Osteoblast Function Research Articles

Tumor- and Osteoblast-Derived Periostin in Prostate Cancer bone Metastases.

Exploring the biological function of periostin (POSTN) in prostate cancer (PCa) bone metastasis is of importance. It was observed that the expression of POSTN was high in PCa, especially highest in PCa metastasized to bone. In this study, we found that inhibiting POSTN in PCa cells could significantly alleviate PCa bone metastasis in vivo, suggesting POSTN is a promising therapeutic target. Since, due to the secreted expression of POSTN in osteoblasts and PCa, we hypothesized the positive feedback loop between osteoblasts and PCa mediated by POSTN in PCa bone metastasis. The in vitro experiments demonstrated that osteoblast-derived POSTN promoted PCa cell proliferation and invasion and PCa cell-derived POSTN promotes proliferation of osteoblasts. Furthermore, we found that POSTN regulated PCa and osteoblast function through integrin receptors. Finally, 18F-Alfatide II was used as the molecule probe of integrin αvβ3 in PET-CT, revealing high intake in metastatic lesions. Our findings together indicate that targeting POSTN in PCa cells as well as in the osteoblastic may be an effective treatment for PCa bone metastasis.

Current concepts from diagnosis to management in Gorham-Stout disease: a systematic narrative review of about 350 cases.

Patients with Gorham–Stout disease (GSD) present progressive destruction and resorption of bone.Typical bone-related symptoms include swelling, pain and functional impairment in the region involved.The three aspects of GSD etiopathology are osteoclasts, angiogenesis/lymphangiogenesis and osteoblast function.Multi-targeted pharmacological approach includes innovative options and represent milestones of treatment, sometimes associated with radiotherapy.Surgery is mainly used to treat complications: pathologic/impending fractures, spinal instability or deformities and chylothorax.In this narrative review, we highlight current standards in diagnosis, clinical management and therapeutic strategies.

Sex-specific differences in direct osteoclastic versus indirect osteoblastic effects underlay the low bone mass of Pannexin1 deletion in TRAP-expressing cells in mice

Pannexin1 (Panx1) is a hemichannel-forming protein that participates in the communication of cells with the extracellular space. To characterize the role of osteoclastic Panx1 on bone, Panx1fl/fl;TRAP-Cre (Panx1ΔOc) mice were generated, and compared to Panx1fl/fl littermates at 6 weeks of age. Total and femoral BMD was ~20% lower in females and males whereas spinal BMD was lower only in female Panx1ΔOc mice. μCT analyses showed that cortical bone of the femoral mid-diaphysis was not altered in Panx1ΔOc mice. In contrast, cancellous bone in the distal femur and lumbar vertebra was significantly decreased in both female and male Panx1ΔOc mice compared to Panx1fl/fl controls and was associated with higher osteoclast activity in female Panx1ΔOc mice, with no changes in the males. On the other hand, vertebral bone formation was decreased for both sexes, resulting from lower mineral apposition rate in the females and lower mineralizing surface in the males. Consistent with an osteoclastic effect in female Panx1ΔOc mice, osteoclast differentiation with RANKL/M-CSF and osteoclast bone resorbing activity in vitro were higher in female, but not male, Panx1ΔOc mice, compared to Panx1fl/fl littermates. Surprisingly, although Panx1 expression was normal in bone marrow stromal-derived osteoblasts from male and female Panx1ΔOc mice, mineral deposition by male (but not female) Panx1ΔOc osteoblasts was lower than controls, and it was reduced in male Panx1fl/fl osteoblasts when conditioned media prepared from male Panx1ΔOc osteoclast cultures was added to the cell culture media. Thus, deletion of Panx1 in TRAP-expressing cells in female mice leads to low bone mass primarily through a cell autonomous effect in osteoclast activity. In contrast, our evidence suggests that changes in the osteoclast secretome drive reduced osteoblast function in male Panx1ΔOc mice, resulting in low bone mass.

Effect of hyponatremia normalization on osteoblast function in patients with SIAD.

Hyponatremia is associated with an increased risk of bone fragility and fractures. Many studies suggest that hyponatremia stimulates osteoclast activation, whereas other studies rather reveal a possible role of acute hyponatremia in impairing osteoblast function. We aimed to assess whether and how correction of hyponatremia in hospitalized patients with the syndrome of inappropriate antidiuresis (SIAD) has an impact on bone metabolism. This was a predefined secondary analysis of 88 hospitalized patients with SIAD undergoing a randomized treatment with SGLT-2 inhibitors or placebo for 4 days. Biochemical markers of bone resorption (CTX) and bone formation (PINP) were collected in serum at baseline and after the intervention (day 5). Bone formation index (defined as PINP/CTX) and its difference between day 5 and baseline were calculated. Patients with steroid therapy (n = 6), fractures (n = 10), or whose data were missing (n = 4) were excluded from the analysis. Out of 68 patients, 27 (39.7%) were normonatremic at day 5. These patients showed an increase in serum PINP (P = 0.04), whereas persistent hyponatremic patients did not (P = 0.38), with a relevant difference between these two subgroups (P = 0.005). Serum CTX increased similarly in the two groups (P = 0.43). This produced a 47.9 points higher PINP/CTX difference between discharge and admission in normonatremic patients (95% CI: 17.0-78.7, P = 0.003) compared to patients with persistent hyponatremia, independent of age, sex, BMI, smoking habits, randomization arm, and baseline cortisol levels. Our predefined post hoc analysis shows that correction of hyponatremia in hospitalized patients with SIAD might have a positive impact on osteoblast function.

Discontinuation of PTH therapy amplifies bone loss by increasing oxidative stress: An event ameliorated by sequential IL-17 neutralizing antibody therapy.

Osteoporosis leads to excessive bone resorption which is not accompanied by equal amount of bone formation. PTH (1-34) forms the mainstay of bone anabolic therapy. Intermittent PTH (iPTH) has the ability to reconstruct skeleton, a property not shared by other anti-resorptives. In initial phases of PTH treatment, bone formation exceeds bone resorption. However, gradually this phase is replaced by increased bone resorption. Thus, a replacement post PTH discontinuation is much needed. Studies with bisphosphonates and Denosumab post PTH withdrawal have yielded promising but variable results. Thus, there is scope for trying new combinations. Our previous studies have shown the superior skeletal effects of neutralizing IL17 antibody (NIL17) over anti-RANKL antibody. Thus, here we investigated if sequential treatment of NIL17 after PTH withdrawal (SHIFT) could serve as a promising therapeutic approach for osteoporosis treatment. Our results show that PTH withdrawal (PTH-W) led to mitigation of its anabolic effects as evidenced by reduced BMD, bone trabecular and cortical microarchitectural parameters. In the continuous PTH (PTH-C) and the Shift group, all these parameters were preserved as par with the sham group. Shift therapy also significantly increased PINP levels. Most importantly, serum CTX-I levels and osteoclast numbers, which were elevated in PTH groups were significantly suppressed in NIL17 monotherapy and shift group. Also, expression of FOXO1 and ATF-4, the main regulators of redox balance and function in osteoblasts, were found to be enhanced maximally in the sequential therapy group. Our study thus advocates use of NIL17 as a replacement therapeutic option post PTH discontinuation.

Silibinin-modified Hydroxyapatite coating promotes the osseointegration of titanium rods by activation SIRT1/SOD2 signaling pathway in diabetic rats

The purpose of this study is to investigate the role of Silibinin (SIL)-modified Hydroxyapatite coating on osseointegration in diabetes in vivo and in vitro and explore the mechanism of osteogenic differentiation of MC3T3-E1. RT-qPCR, Immunofluorescence, and Western blot were used to measure the expression level of oxidative Stress Indicators and osteogenic markers proteins. Moreover, CCK-8 assay was conducted to detect cell viability in hyperglycemia. Alizarin red staining and alkaline phosphatase staining were used to examine osteogenic function and calcium deposits. The diabetic rat model receive titanium rod implantation was set up successfully and Von-Gieson staining was used to examine femoral bone tissue around titanium rod. Our results showed that intracellular oxidative stress in hyperglycemia was overexpressed, while FoxO1, SIRT1, GPX1, and SOD2 were downregulated. SIL suppressed oxidative stress to promote osteogenic differentiation. Additionally, it was confirmed that SIL promoted osteogenic differentiation of MC3T3-E1 and obviously restored the osseointegration ability of diabetic rats. Further study indicated that SIL exerted its beneficial function through activation SIRT1/SOD2 signaling pathway to restore osteoblast function, and improved the osseointegration and stability of titanium rods in vivo. Our research suggested that the SIL-modulated oxidative Stress inhibition is responsible for the activation of the process of osteogenic differentiation through activation SIRT1/SOD2 signaling pathway in hyperglycemia, providing a novel insight into improving prosthetic osseointegration in diabetic patients.Hyperglycemia impaired the activity and function of MC3T3-E1 and inhibits bone formation by up-regulating intracellular ROS levels through inhibition of SIRT1/SOD2 signaling pathway. Local administrator SIL can improve the activity and function of osteoblasts and enhance osseointegration by reducing intracellular ROS through activation of SIRT1/SOD2 signaling pathway in DM rat models.

MiR-138-5p Targets MACF1 to Aggravate Aging-related Bone Loss.

Senile osteoporosis is one of the major health problems in an aging society. Decreased bone formation due to osteoblast dysfunction may be one of the causes of aging-related bone loss. With increasing evidence suggesting that multiple microRNAs (miRNAs) play important roles in osteoblast function, the relationship between miRNAs and senile osteoporosis has become a popular research topic. Previously, we confirmed that mechanoresponsive miR-138-5p negatively regulated bone anabolic action. In this study, the miR-138-5p level was found to be negatively correlated with BMD and osteogenic markers in bone specimens of senile osteoporotic patients by bioinformatic analysis and experimental verification. Furthermore, high miR-138-5p levels aggravated the decrease of aged osteoblast differentiation in vitro and led to worse bone loss in aged osteoblastic miR-138-5p transgenic mice in vivo. We also previously identified that the target of miR-138-5p, microtubule actin cross-linking factor 1 (MACF1), could attenuate senile osteoporosis. Here, miR-138-5p was demonstrated to regulate aged osteoblast differentiation by targeting MACF1. Finally, the therapeutic inhibition of miR-138-5p counteracted the decrease in bone formation and aging-related bone loss in aged mice. Overall, our results highlight the crucial roles and the molecular mechanism of miR-138-5p in aging-related bone loss and may provide a powerful therapeutic target for ameliorating senile osteoporosis.

Endoplasmic Reticulum Stress in Osteoarthritis: A Novel Perspective on the Pathogenesis and Treatment.

Osteoarthritis (OA), the most common degenerative joint disease, causes an enormous socioeconomic burden due to its disabling properties and high prevalence. Increasing evidence suggests that OA is a whole-joint disease involving cartilage degradation, synovitis, meniscal lesions, and subchondral bone remodeling. Endoplasmic reticulum (ER) stress is the accumulation of misfolded/unfolded proteins in the ER. Recent studies have found that ER stress is involved in the OA pathological changes by influencing the physiological function and survival of chondrocytes, fibroblast-like synoviocytes, synovial macrophages, meniscus cells, osteoblasts, osteoclasts, osteocytes, and bone marrow mesenchymal stem cells. Therefore, ER stress is an attractive and promising target for OA. However, although targeting ER stress has been proven to alleviate OA progression in vitro and in vivo, the treatments for OA remain in preclinical stage and require further investigation.

Primena vitamina D u terapiji osteoporoze

Vitamin D is one of the most important nutritional elements, necessary for the regulation of calcium and phosphorus metabolism and for maintaining the health of the skeletal system. It's been shown that vitamin D has an important role in maintaining normal skeletal system function by providing an appropriate balance between osteoblast and osteoclast function. Osteoporosis, ie. metabolic bone disease which increases the risk of pathological fractures, due to the changes of the microarchitecture of the skeleton, is very common consequence of long-term vitamin D deficiency. Vitamin D deficiency is considered the main cause in the pathology of certain malignancies, heart disease, hypertension, autoimmune diseases, diabetes, depression, chronic pain, osteoarthritis, osteoporosis, muscle weakness, muscle loss, periodontal disease. Vitamin D deficiency is extremely common, not only in the elderly population. It has recently been suggested that 50 nmol/l (or 20 ng/ml) is a minimum level of 25(OH)D in serum in general population especially in patients with osteoporosis to ensure optimal bone health. Vitamin D supplementation is recommended when the serum 25(OH)D concentration is below 50 nmol/l (ie 20 ng/ml) for the first 2 months 2000-4000 IU per day, and then depending on the optimal level achieved, at a dose of 1000-2000 IU. Special attention should be paid to elderly patients, with graceful constitutions with an increased risk of falls and fractures. The optimal dose supposed to ensure circulating 25(OH)D on the level of higher than 75 nmol/l. Vitamin D supplements can be given weekly, monthly or at three-month intervals.

Factors secreted by monosodium urate crystal-stimulated macrophages promote a proinflammatory state in osteoblasts: a potential indirect mechanism of bone erosion in gout

BackgroundTophi are lesions commonly present at sites of bone erosion in gout-affected joints. The tophus comprises a core of monosodium urate (MSU) crystals surrounded by soft tissue that contains macrophages and other immune cells. Previous studies found that MSU crystals directly reduce osteoblast viability and function. The aim of the current study was to determine the indirect, macrophage-mediated effects of MSU crystals on osteoblasts.MethodsConditioned medium from the RAW264.7 mouse macrophage cell line cultured with MSU crystals was added to the MC3T3-E1 mouse osteoblastic cell line. Conditioned medium from the THP-1 human monocytic cell line cultured with MSU crystals was added to primary human osteoblasts (HOBs). Matrix mineralization was assessed by von Kossa staining. Gene expression was determined by real-time PCR, and concentrations of secreted factors were determined by enzyme-linked immunosorbent assay.ResultsIn MC3T3-E1 cells cultured for 13 days in an osteogenic medium, the expression of the osteoblast marker genes Col1a1, Runx2, Sp7, Bglap, Ibsp, and Dmp1 was inhibited by a conditioned medium from MSU crystal-stimulated RAW264.7 macrophages. Mineral staining of MC3T3-E1 cultures on day 21 confirmed the inhibition of osteoblast differentiation. In HOB cultures, the effect of 20 h incubation with a conditioned medium from MSU crystal-stimulated THP-1 monocytes on osteoblast gene expression was less consistent. Expression of the genes encoding cyclooxygenase-2 and IL-6 and secretion of the proinflammatory mediators PGE2 and IL-6 were induced in MC3T3-E1 and HOBs incubated with conditioned medium from MSU crystal-stimulated macrophages/monocytes. However, inhibition of cyclooxygenase-2 activity and PGE2 secretion from HOBs indicated that this pathway does not play a major role in mediating the indirect effects of MSU crystals in HOBs.ConclusionsFactors secreted from macrophages stimulated by MSU crystals attenuate osteoblast differentiation and induce the expression and secretion of proinflammatory mediators from osteoblasts. We suggest that bone erosion in joints affected by gout results from a combination of direct and indirect effects of MSU crystals.

The regulatory roles of miR-26a in the development of fracture and osteoblasts.

BackgroundMicroRNAs (miRNAs) play a vital role in the bone development and bone regeneration. In this study, we investigated the effects of miR-26a in osteoblasts and fractures.MethodsHuman osteoblasts were cultured and used for analysis. To identify differential miRNAs in blood samples from patients with fractures and healthy controls, quantitative real-time polymerase chain reaction (qRT-PCR) analysis was performed. Human osteoblasts were transfected with miR-26a mimics, miR-26a inhibitor, or their corresponding negative controls (NCs), respectively. MTT assay was performed to identify the effects of miR-26a on the cell viability of osteoblasts. EdU staining was applied to detect the proliferation of osteoblasts. Trypan blue staining was utilized to analyze the effects of miR-26a on the cell death of osteoblasts. Terminal deoxynucleotidyl transferase mediated dUTP nick-end labeling (TUNEL) staining was used to detect apoptotic osteoblasts. Alizarin red S (ARS) staining and qRT-PCR analysis were utilized to measure the mineralized nodule formation to evaluate the bone formation of osteoblasts. Dual luciferase reporter assay and western blot analysis were performed to detect the relationship between miR-26a and its target gene.ResultsThe results of qRT-PCR analysis identified miR-26a as our miRNA of interest and indicated that miR-26a was significantly decreased in patients with fractures. Overexpression of miR-26a significantly increased the cell viability and proliferation of osteoblasts. An increase in miR-26a reduced the cell death and apoptosis of osteoblasts, and promoted the osteoblastic activity and mineralized nodule formation. Dual luciferase reporter assay, qRT-PCR and western blot analysis showed that miR-26a could negatively regulate the expression of phosphatase and tensin homolog (PTEN).ConclusionsMiR-26a promoted new bone regeneration via regulating the functions of osteoblasts by targeting its target gene PTEN. Therefore, we propose that targeting miR-26a may be a novel therapeutic method for bone regeneration and treating fractures.

Insight into the potential pathogenesis of human osteoarthritis via single-cell RNA sequencing data on osteoblasts.

Osteoarthritis (OA) is the most common degenerative joint disease caused by osteoblastic lineage cells. However, a comprehensive molecular program for osteoblasts in human OA remains underdeveloped. The single-cell gene expression of osteoblasts and microRNA array data were from human. After processing the single-cell RNA sequencing (scRNA-seq) data, it was subjected to principal component analysis (PCA) and T-Stochastic neighbor embedding analysis (TSNE). Differential expression analysis was aimed to find marker genes. Gene-ontology (GO) enrichment, Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis and Gene set enrichment analysis (GSEA) were applied to characterize the molecular function of osteoblasts with marker genes. Protein-protein interaction (PPI) networks and core module were established for marker genes by using the STRING database and Cytoscape software. All nodes in the core module were considered to be hub genes. Subsequently, we predicted the potential miRNA of hub genes through the miRWalk, miRDB and TargetScan database and experimentally verified the miRNA by GSE105027. Finally, miRNA-mRNA regulatory network was constructed using the Cytoscape software. We characterized the single-cell expression profiling of 4387 osteoblasts from normal and OA sample. The proportion of osteoblasts subpopulations changed dramatically in the OA, with 70.42% of the pre-osteoblasts. 117 marker genes were included and the results of GO analysis show that up-regulated marker genes enriched in collagen-containing extracellular matrix were highly expressed in the pre-osteoblasts cluster. Both KEGG and GSEA analyses results indicated that IL-17 and NOD-like receptor signaling pathways were enriched in down-regulated marker genes. We visualize the weight of marker genes and constructed the core module in PPI network. In potential mRNA-miRNA regulatory network, hsa-miR-449a and hsa-miR-218-5p may be involved in the development of OA. Our study found that alterations in osteoblasts state and cellular molecular function in the subchondral bone region may be involved in the pathogenesis of osteoarthritis.

Therapeutic Drug Review on Romosozumab: The First Sclerostin Inhibitor

Osteoporosis is a progressive skeletal disorder which is characterised by low bone mass, normal mineralisation and abnormal bone microarchitecture. This disruption of bone microarchitecture causes subsequent increase in bone fragility and raises risk of fractures. Osteoporosis is a growing public health problem and affects approximately over 200 million people worldwide. In the United Kingdom, it is estimated that around 3 million people have osteoporosis. Since the evolution of drug therapy for osteoporosis in the 1940's with oestrogen therapy several approaches to developing novel therapeutics for osteoporosis in animal studies and clinical observations (e.g., oestrogen, calcitonin, and teriparatide) or opportunistic repurposing of existing compounds (e.g., bisphosphonates) to one driven by advances in fundamental bone biology (e.g., denosumab). The advent of biologic agents has provided a more specific and targeted approach to the treatment of osteoporosis. Sclerostin is a glycoprotein secreted by osteocytes and regulates bone metabolism by inhibiting activation of osteoblast function and bone formation. By inhibiting sclerostin, targeted therapeutic pharmacological agents are being developed to address severe osteoporosis and patients who do not respond well to primary line of medical management of osteoporosis. Romosozumab is humanised as a monoclonal antibody designed to target sclerostin. This review assesses the mechanism and current role of romosozumab in osteoporosis treatment.

MiR-21-5p and canonical Wnt signaling pathway promote osteoblast function through a feed-forward loop induced by fluoride

Long-term excessive exposure to fluoride from environmental sources can cause serious public health problems such as dental fluorosis and skeletal fluorosis. The aberrant activation of osteoblasts in the early stage is one of the critical steps during the pathogenesis of skeletal fluorosis and canonical Wnt signaling pathway participate in the progress. However, the specific mechanism that how canonical Wnt signaling pathway was mediated is not yet clear. In this study, we found that miR-21-5p induced the activation of canonical Wnt signaling pathway via targeting PTEN and DKK2 during fluoride induced osteoblasts activation and firstly demonstrated the forward loop between canonical Wnt signaling and miR-21-5p in the process. These findings suggested an important regulatory role of miR-21-5p on canonical Wnt signaling pathway during skeletal fluorosis and miR-21-5p might be a potential therapeutic target for skeletal fluorosis.

Polymorphisms in Genes Involved in Osteoblast Differentiation and Function Are Associated with Anthropometric Phenotypes in Spanish Women

Much of the genetic variance associated with osteoporosis is still unknown. Bone mineral density (BMD) is the main predictor of osteoporosis risk, although other anthropometric phenotypes have recently gained importance. The aim of this study was to analyze the association of SNPs in genes involved in osteoblast differentiation and function with BMD, body mass index (BMI), and waist (WC) and hip (HC) circumferences. Four genes that affect osteoblast differentiation and/or function were selected from among the differentially expressed genes in fragility hip fracture (FOXC1, CTNNB1, MEF2C, and EBF2), and an association study of four single-nucleotide polymorphisms (SNPs) was conducted in a cohort of 1001 women. Possible allelic imbalance was also studied for SNP rs87939 of the CTNNB1 gene. We found significant associations of SNP rs87939 of the CTNNB1 gene with LS-sBMD, and of SNP rs1366594 of the MEF2C gene with BMI, after adjustment for confounding variables. The SNP of the MEF2C gene also showed a significant trend to association with FN-sBMD (p = 0.009). A possible allelic imbalance was ruled out as no differences for each allele were detected in CTNNB1 expression in primary osteoblasts obtained from homozygous women. In conclusion, we demonstrated that two SNPs in the MEF2C and CTNNB1 genes, both implicated in osteoblast differentiation and/or function, are associated with BMI and LS-sBMD, respectively.

Solid-state 1H NMR-based metabolomics assessment of tributylin effects in zebrafish bone

Tributyltin (TBT), an endocrine disruptor is used globally in agribusiness and industries as biocides, heat stabilizers, and in chemical catalysis. It is known for its deleterious effects on bone by negatively impacting the functions of osteoblasts, osteoclasts and mesenchymal stem cells. However, the impact of TBT on the metabolomics profile in bone is not yet studied. Here, we demonstrate alterations in chemical metabolomics profiles measured by solid state 1H nuclear magnetic resonance (1H NMR) spectroscopy in zebrafish bone following tributyltin (TBT) treatment. TBT of 0, 100, 200, 300, 400 and 500 μg/L were exposed to zebrafish. From this, zebrafish bone has subjected for further metabolomics profiling. Samples were measured via one-dimensional (1D) solvent -suppressed and T2- filtered methods with in vivo zebrafish metabolites. A dose dependent alteration in the metabolomics profile was observed and results indicated a disturbed aminoacid metabolism, TCA cycle, and glycolysis. We found a significant alteration in the levels of glutamate, glutamine, glutathione, trimethylamine N-oxide (TMAO), and other metabolites. This investigation hints us the deleterious effects of TBT on zebrafish bone enabling a comprehensive understanding of metabolomics profile and is expected to play a crucial role in understanding the deleterious effects of various endocrine disruptor on bone.

Enhanced p53 Levels Are Involved in the Reduced Mineralization Capacity of Osteoblasts Derived from Shwachman-Diamond Syndrome Subjects.

Shwachman–Diamond syndrome (SDS) is a rare autosomal recessive disorder characterized by bone marrow failure, exocrine pancreatic insufficiency, and skeletal abnormalities, caused by loss-of-function mutations in the SBDS gene, a factor involved in ribosome biogenesis. By analyzing osteoblasts from SDS patients (SDS-OBs), we show that SDS-OBs displayed reduced SBDS gene expression and reduced/undetectable SBDS protein compared to osteoblasts from healthy subjects (H-OBs). SDS-OBs cultured in an osteogenic medium displayed a lower mineralization capacity compared to H-OBs. Whole transcriptome analysis showed significant differences in the gene expression of SDS-OBs vs. H-OBs, particularly in the ossification pathway. SDS-OBs expressed lower levels of the main genes responsible for osteoblastogenesis. Of all downregulated genes, Western blot analyses confirmed lower levels of alkaline phosphatase and collagen type I in SDS-OBs than in H-OBs. Interestingly, SDS-OBs showed higher protein levels of p53, an inhibitor of osteogenesis, compared to H-OBs. Silencing of Tp53 was associated with higher collagen type I and alkaline phosphatase protein levels and an increase in SDS-OB mineralization capacity. In conclusion, our results show that the reduced capacity of SDS-OBs to mineralize is mediated, at least in part, by the high levels of p53 and highlight an important role of SBDS in osteoblast functions.

Cdc42 in osterix-expressing cells alters osteoblast behavior and myeloid lineage commitment.

Osteoblasts are not only responsible for bone formation. They also support hematopoiesis. This requires responding to cues originating from several signaling pathways, a task performed by Rho GTPases. We therefore examined several transgenic mouse models and used inhibitors of Cdc42 in vitro. Deletion of Cdc42 in vivo using the Osterix promoter suppressed osteoblast function, while its deletion in differentiating osteoblasts using the Collagen-α1(I) promoter decreased osteoblast numbers. In both cases, bone mineral density diminished confirming the importance of Cdc42. Evaluation of hematopoiesis revealed that deletion of Cdc42 using the Osterix, but not the Collagen-α1(I) promoter increased the common myeloid progenitors (CMPs) in the bone marrow as well as the erythrocytes and the thrombocytes/platelets in peripheral blood. Causality between Cdc42 loss in early osteoblasts and increased myelopoiesis was confirmed in vitro. Work in vitro supported the conclusion that interleukin-4 mediated the increase in myelopoiesis. Thus, Cdc42 is required for healthy bone through regulation of bone formation in Osterix-expressing osteoblasts and the number of osteoblasts in differentiating osteoblasts. In addition, its expression in early osteoblasts/stromal cells modulates myelopoiesis. This highlights the importance of osteoblasts in regulating hematopoiesis.

Treatment of Radiation Bone Injury with Transplanted hUCB-MSCs via Wnt/β-Catenin.

Radiation-induced bone injury (RIBI) is one of the complications after radiotherapy for malignant tumors. However, there are no effective measures for the treatment of RIBI in clinical practice, and the mechanism of RIBI is unclear. We use a single high-dose ionizing radiation (6Gy) to analyze the effect of radiotherapy on osteoblast function. Human umbilical cord blood mesenchymal stem cells (hUCB-MSCs) were cocultured with irradiated osteoblasts to examine their therapeutic effects and mechanisms on osteoblast injury. The hUCB-MSC transplantation mouse model is used to confirm the in vivo role of hUCB-MSC treatment in radiation bone injury. Western blot analysis, qRT-PCR, immunohistochemistry, and immunofluorescence staining were used to analyze gene expression and angiogenesis. The apoptosis and migration of osteoblasts were measured by Hoechst staining, scratch test, and transwell. The differentiation of osteoblasts was measured by ALP and Alizarin red staining and transmission electron microscopy. The bone-related parameters of mice were evaluated by micro-CT analysis. We found that radiation can damage the DNA of osteoblasts; induce apoptosis; reduce the differentiation, migration, and adhesion of osteoblasts, leading to lipogenesis of bone marrow mesenchymal stem cells (BMSCs) and reducing the source of osteoblasts; and increase the number of osteoclasts in bone tissue, while MSC treatment prevents these changes. Our results reveal the inhibitory effect of radiation on osteoblast function. hUCB-MSCs can be used as a therapeutic target for the development of new therapeutic strategies for radiotherapy of bone injury diseases.

Influences of Compressive Force and Zoledronic Acid on Osteoblast Proliferation and Differentiation: An In Vitro Study

This study investigates the effects of zoledronic acid (ZA) and compressive force on osteoblast functions, to elucidate the pathogenesis of medication-related osteonecrosis of the jaw (MRONJ). MC3T3-E1 cells were exposed to ZA (1, 10 and 100 µM) to evaluate the effects of ZA on cell proliferation. Furthermore, to investigate the influence of ZA with or without compressive force on osteoblast differentiation, real-time polymerase chain reaction and Alizarin Red S staining were performed. ZA concentrations > 10 μM were highly cytotoxic to MC3T3-E1 cells. Combining 1-μM ZA with compressive force influenced expression levels of osteoblast-related genes and matrix mineralization. The inhibitory effects of ZA on cell proliferation and the combination of ZA and compressive force on osteoblast differentiation may contribute to the pathogenesis of MRONJ.