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Bone marrow (BM) is a heterogeneous niche where bone marrow stromal cells (BMSCs), osteoblasts, osteoclasts, adipocytes, hematopoietic cells, and immune cells coexist. The cellular composition of BM changes with various pathophysiological states. A reduction in osteoblast number and a concomitant increase in adipocyte number in aging and pathological conditions put bone marrow adipose tissue (BMAT) into spotlight. Accumulating evidence strongly supports that an overwhelming production of BMAT is a major contributor to bone loss disorders. Therefore, BMAT-targeted therapy can be an efficient and feasible intervention for osteoporosis. However, compared to blocking bone-destroying molecules produced by BMAT, suppressing BMAT formation is theoretically a more effective and fundamental approach in treating osteoporotic bone diseases. Thus, a deep insight into the molecular basis underlying increased BM adiposity during pathologic bone loss is critical to formulate strategies for therapeutically manipulating BMAT. In this review, we comprehensively summarize the molecular mechanisms involved in adipocyte differentiation of BMSCs as well as the interaction between bone marrow adipocytes and osteoclasts. More importantly, we further discuss the potential clinical implications of therapeutically targeting the upstream of BMAT formation in bone loss diseases.

BACKGROUND Pyogenic arthritis, pyoderma gangrenosum, and acne (PAPA) syndrome is a rare autosomal dominant genetic disease characterized by severe autoimmune inflammation, caused by mutations in the PSTPIP1 gene. Due to PAPA heterogeneous clinical manifestation, misdiagnosis or delayed diagnoses are difficult to avoid. With the use of whole-exome sequencing, we identified a missense mutation in the PSTPIP1 gene in a Chinese family. To the best of our knowledge, this is the first case of PAPA reported in China. CASE SUMMARY A 9-year-old boy suffered from recurrent aseptic pyogenic arthritis triggered by minor trauma or few obvious predisposing causes for more than 3 years. Pyogenic arthritis occurred every 3-5 mo, affecting his knees, elbows, and ankle joints. Treatments, such as glucocorticoids, antibiotics, even surgeries could alleviate joints pain and swelling to some extent but could not inhibit the recurrence of arthritis. Similar symptoms were present in his younger brother but not in his parents. According to the whole-exome sequencing, a missense mutation in exon 11 of the PSTPIP1 gene (c.748G>C; p.E250Q) was detected in the boy, his younger brother and his father. Taking into account the similar phenotypic features with PAPA syndrome reported previously, we confirmed a diagnosis of PAPA syndrome for the family. CONCLUSION In this case, a missense mutation (c.748G>C; p.E250Q) in PSTPIP1 gene was identified in a Chinese family with PAPA syndrome. Previous studies emphasize the fact that PAPA syndrome is hard to diagnose just through the clinical manifestations owing to its heterogeneous expression. Genetic testing is an effectual auxiliary diagnostic method, especially in the early stages of pyogenic arthritis. Only if we have a deep understanding and rich experience of this rare disease can we make a prompt diagnosis, develop the best clinical treatment plan, and give good fertility guidance.

Background: Epidemiologic studies have shown that persons suffering from psychotic disorders are at increased risk of violent behavior. Several factors have been shown to predict violent behavior among persons with psychosis. However, prior research is limited in that these factors have not been explored simultaneously within the same study. Methods: The current study, therefore, aimed to determine which demographic, clinical, cognitive, and developmental characteristics were associated with an increased likelihood of violence among patients diagnosed with a psychotic disorder and which combination of these best predicted a history of violence. Participants (n=53) completed measures of demographics, violence risk, psychotic and personality symptoms, trauma, psychopathy and cognitive functioning. Results: Bivariate relationships were conducted to compare the history of violent behavior between all variables. Additionally, a binary logistic regression was run predicting participants’ history of violence. Several demographic, cognitive, clinical, and developmental factors were associated with increased odds of having a history of violence. The overall correct classification rate for the model was 92.2%, with 87.5% of participants without a history of violence and 91.4% with a history of violence being correctly classified. The model included antisocial personality traits, poor behavioral controls, head injury, not accepting responsibility, lacking goals, prior supervision failures, and HCR-20 total score. Conclusion: The binary logistic regression model showed good accuracy in predicting a history of violence in persons with psychosis. These findings are consistent with prior research and can inform efforts at risk assessment and identification of treatment targets for people with a psychotic disorder who are at highest risk of violence.

Bone metastasis is the result of complex crosstalk between tumor cells and bone marrow cells. Bone marrow adipocytes (BMAs) are the most abundant cell type in adult bone marrow. Therefore, we explore the effects of BMAs on bone metastasis in lung cancer. RNA-seq was used to compare the mRNA expression level of bone metastatic SBC5 cells and non-bone metastatic SBC3 cells. Rosiglitazone-induced marrow adiposity and intra-femoral injection of SBC5 cells were used to demonstrate the relationship between BMAs and SBC5 cells in vivo. Co-culture system, gene co-expression, gene ontology (GO) enrichment analysis and protein–protein interaction (PPI) network were used to explore the potential mechanism. BMAs specially enhance the invasion of bone metastatic SBC5 instead of non-bone metastatic SBC3 in vitro. SBC5 instead of SBC3 promoted osteoblast and osteoclast differentiation as well as de-differentiation of mature BMAs. Rosiglitazone-induced marrow adiposity significantly enhanced osteolytic lesion induced by SBC5 in vivo. RNA-seq revealed that compared with SBC3, S100A9 and S100A8 genes were the most prominent genes up-regulated in SBC5 cells. High expression of S100A8/9 in SBC5 could be responsible for the crosstalk between lung cancer cells and BMAs. More importantly, interleukin 6 receptor (IL6R), which is adjacent to S100A8/A9 in 1q21.3, was significantly up-regulated by BMAs in vitro. S100A8/A9 (1 μg/ml) could obviously enhance the osteoblastic differentiation and inhibit adipogenic differentiation, whereas TLR4 inhibitor TAK242 (10 μmol/l) significantly attenuated this effect. Our study suggested that bone marrow adipocyte may communicate with lung cancer cells via 1q21.3 (S100A8/A9-IL6R)-TLR4 pathway to promote osteolytic bone destruction. 1q21.3 (S100A8/A9-IL6R) is a potential target for the treatment of lung cancer bone metastasis.

Background:Intercellular crosstalk among osteoblast, osteoclast, osteocyte and chondrocyte is involved in the precise control of bone homeostasis. Disruption of this cellular and molecular signaling would lead to metabolic bone diseases such as osteoporosis. Currently a number of anti-osteoporosis interventions are restricted by side effects, complications and long-term intolerance. This review aims to summarize the bone cellular communication involved in bone remodeling and its usage to develop new drugs for osteoporosis.Methods:We searched PubMed for publications from 1 January 1980 to 1 January 2018 to identify relevant and latest literatures, evaluation and prospect of osteoporosis medication were summarized. Detailed search terms were ‘osteoporosis’, ‘osteocyte’, ‘osteoblast’, ‘osteoclast’, ‘bone remodeling’, ‘chondrocyte’, ‘osteoporosis treatment’, ‘osteoporosis therapy’, ‘bisphosphonates’, ‘denosumab’, ‘Selective Estrogen Receptor Modulator (SERM)’, ‘PTH’, ‘romosozumab’, ‘dkk-1 antagonist’, ‘strontium ranelate’.Results:A total of 170 papers were included in the review. About 80 papers described bone cell interactions involved in bone remodeling. The remaining papers were focused on the novel advanced and new horizons in osteoporosis therapies.Conclusion:There exists a complex signal network among bone cells involved in bone remodeling. The disorder of cell-cell communications may be the underlying mechanism of osteoporosis. Current anti-osteoporosis therapies are effective but accompanied by certain drawbacks simultaneously. Restoring the abnormal signal network and individualized therapy are critical for ideal drug development.

Osteoporosis is the most common metabolic skeletal disease. It is characterized by the deterioration of the skeletal microarchitecture and bone loss, leading to ostealgia, and even bone fractures. Accumulating evidence has indicated that there is an inextricable relationship between the gut microbiota (GM) and bone homeostasis involving host-microbiota crosstalk. Any perturbation of the GM can play an initiating and reinforcing role in disrupting the bone remodeling balance during the development of osteoporosis. Although the GM is known to influence bone metabolism, the mechanisms associated with these effects remain unclear. Herein, we review the current knowledge of how the GM affects bone metabolism in health and disease, summarize the correlation between pathogen-associated molecular patterns of GM structural components and bone metabolism, and discuss the potential mechanisms underlying how GM metabolites regulate bone turnover. Deciphering the complicated relationship between the GM and bone health will provide new insights into the prevention and treatment of osteoporosis.

Glucocorticoids are widely used to treat varieties of allergic and autoimmune diseases, however, long-term application results in glucocorticoid-induced osteoporosis (GIOP). Inflammatory cytokines: tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) play important regulatory roles in bone metabolism, but their roles in GIOP remain largely unknown. Osteocytes can modulate the formation and function of both osteoblasts and osteoclasts, directly via gap junctions, or indirectly by transferring molecule signaling. Apoptotic osteocytes release RANKL, HMGB1 and pro-inflammatory cytokines to stimulate osteoclastogenesis. Moreover, osteocytes can secrete FGF23 to regulate bone metabolism. Exposure to high levels of GCs can drive osteocyte apoptosis and influence gap junctions, leading to bone loss. GCs treatment is regarded to produce more FGF23 to inhibit bone mineralization. GCs also disrupt the vascular to decrease osteocyte feasibility and mineral appositional rate, resulting in a decline in bone strength. Apoptotic bodies from osteocytes induced by GCs treatment can enhance production of TNF-α and IL-6. On the other hand, TNF-α and IL-6 show synergistic effects by altering osteocytes signaling towards osteoclasts and osteoblasts. In addition, TNF-α can induce osteocyte apoptosis and attribute to a worsened bone quality in GCs. IL-6 and osteocytes may interact with each other. Therefore, we hypothesize that GCs regulate osteocyteogenesis through TNF-α and IL-6, which are highly expressed around osteocyte undergoing apoptosis. In the present review, we summarized the roles of osteocytes in regulating osteoblasts and osteoclasts. Furthermore, the mechanism of GCs altered relationship between osteocytes and osteoblasts/osteoclasts. In addition, we discussed the roles of TNF-α and IL-6 in GIOP by modulating osteocytes. Lastly, we discussed the possibility of using pro-inflammatory signaling pathway as therapeutic targets to develop drugs for GIOP.

The complex crosstalk between the immune and the skeletal systems plays an indispensable role in the maintenance of skeletal homeostasis. Various cytokines are involved, including interleukin (IL)-17A. A variety of immune and inflammatory cells produces IL-17A, especially Th17 cells, a subtype of CD4+ T cells. IL-17A orchestrates diverse inflammatory and immune processes. IL-17A induces direct and indirect effects on osteoclasts. The dual role of IL-17A on osteoclasts partly depends on its concentrations and interactions with other factors. Interestingly, IL-17A exerts a dual role in osteoblasts in vitro. IL-17A is a bone-destroying cytokine in numerous immune-mediated bone diseases including postmenopausal osteoporosis (PMOP), rheumatoid arthritis (RA), psoriatic arthritis (PsA) and axial spondylarthritis (axSpA). This review will summarize and discuss the pathophysiological roles of IL-17A on the skeletal system and its potential strategies for application in immune-mediated bone diseases.

Accumulating discoveries highlight the importance of interaction between marrow stromal cells and cancer cells for bone metastasis. Bone is the most common metastatic site of breast cancer and bone marrow adipocytes (BMAs) are the most abundant component of the bone marrow microenvironment. BMAs are unique in their origin and location, and recently they are found to serve as an endocrine organ that secretes adipokines, cytokines, chemokines, and growth factors. It is reasonable to speculate that BMAs contribute to the modification of bone metastatic microenvironment and affecting metastatic breast cancer cells in the bone marrow. Indeed, BMAs may participate in bone metastasis of breast cancer through regulation of recruitment, invasion, survival, colonization, proliferation, angiogenesis, and immune modulation by their production of various adipocytokines. In this review, we provide an overview of research progress, focusing on adipocytokines secreted by BMAs and their potential roles for bone metastasis of breast cancer, and investigating the mechanisms mediating the interaction between BMAs and metastatic breast cancer cells. Based on current findings, BMAs may function as a pivotal modulator of bone metastasis of breast cancer, therefore targeting BMAs combined with conventional treatment programs might present a promising therapeutic option.

Objective: To clarify the role and mechanism of miR-17-92 cluster in islet beta-cell repair after streptozotocin intervention. Methods: Genetically engineered mice (miR-17-92βKO) and control RIP-Cre mice were intraperitoneally injected with multiple low dose streptozotocin. Body weight, random blood glucose (RBG), fasting blood glucose, and intraperitoneal glucose tolerance test (IPGTT) were monitored regularly. Mice were sacrificed for histological analysis 8 weeks later. Morphological changes of pancreas islets, quantity, quality, apoptosis, and proliferation of beta-cells were measured. Islets from four groups were isolated. MiRNA and mRNA were extracted and quantified. Results: MiR-17-92βKO mice showed dramatically elevated fasting blood glucose and impaired glucose tolerance after streptozotocin treatment in contrast to control mice, the reason of which is reduced beta-cell number and total mass resulting from reduced proliferation, enhanced apoptosis of beta-cells. Genes related to cell proliferation and insulin transcription repression were significantly elevated in miR-17-92βKO mice treated with streptozotocin. Furthermore, genes involved in DNA biosynthesis and damage repair were dramatically increased in miR-17-92βKO mice with streptozotocin treatment. Conclusion: Collectively, our results demonstrate that homozygous deletion of miR-17-92 cluster in mouse pancreatic beta-cells promotes the development of experimental diabetes, indicating that miR-17-92 cluster may be positively related to beta-cells restoration and adaptation after streptozotocin-induced damage.

Postmenopausal osteoporosis (PMOP) is a prevalent skeletal disorder associated with menopause-related estrogen withdrawal. PMOP is characterized by low bone mass, deterioration of the skeletal microarchitecture, and subsequent increased susceptibility to fragility fractures, thus contributing to disability and mortality. Accumulating evidence indicates that abnormal expansion of marrow adipose tissue (MAT) plays a crucial role in the onset and progression of PMOP, in part because both bone marrow adipocytes and osteoblasts share a common ancestor lineage. The cohabitation of MAT adipocytes, mesenchymal stromal cells, hematopoietic cells, osteoblasts and osteoclasts in the bone marrow creates a microenvironment that permits adipocytes to act directly on other cell types in the marrow. Furthermore, MAT, which is recognized as an endocrine organ, regulates bone remodeling through the secretion of adipokines and cytokines. Although an enhanced MAT volume is linked to low bone mass and fractures in PMOP, the detailed interactions between MAT and bone metabolism remain largely unknown. In this review, we examine the possible mechanisms of MAT expansion under estrogen withdrawal and further summarize emerging findings regarding the pathological roles of MAT in bone remodeling. We also discuss the current therapies targeting MAT in osteoporosis. A comprehensive understanding of the relationship between MAT expansion and bone metabolism in estrogen deficiency conditions will provide new insights into potential therapeutic targets for PMOP.

Bisphosphonates are wildly used in breast cancer patients with bone metastasis and generally administrated every 4 weeks to lessen the risk of subsequent skeletal-related events. Bisphosphonates administration every 12 weeks is also recommended in some guidelines. Recent clinical trials suggested that bisphosphonate treatment with reduced frequency (every 12 weeks) to be non-inferior to standard therapy. The object of this analysis was to contrast the efficacy and safety of these two treatment strategies. We systematically retrieved databases such as MEDLINE, PubMed, Embase, and Cochrane library from 1947 to present for clinical trials comparing the efficacy between standard (every 4 weeks) and de-escalation (every 12 weeks) treatment of bisphosphates. We identified 4 articles with available data from 4 randomized clinical trials (n = 1721). Administration of bisphosphate every 12 weeks was non-inferior to administration every 4 weeks. There existed no significant difference in on-study skeletal-related events, renal dysfunction, and osteonecrosis of jaw. In the exploratory study, patients who received intravenous bisphosphates before enrollment experienced less on-study skeletal-related events and significant difference was observed between groups. This analysis suggested that de-escalation treatment with bisphosphates may be superior to standard treatment in terms of efficacy, safety, and economic costs. But it would be better that all the patients receive bisphosphates every 4 weeks for several months before de-escalation.

Background : Chronic consumption of alcohol has an adverse effect on the skeletal system, which may lead to osteoporosis, delayed fracture healing and osteonecrosis of the femoral head. Currently, the treatment is limited, therefore, there is an urgent need to determine the underline mechanism and develop a new treatment. It is well-known that normal bone remodeling relies on the balance between osteoclast-mediated bone resorption and - mediated bone formation. Various factors can destroy the balance, including the dysfunction of the immune system. In this review, we summarized the relevant research in the alcoholic osteopenia with a focus on the abnormal osteoimmunology signals. We provided a new theoretical basis for the prevention and treatment of the alcoholic bone. Methods: We searched PubMed for publications from 1 January 1980 to 1 February 2020 to identify relevant and recent literature, summarizing evaluation and the prospect of alcoholic osteopenia. Detailed search terms were ‘alcohol’, ‘alcoholic osteoporosis’, ‘alcoholic osteopenia’ ‘immune’, ‘osteoimmunology’, ‘bone remodeling’, ‘osteoporosis treatment’ and ‘osteoporosis therapy’. Results: A total of 135 papers are included in the review. About 60 papers described the mechanisms of alcohol involved in bone remodeling. Some papers were focused on the pathogenesis of alcohol on bone through osteoimmune mechanisms. Conclusion: There is a complex network of signals between alcohol and bone remodeling and intercellular communication of osteoimmune may be a potential mechanism for alcoholic bone. Studying the osteoimmune mechanism is critical for drug development specific to the alcoholic bone disorder.

XLαs, the extra-large isoform of alpha-subunit of the stimulatory guanine nucleotide-binding protein (Gsα), is paternally expressed. The significance of XLαs in humans remains largely unknown. Here, we report a patient who presented with increased bone mass, hypophosphatemia, and elevated parathyroid hormone (PTH) levels. His serum calcium was in the lower limit of the normal range. Whole exome sequencing of this subject found a novel non-sense variant c.424G>T (p. G142*) in the first exon of XLαs, which was inherited from his father and transmitted to his daughter. This variant was predicted to exclusively influence the expression of XLαs, while possibly having no significant effects on other gene products of this locus. Ellsworth-Howard test revealed normal renal response to PTH in proband. Human SaOS2 cells transfected with mutant XLαs failed to generate cyclic adenosine monophosphate under PTH stimulation, indicating skeletal resistance to this hormone. This subject showed higher circulating sclerostin, dickkopf1, and osteoprotegerin (OPG) levels, while lower receptor activator of nuclear factor kappa-B ligand/OPG ratio, leading to reduced bone resorption. Our findings indicate that XLαs plays a critical role in bone metabolism and GNAS locus should be considered as a candidate gene for high bone mass.

We examined the effects of tumor necrosis factor-α (TNFα) and interleukin-6 (IL6) gene knockout in preserving the bone loss induced by ovariectomy (OVX) and the mechanisms involved in bone metabolism. Twenty female wild-type (WT), TNFα-knockout (TNFα−/−) or IL6-knockout (IL6−/−) mice aged 12 weeks were sham-operated (SHAM) or subjected to OVX and killed after 4 weeks. Bone mass and skeletal microarchitecture were determined using micro-CT. Bone marrow stromal cells (BMSCs) from all three groups (WT, TNFα−/− and IL6−/−) were induced to differentiate into osteoblasts or osteoclasts and treated with 17-β-estradiol. Bone metabolism was assessed by histological analysis, serum analyses and qRT-PCR. OVX successfully induced a high turnover in all mice, but a repair effect was observed in TNFα−/− and IL6−/− mice. The ratio of femoral trabecular bone volume to tissue volume, trabecular number and trabecular thickness were significantly decreased in WT mice subjected to OVX, but increased in TNFα−/− mice (1.62, 1.34, 0.27-fold respectively; P −/− mice (1.34, 0.80, 0.22-fold respectively; P −/− mice when compared to the IL6−/− mice. Both, TNFα−/− and IL6−/− BMSCs exhibited decreased numbers of TRAP-positive cells and an increase in ALP-positive cells, with or without E2 treatment (P TNFα or IL6 significantly upregulated mRNA expressions of osteoblast-related genes (Runx2 and Col1a1) and downregulated osteoclast-related mRNA for TRAP, MMP9 and CTSK in vivo and in vitro, TNFα knockout appeared to have roles beyond IL6 knockout in upregulating Col1a1 mRNA expression and downregulating mRNA expressions of WNT-related genes (DKK1 and Sost) and TNF-related activation-induced genes (TRAF6). TNFα seemed to be more potentially invasive in inhibiting bone formation and enhancing TRAF6-mediated osteoclastogenesis than IL6, implying that the regulatory mechanisms of TNFα and IL6 in bone metabolism may be different.

Background MiR-17-92 cluster is coded by MIR17HG in chromosome 13, which is highly conserved in vertebrates. Published literatures have proved that miR-17-92 cluster critically regulates tumorigenesis and metastasis. Recent researches showed that the miR-17-92 cluster also plays novel functions in the endocrine system. Objective To summarize recent findings on the physiological and pathological roles of miR-17-92 cluster in bone, lipid and glucose metabolisms. Results MiR-17-92 cluster plays significant regulatory roles in bone development and metabolism through regulating the differentiation and function of osteoblasts and osteoclasts. In addition, miR-17- 92 cluster is nearly involved in every aspect of lipid metabolism. Last but not the least, the miR-17-92 cluster is closely bound up with pancreatic beta cell function, development of type 1 diabetes and insulin resistance. However, whether miR-17-92 cluster is involved in the communication among bone, fat and glucose metabolisms remains unknown. Conclusion Growing evidence indicates that miR-17-92 cluster plays significant roles in bone, lipid and glucose metabolisms through a variety of signaling pathways. Fully understanding its modulating mechanisms may necessarily facilitate to comprehend the clinical and molecule features of some metabolic disorders such as osteoporosis, arthrosclerosis and diabetes mellitus. It may provide new drug targets to prevent and cure these disorders.

Cellular senescence is the inability of cells to proliferate, which has both beneficial and detrimental effects on tissue development and homeostasis. Chronic accumulation of senescent cells is associated with age-related disease, including osteoarthritis, a common joint disease responsible for joint pain and disability in older adults. The pathology of this disease includes loss of cartilage, synovium inflammation, and subchondral bone remodeling. Senescent cells are present in the cartilage of people with advanced osteoarthritis, but the link between cellular senescence and this disease is unclear. In this review, we summarize current evidence for the role of cellular senescence of different cell types in the onset and progression of osteoarthritis. We focus on the underlying mechanisms of senescence in chondrocytes, which maintain the cartilage in joints, and review the role of the Forkhead family of transcription factors, which are involved in cartilage maintenance and osteoarthritis. Finally, we discuss the potential therapeutic value and implications of targeting senescent cells using senolytic agents or immune therapies, targeting the senescence-associated secretory phenotype of these cells using senomorphic agents, and renewing the plasticity of stem cells and chondrocytes. Our review highlights current gaps in understanding of the mechanism of senescence that may, when addressed, provided new options for modifying and treating disease in osteoarthritis.

Osteoarthritis (OA) is the most common form of arthritic disease, leading to disability and impaired quality of life and no curative treatments exist. Increasing evidence indicates that low-grade inflammation plays a pivotal role in the onset and progression of OA. In this review, we summarize emerging findings on the pathological roles of synovial macrophages, adipose tissue macrophages, and osteoclasts in OA and their potential clinical implications from cell biology to preclinical and preliminary clinical trials. The failure of synovial macrophages to transition from pro-inflammatory M1 to anti-inflammatory M2 subtypes may contribute to the initiation and maintenance of synovitis in OA. M1 macrophages promote the inflammatory microenvironment and progression of OA through interactions with synovial fibroblasts and chondrocytes, thus increasing the secretion of matrix metalloproteinases. Direct inhibition of M1 or promotion of M2 polarization may be useful therapeutic interventions. Adipose tissue macrophages present in the infrapatella fat pad (IPFP) were involved in the progression of obesity-induced OA, which contributed to changes in the integrity of the IPFP. Furthermore, macrophages and osteoclasts in the subchondral bone were involved in bone remodeling and pain through uncoupled osteoclast/osteoblast activity and increased nociceptive signaling. Growing evidence has indicated an important role for macrophage-mediated low-grade inflammation in OA. Fully understanding the link between macrophages and other cells in joints will provide new insights into OA disease modification.

Background: Osteoclastogenesis is a key process in osteolytic bone metastasis (BM). Previous studies indicated that miRNAs could regulate cancer progression and osteoclastogenesis. Our purpose was to investigate the roles of lung cancer cells-derived circulating miR-21 on osteoclastogenesis and its clinical significance in BM patients. Methods: The difference of miRNA expression in two lung cancer cell lines SBC-5 (with characteristic BM ability) and SBC-3 (without BM ability) were analyzed. Circulating miR-21 levels of lung cancer patients with or without BM were compared. The effects of conditioned media from lung cancer cell lines or patients' plasma with different miR-21 levels on osteoclastogenesis were investigated. The diagnostic performance of circulating miR-21 in BM patients was evaluated. Findings: We found that miR-21 expression was specifically higher in SBC-5 than that in SBC-3 cells. The supernatants of SBC-5 cells with higher level miR-21 promoted osteoclastogenesis. Moreover, we demonstrated that the circulating miR-21 level was significantly higher in BM patients than that in non-BM patients. The plasma from BM patients with higher level miR-21 could also promot osteoclastogenesis. Mechanistically, lung cancer cells-derived circulating miR-21 could be transferred into osteoclast precursor cells and promot osteoclastogenesis probably by inhibiting PTEN (Phosphatase and tensin homologue). Finally, we indecated that circulating miR-21 had a potential for the diagnosis of BM. Interpretation: Our findings suggested circulating miR-21 played important roles in BM of lung cancer and may service as a biomarker to diagnose BM in lung cancer patients. Funding: This work was supported by grants from the National Natural Science Foundation of China (No. 81572639, 81770875, 81370969), Department of Science and Technology of Sichuan Province (2018SZ0142), and Sichuan University (2018SCUH0093). Declaration of Interest: No potential conflicts of interest were disclosed. Ethical Approval: The study was approved by the hospital research ethics committee of West China Hospital of Sichuan University and conducted in accordance with the International Ethical Guidelines for Biomedical Research Involving Human Subjects. All patients included in this study had signed the informed consent form.

GNAS is one of the most complex gene loci in the human genome and encodes multiple gene products. XLas, the extra-large isoform of alpha-subunit of the stimulatory guanine nucleotide-binding protein (Gas), is paternally inherited. Although XLas can mimic the action of Gas, its significance remains largely unknown in humans. Here we report a patient presented with increased bone mass, hypophosphatemia, and elevated parathyroid hormone levels. His serum calcium was in the lower limit of normal range. DEXA scan revealed progressive increase in the bone density of this patient. Whole exome sequencing of this subject found a novel nonsense mutation c.424G>T (p. G142X) in the first exon of XLas, which was inherited from his father and transmitted to his daughter. This mutation was predicted to exclusively influence the expression of XLas, while may have no significant effects on other gene products of this locus. SaOS2 cells transfected with mutant XLas failed to generate cAMP under parathyroid hormone stimulation, indicating skeletal resistance to this hormone. This subject showed higher circulating SOST, DKK1 and OPG levels, while lower RANKL levels and RANKL/OPG ratio, leading to reduced bone resorption. It is speculated that this patient may belong to a very rare type of pseudohypoparathyroidism with selective skeletal resistance but normal renal tubular response to parathyroid hormone. Our findings indicate that XLas plays a critical role in bone metabolism and GNAS locus should be considered as a candidate gene for high bone mass.

The high incidences of bone metastasis in patients with breast cancer, prostate cancer and lung cancer still remains a puzzling issue. The “seeds and soil” hypothesis suggested that bone marrow (soil) may provide a favorable “niche” for tumor cells (seed). When seeking for effective ways to prevent and treat tumor bone metastasis, most researchers focus on tumor cells (seed) but not the bone marrow microenvironment (soil). In reality, only a fraction of circulating tumor cells (CTCs) could survive and colonize in bone. Thus, the bone marrow microenvironment could ultimately determine the fate of tumor cells that have migrated to bone. Bone marrow adipocytes (BMAs) are abundant in the bone marrow microenvironment. Mounting evidence suggests that BMAs may play a dominant role in bone metastasis. BMAs could directly provide energy for tumor cells, enhance the tumor cell proliferation, and resistance to chemotherapy and radiotherapy. BMAs are also known for releasing some inflammatory factors and adipocytokines to promote or inhibit bone metastasis. In this review, we made a comprehensive summary for the interaction between BMAs and bone metastasis. More importantly, we discussed the potentially promising methods for the prevention and treatment of bone metastasis. Genetic disruption and pharmaceutical inhibition may be effective in inhibiting the formation and pro-tumor functions of BMAs.

Lung cancer still remains the leading cause of cancer-related mortality worldwide. Bone is one of preferred metastatic sites for lung cancer cells. So far, both accurate diagnosis and effective treatment of lung cancer bone metastases are difficult.This review aimed to evaluate roles of bone turnover markers (BTMs), microRNAs (miRNAs), dickkopf1 (DKK1) and insulin like growth factor binding protein 3 (IGFBP-3) in lung cancer bone metastases.We searched articles about these four biomarkers in lung cancer bone metastases mainly in PubMed.The levels of bone specific alkaline phosphatase (BALP), cross-linked carboxy-terminal telopeptide of type-I collagen (ICTP) and N-terminal telopeptides of type-I collagen (NTX) were reported to be significantly increased in lung cancer patients with bone metastases. ALP, NTX and bone sialoprotein were thought to be associated with prognosis of lung cancer patients with bone metastases. MiRNA-335, miRNA-33a, miRNA-21, DKK1 and IGFBP-3 were revealed to be novel biomarkers in lung cancer bone metastases.Current researches have revealed that BTMs, miRNAs, DKK1 and IGFBP-3 may be useful in diagnosis, prognosis evaluation or treatment of lung cancer bone metastases. More studies about these biomarkers in lung cancer bone metastases are needed.

MicroRNAs (miRNAs) are a new class of small noncoding RNAs of 19-25 nucleotides that function as negative posttranscriptional gene regulators. MiRNAs hybridize to the 3' untranslated region (UTR) of target mRNAs and repress translation or mediate mRNA cleavage. MiRNAs critically regulate tumorigenesis and progression by targeting oncogenes, tumor suppressor genes, or genes related to proliferation, angiogenesis, and apoptosis. Different tumor types and tumors at different stages exhibit unique miRNA profiles. MiRNAs show promise as potential biomarkers for cancer diagnostics, progression, and response to treatment. The role of miRNAs in promoting bone metastases is under investigated. We summarize recent findings on the mechanisms by which miRNAs may regulate bone metastatic spread of breast cancer, prostate cancer, lung cancer and multiple myeloma. We review similarities and differences in miRNA profiles that may explain the variety of molecular pathways underling metastatic spread to the skeleton in different cancers. Finally, we discuss the exciting potential of using miRNAs as diagnostics and therapeutic targets to reduce the risk of bone metastases in cancer, from the perspective of data provided by recent pre-clinical and clinical studies.

Lung cancer is the leading cause of malignancy-related mortality worldwide. Metastases, which account for 90% of lung cancer deaths, frequently target the skeleton, leading to rapid deterioration in quality of life and premature death. The molecular mechanism underlying this progression, especially the development of bone metastases, is largely unknown. MicroRNAs (miRNAs) are small, endogenous, noncoding RNAs that function as negatively posttranscriptional gene regulators. Changes in miRNAs, which may exhibit either oncogenic or tumor suppressive activity, are common in lung cancer. Over-expressed miRNAs may contribute to oncogenesis by down-regulating tumor suppressors, whereas the loss of selected miRNAs may negatively regulate oncogenes or factors related to tumorigenesis and progression. MiRNAs may activate or repress metastases. Specific miRNA expression profiles may correlate with the response in treatment. We summarize recent findings and patents in the pathological roles of miRNAs in the progression and bone metastases in lung cancer, and discuss the diagnostic and therapeutic options in the clinical management of lung cancer.

Background High bone mass (HBM) disorders are a group of clinically and genetically heterogeneous bone diseases characterized by increased bone density on radiographs, due to progressive bone overgrowth or impaired bone resorption, or both. Some HBM cases are secondary to other diseases, such as chronic hepatitis C virus infection. Despite the great advance in gene diagnostic technology, the majority of HBM individuals remain undiagnosed. Objective In this review, we will summarize the clinical, radiological and biochemical characteristics of HBM cases due to varying etiologies, since these features are helpful in the differential diagnosis of HBM. Results Each subgroup of HBM cases shows distinctive clinical, radiological and biochemical characteristics. HBM, due to bone overgrowth, was designated as sclerosteosis, as a result of mutations located in genes critically involved in the Wnt/beta-catenin signal pathway. Mutations in genes encoding factors relevant to the differentiation and maturation of osteoclasts, or critical for the acidification and resorption of osteoclasts may lead to osteopetrosis. Hepatitis C associated osteosclerosis is characterized by a generalized increase in bone mass and markedly elevated serum levels of bone specific alkaline phosphatase. Conclusion The clarification of the etiologies of HBM may have a breakthrough role in understanding the molecular mechanisms involved in bone metabolism and may provide new pathways for the intervention of osteoporosis.

Background Research on the characteristics and mechanisms of diabetes in Tibetans is scant. Especially, there is no study on the relationship between osteocalcin and glucose metabolism. The objective of this study was to investigate the associations of serum total osteocalcin (tOC) and undercarboxylated osteocalcin (ucOC) with glucose and lipid metabolism in Chinese indigenous Tibetans with different degrees of glucose tolerance. Methods In this study, 160 middle-aged Tibetan men were involved, including 46 subjects with normal glucose tolerance (NGT), 52 subjects with impaired glucose regulation (IGR) and 62 subjects with type 2 diabetes. The homeostasis model assessment (HOMA) parameters, including HOMA-IR and HOMA-B, were used to estimate insulin resistance and β-cell function, respectively. Adiponectin, leptin, testosterone, 1,25-dihydroxyvitamin D, tOC and ucOC were measured using ELISA kits. Results After adjustment for age and body mass index, plasma tOC level was correlated negatively with fasting and 30-min post-OGTT glucose, HOMA-IR, leptin and testosterone; plasma ucOC level was correlated negatively with 30-min post-OGTT glucose, total cholesterol and 1,25-dihydroxyvitamin D; ucOC : tOC was correlated positively with leptin. The negative association between HOMA-IR and tOC remained significant after correcting for adiponectin; however, the association disappeared after correcting for leptin. HOMA-IR was correlated negatively with age, adiponectin and tOC, and positively with total cholesterol, triglyceride and leptin. Stepwise linear regression analysis revealed that total cholesterol, leptin and adiponectin were independent predictors for HOMA-IR in all subjects. Conclusions Our data support a link between osteocalcin and glucose metabolism in middle-aged Tibetan men. The improved glucose tolerance exerted by tOC may be related to improved insulin sensitivity rather than improved β-cell function. Copyright © 2013 John Wiley & Sons, Ltd.

Background: Bone metastasis is a common complication of certain types of cancer, and unfortunately, it is still incurable to date. Immune system is a major defence against tumor cells and bone metastasis. However, the immunodeficient mouse models are widely used in most researches of bone metastasis, thereby excluding the regulatory roles of the immune system in bone metastasis. Objective: To provide a comprehensive overview on the cellular and molecular mechanisms by which immune cells interact with tumor cells and bone cells, as well as recent related patents. Method: We performed a literature search of PubMed database for the current knowledge in the interaction between bone metastasis and immune system. Recent related patents were obtained from World Intellectual Property Organization (WIPO) website. Results: Immune cells in the bone-tumor microenvironment include dentritic cells, monocytes/macrophages, myeloid-derived suppressor cells, regulatory T cells, T helper cells, neutrophil, CD4+ T lyphocytes, CD8+cytotoxic T lymphocytes, and natural killer cells, et al. In addition to their well-known immunomodulatory function, recent studies revealed that immune cells could cooperate with tumor cells and bone cells to enhance bone metastasis and tumor progression. There are some patents targeted immune system to inhibit bone metastasis. Conclusion: Immune cells are instigated by tumor cells to enhance the occurrence and the development of bone metastasis. Taking full advantage of anti-tumor roles of immune cells may bring the promise of a possible cure for bone metastasis.

Rationale Currently, the relationship between heterozygous mutations in SLC34A1 and hypophosphatemia is controversial. Here we report an autosomal dominant hypophosphatemia pedigree carrying a novel heterozygous mutation in SLC34A1. Patient concerns The proband is a 32-year old young man, presented with progressive pain and weakness in his lower extremities for more than 5 years. The proband showed persistent hypophosphatemia and low TmPO4/GFR values, indicating renal phosphate leak. His grandfather, father, and one of his uncles showed the similar symptoms. Diagnoses Autosomal dominant hypophosphatemia. Interventions and outcomes Phosphorus supplement was prescribed to the proband and his affected uncle. Both their serum phosphorus levels recovered to normal and their symptoms such as back pain and lower extremity weakness were completely relieved. Whole exome sequencing was performed to identify disease-causing mutations in proband. Lessons A novel heterozygous missense mutation c.680A>G (p. N227S) in exon 7 of SLC34A1 was found in proband by whole exome sequencing, which was also found in other 4 family members of this pedigree. Our report of an autosomal dominant hypophosphatemia pedigree with 5 mutant carriers enriches the clinical phenotype caused by the SLC34A1 mutations and further affirms the heterozygous mutations are causative for hypophosphatemia.

BACKGROUND Obesity was traditionally considered as a positive regulator on the strength of bone. With the in-depth study, obesity is considered as a major risk factor for osteoporosis. Some proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) are the factors that fat uses to negatively regulate bone metabolism. OBJECTIVE This review was aimed to summarize and critically discuss the convincing evidence for the therapeutic effectiveness of pro-inflammatory cytokines for the treatment of obesity-related bone disorders. RESULTS Obese people and animals show a higher level of serum TNF-α and IL-6, which are produced by macrophages derived from adipose tissue. These pro-inflammatory cytokines regulate the proliferation and apoptosis of adipocyte, promote lipolysis, inhibit lipid synthesis and decrease blood lipids through autocrine and paracrine way. On the other hand, TNF-α and IL-6 regulate bone metabolism through the endocrine way. Several reports suggest that TNF-α is a negative regulator of osteoblast at some stages of differentiation and positively regulates osteoclast proliferation and differentiation. In contrast, IL-6 influences osteoblasts and osteoclasts through complex mechanisms, which reflect dual effects. In addition, TNF-α and IL-6 may regulate bone metabolism indirectly by regulating adiponectin and leptin released from adipocytes. CONCLUSION In this review, we first summarize the role of TNF-α and IL-6 in lipid and bone metabolisms. We further discuss how TNF-α and IL-6 regulate the communication between fat and bone, and their pathological roles in obesity-related bone disorders. Lastly, we discuss the possibility of using pro-inflammatory signaling pathway as a therapeutic target to develop drug for obesity-related bone disorders.

Bone has emerged as a novel endocrine organ for its ability to produce hormones and involvement in several regulatory feedback loops. Osteocalcin (OCN) is released into bloodstream during bone resorption and has been demonstrated to exert endocrine regulation on islets, fat and male testis to form feedback loops. We hypothesize that bone delivers its energy metabolism signals to related energy-regulating organs through OCN based on the following evidence: First, OCN has close interactions with islets and fat, and it shows ability to stimulate islets and fat to secret insulin and adiponectin, respectively. Islets and fat are important organs involved in energy metabolism. Second, OCN undergoes physiological fluctuations during a lifetime. In children and adolescents, during the development of osteoporosis or after bone fracture, OCN level increases significantly. The elevated OCN at these stages represents enhanced bone turnover and metabolic activity, which require more energy supply. Therefore, the metabolic activity of bone and the energy-related organs like fat and islets are closely linked by circulating OCN. Through systemic release of OCN, bone delivers its energy-demanding information to other organs to satisfy its energy requirement.

SHARPIN is a novel protein thought to interact with SHANK family and is widely expressed in multiple tissues/cells, including osteoblasts and osteoclasts. Loss-of-function of Sharpin develops the chronic proliferative dermatitis mutation (CPDM) in mice as well as a severe inflammation in other organs. The actual function of SHARPIN is poorly understood. Our aim was to determine the functional roles of SHARPIN in bone metabolism by using CPDM mice. The skeletal phenotypes were determined by peripheral quantitative computed tomography, micro-computed tomography, and quantitative real-time RT-PCR, the cellular functions of osteoblasts and osteoclasts were investigated by ex vivo cell culture. Compared to wild-type controls, CPDM mice demonstrated significantly lower total and cortical bone mineral content and bone mineral density, trabecular and cortical bone volume, and trabecular number. The mRNA expression of Runx2, osterix, type I collagen, and osteocalcin was significantly lower in the bone from CPDM mice. Osteoclasts and osteoblasts from CPDM mice were functionally defective. Our result suggests that SHARPIN plays important regulating roles in bone metabolism. These functional roles may either come from systemic chronic inflammatory or directly signaling pathway within bone cells.

The skeleton is frequently affected in individuals with neurofibromatosis type 1, and some of these bone manifestations can result in significant morbidity. The natural history and pathogenesis of the skeletal abnormalities of this disorder are poorly understood and consequently therapeutic options for these manifestations are currently limited. The Children's Tumor Foundation convened an International Neurofibromatosis Type 1 Bone Abnormalities Consortium to address future directions for clinical trials in skeletal abnormalities associated with this disorder. This report reviews the clinical skeletal manifestations and available preclinical mouse models and summarizes key issues that present barriers to optimal clinical management of skeletal abnormalities in neurofibromatosis type 1. These concepts should help advance optimal clinical management of the skeletal abnormalities in this disease and address major difficulties encountered for the design of clinical trials.

The osteocyte, a terminally differentiated cell comprising 90%–95% of all bone cells1,2, may have multiple functions, including acting as a mechanosensor in bone (re)modeling3. Dentin matrix protein 1 (encoded by DMP1) is highly expressed in osteocytes4 and, when deleted in mice, results in a hypomineralized bone phenotype5. We investigated the potential for this gene not only to direct skeletal mineralization but also to regulate phosphate (Pi) homeostasis. Both Dmp1- null mice and individuals with a newly identified disorder, autosomal recessive hypophosphatemic rickets, manifest rickets and osteomalacia with isolated renal phosphate-wasting associated with elevated fibroblast growth factor 23 (FGF23) levels and normocalciuria. Mutational analyses showed that autosomal recessive hypophosphatemic rickets family carried a mutation affecting the DMP1 start codon, and a second family carried a 7-bp deletion disrupting the highly conserved DMP1 C terminus. Mechanistic studies using Dmp1-null mice demonstrated that absence of DMP1 results in defective osteocyte maturation and increased FGF23 expression, leading to pathological changes in bone mineralization. Our findings suggest a bone-renal axis that is central to guiding proper mineral metabolism.

Obesity and osteoporosis are two common chronic diseases, however, the basis for the correlation between them remains largely unknown. The pro-inflammation cytokine tumor necrosis factor-alpha (TNF-α) plays important roles in lipid and bone metabolisms, which may be a good candidate in the correlation between obesity and osteoporosis. We investigated the pathological roles of TNF-α in high-fat diet (HFD)-induced bone loss. Wild-type (WT) mice and TNF-α knockout (TNF-α(-/-)) mice were fed with the standard diet or the HFD for 12 weeks. Bone marrow stromal cells (BMSCs) from both genotypes were induced to differentiate into osteoblasts and treated with palmitic acid (PA). Bone mass and microstructure of femurs were evaluated by micro-CT. Lipid and bone metabolisms were investigated by histological and plasma analyses, and real-time PCR. On the HFD, both TNF-α(-/-) and WT mice presented notable visceral obesity, dyslipidemia. Adipogenesis and osteoclastogenesis were enhanced, while osteoblastogenesis was reduced in both genotypes. However, the changes were significantly different between TNF-α(-/-) and WT mice after the HFD. The gain of body and fat-pad weight was less and adipocyte area was smaller by 22 % in TNF-α(-/-) mice. Osteoclast numbers and plasma CTX level were lower by 40 % and by 23 % in TNF-α(-/-) mice. There were more ALP positive cells in the PA-treated TNF-α(-/-) BMSCs. mRNA expression of PPAR-γ was lower while that of Runx2 was higher in the bone from TNF-α(-/-) HFD group and in the PA-treated TNF-α(-/-) BMSCs, compared to WT on the same treatment. Furthermore, femoral trabecular bone mass and trabecular bone number were significantly decreased in WT mice on the HFD, whereas they were increased by 1.56-fold and 1.53-fold, respectively, in TNF-α(-/-) mice on the same diet (P0.05). Our results demonstrated that TNF-α gene knockout retained HFD-induced femoral trabecular bone loss mainly by suppressing adipogenesis and osteoclastogenesis, and enhancing osteoblastogenesis, which suggests that TNF-α plays a critical role in the development of HFD-related bone metabolic disorders and it may be a new potential therapeutic target for obesity-related bone loss.

Fibroblast growth factor-23 (FGF23) is a circulating factor that plays critical roles in phosphate and vitamin D metabolism. The goal of our studies was to dissect the pathways directing the vitamin D-phosphate-FGF23 homeostatic axis. To test the role of diet in the regulation of Fgf23, wild-type (WT) mice were fed either a standard (0.44% phosphorus) or a low-phosphate (0.02%) diet. WT mice on standard diet had a serum phosphate of 9.5 +/- 0.3 mg/dl and an Fgf23 concentration of 99.0 +/- 10.6 pg/ml; mice on the low-phosphate diet had a phosphate of 5.0 +/- 0.2 mg/dl (P0.01) and an Fgf23 of 10.6 +/- 3.7 pg/ml (P0.01). To genetically separate the effects of phosphate and vitamin D on Fgf23, we examined vitamin D receptor null (VDR(-/-)) mice, which are hypocalcemic and hypophosphatemic secondary to hyperparathyroidism. On standard diets, WT and VDR(+/-) mice had Fgf23 levels of 106.0 +/- 30.7 and 90.6 +/- 17.3 pg/ml, respectively, whereas Fgf23 was undetectable in the VDR(-/-). Animals were then placed on a diet that normalizes serum calcium and phosphorus. This 'rescue' increased Fgf23 in WT to 192.3 +/- 32.5 pg/ml and in VDR(+/-) to 388.2 +/- 89.6pg/ml, and importantly, in VDR(-/-) to 476.9 +/- 60.1 pg/ml (P0.01 vs. WT). In addition, renal vitamin D 1-alpha hydroxylase (1alpha-OHase) mRNA levels were corrected to WT levels in the VDR(-/-) mice. In summary, Fgf23 is suppressed in diet-induced hypophosphatemia and in hypophosphatemia associated with secondary hyperparathyroidism. Normalization of serum phosphate by diet in VDR(-/-) mice increases Fgf23. Thus, our results demonstrate that Fgf23 is independently regulated by phosphate and by vitamin D.

Gain-of-function mutations in fibroblast growth factor-23 (FGF23) are responsible for autosomal dominant hypophosphatemic rickets, a disorder of isolated renal phosphate wasting. Patients with the disorder display hypophosphatemia with normocalcemia as well as inappropriately normal 1,25-dihydroxyvitamin D [1,25(OH)2D3] concentrations. Reciprocally tumoral calcinosis (TC) patients are often hyperphosphatemic with inappropriately normal or elevated serum 1,25(OH)2D3 levels and have ectopic and vascular calcifications, a phenotype similar to that of Fgf23 null mice. Therefore, the goal of the present studies was to test whether FGF23 was a candidate gene for TC. Two sisters in a consanguineous TC family had hyperphosphatemia and normal 1,25(OH)2D3 levels with characteristic ectopic and vascular calcifications. Interestingly, these patients had low-normal intact serum FGF23 levels but demonstrated FGF23 concentrations approximately 40 times normal when assessed with a C-terminal FGF23 serum assay. Mutational analyses identified a homozygous S71G mutation in FGF23 in the TC patients, which was not found in control alleles. Finally, modeling demonstrated that the S71G mutation most likely destabilizes full-length FGF23. In summary, recessive FGF23 mutations can lead to TC. Additionally, our findings indicate that FGF23 may adopt an unstable conformation in some TC patients, possibly leading to nonfunctional FGF23 protein.

The association between lipid and bone metabolism has become an increasing focus of interest in recent years, and accumulating evidence has shown that atherosclerosis (AS) and osteoporosis (OP), a disorder of bone metabolism, frequently co-exist. Fat and bone are known to share a common progenitor cell: Multipotent mesenchymal stem cells (MSC) in the bone marrow (BM), which are able to differentiate into various cell phenotypes, including osteoblasts, adipocytes and chondrocytes. Laboratory-based and clinical trials have shown that increasing adipocytes are accompanied by a decrease in bone mineral density (BMD) and bone mass. Statins, lipid-lowering drugs used to treat hyperlipidemia, also provide benefit in the treatment of OP. There is thus evidence that the metabolism of lipids is correlated with that of bone, and that the two are mutually regulated. The present review primarily focuses on the potential association between lipid metabolism disturbance and OP, based on biological metabolism, pathophysiological processes, results from clinical and experimental animal studies, processes involved in the differentiation of adipocytes and osteoblasts, as well as pharmacological treatments of these diseases.

Type II autosomal dominant osteopetrosis (ADO2), which is the most common form of osteopetrosis, is caused by heterozygous mutations in the chloride channel 7 (CLCN7) gene. The osteopetrosis of ADO2 has been attributed to hypofunctional osteoclasts. The mechanism underlying the abnormality in osteoclast function remains largely unknown. This study was designed to investigate gene mutations and osteoclast function in a case that was clinically diagnosed as ADO2. Genomic DNA was extracted from blood samples of this patient, and the 25 exons of CLCN7 were amplified. Peripheral blood from the ADO2 subject and a healthy age- and sex-matched control was used to evaluate osteoclastogenesis, osteoclast morphology, and bone resorption. Analysis of DNA from the patient showed a germline heterozygous missense mutation, c.1856C>T (p.P619L), in exon 20 of CLCN7. A similar homozygous mutation at this site was previously reported in a patient with autosomal recessive osteopetrosis. When cultured, the peripheral blood mononuclear cells (PBMCs) from the ADO2 patient spontaneously differentiated into mature osteoclasts in vitro. The ADO2 patient’s PBMCs formed enhanced, but heterogeneous, osteoclasts in both the presence and absence of macrophage-colony stimulating factor, and nuclear factor-ĸB ligand. Bone resorption was reduced in the ADO2 patient’s osteoclasts, which exhibited aberrant morphology and abnormal distribution of integrin avβ3. Gene analysis found increased c-fos expression and reduced RhoA and integrin beta 3 expression in ADO2 cells. In conclusion, our data suggest that enhanced, heterogeneous osteoclast induction may be an intrinsic characteristic of ADO2. A mutation that reduces activity of bone-resorbing cells is responsible for a rare inherited disorder characterised by dense, brittle bones. Healthy bones undergo constant remodeling; osteoclasts resorb mature bone and osteoblasts generate new tissue. Patients with autosomal dominant osteopetrosis Type II (ADO2), the most common form of osteopetrosis, show impaired bone remodelling, resulting in overly dense, fragile bone tissue. No treatment is available, and although mutations in the chloride channel 7 gene (CLCN7) have been implicated, the mechanism underlying the disease remains unclear. Xijie Yu at Sichuan University and colleagues investigated gene mutations and osteoclast function in a recently diagnosed patient. The researchers found a single mutation of CLCN7 and higher than normal osteoclast generation; however, the osteoclasts were irregularly shaped and showed poor bone resorption. These results may help to identify treatments for osteopetrosis.

Abnormal osteoclast formation and resorption play a fundamental role in osteoporosis pathogenesis. Over the past two decades, much progress has been made to target osteoclasts. The existing therapeutic drugs include bisphosphonates, hormone replacement therapy, selective estrogen receptor modulators, calcitonin and receptor activator of nuclear factor NF-κB ligand (RANKL) inhibitor (denosumab), etc. Among them, bisphosphonates are most widely used due to their low price and high efficiency in reducing the risk of fracture. However, bisphosphonates still have their limitations, such as the gastrointestinal side-effects, osteonecrosis of the jaw, and atypical subtrochanteric fracture. Based on the current situation, research for new drugs to regulate bone resorption remains relevant. MicroRNAs (miRNAs) are a new group of small, noncoding RNAs of 19–25 nucleotides, which negatively regulate gene expression after transcription. Recent studies discovered miRNAs play a considerable function in bone remodeling by regulating osteoblast and osteoclast differentiation and function. An increasing number of miRNAs have been identified to participate in osteoclast formation, differentiation, apoptosis, and resorption. miRNAs show great promise to serve as biomarkers and potential therapeutic targets for osteoporosis. In this review, we will summarize our current understanding of how miRNAs regulate osteoclastogenesis and function. We will further discuss the approach to develop drugs for osteoporosis based on these miRNA networks.

Malignant peripheral nerve sheath tumors (MPNSTs) are highly aggressive soft tissue sarcomas accounting for 3%–10% of all soft tissue sarcomas. Neurofibromatosis type 1 (NF1) is the most important known risk factor. MPNSTs are often diagnosed at an advanced stage when distant metastases have developed. Although surgical resection remains the main treatment for MPNSTs, complete surgical resection is rarely possible. The prognosis for patients with MPNSTs is poor. There is an urgent need for improved therapies. To this end, we investigated whether microRNA (miR), specifically miR-204, might be implicated in MPNSTs because it is located at a cancer-associated genomic region exhibiting high frequency of loss of heterozygosity in tumors. We show that miR-204 expression is downregulated in NF1 and non-NF1 MPNST tumor tissues and in tumor cell lines. Restoring miR-204 expression in MPNST cell lines STS26T (non-NF1), ST88-14 (NF1), and T265p21 (NF1) significantly reduces cellular proliferation, migration, and invasion in vitro. Restoring miR-204 expression in STS26T decreases tumor growth and malignant progression in vivo. We also report that miR-204 inhibits Ras signaling and expression of high mobility group gene A2. These findings support the hypothesis that miR-204 plays critical roles in MPNST development and tumor progression. miR-204 may represent a novel biomarker for diagnosis and a candidate target with which to develop effective therapies for MPNSTs.

Metastases account for 90% of lung cancer mortalities, frequently target the skeleton and lead to rapid deterioration in quality of life. The molecular mechanism underlying bone metastases is largely unknown. Development of xenograft mouse models, such as the severe combined immunodeficient (SCID) CB-17 mouse and the non-obese diabetic (NOD)/SCID mouse, both of which lack functional B- and T-cells and are able to host allogeneic or xenogeneic tumor cells, has made great contributions in this area. However, residual natural killer (NK) cells in these models are able to significantly modify local tumor growth and metastasis. Treatment with anti-murine IL-2 receptor β chain Ab (TM-β1) antibody can abrogate NK cell activity in vivo; however, the antibody treatment may result in unexpected effects and the stability is hard to control. To overcome these shortcomings, we evaluated xenografts in NOD-scid IL2Rγ(null) immunodeficient mice that lacked mature T cells, B cells and functional NK cells. We compared the target tissue distribution of the human small cell lung cancer cell lines SBC-5 and SBC-3. Gross necropsy and whole skeletal X-ray film examination of the host mice were conducted 30 days post-tail vein injection. The SBC-5 cells colonized bone and formed lytic lesions. The cells also colonized liver, spleen and, less frequently, the pancreas, ovary and kidney. The SBC-3 cell xenografts formed easily visible tumor foci in the liver, pancreas, ovary/uterus and kidney, but not bone metastases. Our results showed that SBC-5 cells in NOD-scid IL2Rγ(null) immunodeficient mice provide a suitable xenograft model system for bone metastasis of human lung cancer. This novel animal model may therefore be used to study the molecular pathway of bone metastases and to evaluate targets for effective therapies.

Autosomal dominant hypophosphatemic rickets (ADHR) is unique among the disorders involving Fibroblast growth factor 23 (FGF23) because individuals with R176Q/W and R179Q/W mutations in the FGF23 176 RXXR 179 /S 180 proteolytic cleavage motif can cycle from unaffected status to delayed onset of disease. This onset may occur in physiological states associated with iron deficiency, including puberty and pregnancy. To test the role of iron status in development of the ADHR phenotype, WT and R176Q-Fgf23 knock-in (ADHR) mice were placed on control or low-iron diets. Both the WT and ADHR mice receiving low-iron diet had significantly elevated bone Fgf23 mRNA. WT mice on a low-iron diet maintained normal serum intact Fgf23 and phosphate metabolism, with elevated serum C-terminal Fgf23 fragments. In contrast, the ADHR mice on the low-iron diet had elevated intact and C-terminal Fgf23 with hypophosphatemic osteomalacia. We used in vitro iron chelation to isolate the effects of iron deficiency on Fgf23 expression. We found that iron chelation in vitro resulted in a significant increase in Fgf23 mRNA that was dependent upon Mapk. Thus, unlike other syndromes of elevated FGF23, our findings support the concept that late-onset ADHR is the product of gene–environment interactions whereby the combined presence of an Fgf23-stabilizing mutation and iron deficiency can lead to ADHR.

MicroRNAs (miRNAs) are frequently deregulated in human tumors, and play important roles in tumor development and progression. The pathological roles of miRNAs in neurofibromatosis type 1 (NF1) tumorigenesis are largely unknown. We demonstrated that miR-10b was up-regulated in primary Schwann cells isolated from NF1 neurofibromas and in cell lines and tumor tissues from malignant peripheral nerve sheath tumors (MPNSTs). Intriguingly, a significantly high level of miR-10b correlated with low neurofibromin expression was found in a neuroectodermal cell line: Ewing's sarcoma SK-ES-1 cells. Antisense inhibiting miR-10b in NF1 MPNST cells reduced cell proliferation, migration and invasion. Furthermore, we showed that NF1 mRNA was the target for miR-10b. Overexpression of miR-10b in 293T cells suppressed neurofibromin expression and activated RAS signaling. Antisense inhibition of miR-10b restored neurofibromin expression in SK-ES-1 cells, and decreased RAS signaling independent of neurofibromin in NF1 MPNST cells. These results suggest that miR-10b may play an important role in NF1 tumorigenesis through targeting neurofibromin and RAS signaling.

Fibroblast growth factor 23 (FGF23) is a hormone required for normal renal phosphate reabsorption. FGF23 gain-of-function mutations result in autosomal dominant hypophosphatemic rickets (ADHR), and FGF23 loss-of-function mutations cause familial hyperphosphatemic tumoral calcinosis (TC). In this study, we identified a novel recessive FGF23 TC mutation, a lysine (K) substitution for glutamine (Q) (160 C > A) at residue 54 (Q54K). To understand the molecular consequences of all known FGF23-TC mutants (H41Q, S71G, M96T, S129F, and Q54K), these proteins were stably expressed in vitro. Western analyses revealed minimal amounts of secreted intact protein for all mutants, and ELISA analyses demonstrated high levels of secreted COOH-terminal FGF23 fragments but low amounts of intact protein, consistent with TC patients' FGF23 serum profiles. Mutant protein function was tested and showed residual, yet decreased, bioactivity compared with wild-type protein. In examining the role of the FGF23 COOH-terminal tail (residues 180–251) in protein processing and activity, truncated mutants revealed that the majority of the residues downstream from the known FGF23 SPC protease site (176RXXR179/S180) were not required for protein secretion. However, residues adjacent to the RXXR site (between residues 188 and 202) were required for full bioactivity. In summary, we report a novel TC mutation and demonstrate a common defect of reduced FGF23 stability for all known FGF23-TC mutants. Finally, the majority of the COOH-terminal tail of FGF23 is not required for protein secretion but is required for full bioactivity.

Familial tumoral calcinosis is characterized by ectopic calcifications and hyperphosphatemia due to inactivating mutations in FGF23 or UDP-N-acetyl-alpha-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase 3 (GALNT3). Herein we report a homozygous missense mutation (H193R) in the KLOTHO (KL) gene of a 13-year-old girl who presented with severe tumoral calcinosis with dural and carotid artery calcifications. This patient exhibited defects in mineral ion homeostasis with marked hyperphosphatemia and hypercalcemia as well as elevated serum levels of parathyroid hormone and FGF23. Mapping of H193R mutation onto the crystal structure of myrosinase, a plant homolog of KL, revealed that this histidine residue was at the base of the deep catalytic cleft and mutation of this histidine to arginine should destabilize the putative glycosidase domain (KL1) of KL, thereby attenuating production of membrane-bound and secreted KL. Indeed, compared with wild-type KL, expression and secretion of H193R KL were markedly reduced in vitro, resulting in diminished ability of FGF23 to signal via its cognate FGF receptors. Taken together, our findings provide what we believe to be the first evidence that loss-of-function mutations in human KL impair FGF23 bioactivity, underscoring the essential role of KL in FGF23-mediated phosphate and vitamin D homeostasis in humans.

Fibroblast growth factor 23 (FGF23) is a circulating factor that plays critical roles in phosphate and vitamin D metabolism, as evidenced by the fact that FGF23 missense mutations cause autosomal dominant hypophosphatemic rickets (ADHR). Autosomal dominant hypophosphatemic rickets is characterized by hypophosphatemia with inappropriately normal 1,25-dihydroxyvitamin D concentrations, as well as bone pain, fracture and rickets. This phenotype parallels that of patients with tumor induced osteomalacia (TIO), X-linked hypophosphatemic rickets (XLH), and fibrous dysplasia (FD), in whom elevated serum FGF23 levels are often observed. The fibroblast growth factor receptors (FGFR1-4) play key roles in skeletal development, as well as in normal metabolic processes. Several FGFR isoforms that potentially mediate the activity of FGF23 have been implicated. In the short term, these findings will lead to further understanding of FGF23 function, and potentially in the long term, to targeted therapies in disorders of hypo- and hyperphosphatemia that involve FGF23.