Impaired bone remodeling in children with osteogenesis imperfecta treated and untreated with bisphosphonates: the role of DKK1, RANKL, and TNF-α

Correlation of serum DKK1 level with skeletal phenotype in children with osteogenesis imperfecta

PURPOSE

We aim to detect serum DKK1 level of pediatric patients with OI and to analyze its relationship with the genotype and phenotype of OI patients.

METHODS

A cohort of pediatric OI patients and age-matched healthy children were enrolled. Serum levels of DKK1 and bone turnover biomarkers were measured by enzyme-linked immunosorbent assay. Bone mineral density (BMD) was measured by Dual-energy X-ray absorptiometry. Pathogenic mutations of OI were detected by next-generation sequencing and confirmed by Sanger sequencing.

RESULTS

A total of 62 OI children with mean age of 9.50 (4.86, 12.00) years and 29 healthy children were included in this study. The serum DKK1 concentration in OI children was significantly higher than that in healthy children [5.20 (4.54, 6.32) and 4.08 (3.59, 4.92) ng/mL, P < 0.001]. The serum DKK1 concentration in OI children was negatively correlated with height (r = - 0.282), height Z score (r = - 0.292), ALP concentration (r = - 0.304), lumbar BMD (r = - 0.276), BMD Z score of the lumbar spine and femoral neck (r = - 0.32; r = - 0.27) (all P < 0.05). No significant difference in serum DKK1 concentration was found between OI patients with and without vertebral compression fractures. In patients with spinal deformity (22/62), serum DKK1 concentration was positively correlated with SDI (r = 0.480, P < 0.05). No significant correlation was observed between serum DKK1 concentration and the annual incidence of peripheral fractures, genotype and types of collagen changes in OI children.

CONCLUSION

The serum DKK1 level was not only significantly elevated in OI children, but also closely correlated to their skeletal phenotype, suggesting that DKK1 may become a new biomarker and a potential therapeutic target of OI.

Antimicrobial and Hemostatic Diatom Biosilica Composite Sponge

The 3D nanopatterned silica shells of diatoms have gained attention as drug delivery vehicles because of their high porosity, extensive surface area, and compatibility with living organisms. Tooth extraction may result in various complications, including impaired blood clotting, desiccation of the root canal, and infection. Therapeutic sponges that possess multiple properties, such as the ability to stop bleeding and kill bacteria, provide numerous advantages for the healing of the area where a tooth has been removed. This study involved the fabrication of a composite material with antibacterial and hemostatic properties for dental extraction sponges. We achieved this by utilizing the porous nature and hemostatic capabilities of diatom biosilica. The antibiotic used was doxycycline. The gelatin-based diatom biosilica composite with antibiotics had the ability to prevent bleeding and release the antibiotic over a longer time compared to gelatin sponge. These properties indicate its potential as a highly promising medical device for facilitating rapid healing following tooth extraction.

Dickkopf-1 (DKK1) blockade mitigates osteogenesis imperfecta (OI) related bone disease

BACKGROUND

The current treatment of osteogenesis imperfecta (OI) is imperfect. Our study thus delves into the potential of using Dickkopf-1 antisense (DKK1-AS) to treat OI.

METHODS

We analysed serum DKK1 levels and their correlation with lumbar spine and hip T-scores in OI patients. Comparative analyses were conducted involving bone marrow stromal cells (BMSCs) and bone tissues from wild-type mice, untreated OI mice, and OI mice treated with DKK1-ASor DKK1-sense (DKK1-S).

RESULTS

Significant inverse correlations were noted between serum DKK1 levels and lumbar spine (correlation coefficient = - 0.679, p = 0.043) as well as hip T-scores (correlation coefficient = - 0.689, p = 0.042) in OI patients. DKK1-AS improved bone mineral density (p = 0.002), trabecular bone volume/total volume fraction (p < 0.001), trabecular separation (p = 0.010), trabecular thickness (p = 0.001), trabecular number (p < 0.001), and cortical thickness (p < 0.001) in OI mice. DKK1-AS enhanced the transcription of collagen 1α1, osteocalcin, runx2, and osterix in BMSC from OI mice (all p < 0.001), resulting in a higher von Kossa-stained matrix area (p < 0.001) in ex vivo osteogenesis assays. DKK1-AS also reduced osteoclast numbers (p < 0.001), increased β-catenin and T-cell factor 4 immunostaining reactivity (both p < 0.001), enhanced mineral apposition rate and bone formation rate per bone surface (both p < 0.001), and decreased osteoclast area (p < 0.001) in OI mice. DKK1-AS upregulated osteoprotegerin and downregulated nuclear factor-kappa B ligand transcription (both p < 0.001). Bone tissues from OI mice treated with DKK1-AS exhibited significantly higher breaking force compared to untreated OI mice (p < 0.001).

CONCLUSIONS

Our study elucidates that DKK1-AS has the capability to enhance bone mechanical properties, restore the transcription of osteogenic genes, promote osteogenesis, and inhibit osteoclastogenesis in OI mice.

Correlation of lipocalin 2 and glycolipid metabolism and body composition in a large cohort of children with osteogenesis imperfecta

PURPOSE

Lipocalin 2 (LCN2) is a newly recognized bone-derived factor that is important in regulation of energy metabolism. We investigated the correlation of serum LCN2 levels and glycolipid metabolism, and body composition in a large cohort of patients with osteogenesis imperfecta (OI).

METHODS

A total of 204 children with OI and 66 age- and gender-matched healthy children were included. Circulating levels of LCN2 and osteocalcin were measured by enzyme-linked immunosorbent assay. Serum levels of fasting blood glucose (FBG), triglyceride (TG), total cholesterol (TC), and low- and high-density lipoprotein cholesterol (LDL-C, HDL-C) were measured by automated chemical analyzers. The body composition was measured by dual-energy X-ray absorptiometry. Grip strength and timed-up-and-go (TUG) were tested to evaluate the muscle function.

RESULTS

Serum LCN2 levels were 37.65 ± 23.48 ng/ml in OI children, which was significantly lower than those in healthy control (69.18 ± 35.43 ng/ml, P < 0.001). Body mass index (BMI) and serum FBG level were significantly higher and HDL-C levels were lower in OI children than healthy control (all P < 0.01). Grip strength was significantly lower (P < 0.05), and the TUG was significantly longer in OI patients than healthy control (P < 0.05). Serum LCN2 level was negatively correlated to BMI, FBG, HOMA-IR, HOMA-β, total body, and trunk fat mass percentage, and positively correlated to total body and appendicular lean mass percentage (all P < 0.05).

CONCLUSIONS

Insulin resistance, hyperglycemia, obesity, and muscle dysfunction are common in OI patients. As a novel osteogenic cytokine, LCN2 deficiency may be relevant to disorders of glucose and lipid metabolism, and dysfunction of muscle in OI patients.

Abnormal changes of bone metabolism markers with age in children with cerebral palsy

Cerebral palsy (CP) is a broad range of diseases with permanent and nonprogressive motor impairments, carrying a high cost for both the individual and the society. The characteristics of low bone mineral density and high risk of fractures suggest that bone metabolism disorders are present in CP. This study aims to investigate the association between indicators of bone metabolism and children with CP. A total of 139 children (75 children with CP and 64 healthy controls) were included in this cross-sectional study. Participants were divided into three age groups (0-2 years, 2.1-4 years, and 4.1-7 years). All children with CP were diagnosed according to clinical criteria and furtherly divided into clinical subtypes. The levels of total procollagen type I N-terminal propeptide (TPINP), N-MID osteocalcin (OC), beta-crosslaps (β-CTX), 25-hydroxyvitamin D (25-OHD) and parathyroid hormone (PTH) in the serum were measured with corresponding detection kits according to the manufacturer's instructions. Serum levels of TPINP and 25-OHD were lower with older age, whereas β-CTX and PTH were higher with older age. In the CP group, TPINP (age 0-2 years and 2.1-4 years) and OC (age 2.1-4 years) levels were higher, while β-CTX (age 2.1-4 years and 4.1-7 years) and PTH (age 2.1-4 years) values were lower than the control group. In addition, there were no statistically significant differences in the levels of these indicators among the CP subgroups with different clinical characteristics. Our study shows that bone turnover markers, indicators of bone metabolism, in children with CP differ significantly from healthy controls. The indicators we studied changed with age, and they did not correlate with disease severity.

Whole-Body Metabolism and the Musculoskeletal Impacts of Targeting Activin A and Myostatin in Severe Osteogenesis Imperfecta

Mutations in the COL1A1 and COL1A2 genes, which encode type I collagen, are present in around 85%-90% of osteogenesis imperfecta (OI) patients. Because type I collagen is the principal protein composition of bones, any changes in its gene sequences or synthesis can severely affect bone structure. As a result, skeletal deformity and bone frailty are defining characteristics of OI. Homozygous oim/oim mice are utilized as models of severe progressive type III OI. Bone adapts to external forces by altering its mass and architecture. Previous attempts to leverage the relationship between muscle and bone involved using a soluble activin receptor type IIB-mFc (sActRIIB-mFc) fusion protein to lower circulating concentrations of activin A and myostatin. These two proteins are part of the TGF-β superfamily that regulate muscle and bone function. While this approach resulted in increased muscle masses and enhanced bone properties, adverse effects emerged due to ligand promiscuity, limiting clinical efficacy and obscuring the precise contributions of myostatin and activin A. In this study, we investigated the musculoskeletal and whole-body metabolism effect of treating 5-week-old wildtype (Wt) and oim/oim mice for 11 weeks with either control antibody (Ctrl-Ab) or monoclonal anti-activin A antibody (ActA-Ab), anti-myostatin antibody (Mstn-Ab), or a combination of ActA-Ab and Mstn-Ab (Combo). We demonstrated that ActA-Ab treatment minimally impacts muscle mass in oim/oim mice, whereas Mstn-Ab and Combo treatments substantially increased muscle mass and overall lean mass regardless of genotype and sex. Further, while no improvements in cortical bone microarchitecture were observed with all treatments, minimal improvements in trabecular bone microarchitecture were observed with the Combo treatment in oim/oim mice. Our findings suggest that individual or combinatorial inhibition of myostatin and activin A alone is insufficient to robustly improve femoral biomechanical and microarchitectural properties in severely affected OI mice. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

DNA methyltransferases inhibitor azacitidine improves the skeletal phenotype of mild osteogenesis imperfecta by reversing the impaired osteogenesis and excessive osteoclastogenesis

BACKGROUND

Osteogenesis imperfecta (OI), as a disease of congenital bone dysplasia, is often accompanied by the abnormal alteration of bone absorption and bone formation. DNA methyltransferases (Dnmts) can regulate the gene expression involved in osteogenesis and osteoclastogenesis. Dnmts changes and their effects on bone cells under OI is poorly understood.

METHODS

The Dnmts expression in adipose derived mesenchymal stem cells (ADSCs), bone marrow derived pre-osteoclasts (pre-Ocs) and femurs of Col1a2^oim/+ and Col1a1^+/-365 mice, both modeling mild OI types, were determined. The effects of azacitidine (Aza) administration and Dnmt3a knockdown by ShRNA on the osteogenic differentiation of ADSCs together with osteoclasts (Ocs) production of pre-Ocs were studied in vitro. The synthesis and secretion of collagen fibers of OI derived ADSCs were examined. The therapeutic outcomes of intraperitoneal (i.p.) infused Aza (1 mg/kg/2d) for 30 days were evaluated in OI mice.

RESULTS

Obviously elevated expression of Dnmts, especially Dnmt3a, existed in ADSCs, pre-Ocs, and femurs isolated from OI modeled mice. Much more collagen molecules of mutant ADSCs were secreted into the extracellular medium post Aza addition. Both Aza administration and Dnmt3a knockdown effectively enhanced the bone-forming capacity of affected ADSCs and reduced Ocs formation of OI mice in vitro. Aza treatment apparently improved the femora microstructure and biomechanical properties, increased bone formation and decreased the number of Ocs in mice with OI.

CONCLUSION

Highly expressed Dnmt3a contributed to the impaired osteogenesis and enhanced osteoclastogenesis of collagen defect-related OI. Aza medication effectively improved the femora phenotype of the two types of OI modeled mice partly by Dnmts inhibition and modulating cell stress response. These findings facilitated understanding the role of Dnmts alteration in skeletal pathological development of mild OI and preliminary confirmed the therapeutic potential of Dnmts depressants in mild OI treatment. Still, further researches are needed to explore the specific function of Dnmts in OI bones and clarify the benefits of Aza administration in OI treatment.

The role of wnt signaling in diabetes-induced osteoporosis

Osteoporosis, a chronic complication of diabetes mellitus, is characterized by a reduction in bone mass, destruction of bone microarchitecture, decreased bone strength, and increased bone fragility. Because of its insidious onset, osteoporosis renders patients highly susceptible to pathological fractures, leading to increased disability and mortality rates. However, the specific pathogenesis of osteoporosis induced by chronic hyperglycemia has not yet been fully elucidated. But it is currently known that the disruption of Wnt signaling triggered by chronic hyperglycemia is involved in the pathogenesis of diabetic osteoporosis. There are two main types of Wnt signaling pathways, the canonical Wnt signaling pathway (β-catenin-dependent) and the non-canonical Wnt signaling pathway (non-β-catenin-dependent), both of which play an important role in regulating the balance between bone formation and bone resorption. Therefore, this review systematically describes the effects of abnormal Wnt pathway signaling on bone homeostasis under hyperglycemia, hoping to reveal the relationship between Wnt signaling and diabetic osteoporosis to further improve understanding of this disease.

Brain-Type Creatine Kinase Release from Cultured Osteoclasts Exposed to Neridronate in Children Affected by Osteogenesis Imperfecta Type 1

Brain-type creatine kinase (CK-BB) increases during osteoclastogenesis, with high circulating amounts in type I osteogenesis imperfecta (OI) following treatment with neridronate, a bisphosphonate able to inhibit osteoclast activity and survival. The aim of this study was to demonstrate the correlation between osteoclastogenesis and CK-BB release from OI patients' osteoclasts treated with different concentrations of neridronate. Our patients showed reduced bone quality, increased levels of CTX I, a marker of bone resorption, and decreased levels of OPG, an inhibitor of osteoclastogenesis. In OI patients, the presence of MCSF and RANKL determined an increased secretion of CK-BB from osteoclasts (p = 0.04) compared with control conditions without these cytokines; interestingly, in the absence of these factors, the secretion of CK-BB is significantly elevated at 3 µmol/L compared with 0.03 and 1 µmol/L (p = 0.007). In healthy donors' cultures, the higher concentration of CK-BB can be detected following stimulation with 3 µmol/L neridronate compared with the untreated condition both with and without MCSF and RANKL (p = 0.03 and p = 0.006, respectively). Consistently, in osteoclast cultures, neridronate treatment is associated with a decrease in multinucleated TRAP+ cells, together with morphology changes typical of apoptosis. Consistently, in the media of the same osteoclast cultures, we demonstrated a significant increase in caspase-3 levels. In conclusion, our findings support the idea that CK-BB levels increase in the serum of OI-treated patients.

Serum Sclerostin and Its Association with Bone Turnover Marker in Metabolic Bone Diseases

Sclerostin is a secreted inhibitor of Wnt/β-catenin signaling that is mainly produced by osteocytes and is an important regulator of bone remodeling. Some studies have evaluated serum sclerostin levels in metabolic bone diseases, but the results have been contradictory. The profile of serum sclerostin levels in patients with osteogenesis imperfecta (OI), X-linked hypophosphatemia (XLH), and Paget's disease of bone (PDB) was obtained to determine their association with bone turnover marker. Serum sclerostin levels, biochemical parameters, and the bone turnover marker, β-CrossLaps of type 1 collagen containing cross-linked C-telopeptide (β-CTX), were measured in 278 individuals, comprising 71 patients with OI, 51 patients with XLH, 17 patients with PDB, and 139 age- and sex-matched healthy controls. A correlation analysis was performed between sclerostin and β-CTX concentration. The univariate logistic regression analysis was used to analyze factors associated with OI, XLH, and PDB. Patients with PDB (11 male 6 female), aged 44.47 ± 14.75 years; XLH (17 male, 34 female), aged 19.29 ± 15.65 years; and OI (43 male, 28 female), aged 19.57 ± 16.45 years, had higher sclerostin level than age- and sex-matched healthy controls [median(interquartile range): 291.60 (153.42, 357.35) vs. 38.00 (27.06, 68.52) pmol/L, 163.40 (125.10, 238.20) vs. 31.13 (20.37, 45.84) pmol/L, and 130.50 (96.12, 160.80) vs. 119.00 (98.89, 194.80) pmol/L, respectively; P < 0.001]. Patients with PDB had the highest level of serum sclerostin, followed by those with XLH and OI (P < 0.05). Sclerostin was positively correlated with β-CTX in OI and XLH (r = 0.541 and r = 0.661, respectively; P < 0.001). Higher β-CTX and sclerostin levels were associated with a higher risk of OI, XLH, and PBD. Sclerostin may be a biomarker of OI, XLH, and PDB. Whether sclerostin inhibitors can be used in these patients requires further analysis using additional cohorts.

The use of quantitative ultrasound in a tertiary-level children hospital: role in the follow-up of chronically ill patients

PURPOSE

To evaluate the use of QUS for the bone status assessment in children cared because of a chronic disease such as: inherited metabolic disorder, kidney disease and endocrine defect and considered by the attending physician as at specific risk.

METHODS

QUS outputs were calculated for each disorder and compared to: sex, age, Tanner stage, Z-score for height, weight and BMI (body mass index).

RESULTS

One-hundred-sixty-eight subjects aged between 3.5 and 18 years met the inclusion criteria. The overall bone quality indexes were under the normal range in all the groups considered. Impairment of bone quality parameters was more evident in the group of patients with inherited metabolic disorders, in which 65% of patients in charge were studied by QUS. Older age and sexual development were associated with less pronounced bone quality impairment, as measured by QUS, in the vast majority of conditions. Overall, the diseases for which the prediction of outcome was the strongest were: hyperphenylalaninemia, nephrotic syndrome and insulin dependent diabetes mellitus.

CONCLUSIONS

QUS is capable to provide information on skeletal status in children. Initial evaluation by QUS may allow defining patients with chronic disorders who deserve further, more invasive diagnostic studies. Inherited metabolic disorders warrant specific attention and strict monitoring for their potential effect on bone.

Up-regulated IL-17 and Tnf signaling in bone marrow cells of young male osteogenesis imperfecta mice

Osteogenesis imperfecta (OI) is a congenital bone dysplasia mainly caused by either defective production or assembly of type I collagen. The skeletal phenotypes especially fractures are often seen in OI adolescents. Studies have found that an increased number of osteoclasts and excessive bone resorption existed in collagen-related OI, which has not been well understood. Emerging evidence has suggested that inflammation may be associated with OI. We speculated that the bone marrow (BM) niche had similar inflammatory changes and performed RNA-sequencing (RNA-seq) in BM cells derived from young male mice to analyze the related differentially expressed genes (DEGs) and pathways. Data showed that there were 117 shared DEGs (Q ≤ 0.05, |log₂FC| ≥ 1) in BM cells isolated from two types of OI murine models that respectively simulate different OI types. Gene Ontology (GO) (Q ≤ 0.05) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) (Q ≤ 0.05) analysis and real-time PCR validation indicated the dysregulated biology process of cellular response to interferon (Ifn) together with upregulated IL-17 signaling, tumor necrosis factor (Tnf) signaling and osteoclast differentiation in OI BM niche. Either defective collagen production or abnormal collagen assembly shared similar alterations in gene profiles and pathways involving inflammation and osteoclast activation. Data presented here not only contributed to understanding of the mechanism of the enhanced bone absorption in the bones of OI, but also provided more evidence to develop potential anti-inflammation therapies.

High Dickkopf-1 (DKK-1) levels are associated with chronic inflammation in children with Sickle Cell Disease

OBJECTIVES

Sickle bone disease (SBD) is a chronic complication of Sickle Cell Disease (SCD) whose pathogenesis is not completely understood. Chronic inflammation associated with SCD could alter bone remodeling. Our aim was to analyze the serum levels of bone remodeling markers in a group of SCD children to evaluate their involvement in the SBD.

METHODS

We enrolled 26 SCD subjects and 26 age-matched controls, who lived in the same geographic area. DKK-1, sclerostin, RANKL, and OPG serum levels were evaluated. Neutrophil-lymphocyte ratio (NLR) was also evaluated as a marker of inflammation.

RESULTS

The analysis of bone remodeling markers did not show any significant difference between the two groups except for DKK-1 levels that were significantly higher in the patients than controls (p<0.05). A significant direct correlation between NLR and DKK-1 (p=0.004) was found. An inverse correlation between NLR and osteocalcin (p=0.01) has also been observed.

CONCLUSIONS

The chronic inflammation, which represents a peculiar characteristic in SCD patients, would represent the primary causal agent of the activation of osteoblastogenesis inhibitors responsible of bone impairment in these subjects. Further studies will be needed to better explain the role of these inhibitors in SCD, to prevent or treat bone damage in this population.

Male but not female mice with severe osteogenesis imperfecta are partially protected from high-fat diet-induced obesity

Previously we have shown that young mice with a dominant severe form of osteogenesis imperfecta (OI), caused by mutated collagen type I, exhibit an altered glucose/insulin metabolism and energy expenditure along with elevated levels of osteocalcin, a bone-derived hormone involved in the regulation of whole-body metabolism. This study aimed to examine the long-term effects of a western diet in these OI mice. Male and female OI mice and wild type littermates (WT) were fed a high-fat diet (HFD) or a matched low-fat diet (LFD) for 26 weeks. HFD-induced obesity was observed in male and female WT and female OI mice, but not in male OI mice. HFD-fed WT and OI mice of both sexes developed hyperglycemia and glucose intolerance, but the degree of glucose intolerance was significantly lower in male and female OI mice compared to sex- and diet-matched WT mice. Indirect calorimetry revealed increased movement of male OI mice on HFD compared to LFD and, while HFD lowered energy expenditure in WT mice, energy expenditure was not changed in OI mice. Further, HFD-fed male OI mice demonstrated a diet-induced increased expression of the thermogenesis genes, Ucp1 and Pgc1α, in brown adipose tissue. On LFD, total and Gla-13 osteocalcin levels were similar in 30-week-old WT and OI mice, but on HFD, both were significantly higher in OI mice than WT. Thus, male OI mice respond to HFD with increased movement, energy expenditure, brown adipose tissue thermogenesis, and higher levels of osteocalcin, resulting in partial protection against HFD-induced obesity.

Increased Osteocyte Lacunae Density in the Hypermineralized Bone Matrix of Children with Osteogenesis Imperfecta Type I

Osteocytes are terminally differentiated osteoblasts embedded within the bone matrix and key orchestrators of bone metabolism. However, they are generally not characterized by conventional bone histomorphometry because of their location and the limited resolution of light microscopy. OI is characterized by disturbed bone homeostasis, matrix abnormalities and elevated bone matrix mineralization density. To gain further insights into osteocyte characteristics and bone metabolism in OI, we evaluated 2D osteocyte lacunae sections (OLS) based on quantitative backscattered electron imaging in transiliac bone biopsy samples from children with OI type I (n = 19) and age-matched controls (n = 24). The OLS characteristics were related to previously obtained, re-visited histomorphometric parameters. Moreover, we present pediatric bone mineralization density distribution reference data in OI type I (n = 19) and controls (n = 50) obtained with a field emission scanning electron microscope. Compared to controls, OI has highly increased OLS density in cortical and trabecular bone (+50.66%, +61.73%; both p < 0.001), whereas OLS area is slightly decreased in trabecular bone (−10.28%; p = 0.015). Correlation analyses show a low to moderate, positive association of OLS density with surface-based bone formation parameters and negative association with indices of osteoblast function. In conclusion, hyperosteocytosis of the hypermineralized OI bone matrix associates with abnormal bone cell metabolism and might further impact the mechanical competence of the bone tissue.

Impact of Genetic and Pharmacologic Inhibition of Myostatin in a Murine Model of Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is a genetic connective tissue disorder characterized by compromised skeletal integrity, altered microarchitecture, and bone fragility. Current OI treatment strategies focus on bone antiresorptives and surgical intervention with limited effectiveness, and thus identifying alternative therapeutic options remains critical. Muscle is an important stimulus for bone formation. Myostatin, a TGF-β superfamily myokine, acts through ActRIIB to negatively regulate muscle growth. Recent studies demonstrated the potential benefit of myostatin inhibition with the soluble ActRIIB fusion protein on skeletal properties, although various OI mouse models exhibited variable skeletal responses. The genetic and clinical heterogeneity associated with OI, the lack of specificity of the ActRIIB decoy molecule for myostatin alone, and adverse events in human clinical trials further the need to clarify myostatin's therapeutic potential and role in skeletal integrity. In this study, we determined musculoskeletal outcomes of genetic myostatin deficiency and postnatal pharmacological myostatin inhibition by a monoclonal anti-myostatin antibody (Regn647) in the G610C mouse, a model of mild-moderate type I/IV human OI. In the postnatal study, 5-week-old wild-type and +/G610C male and female littermates were treated with Regn647 or a control antibody for 11 weeks or for 7 weeks followed by a 4-week treatment holiday. Inhibition of myostatin, whether genetically or pharmacologically, increased muscle mass regardless of OI genotype, although to varying degrees. Genetic myostatin deficiency increased hindlimb muscle weights by 6.9% to 34.4%, whereas pharmacological inhibition increased them by 13.5% to 29.6%. Female +/mstn +/G610C (Dbl.Het) mice tended to have similar trabecular and cortical bone parameters as Wt showing reversal of +/G610C characteristics but with minimal effect of +/mstn occurring in male mice. Pharmacologic myostatin inhibition failed to improve skeletal bone properties of male or female +/G610C mice, although skeletal microarchitectural and biomechanical improvements were observed in male wild-type mice. Four-week treatment holiday did not alter skeletal outcomes. © 2020 American Society for Bone and Mineral Research (ASBMR).

Osteogenesis imperfecta: treatment and surgical management

PURPOSE OF REVIEW

Osteogenesis imperfecta is a disease with many different causes and clinical presentations. Surgery at a young age is the often required in order to improve the patients' growth development and quality of life. This manuscript highlights the current approach to treat children with osteogenesis imperfecta. The main purpose of this review is to compare and discuss the latest surgical techniques and procedures.

RECENT FINDINGS

Recent studies have indicated that telescoping intramedullary Faisser-Duval rods are one of the most suitable surgical devices to correct long bone deformities. The design permits elongation with growth and helps reduce the number of revision surgeries compared to previous static devices.

SUMMARY

Osteogenesis imperfecta patients require an interdisciplinary and tailored treatment that involves both medical and surgical components. On the basis of the most recent surgical and medical findings, the authors recommend treating osteogenesis imperfecta patients early with bisphosphonates prior to surgical intervention and then utilizing Faisser-Duval rods in a surgical setting to correct lower extremity deformities and fractures.

Growth plate gene involment and isolated short stature

PURPOSE

Short stature is a common clinical presentation, thus it is widely accepted that it is a polygenic trait. However, genome wide association and next generation sequencing studies have recently challenged this view, suggesting that many of the children classified as idiopathic short stature could instead have monogenic defects. Linear growth is determined primarily by chondrogenesis at the growth plate. This process results from chondrocyte proliferation, hypertrophy, and extracellular matrix secretion, and it is perfectly coordinated by complex networks of local paracrine and endocrine factors. Alterations in genes which control growth plate development can explain a large number of cases of isolated short stature, allowing an etiological diagnosis.

METHODS/RESULTS

We reviewed recent data on the genetic alterations in fundamental cellular processes, paracrine signaling, and cartilage matrix formation associated with impaired growth plate chondrogenesis. In particular we focused on growth plate gene involvement in nonsyndromic short stature.

CONCLUSIONS

The identification of genetic basis of growth failure will have a significant impact on the care of children affected with short stature.

Signaling pathways affected by mutations causing osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a clinically and genetically heterogeneous connective tissue disorder characterized by bone fragility and skeletal deformity. To maintain skeletal strength and integrity, bone undergoes constant remodeling of its extracellular matrix (ECM) tightly controlled by osteoclast-mediated bone resorption and osteoblast-mediated bone formation. There are at least 20 recognized OI-forms caused by mutations in the two collagen type I-encoding genes or genes implicated in collagen folding, posttranslational modifications or secretion of collagen, osteoblast differentiation and function, or bone mineralization. The underlying disease mechanisms of non-classical forms of OI that are not caused by collagen type I mutations are not yet completely understood, but an altered ECM structure as well as disturbed intracellular homeostasis seem to be the main defects. The ECM orchestrates local cell behavior in part by regulating bioavailability of signaling molecules through sequestration, release and activation during the constant bone remodeling process. Here, we provide an overview of signaling pathways that are associated with known OI-causing genes and discuss the impact of these genes on signal transduction. These pathways include WNT-, RANK/RANKL-, TGFβ-, MAPK- and integrin-mediated signaling as well as the unfolded protein response.

How Physical Activity across the Lifespan Can Reduce the Impact of Bone Ageing: A Literature Review

Bone remodeling is a lifelong process, due to the balanced activity of the osteoblasts (OBs), the bone-forming cells, and osteoclasts (OCs), the bone-resorbing cells. This equilibrium is mainly regulated by the WNT-ß-cathenin pathway and the RANK-RANKL/OPG system, respectively. Bone ageing is a process which normally occurs during life due to the imbalance between bone formation and bone resorption, potentially leading to osteoporosis. Bone loss associated with bone ageing is determined by oxidative stress, the result of the increasing production of reactive oxygen species (ROS). The promotion of physical exercise during growth increases the chances of accruing bone and delaying the onset of osteoporosis. Several studies demonstrate that physical exercise is associated with higher bone mineral density and lower fracture incidence, and the resulting bone mineral gain is maintained with ageing, despite a reduction of physical activity in adulthood. The benefits of exercise are widely recognized, thus physical activity is considered the best non-pharmacologic treatment for pathologies such as osteoporosis, obesity, diabetes and cardiovascular disease. We reviewed the physiological mechanisms which control bone remodeling, the effects of physical activity on bone health, and studies on the impact of exercise in reducing bone ageing.

Osteogenesis imperfecta and rheumatoid arthritis: is there a link?

We present the cases of a mother and daughter with osteogenesis imperfecta, also diagnosed later with rheumatoid arthritis. In our patients finding and treating the over-imposed arthritis improved the joint pain initially attributed to osteogenesis imperfecta. Exploring joint inflammation in this setting could help ease the disease burden.

PURPOSE

Osteogenesis imperfecta (OI) is a rare hereditary disease evolving with recurrent fractures upon minor trauma, blue sclerae, and hearing loss. Although inflammation was not generally considered a feature of the disease, systemic inflammation was recently reported in children with OI and in murine models of OI.

METHOD

We present the cases of a mother and a daughter with OI, without a personal or family history of autoimmune diseases, who were also diagnosed with rheumatoid arthritis seropositive for anti-cyclic citrullinated peptide autoantibodies and rheumatoid factor.

RESULTS

The genetic tests identified in both patients a deletion in COL1A1 gene (c.3399del, p.Ala1134Profs*105), not previously reported, not present in population databases, creating a premature translational stop signal in the COL1A1 gene in the collagen I major ligand binding region 3. In our patients finding and treating the over-imposed arthritis improved the joint pain initially attributed to OI. Possible pathogenic links between OI and RA are discussed.

CONCLUSION

The prevalence of joint inflammation in OI is unknown and may be underestimated. As musculoskeletal involvement affects the quality of life in most OI patients, exploring this relation may help ease the disease burden.

The Bones of Children With Obesity

Excess adiposity in childhood may affect bone development, ultimately leading to bone frailty. Previous reports showing an increased rate of extremity fractures in children with obesity support this fear. On the other hand, there is also evidence suggesting that bone mineral content is higher in obese children than in normal weight peers. Both adipocytes and osteoblasts derive from multipotent mesenchymal stem cells (MSCs) and obesity drives the differentiation of MSCs toward adipocytes at the expense of osteoblast differentiation. Furthermore, adipocytes in bone marrow microenvironment release a number of pro-inflammatory and immunomodulatory molecules that up-regulate formation and activation of osteoclasts, thus favoring bone frailty. On the other hand, body adiposity represents a mechanical load, which is beneficial for bone accrual. In this frame, bone quality, and structure result from the balance of inflammatory and mechanical stimuli. Diet, physical activity and the hormonal milieu at puberty play a pivotal role on this balance. In this review, we will address the question whether the bone of obese children and adolescents is unhealthy in comparison with normal-weight peers and discuss mechanisms underlying the differences in bone quality and structure. We anticipate that many biases and confounders affect the clinical studies conducted so far and preclude us from achieving robust conclusions. Sample-size, lack of adequate controls, heterogeneity of study designs are the major drawbacks of the existing reports. Due to the increased body size of children with obesity, dual energy absorptiometry might overestimate bone mineral density in these individuals. Magnetic resonance imaging, peripheral quantitative CT (pQCT) scanning and high-resolution pQCT are promising techniques for the accurate estimate of bone mineral content in obese children. Moreover, no longitudinal study on the risk of incident osteoporosis in early adulthood of children and adolescents with obesity is available. Finally, we will address emerging dietary issues (i.e., the likely benefits for the bone health of polyunsaturated fatty acids and polyphenols) since an healthy diet (i.e., the Mediterranean diet) with balanced intake of certain nutrients associated with physical activity remain the cornerstones for achieving an adequate bone accrual in young individuals regardless of their adiposity degree.

WNT Signaling and Bone: Lessons From Skeletal Dysplasias and Disorders

Skeletal dysplasias are a diverse group of heritable diseases affecting bone and cartilage growth. Throughout the years, the molecular defect underlying many of the diseases has been identified. These identifications led to novel insights in the mechanisms regulating bone and cartilage growth and homeostasis. One of the pathways that is clearly important during skeletal development and bone homeostasis is the Wingless and int-1 (WNT) signaling pathway. So far, three different WNT signaling pathways have been described, which are all activated by binding of the WNT ligands to the Frizzled (FZD) receptors. In this review, we discuss the skeletal disorders that are included in the latest nosology of skeletal disorders and that are caused by genetic defects involving the WNT signaling pathway. The number of skeletal disorders caused by defects in WNT signaling genes and the clinical phenotype associated with these disorders illustrate the importance of the WNT signaling pathway during skeletal development as well as later on in life to maintain bone mass. The knowledge gained through the identification of the genes underlying these monogenic conditions is used for the identification of novel therapeutic targets. For example, the genes underlying disorders with altered bone mass are all involved in the canonical WNT signaling pathway. Consequently, targeting this pathway is one of the major strategies to increase bone mass in patients with osteoporosis. In addition to increasing the insights in the pathways regulating skeletal development and bone homeostasis, knowledge of rare skeletal dysplasias can also be used to predict possible adverse effects of these novel drug targets. Therefore, this review gives an overview of the skeletal and extra-skeletal phenotype of the different skeletal disorders linked to the WNT signaling pathway.

Comprehensive genetic analyses using targeted next-generation sequencing and genotype-phenotype correlations in 53 Japanese patients with osteogenesis imperfecta

To elucidate mutation spectrum and genotype-phenotype correlations in Japanese patients with OI, we conducted comprehensive genetic analyses using NGS, as this had not been analyzed comprehensively in this patient population. Most mutations were located on COL1A1 and COL1A2. Glycine substitutions in COL1A1 resulted in the severe phenotype.

INTRODUCTION

Most cases of osteogenesis imperfecta (OI) are caused by mutations in COL1A1 or COL1A2, which encode α chains of type I collagen. However, mutations in at least 16 other genes also cause OI. The mutation spectrum in Japanese patients with OI has not been comprehensively analyzed, as it is difficult to identify using classical Sanger sequencing. In this study, we aimed to reveal the mutation spectrum and genotype-phenotype correlations in Japanese patients with OI using next-generation sequencing (NGS).

METHODS

We designed a capture panel for sequencing 15 candidate OI genes and 19 candidate genes that are associated with bone fragility or Wnt signaling. Using NGS, we examined 53 Japanese patients with OI from unrelated families.

RESULTS

Pathogenic mutations were detected in 43 out of 53 individuals. All mutations were heterozygous. Among the 43 individuals, 40 variants were identified including 15 novel mutations. We found these mutations in COL1A1 (n = 30, 69.8%), COL1A2 (n = 12, 27.9%), and IFITM5 (n = 1, 2.3%). Patients with glycine substitution on COL1A1 had a higher frequency of fractures and were more severely short-statured. Although no significant genotype-phenotype correlation was observed for bone mineral density, the trabecular bone score was significantly lower in patients with glycine substitutions.

CONCLUSION

We identified pathogenic mutations in 81% of our Japanese patients with OI. Most mutations were located on COL1A1 and COL1A2. This study revealed that glycine substitutions on COL1A1 resulted in the severe phenotype among Japanese patients with OI.

Bone Matrix Levels of Dickkopf and Sclerostin are Positively Correlated with Bone Mass and Strength in Postmenopausal Osteoporosis

Wnt signaling plays a pivotal role in maintaining bone mass. Secreted pathway modulators such as sclerostin (SOST) and Dickkopfs (DKKs) may influence bone mass inhibiting the canonical Wnt pathway. We evaluated whether bone protein content of secreted Wnt antagonists is related to age, bone mass, and strength in postmenopausal osteoporosis. We measured cortical and trabecular bone contents of SOST and Dickkopf-1 (DKK1) in combined extracts obtained after ethylenediaminetetraacetic acid and guanidine hydrochloride extraction in 56 postmenopausal women aged 47–74 (mean, 63) yr with a previous distal forearm fracture and a hip or spine Z-score less than 0. Our findings were (i) SOST and DKK1 protein levels were higher in trabecular bone, (ii) cortical and trabecular DKK1 and trabecular SOST correlated positively with bone matrix levels of osteocalcin (r between 0.28 and 0.45, p < 0.05), (iii) cortical DKK1 correlated with lumbar spine bone mineral density (BMD) (r = 0.32, p < 0.05) and femoral neck BMD (r = 0.41, p < 0.01), and (iv) cortical DKK1 and SOST correlated with apparent bone volumetric density and compressive strength (r between 0.34 and 0.51, p < 0.01). In conclusion, cortical bone matrix levels of DKK1 and SOST were positively correlated with bone mass and bone strength in postmenopausal osteoporotic women.

Irisin and Bone: From Preclinical Studies to the Evaluation of Its Circulating Levels in Different Populations of Human Subjects

Almost four years after the discovery of the anabolic action of irisin on bone in mice, ample clinical evidence is emerging in support of its additional physiological relevance in human bone. Irisin inversely correlates with sclerostin levels in adults with prediabetes and with vertebral fragility fractures in post-menopausal women. Furthermore, in athletes we observed a positive correlation between irisin and bone mineral density at different anatomical sites. Our group also described a positive association between serum irisin and bone status in healthy children and multivariate regression analysis showed that irisin is a stronger determinant of bone mineral status than bone alkaline phosphatase. In children with type 1 diabetes mellitus, serum irisin concentrations are positively associated with bone quality and with glycemic control following continuous subcutaneous insulin infusion. Additionally, our in vitro studies suggest the existence of a negative interplay between PTH and irisin biology and these results were also supported by the observation that post-menopausal women with primary hyperparathyroidism have lower levels of irisin compared to matched controls. In this review, we will focus on recent findings about circulating level of irisin in different populations of human subjects and its correlation with their bone status.

Effects of Sweet Cherry Polyphenols on Enhanced Osteoclastogenesis Associated With Childhood Obesity

Childhood obesity is associated with the development of severe comorbidities, such as diabetes, cardiovascular diseases, and increased risk of osteopenia/osteoporosis and fractures. The status of low-grade inflammation associated to obesity can be reversed through an enhanced physical activity and by consumption of food enrich of anti-inflammatory compounds, such as omega-3 fatty acids and polyphenols. The aim of this study was to deepen the mechanisms of bone impairment in obese children and adolescents through the evaluation of the osteoclastogenic potential of peripheral blood mononuclear cells (PBMCs), and the assessment of the serum levels of RANKL and osteoprotegerin (OPG). Furthermore, we aimed to evaluate the in vitro effects of polyphenol cherry extracts on osteoclastogenesis, as possible dietary treatment to improve bone health in obese subjects. High RANKL levels were measured in obese with respect to controls (115.48 ± 35.20 pg/ml vs. 87.18 ± 17.82 pg/ml; p < 0.01), while OPG levels were significantly reduced in obese than controls (378.02 ± 61.15 pg/ml vs. 436.75 ± 95.53 pg/ml, respectively, p < 0.01). Lower Ad-SoS- and BTT Z-scores were measured in obese compared to controls (p < 0.05). A significant elevated number of multinucleated TRAP⁺ osteoclasts (OCs) were observed in the un-stimulated cultures of obese subjects compared to the controls. Interestingly, obese subjects displayed a higher percentage of CD14⁺/CD16⁺ than controls. Furthermore, in the mRNA extracts of obese subjects we detected a 2.5- and 2-fold increase of TNFα and RANKL transcripts compared to controls, respectively. Each extract of sweet cherries determined a dose-dependent reduction in the formation of multinucleated TRAP⁺ OCs. Consistently, 24 h treatment of obese PBMCs with sweet cherry extracts from the three cultivars resulted in a significant reduction of the expression of TNFα. In conclusion, the bone impairment in obese children and adolescents is sustained by a spontaneous osteoclastogenesis that can be inhibited in vitro by the polyphenol content of sweet cherries. Thus, our study opens future perspectives for the use of sweet cherry extracts, appropriately formulated as nutraceutical food, as preventive in healthy children and therapeutic in obese ones.

Irisin serum levels are positively correlated with bone mineral status in a population of healthy children

BACKGROUND

Irisin is a myokine secreted by skeletal muscle during physical activity. Irisin treatment increased cortical bone mineral density (BMD) in young healthy mice and restored bone and muscle mass loss in a mouse model of disuse-induced osteoporosis and muscular atrophy. In humans, Irisin was positively correlated with BMD in young athletes. Considering that the bone mass reached during childhood is one of the most important determinants of lifelong skeletal health, we sought to determine if Irisin levels were correlated with bone mineral status in children.

METHODS

Irisin and bone metabolic markers were quantified in sera and bone mineral status was evaluated by quantitative ultrasound in a population of 34 healthy children (9.82 ± 3.2 years).

RESULTS

We found that Irisin levels were positively correlated with the amplitude-dependent speed of sound Z-score (r = 0.305; p < 0.001), bone transmission time Z-score (r = 0.375; p < 0.001) and osteocalcin (r = 0.370; p < 0.001), and negatively with Dickkopf WNT Signaling Pathway Inhibitor 1 (r = -0.274; p < 0.001).

CONCLUSION

In a regression analysis model, Irisin was one of the determinants of bone mineral status to a greater extent than bone alkaline phosphatase and parathyroid hormone, indicating that Irisin might be considered as one of the bone formation markers during childhood.

An update on the role of RANKL-RANK/osteoprotegerin and WNT-ß-catenin signaling pathways in pediatric diseases

BACKGROUND

Bone remodeling is a lifelong process due to the balanced activity of osteoclasts (OCs), the bone-reabsorbing cells, and osteoblasts (OBs), and the bone-forming cells. This equilibrium is regulated by numerous cytokines, but it has been largely demonstrated that the RANK/RANKL/osteoprotegerin and Wnt/β-catenin pathways play a key role in the control of osteoclastogenesis and osteoblastogenesis, respectively. The pro-osteoblastogenic activity of the Wnt/β-catenin can be inhibited by sclerostin and Dickkopf-1 (DKK-1). RANKL, sclerostin and DKKs-1 are often up-regulated in bone diseases, and they are the target of new monoclonal antibodies.

DATA SOURCES

The authors performed a systematic literature search in PubMed and EMBASE to June 2018, reviewed and selected articles, based on pre-determined selection criteria.

RESULTS

We re-evaluated the role of RANKL, osteoprotegerin, sclerostin and DKK-1 in altered bone remodeling associated with some inherited and acquired pediatric diseases, such as type 1 diabetes mellitus (T1DM), alkaptonuria (AKU), hemophilia A, osteogenesis imperfecta (OI), 21-hydroxylase deficiency (21OH-D) and Prader-Willi syndrome (PWS). To do so, we considered recent clinical studies done on pediatric patients in which the roles of RANKL-RANK/osteoprotegerin and WNT-ß-catenin signaling pathways have been investigated, and for which innovative therapies for the treatment of osteopenia/osteoporosis are being developed.

CONCLUSIONS

The case studies taken into account for this review demonstrated that quite frequently both bone reabsorbing and bone deposition are impaired in pediatric diseases. Furthermore, for some of them, bone damage began in childhood but only manifested with age. The use of denosumab could represent a valid alternative therapeutic approach to improve bone health in children, although further studies need to be carried out.

Management of Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is the term used to describe a group of rare inherited skeletal disorders characterized by a greatly increased risk of fragility fractures (1). Mutations in several genes can cause OI but the condition is most commonly caused by mutations of COLIA1 or COL1A2 resulting in the production of collagen which is abnormal or present in reduced amounts. Fractures in OI are particularly common during childhood but the elevated fracture risk continues throughout life. Bone mineral density (BMD) can be reduced in OI but the magnitude of increase in fracture risk is far greater than can be accounted for by low BMD, highlighting that a key mechanism of bone fragility is reduced bone quality due to defects of bone matrix and mineralization. A multidisciplinary approach is needed to optimize management of OI, with input from physicians, orthopedic surgeons, physiotherapists, occupational therapists, and other allied health professionals. Orthopedic surgery plays a key role both in the fixation of fractures and in the correction of limb deformities. Bisphosphonates have been widely used in the treatment of children and adults with OI. Although there is good evidence that they increase BMD, it is uncertain to what extent they reduce fracture risk. Clinical trials of bone anabolic drugs such as teriparatide and inhibitors of sclerostin have also been studied; although they increase BMD, studies of these agents have not been powered to look at fracture endpoints. Various other treatment modalities including denosumab, and cell therapy have been explored but haven't gained acceptance in routine clinical practice. There have been huge advances in understanding the pathogenesis of OI but these have not been accompanied by advances in treatment. This signals need for well-designed clinical trials with fracture endpoints in OI, both with existing agents and with the newer therapeutic agents that are now starting to emerge.

Dkk1 involvement and its potential as a biomarker in pancreatic ductal adenocarcinoma

Dickkopf-1 (Dkk1)'s dysregulation has been implicated in the pathogenesis of a variety of cancers. It is part of the Dkk family of proteins that includes Dkk2, Dkk3 and Dkk4. This family of secreted proteins shares similar conserved cysteine domains and inhibits the Wnt/b-catenin pathway by causing proteasomal B-catenin degradation, inducing apoptosis, and preventing cell proliferation. Pancreatic ductal adenocarcinoma (PDAC) is the 4th leading cause of cancer mortality in the United States due to the late stage of diagnosis and the limited effectiveness of current therapy. Dkk1 is found increased in PADC patients' specimens and serum. Dkk1 can be a promising biomarker specific to PDAC, which has the potential to increase PDAC survival rates through improving early stage detection and monitoring progression compared to current biomarker gold standards. In addition, recent studies suggest that Dkk1 could be an excellent target for cancer immunotherapy. Interestingly, Dkk1-CKAP4-PI3K/AKT signal pathway also plays role in pancreatic cancer cell proliferation. In this review, we present the multiple mechanisms of Dkk1 in PDAC studied thus far and explore its function, regulation, and clinical applications in gynecological cancers including pancreatic ductal adenocarcinoma (PDAC), breast, ovarian, cervical, and endometrial cancer. Further research into Dkk1's mechanism and use as a diagnostic tool, alone or in combination with other biomarkers, could prove clinically useful for better understanding the pathology of PDAC and improving its early detection and treatment.

Mechanisms Involved in Childhood Obesity-Related Bone Fragility

Childhood obesity is one of the major health problems in western countries. The excessive accumulation of adipose tissue causes inflammation, oxidative stress, apoptosis, and mitochondrial dysfunctions. Thus, obesity leads to the development of severe co-morbidities including type 2 diabetes mellitus, liver steatosis, cardiovascular, and neurodegenerative diseases which can develop early in life. Furthermore, obese children have low bone mineral density and a greater risk of osteoporosis and fractures. The knowledge about the interplay bone tissue and between adipose is still growing, although recent findings suggest that adipose tissue activity on bone can be fat-depot specific. Obesity is associated to a low-grade inflammation that alters the expression of adiponectin, leptin, IL-6, Monocyte Chemotactic Protein 1 (MCP1), TRAIL, LIGHT/TNFSF14, OPG, and TNFα. These molecules can affect bone metabolism, thus resulting in osteoporosis. The purpose of this review was to deepen the cellular mechanisms by which obesity may facilitate osteoporosis and bone fractures.

Metabolic Bone Disease of Prematurity: Diagnosis and Management

Metabolic Bone Disease (MBD) of prematurity is a multifactorial disorder commonly observed in very low birth weight (VLBW, <1,500 g) newborns, with a greater incidence in those extremely low birth weight (ELBW, <1,000 g). MBD is characterized by biochemical and radiological findings related to bone demineralization. Several antenatal and postnatal risk factors have been associated to MBD of prematurity, although the main pathogenetic mechanism is represented by the reduced placental transfer of calcium and phosphate related to preterm birth. The diagnosis of MBD of prematurity requires the assessment of several biochemical markers, radiological, and ultrasonographic findings. However, the best approach is the prevention of the symptomatic disease, based on the screening of subjects exposed to the risks of developing MBD. Regarding the subjects who need to be screened, there is a substantial agreement on the potential risk factors for MBD. On the contrary, different recommendations exist on the diagnosis, management and treatment of this disorder of bone metabolism. This review was aimed at: (1) identifying the subjects at risk for MBD of prematurity; (2) indicating the biochemical findings to take in consideration for the prevention of MBD of prematurity; (3) suggesting practical recommendations on nutritional intake and supplementation in these subjects. We searched for papers which report the current recommendations for biochemical assessment of MBD of prematurity and for its prevention and treatment. The majority of the authors suggest that MBD of prematurity is a disease which tends to normalize overtime, thus it is not mandatory to mimic the rate of mineral fetal accretion through parenteral or enteral supplementation. The optimization of total parenteral nutrition (TPN) and the early achievement of a full enteral feeding are important goals for the prevention and management of MBD of prematurity.

Osteogenesis Imperfecta: Muscle-Bone Interactions when Bi-directionally Compromised

PURPOSE OF REVIEW

Osteogenesis imperfecta (OI) is a hereditary connective tissue disorder of skeletal fragility and more recently muscle weakness. This review highlights our current knowledge of the impact of compromised OI muscle function on muscle-bone interactions and skeletal strength in OI.

RECENT FINDINGS

The ramifications of inherent muscle weakness in OI muscle-bone interactions are just beginning to be elucidated. Studies in patients and in OI mouse models implicate altered mechanosensing, energy metabolism, mitochondrial dysfunction, and paracrine/endocrine crosstalk in the pathogenesis of OI. Compromised muscle-bone unit impacts mechanosensing and the ability of OI muscle and bone to respond to physiotherapeutic and pharmacologic treatment strategies. Muscle and bone are both compromised in OI, making it essential to understand the mechanisms responsible for both impaired muscle and bone functions and their interdependence, as this will expand and drive new physiotherapeutic and pharmacological approaches to treat OI and other musculoskeletal disorders.

Elevated platelet counts in a cohort of children with moderate-severe osteogenesis imperfecta suggest that inflammation is present

BACKGROUND

Elevated platelet counts are observed in cancer, autoimmunity and inflammation with concurrent illness. Proinflammatory cytokines are elevated in murine osteogenesis imperfecta (OI) models. We hypothesised that platelet counts might be elevated in children with moderate-severe OI.

METHODS

We reviewed the hospital records of 71 children with moderate-severe OI, treated in the Sheffield Children's Hospital's Severe, Complex and Atypical Osteogenesis Imperfecta Highly Specialised Service. Data relating platelet count (below/above average, above upper limit) to prior and concurrent events were summarised as event proportions per child. Additionally, we created platelet SD scores to assess age and time-related trends, and relationship with OI type.

RESULTS

1206 platelet counts were recorded. Platelet SD scores were right-shifted by 0.89 SD overall. 49 of 71 (69%) patients had at least one platelet count above the normal range and 246 (20.4%) of all counts were above the upper limit of normal. Of these, 101 (41%) were high despite no confounding factors being present. For the 47 children with data at age less than 2 years, 89 (30.0%) platelet counts were above the upper limit of normal and 39 (44%) had no associated confounding factor. Elevated platelet counts were recorded most often for children with new or existing vertebral fractures.

CONCLUSIONS

Raised platelet counts were observed in association with new and healing vertebral fractures, but also (41%-44%) in the absence of identified proinflammatory factors or events. We speculate that these findings are evidence for a proinflammatory component to OI that could be a target for therapeutic intervention.

Analysis of Circulating Mediators of Bone Remodeling in Prader-Willi Syndrome

We tested the hypothesis that the levels of bone remodeling mediators may be altered in Prader-Willi syndrome (PWS). We assessed RANKL, OPG, sclerostin, DKK-1 serum levels, and bone metabolism markers in 12 PWS children (7.8 ± 4.3 years), 14 PWS adults (29.5 ± 7.2 years), and 31 healthy controls matched for sex and age. Instrumental parameters of bone mineral density (BMD) were also evaluated. Lumbar spine BMD Z-scores were reduced in PWS children (P < 0.01), reaching osteopenic levels in PWS adults. PWS patients showed lower 25(OH)-vitamin D serum levels than controls (P < 0.001). Osteocalcin was increased in PWS children but reduced in adults respect to controls (P < 0.005 and P < 0.01, respectively). RANKL levels were higher in both pediatric and PWS adults than controls (P < 0.004), while OPG levels were significantly reduced (P < 0.004 and P < 0.006, respectively). Sclerostin levels were increased in children (P < 0.04) but reduced in adults compared to controls (P < 0.01). DKK-1 levels did not show significant difference between patients and controls. In PWS patients, RANKL, OPG, and sclerostin significantly correlated with metabolic and bone instrumental parameters. Consistently, with adjustment for age, multiple linear regression analysis showed that BMD and osteocalcin were the most important predictors for RANKL, OPG, and sclerostin in children, and GH and sex steroid replacement treatment in PWS adults. We demonstrated the involvement of RANKL, OPG, and sclerostin in the altered bone turnover of PWS subjects suggesting these molecules as markers of bone disease and new potential pharmacological targets to improve bone health in PWS.

The Assessment of Bone Regulatory Pathways, Bone Turnover, and Bone Mineral Density in Vegetarian and Omnivorous Children

Vegetarian diets contain many beneficial properties as well as carry a risk of inadequate intakes of several nutrients important to bone health. The aim of the study was to evaluate serum levels of bone metabolism markers and to analyze the relationships between biochemical bone markers and anthropometric parameters in children on vegetarian and omnivorous diets. The study included 70 prepubertal children on a lacto-ovo-vegetarian diet and 60 omnivorous children. Body composition, bone mineral content (BMC), and bone mineral density (BMD) were assessed by dual-energy X-ray absorptiometry. Biochemical markers—bone alkaline phosphatase (BALP), C-terminal telopeptide of type I collagen (CTX-I), osteoprotegerin (OPG), nuclear factor κB ligand (RANKL), sclerostin, and Dickkopf-related protein 1 (Dkk-1)—were measured using immunoenzymatic assays. In vegetarians, we observed a significantly higher level of BALP (p = 0.002) and CTX-I (p = 0.027), and slightly lower spine BMC (p = 0.067) and BMD (p = 0.060) than in omnivores. Concentrations of OPG, RANKL, sclerostin, and Dkk-1 were comparable in both groups of children. We found that CTX-I was positively correlated with BMC, total BMD, and lumbar spine BMD in vegetarians, but not in omnivores. A well-planned vegetarian diet with proper dairy and egg intake does not lead to significantly lower bone mass; however, children following a lacto-ovo-vegetarian diet had a higher rate of bone turnover and subtle changes in bone regulatory markers. CTX-I might be an important marker for the protection of vegetarians from bone abnormalities.

Mechanisms of Enhanced Osteoclastogenesis in Alkaptonuria

Alkaptonuria (AKU) is a rare disorder characterized by the deficiency of the enzyme homogentisate 1,2-dioxygenase and consequent homogentisate accumulation, which leads to progressive and severe osteoarthopathy starting from the second decade of life. Thus, in AKU patients, bone involvement represents an important clinical issue, which we investigated. Serum levels of receptor activator of NF-κB ligand (RANKL), osteoprotegerin, sclerostin, Dickkopf-1, and bone remodeling markers were measured in nine AKU patients (two children and seven adults) and 22 controls, together with lumbar spine bone mineral density (LS-BMD) and femoral-BMD. In the two AKU children, the average of LS-BMD and femoral-BMD Z-scores were within the normal range, but reduced with respect to the controls. Otherwise, in the adult AKU patients, LS-BMD T-score was inside the normal range, but femoral-BMD T-score reached osteopenic levels. Consistently, in AKU adults, higher RANKL and C-terminal telopeptide of collagen type 1 and lower osteoprotegerin levels were observed than in controls. Otherwise, spontaneous osteoclastogenesis was already evident in peripheral blood mononuclear cell cultures from AKU children, together with a high percentage of circulating osteoclast precursors. Osteoclastogenesis was sustained by the high levels of tumor necrosis factor-α, RANK, RANKL, and LIGHT. In conclusion, the altered osteoclastogenesis was observed already in AKU children, despite the absence of evident injury. Thus, a preventive approach in young patients, targeting osteoclast activity, may prevent the macroscopic bone disease that appears in adult AKU.

Dickkopf-1 may regulate bone coupling by attenuating wnt/β-catenin signaling in chronic apical periodontitis

OBJECTIVE

Alveolar bone loss is a common outcome of chronic apical periodontitis. In this study, we investigated the involvement of the Dickkopf-1-Wnt/β-catenin signaling pathway in the attenuation of osteogenic differentiation induced by Escherichia coli lipopolysaccharide, and we evaluated the use of Dickkopf-1 inhibitor and Dickkopf-1 recombinant protein to reverse bone loss in different phases of osteogenic differentiation.

METHODS

MC3T3-E1 cells grown in osteogenic medium were treated with Escherichia coli lipopolysaccharide for 24h during osteogenic induction on days 0, 1, 7, 14 and 21. Dickkopf-1 siRNA was added on days 0 and 1, and Dickkopf-1 recombinant was added on days 7, 14, and 21. Quantitative real-time PCR, Western blotting and alkaline phosphatase activity assays were performed to measure osteogenic marker expression and Wnt/β-catenin signaling. A rat apical periodontitis model was used to further evaluate the function of Dickkopf-1 in relation to bone loss.

RESULTS

MC3T3-E1 cells treated with Escherichia coli lipopolysaccharide showed decreased mRNA expression of osteogenic markers. Wnt/β-catenin signaling was also inhibited, and Dickkopf-1 showed corresponding variations as quantified by Western blotting. Using Dickkopf-1 inhibitor or Dickkopf-1 recombinant protein at different phases of osteogenic differentiation in vitro partially reversed the decrease in osteogenic marker expression. The rat apical periodontitis model indicated that the Dickkopf-1 inhibitor could restore bone loss in the periapical area in vivo.

CONCLUSIONS

Dickkopf-1 may play a key regulatory role in determining the outcome for bone in inflammatory environments, and modulating the Wnt/β-catenin signaling pathway via Dickkopf-1 inhibitor or recombinant protein may provide a potential therapeutic option to prevent bone destruction in endodontic disease.

Monoclonal antibodies for treating osteoporosis

INTRODUCTION

Osteoporosis is the most widespread skeletal disease requiring innovative therapeutic strategies for its management. The understanding of receptor activator of nuclear factor kappa-B ligand (RANKL) and sclerostin's role in bone cell biology is completely changing the therapeutic landscape. RANKL supports osteoclast formation and activity and is mainly produced by cells of osteoblastic lineage. Sclerostin, an antagonist of the Wnt pathway, has a key role in bone formation and is mainly secreted by osteocytes. High levels of RANKL and sclerostin have been detected in osteoporosis, leading to the production of antibodies able to neutralize their activity.

AREAS COVERED

In this review, the authors give an overview and discuss the literature and data on denosumab and romosozumab to treat osteoporosis. Clinical studies indicate that long-term treatment with denosumab causes a continuous increase in bone mineral density with low incidence of adverse effects. Romosozumab treatment gives increases bone formation and improves bone mineral density (BMD) though further studies are needed to better evaluate the adverse effects.

EXPERT OPINION

Denosumab and romosozumab show promise in the treatment of osteoporosis. Furthermore, their different mechanisms of action compared to existing anti-osteoporotic drugs may permit alternative strategies for osteoporosis treatment down the line

Efficacy of teriparatide vs neridronate in adults with osteogenesis imperfecta type I: a prospective randomized international clinical study

Osteogenesis imperfecta (OI) is an hereditary disease characterized by low bone mass, increased bone fragility, short stature, and skeletal deformities, few treatment options are currently available. Neridronate is an amino-bisphosphonate, licensed in Italy for the treatment of OI and Paget's disease of bone. A characteristic property of neridronate is that it can be administered both intravenously and intramuscularly, providing an useful system for administration in homecare. Neridronate appears to increase Bone Mineral Density (BMD) in adults with OI and reduces bone resorption by inhibition of osteoclastic activity. Teriparatide (recombinant 1-34 N terminal sequence of human parathyroid hormone) is the first anabolic agent approved for the treatment of patients with osteoporosis and has been reported to increase bone formation by stimulating osteoblast differentiation, osteoblast function, and survival. The results of this study showed a promising role of teriparatide in the therapy of OI type I.

Splenomegaly, myeloid lineage expansion and increased osteoclastogenesis in osteogenesis imperfecta murine

Osteogenesis imperfecta (OI) is a disease caused by defects in type I collagen production that results in brittle bones. While the pathology is mainly caused by defects in the osteoblast lineage, there is also elevated bone resorption by osteoclasts resulting in high bone turnover in severe forms of the disease. Osteoclasts originate from hematopoietic myeloid cells, however changes in hematopoiesis have not been previously documented in OI. In this study, we evaluated hematopoietic lineage distribution and osteoclast progenitor cell frequency in bone marrow, spleen and peripheral blood of osteogenesis imperfecta murine (OIM) mice, a model of severe OI. We found splenomegaly in all ages examined, and expansion of myeloid lineage cells (CD11b⁺) in bone marrow and spleen of 7-9week old male OIM animals. OIM spleens also showed an increased frequency of purified osteoclast progenitors. This phenotype is suggestive of chronic inflammation. Isolated osteoclast precursors from both spleen and bone marrow formed osteoclasts more rapidly than wild-type controls. We found that serum TNFα levels were increased in OIM, as was IL1α in OIM females. We targeted inflammation therapeutically by treating growing animals with murine TNFR2:Fc, a compound that blocks TNFα activity. Anti-TNFα treatment marginally decreased spleen mass in OIM females, but failed to reduce bone resorption, or improve bone parameters or fracture rate in OIM animals. We have demonstrated that OIM mice have changes in their hematopoietic system, and form osteoclasts more rapidly even in the absence of OI osteoblast signals, however therapy targeting TNFα did not improve disease parameters.

Circulating levels of dickkopf-1, osteoprotegerin and sclerostin are higher in old compared with young men and women and positively associated with whole-body bone mineral density in older adults

Bone mineral density declines with increasing older age. We examined the levels of circulating factors known to regulate bone metabolism in healthy young and older adults. The circulating levels of dickkopf-1, osteocalcin, osteoprotegerin and sclerostin were positively associated with whole-body bone mineral density (WBMD) in older adults, despite the average WBMD being lower and circulating dickkopf-1, osteoprotegerin and sclerostin being higher in old than young.

INTRODUCTION

This study aims to investigate the relationship between whole-body bone mineral density (WBMD) and levels of circulating factors with known roles in bone remodelling during 'healthy' ageing.

METHODS

WBMD and fasting plasma concentrations of dickkopf-1, fibroblast growth factor-23, osteocalcin, osteoprotegerin, osteopontin and sclerostin were measured in 272 older subjects (69 to 81 years; 52% female) and 171 younger subjects (18-30 years; 53% female).

RESULTS

WBMD was lower in old than young. Circulating osteocalcin was lower in old compared with young, while dickkopf-1, osteoprotegerin and sclerostin were higher in old compared with young. These circulating factors were each positively associated with WBMD in the older adults and the relationships remained after adjustment for covariates (r values ranging from 0.174 to 0.254, all p < 0.01). In multivariate regression, the body mass index, circulating sclerostin and whole-body lean mass together accounted for 13.8% of the variation with WBMD in the older adults. In young adults, dickkopf-1 and body mass index together accounted for 7.7% of variation in WBMD.

CONCLUSION

Circulating levels of dickkopf-1, osteocalcin, osteoprotegerin and sclerostin are positively associated with WBMD in community-dwelling older adults, despite the average WBMD being lower and circulating dickkopf-1, osteoprotegerin and sclerostin being higher in old than young.

Metabolic phenotype in the mouse model of osteogenesis imperfecta

Osteogenesis imperfecta (OI) is the most common heritable bone fragility disorder, usually caused by dominant mutations in genes coding for collagen type I alpha chains, COL1A1 or COL1A2 Osteocalcin (OCN) is now recognized as a bone-derived regulator of insulin secretion and sensitivity and glucose homeostasis. Since OI is associated with increased rates of bone formation and resorption, we hypothesized that the levels of undercarboxylated OCN are increased in OI. The objective of this study was to determine changes in OCN and to elucidate the metabolic phenotype in the Col1a1^Jrt/+ mouse, a model of dominant OI caused by a Col1a1 mutation. Circulating levels of undercarboxylated OCN were higher in 4-week-old OI mice and normal by 8 weeks of age. Young OI animals exhibited a sex-dependent metabolic phenotype, including increased insulin levels in males, improved glucose tolerance in females, lower levels of random glucose and low adiposity in both sexes. The rates of O₂ consumption and CO₂ production, as well as energy expenditure assessed using indirect calorimetry were significantly increased in OI animals of both sexes, whereas respiratory exchange ratio was significantly higher in OI males only. Although OI mice have significant physical impairment that may contribute to metabolic differences, we specifically accounted for movement and compared OI and WT animals during the periods of similar activity levels. Taken together, our data strongly suggest that OI animals have alterations in whole body energy metabolism that are consistent with the action of undercarboxylated osteocalcin.

Molecular diagnosis in children with fractures but no extraskeletal signs of osteogenesis imperfecta

In 26 of 94 individuals (28%) below 21 years of age who had a significant fracture history but did not have extraskeletal features of osteogenesis imperfecta (OI), we detected disease-causing mutations in OI-associated genes.

INTRODUCTION

In children who have mild bone fragility but do not have extraskeletal features of OI, it can be difficult to establish a diagnosis on clinical grounds. Here, we assessed the diagnostic yield of genetic testing in this context, by sequencing a panel of genes that are associated with OI.

METHODS

DNA sequence analysis was performed on 94 individuals below 21 years of age who had a significant fracture history but had white sclera and no signs of dentinogenesis imperfecta.

RESULTS

Disease-causing variants were detected in 28% of individuals and affected 5 different genes. Twelve individuals had mutations in COL1A1 or COL1A2, 8 in LRP5, 4 in BMP1, and 2 in PLS3.

CONCLUSIONS

DNA sequence analysis of currently known OI-associated genes identified disease-causing variants in more than a quarter of individuals with a significant fracture history but without extraskeletal manifestations of OI.

The Biological Effects of Dickkopf1 on Small Cell Lung Cancer Cells and Bone Metastasis

The bone is among the most common sites of metastasis in patients with lung cancer. Over 30%–40% of lung cancers can develop bone metastasis, and no effective therapeutic methods exist in clinic cases. Wnt/β-catenin signaling and Dickkopf1 (DKK1) play important roles in the progression of lung cancer, which preferentially metastasizes to the skeleton. However, the role of DKK1 in osteotropism of small cell lung cancer (SCLC) remains to be elucidated. This study aimed to define the role of DKK1 in SCLC bone metastasis and investigate the underlying mechanisms. Our results demonstrated that the expression level of DKK1 was dramatically higher in bone metastatic SCLC cells (SBC-5 cell line) compared with that in cells without bone metastatic ability (SBC-3 cell line). Therefore, we hypothesized that DKK1 was involved in the bone metastasis of SCLC. We then suppressed the DKK1 expression in SBC-5 cells by RNAi and found that downregulation of DKK1 can inhibit cell proliferation, colony formation, cell migration, and invasion, but increase the apoptosis rate. Downregulation of DKK1 did not affect the cell cycle progression of SBC-5 cells in vitro. In vivo, downregulated DKK1 in SBC-5 cells resulted in attenuated bone metastasis. These results indicated that DKK1 may be an important regulator in bone metastases of SCLC, and targeting DKK1 may be an effective method to prevent and treat skeleton metastases in SCLC cases.