WNT11, a new gene associated with early onset osteoporosis, is required for osteoblastogenesis.

Monogenic early onset osteoporosis (EOOP) is a rare disease defined by low bone mineral density (BMD) that results in increased risk of fracture in children and young adults. Although several causative genes have been identified, some of the EOOP causation remains unresolved. Whole-exome sequencing revealed a de novo heterozygous loss-of-function mutation in Wnt family member 11 (WNT11) (NM_004626.2:c.677_678dup p.Leu227Glyfs*22) in a 4-year-old boy with low BMD and fractures. We identified two heterozygous WNT11 missense variants (NM_004626.2:c.217G > A p.Ala73Thr) and (NM_004626.2:c.865G > A p.Val289Met) in a 51-year-old woman and in a 61-year-old woman, respectively, both with bone fragility. U2OS cells with heterozygous WNT11 mutation (NM_004626.2:c.690_721delfs*40) generated by CRISPR-Cas9 showed reduced cell proliferation (30%) and osteoblast differentiation (80%) as compared with wild-type U2OS cells. The expression of genes in the Wnt canonical and non-canonical pathways was inhibited in these mutant cells, but recombinant WNT11 treatment rescued the expression of Wnt pathway target genes. Furthermore, the expression of RSPO2, a WNT11 target involved in bone cell differentiation, and its receptor leucine-rich repeat containing G protein-coupled receptor 5 (LGR5), was decreased in WNT11 mutant cells. Treatment with WNT5A and WNT11 recombinant proteins reversed LGR5 expression, but Wnt family member 3A (WNT3A) recombinant protein treatment had no effect on LGR5 expression in mutant cells. Moreover, treatment with recombinant RSPO2 but not WNT11 or WNT3A activated the canonical pathway in mutant cells. In conclusion, we have identified WNT11 as a new gene responsible for EOOP, with loss-of-function variant inhibiting bone formation via Wnt canonical and non-canonical pathways. WNT11 may activate Wnt signaling by inducing the RSPO2-LGR5 complex via the non-canonical Wnt pathway.

Osteoporosis and Fragility Fractures in Patients With Cirrhosis Evaluated for Liver Transplantation: Identification of High-Risk Patients Based on Computed Tomography at Evaluation.

INTRODUCTION: Osteoporosis in candidates for liver transplantation (LT) is often underdiagnosed despite the important consequences of morbidity. METHODS: We included 376 patients with cirrhosis evaluated for LT with available computed tomography (CT) scans. Prevalent vertebral fractures (VFs) were identified on CT reconstructions, and bone density was assessed by measuring CT attenuation of the L1 vertebra (L1-CT). RESULTS: We identified 139 VFs in 55 patients (14.6%). Logistic regression models showed that low L1-CT was the only independent determinant of VF. DISCUSSION: In patients with cirrhosis evaluated for LT, CT scans identified persons with severe osteoporosis without additional costs.

SerpinA3N limits cartilage destruction in osteoarthritis by inhibiting macrophage-derived leucocyte elastase.

OBJECTIVES: Inflammatory mediators such as interleukin 6 (IL-6) are known to activate catabolic responses in chondrocytes during osteoarthritis (OA). This study aimed to investigate the role of a downstream target gene of IL-6, the serine protease inhibitor SerpinA3N, in the development of cartilage damage in OA. METHODS: RNA sequencing was performed in murine primary chondrocytes treated with IL-6, and identified target genes were confirmed in human and murine OA cartilage samples. Male cartilage-specific Serpina3n-deficient mice and control mice underwent meniscectomy (MNX) or sham surgery at 10 weeks of age. Intra-articular injections of SerpinA3N or sivelestat (an inhibitor of leucocyte elastase (LE), a substrate for SerpinA3N) were performed in wild-type mice after MNX. Joint damage was assessed 3-9 weeks after surgery by histology and micro-CT. The effect of sivelestat was assessed in cartilage explants exposed to macrophage-derived conditioned media. RESULTS: RNA sequencing revealed that SerpinA3N is a major target gene of IL-6 in chondrocytes. The expression of SerpinA3N is increased in OA cartilage. Conditional loss of SerpinA3N in chondrocytes aggravated OA in mice, while intra-articular injection of SerpinA3N limited joint damage. Chondrocytes did not produce serine proteases targeted by SerpinA3N. By contrast, macrophages produced LE on IL-6 stimulation. Sivelestat limited the cartilage catabolism induced by conditioned media derived from IL-6-stimulated macrophages. Additionally, an intra-articular injection of sivelestat is protected against OA in the MNX model. CONCLUSIONS: SerpinA3N protects cartilage against catabolic factors produced by macrophages, including LE. SerpinA3N and LE represent new therapeutic targets to dampen cartilage damage in OA.

Early-Onset Osteoporosis: Molecular Analysis in Large Cohort and Focus on the PLS3 Gene.

Osteoporosis is a skeletal disorder characterized by abnormal bone microarchitecture and low bone mineral density (BMD), responsible for an increased risk of fractures and skeletal fragility. It is a common pathology of the aging population. However, when osteoporosis occurs in children or young adults, it strongly suggests an underlying genetic etiology. Over the past two decades, several genes have been identified as responsible for this particular kind of considered monogenic early-onset osteoporosis (EOOP) or juvenile osteoporosis, the main ones being COL1A1, COL1A2, LRP5, LRP6, WNT1, and more recently PLS3. In this study, the objective was to characterize a large cohort of patients diagnosed with primary osteoporosis and to establish its diagnosis yield. The study included 577 patients diagnosed with primary osteoporosis and its diagnosis yield was established. To this end, next-generation sequencing (NGS) of a panel of 21 genes known to play a role in bone fragility was carried out. A genetic etiology was explained in about 18% of cases, while the others remain unexplained. The most frequently identified gene associated with EOOP is LRP5, which was responsible for 8.2% of the positive results (47 patients). As unexpected, 17 patients (2.9%) had a variant in PLS3 which encodes plastin 3. Alterations of PLS3 are associated with dominant X-linked osteoporosis, an extremely rare disease. Given the rarity of this disease, we focused on it. It was observed that males were more affected than females, but it is noteworthy that three females with a particularly severe phenotype were identified. Of these three, two had a variant in an additional gene involved in EOP, illustrating the probable existence of digenism. We significantly increase the number of variants potentially associated with EOOP, especially in PLS3. The results of our study demonstrate that molecular analysis in EOOP is beneficial and useful.

Serum phosphate is associated with increased risk of bone fragility fractures in hemodialysis patients.

BACKGROUND: Bone fragility fractures are associated with high morbidity and mortality. This study analysed the association between the current biochemical parameters of CKD-MBD and bone fragility fractures in the COSMOS project. METHODS: COSMOS is a 3-year, multicentre, open cohort, prospective, observational study carried out in 6797 hemodialysis patients (227 centres from 20 European countries). The association of bone fragility fractures (outcome) with serum calcium, phosphate and PTH (exposure), was assessed using Standard Cox proportional hazards regression and Cox proportional hazards regression for recurrent events. Additional analyses were performed considering all-cause mortality as a competitive event for bone fragility fracture occurrence. Multivariable models were used in all strategies, with the fully adjusted model including a total of 24 variables. RESULTS: During a median follow-up of 24 months 252 (4%) patients experienced at least one bone fragility fracture (incident bone fragility fracture rate 28.5 per 1000 patient-years). In the fractured and non-fractured patients, the percentage of men was 43.7% and 61.4%, mean age 68.1 and 63.8 years and a haemodialysis vintage of 55.9 and 38.3 months respectively. Baseline serum phosphate > 6.1 mg/dL (reference value 4.3-6.1 mg/dL) was significantly associated with a higher bone fragility fracture risk in both regression models (HR: 1.53[95%CI: 1.10-2.13] and HR: 1.44[95%CI: 1.02-2.05]. The significant association persisted after competitive risk analysis (subHR: 1.42[95%CI: 1.02-1.98]) but the finding was not confirmed when serum phosphate was considered as a continuous variable. Baseline serum calcium showed no association with bone fragility fracture risk in any regression model. Baseline serum PTH > 800 pg/mL was significantly associated with a higher bone fragility fracture risk in both regression models, but the association disappeared after a competitive risk analysis. CONCLUSIONS: Hyperphosphatemia was independently and consistently associated with an increased bone fracture risk, suggesting serum phosphate could be a novel risk factor for bone fractures in hemodialysis patients.

Efficacy of Burosumab in Adults with X-linked Hypophosphatemia (XLH): A Post Hoc Subgroup Analysis of a Randomized Double-Blind Placebo-Controlled Phase 3 Study.

The anti-fibroblast growth factor 23 monoclonal antibody burosumab corrects hypophosphatemia in adults with X-linked hypophosphatemia (XLH) and improves pain, stiffness, physical function, and fatigue. This post hoc subgroup analysis used data from the 24-week placebo-controlled period of a phase 3 study in 134 adults with XLH (ClinicalTrials.gov NCT02526160), to assess whether the benefits of burosumab are evident in 14 clinically relevant subgroups defined by baseline demographic and functional criteria, including sex, Brief Pain Inventory-short form (BPI-SF) Average And Worst Pain, region, race, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC®) Stiffness, Physical Function and Pain domains and total score, use of opioid/other pain medication, active fractures/pseudo-fractures, and 6-min walk test distance. There were no statistically significant interactions between any of the subgroups and treatment arm for any endpoint. Higher proportions of subjects achieved mean serum phosphate concentration above the lower limit of normal (the primary endpoint) with burosumab than with placebo in all subgroups. For the key secondary endpoints (WOMAC Stiffness and Physical Function; BPI-SF Worst Pain) individual subgroup categories showed improvements with burosumab relative to placebo. For additional efficacy endpoints, burosumab was favored in some subgroups but differences were not significant and confidence intervals were wide. For some endpoints the treatment effect is small at 24 weeks in all subjects. This subgroup analysis shows that burosumab was largely superior to placebo across endpoints in the 14 clinically relevant subgroup variables at 24 weeks and is likely to benefit all symptomatic adults with active XLH.

Mechanical loading activates the YAP/TAZ pathway and chemokine expression in the MLO-Y4 osteocyte-like cell line.

Osteocytes are mechanosensitive cells that control bone remodeling in response to mechanical loading. To date, specific signaling pathways modulated by mechanical loading in osteocytes are not well understood. Yes associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ), the main effectors of the Hippo pathway, are reported to play a role in mechanotransduction and during osteoblastogenesis. Here, we hypothesized that YAP/TAZ signaling mediates osteocyte mechanosensing to target genes of the bone remodeling process. We aimed to investigate the contribution of YAP/TAZ in modulating the gene expression in an osteocyte-like cell line MLO-Y4. We developed a 3D osteocyte compression culture model from an MLO-Y4 osteocyte cell line embedded in concentrated collagen hydrogel. 3D-mechanical loading led to the increased expression of mechanosensitive genes and a subset of chemokines, including M-csf, Cxcl1, Cxcl2, Cxcl3, Cxcl9, and Cxcl10. The transcription regulators YAP and TAZ translocated to the nucleus and upregulated their target genes and proteins. RNAseq analysis revealed that YAP/TAZ knockdown mediated the regulation of several genes including osteocyte dendrite formation. Use of YAP/TAZ knockdown partially blunted the increase in M-csf and Cxcl3 levels in response to MLO-Y4 compression. These findings demonstrate that YAP/TAZ signaling is required for osteocyte-like cell mechano-transduction, regulates the gene expression profiles and controls chemokine expression.

The Role of Bone Biopsy in the Management of CKD-MBD.

A bone biopsy is still considered the gold standard for diagnosis of renal osteodystrophy. It allows to measure both static and dynamic parameters of bone remodeling and is the only method able to evaluate mineralization and allows analysis of both cortical and trabecular bone. Although bone volume can be measured indirectly by dual-energy X-ray absorptiometry, mineralization defects, bone metal deposits, cellular number/activity, and even turnover abnormalities are difficult to determine by techniques other than qualitative bone histomorphometry. In this review, we evaluate the role of bone biopsy in the clinical practice.

Bone Fragility Fractures in CKD Patients.

Chronic kidney diseases (CKD) are associated with mineral and bone diseases (MBD), including pain, bone loss, and fractures. Bone fragility related to CKD includes the risk factors observed in osteoporosis in addition to those related to CKD, resulting in a higher risk of mortality related to fractures. Unawareness of such complications led to a poor management of fractures and a lack of preventive approaches. The current guidelines of the Kidney Disease Improving Global Outcomes (KDIGO) recommend the assessment of bone mineral density if results will impact treatment decision. In addition to bone density, circulating biomarkers of mineral, serum bone turnover markers, and imaging techniques are currently available to evaluate the fracture risk. The purpose of this review is to provide an overview of the epidemiology and pathogenesis of CKD-associated bone loss. The contribution of the current tools and other techniques in development are discussed. We here propose a current view of how to better predict bone fragility and the therapeutic options in CKD.

Gout and pseudo-gout-related crystals promote GLUT1-mediated glycolysis that governs NLRP3 and interleukin-1ß activation on macrophages.

OBJECTIVE: Macrophage activation by monosodium urate (MSU) and calcium pyrophosphate (CPP) crystals mediates an interleukin (IL)-1ß-dependent inflammation during gout and pseudo-gout flare, respectively. Since metabolic reprogramming of macrophages goes along with inflammatory responses dependently on stimuli and tissue environment, we aimed to decipher the role of glycolysis and oxidative phosphorylation in the IL-1ß-induced microcrystal response. METHODS: Briefly, an in vitro study (metabolomics and real-time extracellular flux analysis) on MSU and CPP crystal-stimulated macrophages was performed to demonstrate the metabolic phenotype of macrophages. Then, the role of aerobic glycolysis in IL-1ß production was evaluated, as well in vitro as in vivo using 18F-fluorodeoxyglucose positron emission tomography imaging and glucose uptake assay, and molecular approach of glucose transporter 1 (GLUT1) inhibition. RESULTS: We observed that MSU and CPP crystals led to a metabolic rewiring toward the aerobic glycolysis pathway explained by an increase in GLUT1 plasma membrane expression and glucose uptake on macrophages. Also, neutrophils isolated from human synovial fluid during gout flare expressed GLUT1 at their plasma membrane more frequently than neutrophils isolated from bloodstream. Both glucose deprivation and treatment with either 2-deoxyglucose or GLUT1 inhibitor suppressed crystal-induced NLRP3 activation and IL-1ß production, and microcrystal inflammation in vivo. CONCLUSION: In conclusion, we demonstrated that GLUT1-mediated glucose uptake is instrumental during the inflammatory IL-1ß response induced by MSU and CPP crystals. These findings open new therapeutic paths to modulate crystal-related inflammation.

Cortical Bone Microarchitecture in Dialysis Patients.

BACKGROUND: The incidence of skeletal fractures is high in dialysis patients. Current available tools are insufficient to predict bone fragility. We analyzed the microarchitecture in patients on dialysis therapy using bone biopsies and peripheral microcomputed tomography. METHODS: We analyzed 12 trans-iliac bone biopsies of patients with recent fractures. Bone microarchitecture was assessed in the bone cores by histology (2D-), microcomputed tomography (3D-µCT), and high-resolution peripheral quantitative computed tomography (HR-pQCT) at the tibia. RESULTS: Trabecular bone volume/tissue volume was similar in 2D histology and 3D-µCT (p = 0.40), while lower in HR-pQCT (p < 0.01). There was no correlation in trabecular microarchitectural indices between 2-histology and 3D-µCT, or HR-pQCT. The 3D-µCT cortical thickness (Ct.Th) were positively correlated with 2D (p < 0.05), but with HR-pQCT (p = 0.33). Ct.Th was lower in patients with ≥2 vertebral fractures than with one fracture. CONCLUSIONS: 3D-µCT is a reliable method for the measurement of cortical bone in bone biopsies. Prospective studies are awaited to address its value in discriminating fracture risk.

Cherubism as a systemic skeletal disease: evidence from an aggressive case.

BACKGROUND: Cherubism is a rare autosomal dominant genetic condition caused by mutations in the SH3BP2 gene. This disease is characterized by osteolysis of the jaws, with the bone replaced by soft tissue rich in fibroblasts and multinuclear giant cells. SH3BP2 is a ubiquitous adaptor protein yet the consequences of SH3BP2 mutation have so far been described as impacting only face. Cherubism mouse models have been generated and unlike human patients, the knock-in mice exhibit systemic bone loss together with a systemic inflammation. CASE PRESENTATION: In light of these observations, we decided to search for a systemic cherubism phenotype in a 6-year-old girl with an aggressive cherubism. We report here the first case of cherubism with systemic manifestations. Bone densitometry showed low overall bone density (total body Z-score = - 4.6 SD). Several markers of bone remodelling (CTx, BALP, P1NP) as well as inflammation (TNFα and IL-1) were elevated. A causative second-site mutation in other genes known to influence bone density was ruled out by sequencing a panel of such genes. CONCLUSIONS: If this systemic skeletal cherubism phenotype should be confirmed, it would simplify the treatment of severe cherubism patients and allay reservations about applying a systemic treatment such as those recently published (tacrolimus or imatinib) to a disease heretofore believed to be localised to the jaws.

Disruption of Bone Zinc Metabolism during Postnatal Development of Rats after Early Life Exposure to Cadmium.

This current study was conducted to investigate whether bone tissue impairment induced by early life exposure to cadmium (Cd) during postnatal development could result from disruption to zinc (Zn) metabolism. For this reason, the offspring from mothers receiving either tap water, Cd, Zn or Cd + Zn during gestation and lactation periods were euthanized at PND21 and PND70. At the end of the lactation period (PND21), our results showed that exposure to Cd increased Cd accumulation and Zn depletion in the femur. Furthermore, calcium (Ca) level was reduced. At the molecular level, Cd induced an increase of MT-1 expression and caused an upregulation of ZIP2 accompanied with a down-regulation of ZnT5. Runx2, ALP, colα-1 and Oc mRNA levels were also decreased. In plasma, IGF-1 and osteocalcin concentrations were decreased. Further, Cd altered femoral growth by generating changes in the growth plate. Consequently, the toxic effect of Cd persisted at adult age (PND70) by decreasing bone volume (%BV/TV), bone mineral density (BMD) and Ca content and by increasing trabecular separation (Tb.Sp) in the distal femur. Interestingly, Zn supply provided total or partial corrections of several toxic effects of Cd. These data suggest that the increases of Zn bioavailability as well as the reduction of Cd accumulation in the femur following the changes in ZIP2 and ZnT5 expression are part of the mechanism involved in Zn protection against Cd toxicity on bone tissue.

Galectin 3 Deficiency Alters Chondrocyte Primary Cilium Formation and Exacerbates Cartilage Destruction via Mitochondrial Apoptosis.

Mechanical overload and aging are the main risk factors of osteoarthritis (OA). Galectin 3 (GAL3) is important in the formation of primary cilia, organelles that are able to sense mechanical stress. The objectives were to evaluate the role of GAL3 in chondrocyte primary cilium formation and in OA in mice. Chondrocyte primary cilium was detected in vitro by confocal microscopy. OA was induced by aging and partial meniscectomy of wild-type (WT) and Gal3-null 129SvEV mice (Gal3-/-). Primary chondrocytes were isolated from joints of new-born mice. Chondrocyte apoptosis was assessed by Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), caspase 3 activity and cytochrome c release. Gene expression was assessed by qRT-PCR. GAL3 was localized at the basal body of the chondrocyte primary cilium. Primary cilia of Gal3-/- chondrocytes were frequently abnormal and misshapen. Deletion of Gal3 triggered premature OA during aging and exacerbated joint instability-induced OA. In both aging and surgery-induced OA cartilage, levels of chondrocyte catabolism and hypertrophy markers and apoptosis were more severe in Gal3-/- than WT samples. In vitro, Gal3 knockout favored chondrocyte apoptosis via the mitochondrial pathway. GAL3 is a key regulator of cartilage homeostasis and chondrocyte primary cilium formation in mice. Gal3 deletion promotes OA development.

Pycnodysostosis: Natural history and management guidelines from 27 French cases and a literature review.

Pycnodysostosis is a lysosomal autosomal recessive skeletal dysplasia characterized by osteosclerosis, short stature, acro-osteolysis, facial features and an increased risk of fractures. The clinical heterogeneity of the disease and its rarity make it difficult to provide patients an accurate prognosis, as well as appropriate care and follow-up. French physicians from the OSCAR network have been asked to fill out questionnaires collecting molecular and clinical data for 27 patients issued from 17 unrelated families. All patients showed short stature (mean = -3.5 SD) which was more severe in females (P = .006). The mean fracture rate was moderate (0.21 per year), with four fractures in total average. About 75% underwent at least one surgery, with an average number of 2.1 interventions per patient. About 50% required non-invasive assisted ventilation due to sleep apnea (67%). About 29% showed psychomotor difficulties and 33% needed a school assistant or adapted schooling. No patient had any psychological evaluation or follow-up. Molecular data were available for 14 families. Growth hormone administration was efficient on linear growth in 40% of cases. We propose several axis of management, such as systematic cerebral MRI for Chiari malformation screening at diagnosis and regular psychological follow-up.

Continued Beneficial Effects of Burosumab in Adults with X-Linked Hypophosphatemia: Results from a 24-Week Treatment Continuation Period After a 24-Week Double-Blind Placebo-Controlled Period.

Burosumab, a fully human monoclonal antibody to FGF23, is the only approved treatment for X-linked hypophosphatemia (XLH), a rare genetic disorder characterized by renal phosphate wasting and substantial cumulative musculoskeletal morbidity. During an initial 24-week randomized, controlled trial, 134 adults with XLH received burosumab 1 mg/kg (n = 68) or placebo (n = 66) every 4 weeks. After 24 weeks, all subjects received open-label burosumab until week 48. This report describes the efficacy and safety of burosumab during the open-label treatment period. From weeks 24-48, serum phosphorus concentrations remained normal in 83.8% of participants who received burosumab throughout and were normalized in 89.4% who received burosumab after placebo. By week 48, 63.1% of baseline fractures/pseudofractures healed fully with burosumab, compared with 35.2% with burosumab after placebo. In both groups, burosumab was associated with clinically significant and sustained improvement from baseline to week 48 in scores for patient-reported outcomes of stiffness, pain, physical function, and total distance walked in 6 min. Rates of adverse events were similar for burosumab and placebo. There were no fatal adverse events or treatment-related serious adverse events. Nephrocalcinosis scores did not change from baseline by more than one grade at either week 24 or 48. These data demonstrate that in participants with XLH, continued treatment with burosumab is well tolerated and leads to sustained correction of serum phosphorus levels, continued healing of fractures and pseudofractures, and sustained improvement in key musculoskeletal impairments.

Interaction of HIF1α and ß-catenin inhibits matrix metalloproteinase 13 expression and prevents cartilage damage in mice.

Low oxygen tension (hypoxia) regulates chondrocyte differentiation and metabolism. Hypoxia-inducible factor 1α (HIF1α) is a crucial hypoxic factor for chondrocyte growth and survival during development. The major metalloproteinase matrix metalloproteinase 13 (MMP13) is also associated with chondrocyte hypertrophy in adult articular cartilage, the lack of which protects from cartilage degradation and osteoarthritis (OA) in mice. MMP13 is up-regulated by the Wnt/ß-catenin signaling, a pathway involved in chondrocyte catabolism and OA. We studied the role of HIF1α in regulating Wnt signaling in cartilage and OA. We used mice with conditional knockout of Hif1α (∆Hif1α(chon)) with joint instability. Specific loss of HIF1α exacerbated MMP13 expression and cartilage destruction. Analysis of Wnt signaling in hypoxic chondrocytes showed that HIF1α lowered transcription factor 4 (TCF4)-ß-catenin transcriptional activity and inhibited MMP13 expression. Indeed, HIF1α interacting with ß-catenin displaced TCF4 from MMP13 regulatory sequences. Finally, ΔHif1α(chon) mice with OA that were injected intraarticularly with PKF118-310, an inhibitor of TCF4-ß-catenin interaction, showed less cartilage degradation and reduced MMP13 expression in cartilage. Therefore, HIF1α-ß-catenin interaction is a negative regulator of Wnt signaling and MMP13 transcription, thus reducing catabolism in OA. Our study contributes to the understanding of the role of HIF1α in OA and highlights the HIF1α-ß-catenin interaction, thus providing new insights into the impact of hypoxia in articular cartilage.

Maternal embryonic leucine zipper kinase inhibitor OTSSP167 has preclinical activity in multiple myeloma bone disease.

Multiple myeloma bone disease is characterized by an uncoupling of bone remodeling in the multiple myeloma microenvironment, resulting in the development of lytic bone lesions. Most myeloma patients suffer from these bone lesions, which not only cause morbidity but also negatively impact survival. The development of novel therapies, ideally with a combined anti-resorptive and bone-anabolic effect, is of great interest because lesions persist with the current standard of care, even in patients in complete remission. We have previously shown that MELK plays a central role in proliferation-associated high-risk multiple myeloma and its inhibition with OTSSP167 resulted in decreased tumor load. MELK inhibition in bone cells has not yet been explored, although some reports suggest that factors downstream of MELK stimulate osteoclast activity and inhibit osteoblast activity, which makes MELK inhibition a promising therapeutic approach. Therefore, we assessed the effect of OTSSP167 on bone cell activity and the development of myeloma-induced bone disease. OTSSP167 inhibited osteoclast activity in vitro by decreasing progenitor viability as well as via a direct anti-resorptive effect on mature osteoclasts. In addition, OTSSP167 stimulated matrix deposition and mineralization by osteoblasts in vitro This combined anti-resorptive and osteoblast-stimulating effect of OTSSP167 resulted in the complete prevention of lytic lesions and bone loss in myeloma-bearing mice. Immunohistomorphometric analyses corroborated our in vitro findings. In conclusion, we show that OTSSP167 has a direct effect on myeloma-induced bone disease in addition to its anti-multiple myeloma effect, which warrants further clinical development of MELK inhibition in multiple myeloma.

What are the predictors of clinical success after percutaneous vertebroplasty for osteoporotic vertebral fractures?

OBJECTIVES: Osteoporotic vertebral fractures are responsible for acute pain and disability that may persist for more than 2 months. We wanted to identify predicting factors for mid-term outcome after vertebroplasty. METHODS: We included consecutive patients who underwent vertebroplasty for fragility fractures with persistent and intense pain between January 2014-June 2016. Outcome was assessed by an independent clinician after 1 month using a standardized questionnaire. Patients were classified as having either a favorable or a poor outcome. Presence of an intravertebral cleft and bone oedema mean signal intensity was assessed by an independent radiologist blinded to the clinical data. Pre-intervention clinical or radiological factors were analysed as predictors for outcome. RESULTS: In the 78 included patients (females 71%, age 75 ± 8.3 years), 61.5% had a favourable outcome. When vertebroplasty was performed within 2 months after fracture, the outcome was favourable in 19 patients (39.6%) and poor in five (16.7%; estimate for favourable outcome: OR = 4.1, 95% CI 1.2-13.8, p = 0.021). Absence of intravertebral cleft on pre-intervention imaging was also a predictor of favourable outcome (OR = 3.7, 95% CI 1.2-11.8, p = 0.024). On pre-intervention MRI, vertebral body oedema intensity signal did not influence the outcome. CONCLUSIONS: In patients with persistent and intense pain after an osteoporotic vertebral fracture, early intervention and absence of intravertebral cleft were predictors of favourable outcome at 1 month after vertebroplasty. KEY POINTS: • Performing vertebroplasty within 2 months following a fragility fracture increases success rate. • Presence of an intravertebral cleft at baseline is a predictor of poor mid-term outcome. • A pre-intervention MRI should be performed to ascertain the indication of vertebroplasty.

Teenagers and young adults with nephropathic cystinosis display significant bone disease and cortical impairment.

BACKGROUND: Bone impairment appears to be a novel complication of nephropathic cystinosis despite cysteamine therapy. Its exact underlying pathophysiology is nevertheless unclear. The objective of this study was to evaluate bone status among patients included in the French Crystobs study. METHODS: In addition to clinical data, bone status was evaluated using biomarkers (ALP, PTH, 25-D, 1-25D, FGF23), DXA (spine and total body), and high-resolution peripheral quantitative computed tomography (HR-pQCT) at the tibia and radius. Results were compared to age- and gender-matched healthy controls (1:2 basis) from the local reference cohorts. RESULTS: At a median age of 22.5 (10.2-34.6) years, 10 patients with nephropathic cystinosis were included (2 receiving conservative therapies, 2 undergoing hemodialysis, 6 with a past of renal transplantation); 7 out of 10 patients complained of a bone symptom (past of fracture, bone deformations, and/or bone pain). Biochemicals and spine DXA did not show any significant abnormalities. Using HR-pQCT, significant decreases in cortical parameters (e.g., cortical thickness 850 (520-1100) versus 1225 (480-1680) µm; p < 0.05) and total volumetric bone mineral density (290 (233-360) versus 323 (232-406) mg/cm3; p < 0.05) were observed in cystinotic patients in comparison to controls at the tibia. There were no differences for trabecular parameters. Similar results were observed at the radius. CONCLUSIONS: In this pilot study, bone impairment (rather cortical than trabecular) is a significant clinical problem in nephropathic cystinosis; 70% of patients displayed significant bone symptoms, during teenage or young adulthood. This new complication should be known by physicians because of its potential dramatic impact on quality of life.