH). METHODS: A novel procedure, PEATCD, was performed on 36 patients with CIVDH between June 2015 and June 2016. A retrospective study of these patients was carried out over a follow-up period of 12-24 months. The visual analog scale scores, Japanese Orthopedic Association (JOA) scores, and improvement rates (IRs) of the JOA scores were used to evaluate neurologic symptoms. Radiologic follow-up included magnetic resonance imaging, computed tomography scan, and standard radiographs. RESULTS: All patients reported immediate postoperative relief of neck and arm pain compared with the recorded preoperative levels of discomfort, and the JOA scores improved gradually during the follow-up period. The IRs of the neurologic evaluations ranged from 60% to 100%, the average being 85.47% ± 9.32%. The decrease in the intervertebral disc height was statistically significant (P < 0.0001), and there were no adverse clinically related symptoms. No collapse of the drilled vertebrae was recorded, and the bone defects showed significant decreases within 3 months after the operation. There were no surgery-related complications. CONCLUSIONS: PEATCD combines the benefits of an anterior transcorporeal approach with endoscopy, preserves the cervical motion segment and causes less damage to the disc, and significantly decreases surgical trauma. Therefore, PEATCD is a safe, effective, minimally invasive, alternative procedure for patients with CIVDH.

Mixed cell therapy of bone marrow-derived mesenchymal stem cells and articular cartilage chondrocytes ameliorates osteoarthritis development.

Of the many cell-based treatments that have been tested in an effort to regenerate osteoarthritic articular cartilage, none have ever produced cartilage that compare with native hyaline cartilage. Studies show that different cell types lead to inconsistent results and for cartilage regeneration to be considered successful, there must be an absence of fibrotic tissue. Here we report of a series of experiments in which bone marrow-derived stem cells (BMSCs) and articular cartilage chondrocytes (ACCs) were mixed in a 1:1 ratio and tested for their ability to enhance cartilage regeneration in three different conditions: (1) in an in vitro differentiation model; (2) in an ex vivo cartilage defect model implanted subcutaneously in mice; and (3) as an intra-articular injection in a meniscectomy-induced OA model in rats. The mixed cells were compared with monocultures of BMSCs and ACCs. In all three experimental models there was significantly enhanced cartilage regeneration and decreased fibrosis in the mixed BMSCs+ACCs group compared with the monocultures. Molecular analysis showed a reduction in vascularization and hypertrophy, coupled with higher chondrogenic gene expression resulting from the BMSCs+ACCs treatment. Together, our data suggest that mixed BMSCs+ACCs treatment is highly chondro-protective and is more effective in regenerating damaged cartilage in both the ex vivo cartilage defect and post-trauma OA disease models. The results from this approach could potentially be used for regeneration of cartilage in OA patients.

Effective Range of Percutaneous Posterior Full-Endoscopic Paramedian Cervical Disc Herniation Discectomy and Indications for Patient Selection.

The objective was to investigate the effective and safe range of paramedian CDH by percutaneous posterior full-endoscopy cervical intervertebral disc nucleus pulposus resection (PPFECD) to provide a reference for indications and patient selection. Sixteen patients with CDH satisfied the inclusion criteria. Before surgery the patients underwent cervical spine MRI, and the distance between the dural sac and herniated disc was measured. An assessment was performed by MRI immediately after surgery, measuring the distance between dural sac and medial border of discectomy (DSMD). The preoperative average distance between the dural sac and peak of the herniated disc (DSPHD) was 3.87 ± 1.32 mm; preoperative average distance between dural sac and medial border of herniated disc (DSMHD) was 6.91 ± 1.21 mm and an average distance of postoperative DSMD was 5.41 ± 1.40 mm. Postoperative VAS of neck and shoulder pain was significantly decreased but JOA was significantly increased in each time point compared with preoperative ones. In summary, the effective range of PPFECD to treat paramedian CDH was 5.41 ± 1.40 mm, indicating that DSMHD and DSPHD were within 6.91 ± 1.21 mm and 3.87 ± 1.32 mm, respectively. PPFECD surgery is, therefore, a safe and effective treatment option for patients with partial paramedian cervical disc herniation.

Obesity-associated metabolic syndrome spontaneously induces infiltration of pro-inflammatory macrophage in synovium and promotes osteoarthritis.

OBJECTIVES: Epidemiological and experimental studies have established obesity to be an important risk factor for osteoarthritis (OA), however, the mechanisms underlying this link remains largely unknown. Here, we studied local inflammatory responses in metabolic-OA. METHODS: Wistar rats were fed with control diet (CD) and high-carbohydrate, high-fat diet (HCHF) for period of 8 and 16 weeks. After euthanasia, the knees were examined to assess the articular cartilage changes and inflammation in synovial membrane. Further IHC was conducted to determine the macrophage-polarization status of the synovium. In addition, CD and HCHF synovial fluid was co-cultured with bone marrow-derived macrophages to assess the effect of synovial fluid inflammation on macrophage polarisation. RESULTS: Our study showed that, obesity induced by a high-carbohydrate, high-fat (HCHF) diet is associated with spontaneous and local inflammation of the synovial membranes in rats even before the cartilage degradation. This was followed by increased synovitis and increased macrophage infiltration into the synovium and a predominant elevation of pro-inflammatory M1 macrophages. In addition, bone marrow derived macrophages, cultured with synovial fluid collected from the knees of obese rats exhibited a pro-inflammatory M1 macrophage phenotype. CONCLUSION: Our study demonstrate a strong association between obesity and a dynamic immune response locally within synovial tissues. Furthermore, we have also identified synovial resident macrophages to play a vital role in the inflammation caused by the HCHF diet. Therefore, future therapeutic strategies targeted at the synovial macrophage phenotype may be the key to break the link between obesity and OA.

Bio-inspired hybrid nanoparticles promote vascularized bone regeneration in a morphology-dependent manner.

Current major obstacles for translating the nanoparticle (NP) morphology-related function into therapeutic purposes come from the challenges in understanding the mechanisms that determine cell lineage commitment and constructing a NP-based 3D functional structure, and few studies have successfully demonstrated clear evidence of regulating in vivo tissue regeneration by NP morphology so far. Here, we show that nanoparticle geometry can be harnessed to mediate bone regeneration in a rat cranial defect model. We successfully synthesized hydroxyapatite NPs with well-defined morphologies using a modified liquid-solution-solid (LSS) method. The NPs showed differential effects on stem cell behaviors such as particle uptake, autophagy activation and osteogenic differentiation. By integrating nanoparticles within gelatin, we achieved 3D scaffolds with uniformly-distributed nano-topologies which, can mediate in vivo osteogenesis through stimulation of autophagy, with spherical particles demonstrating the most robust bone formation capacity compared to other NPs. Our current work proposes a morphology-dependent effect of NPs on vascularization and bone formation and provides an innovative and feasible strategy for bone regenerative therapies.

Structural properties of fracture haematoma: current status and future clinical implications.

Blood clots (haematomas) that form immediately following a bone fracture have been shown to be vital for the subsequent healing process. During the clotting process, a number of factors can influence the fibrin clot structure, such as fibrin polymerization, growth factor binding, cellular infiltration (including platelet retraction), protein concentrations and cytokines. The modulation of the fibrin clot structure within the fracture site has important clinical implications and could result in the development of multifunctional scaffolds that mimic the natural structure of a haematoma. Artificial haematoma structures such as these can be created from the patient's own blood and can therefore act as an ideal bone defect filling material for potential clinical application to accelerate bone regeneration. Copyright © 2016 John Wiley & Sons, Ltd.

Protective effects of mitochondria-targeted antioxidants and statins on cholesterol-induced osteoarthritis.

The contribution of metabolic factors on the severity of osteoarthritis (OA) is not fully appreciated. This study aimed to define the effects of hypercholesterolemia on the progression of OA. Apolipoprotein E-deficient (ApoE-/-) mice and rats with diet-induced hypercholesterolemia (DIHC) rats were used to explore the effects of hypercholesterolemia on the progression of OA. Both models exhibited OA-like changes, characterized primarily by a loss of proteoglycans, collagen and aggrecan degradation, osteophyte formation, changes to subchondral bone architecture, and cartilage degradation. Surgical destabilization of the knees resulted in a dramatic increase of degradative OA symptoms in animals fed a high-cholesterol diet compared with controls. Clinically relevant doses of free cholesterol resulted in mitochondrial dysfunction, overproduction of reactive oxygen species (ROS), and increased expression of degenerative and hypertrophic markers in chondrocytes and breakdown of the cartilage matrix. We showed that the severity of diet-induced OA changes could be attenuated by treatment with both atorvastatin and a mitochondrial targeting antioxidant. The protective effects of the mitochondrial targeting antioxidant were associated with suppression of oxidative damage to chondrocytes and restoration of extracellular matrix homeostasis of the articular chondrocytes. In summary, our data show that hypercholesterolemia precipitates OA progression by mitochondrial dysfunction in chondrocytes, in part by increasing ROS production and apoptosis. By addressing the mitochondrial dysfunction using antioxidants, we were able attenuate the OA progression in our animal models. This approach may form the basis for novel treatment options for this OA risk group in humans.-Farnaghi, S., Prasadam, I., Cai, G., Friis, T., Du, Z., Crawford, R., Mao, X., Xiao, Y. Protective effects of mitochondria-targeted antioxidants and statins on cholesterol-induced osteoarthritis.

The impact of Wnt signalling and hypoxia on osteogenic and cementogenic differentiation in human periodontal ligament cells.

Cementum is a periodontal support tissue that is directly connected to the periodontal ligament. It shares common traits with bone tissues, however, unlike bone, the cementum has a limited capacity for regeneration. As a result, following damage the cementum rarely, if ever, regenerates. Periodontal ligament cells (PDLCs) are able to differentiate into osteoblastic and cementogenic lineages according to specific local environmental conditions, including hypoxia, which is induced by inflammation or activation of the Wnt signalling pathway by local loading. The interactions between the Wnt signalling pathway and hypoxia during cementogenesis are of particular interest to improve the understanding of periodontal tissue regeneration. In the present study, osteogenic and cementogenic differentiation of PDLCs was investigated under hypoxic conditions in the presence and absence of Wnt pathway activation. Protein and gene expression of the osteogenic markers type 1 collagen (COL1) and runt­related transcription factor 2 (RUNX2), and cementum protein 1 (CEMP1) were used as markers for osteogenic and cementogenic differentiation, respectively. Wnt signalling activation inhibited cementogenesis, whereas hypoxia alone did not affect PDLC differentiation. However, hypoxia reversed the inhibition of cementogenesis that resulted from overexpression of Wnt signalling. Cross-talk between hypoxia and Wnt signalling pathways was, therefore, demonstrated to be involved in the differentiation of PDLCs to the osteogenic and cementogenic lineages. In summary, the present study suggests that the differentiation of PDLCs into osteogenic and cementogenic lineages is partially regulated by the Wnt signalling pathway and that hypoxia is also involved in this process.

Alteration of blood clot structures by interleukin-1 beta in association with bone defects healing.

The quality of hematomas are crucial for successful early bone defect healing, as the structure of fibrin clots can significantly influence the infiltration of cells, necessary for bone regeneration, from adjacent tissues into the fibrin network. This study investigated if there were structural differences between hematomas from normal and delayed healing bone defects and whether such differences were linked to changes in the expression of IL-1ß. Using a bone defect model in rats, we found that the hematomas in the delayed healing model had thinner fibers and denser clot structures. Moreover, IL-1ß protein levels were significantly higher in the delayed healing hematomas. The effects of IL-1ß on the structural properties of human whole blood clots were evaluated by thrombelastograph (TEG), scanning electronic microscopy (SEM), compressive study, and thrombolytic assays. S-nitrosoglutathione (GSNO) was applied to modulate de novo hematoma structure and the impact on bone healing was evaluated in the delayed healing model. We found that GSNO produced more porous hematomas with thicker fibers and resulted in significantly enhanced bone healing. This study demonstrated that IL-1ß and GSNO had opposing effects on clot architecture, the structure of which plays a pivotal role in early bone healing.

Characterization of nano-structural and nano-mechanical properties of osteoarthritic subchondral bone.

BACKGROUND: Although articular cartilage is the primary tissues affected by osteoarthritis (OA), the underlying subchondral bone also undergoes noticeable changes. Despite the growing body of research into the biophysical and mechanical properties of OA bone there are few studies that have analysed the structure of the subchondral sclerosis at the nanoscale. In this study, the composition and nano-structural changes of human osteoarthritis (OA) subchondral bone were investigated to better understand the site-specific changes. METHODS: OA bone samples were collected from patients undergoing total knee replacement surgery and graded according to disease severity (grade I: mild OA; grade IV: severe OA). Transmission electron microscopy (TEM), Electron Diffraction, and Elemental Analysis techniques were used to explore the cross-banding pattern, nature of mineral phase and orientation of the crystal lattice. Subchondral bone nano-hydroxyapatite powders were prepared and characterised using high resolution transmission electron microscopy (HR-TEM) and fourier transform infrared spectroscopy (FTIR). Subchondal bone mechanical properties were investigated using a nano-indentation method. RESULTS: In grade I subchondral bone samples, a regular periodic fibril banding pattern was observed and the c-axis orientation of the apatite crystals was parallel to the long axis of the fibrils. By contrast, in grade IV OA bone samples, the bulk of fibrils formed a random and undulated arrangement accompanied by a circular oriented pattern of apatite crystals. Fibrils in grade IV bone showed non-hierarchical intra-fibrillar mineralization and higher calcium (Ca) to phosphorous (P) (Ca/P) ratios. Grade IV OA bone showed higher crystallinity of the mineral content, increased modulus and hardness compared with grade I OA bone. CONCLUSIONS: The findings from this study suggest that OA subchondral sclerotic bone has an altered mineralization process which results in nano-structural changes of apatite crystals that is likely to account for the compromised mechanical properties of OA subchondral bones.

Is Synovial Macrophage Activation the Inflammatory Link Between Obesity and Osteoarthritis?

Osteoarthritis (OA) is the most common musculoskeletal disease, affecting nearly 25 % of the world population (WHO reports), leading to pain and disability. There are as yet no clinically proven therapies to halt OA onset or progression; the development of such therapies is, therefore, a national as well as international research priority. Obesity-related metabolic syndrome has been identified as the most significant, but also an entirely preventable risk factor for OA; however, the mechanisms underlying this link remain unclear. We have examined the available literature linking OA and metabolic syndrome. The two conditions have a shared pathogenesis in which chronic low-grade inflammation of affected tissues is recognized as a major factor that is associated with systemic inflammation. In addition, the occurrence of metabolic syndrome appears to alter systemic and local pro-inflammatory cytokines that are also related to the development of OA-like pathologies. Recent findings highlight the importance not only of the elevated number of macrophage in inflamed synovium but also the activation and amplification of the inflammatory state and other pathological changes. The role of local inflammation on the synovium is now considered to be a pharmacological target against which to aim disease-modifying drugs. In this review, we evaluate evidence linking OA, synovitis and metabolic syndrome and discuss the merits of targeting macrophage activation as a valid treatment option for OA.

Multi-Elemental Profiling of Tibial and Maxillary Trabecular Bone in Ovariectomised Rats.

Atomic minerals are the smallest components of bone and the content of Ca, being the most abundant mineral in bone, correlates strongly with the risk of osteoporosis. Postmenopausal women have a far greater risk of suffering from OP due to low Ca concentrations in their bones and this is associated with low bone mass and higher bone fracture rates. However, bone strength is determined not only by Ca level, but also a number of metallic and non-metallic elements in bone. Thus, in this study, the difference of metallic and non-metallic elements in ovariectomy-induced osteoporosis tibial and maxillary trabecular bone was investigated in comparison with sham operated normal bone by laser ablation inductively-coupled plasma mass spectrometry using a rat model. The results demonstrated that the average concentrations of (25)Mg, (28)Si, (39)K, (47)Ti, (56)Fe, (59)Co, (77)Se, (88)Sr, (137)Ba, and (208)Pb were generally higher in tibia than those in maxilla. Compared with the sham group, Ovariectomy induced more significant changes of these elements in tibia than maxilla, indicating tibial trabecular bones are more sensitive to changes of circulating estrogen. In addition, the concentrations of (28)Si, (77)Se, (208)Pb, and Ca/P ratios were higher in tibia and maxilla in ovariectomised rats than those in normal bone at all time-points. The present study indicates that ovariectomy could significantly impact the element distribution and concentrations between tibia and maxilla.

Copper-doped mesoporous silica nanospheres, a promising immunomodulatory agent for inducing osteogenesis.

The application of mesoporous silica nanospheres (MSNs) loaded with drugs/growth factors to induce osteogenic differentiation of stem cells has been trialed by a number of researchers recently. However, limitations such as high cost, complex fabrication and unintended side effects from supraphysiological concentrations of the drugs/growth factors represent major obstacles to any potential clinical application in the near term. In this study we reported an in situ one-pot synthesis strategy of MSNs doped with hypoxia-inducing copper ions and systematically evaluated the nanospheres by in vitro biological assessments. The Cu-containing mesoporous silica nanospheres (Cu-MSNs) had uniform spherical morphology (∼100nm), ordered mesoporous channels (∼2nm) and homogeneous Cu distribution. Cu-MSNs demonstrated sustained release of both silicon (Si) and Cu ions and controlled degradability. The Cu-MSNs were phagocytized by immune cells and appeared to modulate a favorable immune environment by initiating proper pro-inflammatory cytokines, inducing osteogenic/angiogenic factors and suppressing osteoclastogenic factors by the immune cells. The immune microenvironment induced by the Cu-MSNs led to robust osteogenic differentiation of bone mesenchymal stem cells (BMSCs) via the activation of Oncostation M (OSM) pathway. These results suggest that the novel Cu-MSNs could be used as an immunomodulatory agent with osteostimulatory capacity for bone regeneration/therapy application. STATEMENT OF SIGNIFICANCE: In order to stimulate both osteogenesis and angiogenesis of stem cells for further bone regeneration, a new kind of hypoxia-inducing copper doped mesoporous silica nanospheres (Cu-MSNs) were prepared via one-pot synthesis. Biological assessments under immune environment which better reflect the in vivo response revealed that the nanospheres possessed osteostimulatory capacity and had potential as immunomodulatory agent for bone regeneration/therapy application. The strategy of introducing controllable amount of therapeutic ions instead of loading expensive drugs/growth factors in mesoporous silica nanosphere provides new options for bioactive nanomaterial functionalization.