Healthy bone metabolism is a tightly coupled dynamic process that relies on a balance between bone resorption (catabolism) by osteoclasts and bone formation (anabolism) by osteoblasts. Traditionally, tissue-engineering approaches for non-union fracture repair employ local anabolic therapeutic delivery strategies that target mesenchymal stem cells (MSCs) and osteoblasts to induce bone formation, however, the challenge of healing non-union defects depends on the cause of defect e.g. trauma or disease, and targeting bone formation alone is often not sufficient. Our research focuses on utilising both anabolic therapeutics, including recombinant human bone morphogenic protein (rhBMP) −2 and parathyroid hormone (PTH). (1–34). , and anti-catabolic bisphosphonates (BPs) to target bone metabolism. A major challenge with harnessing a combined dosing regimen is controlling the release of the individual therapeutics to target cells. We have developed a number of polymer-ceramic based biomaterial delivery systems, including injectable and implantable scaffolds, for the controlled release of rhBMP-2 and the BP zoledronic acid (ZA) and demonstrated their efficacy in vivo. A dual therapeutic load provided a synergistic enhancement of bone regeneration, demonstrating significantly increased bone formation and remodelling compared to anabolic therapies alone. Utilising hydroxyapatite as the ceramic phase in our scaffolds further increased bone formation, demonstrating the polymer-ceramic scaffolds to be osteoconductive in the absence of therapeutics. In addition, we have demonstrated the manipulation of bone metabolism through a specific dosing regimen of PTH. (1–34). , a therapeutic traditionally used as an anabolic, to induce bone remodelling and drive healing in BP loaded fractures. Our research to date has shown that optimising the delivery and regimen of anabolic and anti-catabolic therapeutics to control bone metabolism, augments the bone regenerative potential of these therapeutics in orthopaedic applications

Introduction: Since Albright first proposed the concept of diabetic osteopenia, many studies have investigated the levels of mineral bone density (BMD) and risk of osteoporosis. In this study we investigate the effect of exercise, alfacalcidol and parathyroid hormone (1–34) on bone marker, BMD and bone mechanical properties in spontaneously diabetic GK/Jcl rats. Methods: 18 week-old male GK/Jcl rats were divided into 4 groups; no treatment (NT), exercise (Ex), alfacalcidol (ALF), and parathyroid hormone (PTH). The bone mineral density (BMD) of the lumbar vertebrae (L2-L4) and the left femur was measured by dual energy X-ray absorptiometry (DXA). Serum calcium (Ca), inorganic phosphorus (Pi) and osteocalcin (OC) were measured. Urinary Ca, Po, and creatinine (Cre) were measured. Urinary deoxypyridinoline (D-Pyr) was measured and the data were corrected for urinary Cre concentration. Mechanical strength of L5 was measured by the compression test. The mechanical strength of the right femur was measured by the three-point bending test. Results: The serum Oc levels in Ex and ALF group slightly increased (mean 5%). The serum Oc in PTH group increased significantly compared with that in the NT group (mean 70%). The urinary D-Pyr/Cre in the Ex group decreased compared with that in the NT group (mean 9 %). The urinary D-Pyr/Cre in the groups treated with ALF for 3 months were significantly decreased compared with that in the NT group (mean 20%). The urinary D-Pyr/Cre in the PTH group significantly increased compared with that in the NT group (mean 10%). The BMD of the L2–L4 in ALF group increased compared with NT group (mean 12%). The BMD of the L2–L4 in PTH group significantly increased compared with NT group (mean 10%). In the ALF group, however, the mechanical strength of the lumber vertebra was significantly higher (mean 25%) than that in the NT group. In the PTH group, the compressive load of the lumber vertebra (mean 70%) and breaking strength of the femur (mean 9%) was significantly higher than that in the NT group. Discussion: Treatment of osteoporosis has so far mainly utilized anti-resorptive agents such as estrogen, calcitonin and bisphosphonate, and bone anabolic agents stimulating bone resorption would be useful especially in low-turnover type of osteoporosis such as diabetic osteopenia. ALF treatment suppressed osteoclastic bone resorption while maintaining or even stimulating bone formation, and consequently increased bone mass with a parallel improvement in the mechanical strength of bone. PTH (1–34) had strong effects for improve the mechanical strength of the spine. In conclusion, it was demonstrated that ALF and PTH differed in their potency for improving the strength of the spine. Our results of biochemical parameter analysis demonstrated that ALF caused a significant suppression of bone resorption and maintained formation. The other hand, PTH had a strong effect on stimulating the bone turnover and bone strength, whereas it could affect the bone quality and reduce the risk of the spine fracture. These results provide important clues in understanding the action mechanisms of these agents on bone metabolism in the treatment of diabetic osteopenia

Aims. This study intended to investigate the effect of vericiguat (VIT) on titanium rod osseointegration in aged rats with iron overload, and also explore the role of VIT in osteoblast and osteoclast differentiation. Methods. In this study, 60 rats were included in a titanium rod implantation model and underwent subsequent guanylate cyclase treatment. Imaging, histology, and biomechanics were used to evaluate the osseointegration of rats in each group. First, the impact of VIT on bone integration in aged rats with iron overload was investigated. Subsequently, VIT was employed to modulate the differentiation of MC3T3-E1 cells and RAW264.7 cells under conditions of iron overload. Results. Utilizing an OVX rat model, we observed significant alterations in bone mass and osseointegration due to VIT administration in aged rats with iron overload. The observed effects were concomitant with reductions in bone metabolism, oxidative stress, and inflammation. To elucidate whether these effects are associated with osteoclast and osteoblast activity, we conducted in vitro experiments using MC3T3-E1 cells and RAW264.7 cells. Our findings indicate that iron accumulation suppressed the activity of MC3T3-E1 while enhancing RAW264.7 function. Furthermore, iron overload significantly decreased oxidative stress levels; however, these detrimental effects can be mitigated by VIT treatment. Conclusion. Collectively, our data provide compelling evidence that VIT has the potential to reverse the deleterious consequences of iron overload on osseointegration and bone mass during ageing. Cite this article: Bone Joint Res 2024;13(9):427–440

Aims. The management of periprosthetic joint infection (PJI) remains a major challenge in orthopaedic surgery. In this study, we aimed to characterize the local bone microstructure and metabolism in a clinical cohort of patients with chronic PJI. Methods. Periprosthetic femoral trabecular bone specimens were obtained from patients suffering from chronic PJI of the hip and knee (n = 20). Microbiological analysis was performed on preoperative joint aspirates and tissue specimens obtained during revision surgery. Microstructural and cellular bone parameters were analyzed in bone specimens by histomorphometry on undecalcified sections complemented by tartrate-resistant acid phosphatase immunohistochemistry. Data were compared with control specimens obtained during primary arthroplasty (n = 20) and aseptic revision (n = 20). Results. PJI specimens exhibited a higher bone volume, thickened trabeculae, and increased osteoid parameters compared to both control groups, suggesting an accelerated bone turnover with sclerotic microstructure. On the cellular level, osteoblast and osteoclast parameters were markedly increased in the PJI cohort. Furthermore, a positive association between serum (CRP) but not synovial (white blood cell (WBC) count) inflammatory markers and osteoclast indices could be detected. Comparison between different pathogens revealed increased osteoclastic bone resorption parameters without a concomitant increase in osteoblasts in bone specimens from patients with Staphylococcus aureus infection, compared to those with detection of Staphylococcus epidermidis and Cutibacterium spp. Conclusion. This study provides insights into the local bone metabolism in chronic PJI, demonstrating osteosclerosis with high bone turnover. The fact that Staphylococcus aureus was associated with distinctly increased osteoclast indices strongly suggests early surgical treatment to prevent periprosthetic bone alterations. Cite this article: Bone Joint Res 2023;12(10):644–653

Aims. This study examined whether systemic administration of melatonin would have different effects on osseointegration in ovariectomized (OVX) rats, depending on whether this was administered during the day or night. Methods. In this study, a titanium rod was implanted in the medullary cavity of one femoral metaphysis in OVX rats, and then the rats were randomly divided into four groups: Sham group (Sham, n = 10), OVX rat group (OVX, n = 10), melatonin day treatment group (OVX + MD, n = 10), and melatonin night treatment group (OVX + MN, n = 10). The OVX + MD and OVX + MN rats were treated with 30 mg/kg/day melatonin at 9 am and 9 pm, respectively, for 12 weeks. At the end of the research, the rats were killed to obtain bilateral femora and blood samples for evaluation. Results. Micro-CT and histological evaluation showed that the bone microscopic parameters of femoral metaphysis trabecular bone and bone tissue around the titanium rod in the OVX + MD group demonstrated higher bone mineral density, bone volume fraction, trabecular number, connective density, trabecular thickness, and lower trabecular speculation (p = 0.004) than the OVX + MN group. Moreover, the biomechanical parameters of the OVX + MD group showed higher pull-out test and three-point bending test values, including fixation strength, interface stiffness, energy to failure, energy at break, ultimate load, and elastic modulus (p = 0.012) than the OVX + MN group. In addition, the bone metabolism index and oxidative stress indicators of the OVX + MD group show lower values of Type I collagen cross-linked C-telopeptide, procollagen type 1 N propeptide, and malondialdehyde (p = 0.013), and higher values of TAC and SOD (p = 0.002) compared with the OVX + MN group. Conclusion. The results of our study suggest that systemic administration with melatonin at 9 am may improve the initial osseointegration of titanium rods under osteoporotic conditions more effectively than administration at 9 pm. Cite this article: Bone Joint Res 2022;11(11):751–762

Aims. Tobacco, in addition to being one of the greatest public health threats facing our world, is believed to have deleterious effects on bone metabolism and especially on bone healing. It has been described in the literature that patients who smoke are approximately twice as likely to develop a nonunion following a non-specific bone fracture. For clavicle fractures, this risk is unclear, as is the impact that such a complication might have on the initial management of these fractures. Methods. A systematic review and meta-analysis were performed for conservatively treated displaced midshaft clavicle fractures. Embase, PubMed, and Cochrane Central Register of Controlled Trials (via Cochrane Library) were searched from inception to 12 May 2022, with supplementary searches in Open Grey, ClinicalTrials.gov, ProQuest Dissertations & Theses, and Google Scholar. The searches were performed without limits for publication date or languages. Results. The meta-analysis included eight studies, 2,285 observations, and 304 events (nonunion). The random effects model predicted a pooled risk ratio (RR) of 3.68 (95% confidence interval 1.87 to 7.23), which can be considered significant (p = 0.003). It indicates that smoking more than triples the risk of nonunion when a fracture is treated conservatively. Conclusion. Smoking confers a RR of 3.68 for developing a nonunion in patients with a displaced middle third clavicle fracture treated conservatively. We know that most patients with pseudarthrosis will have pain and a poor functional outcome. Therefore, patients should be informed of the significantly higher risks of nonunion and offered smoking cessation efforts and counselling. Moreover, surgery should be considered for any patient who smokes with this type of fracture. Cite this article: Bone Joint J 2023;105-B(7):801–807

Aims. Low-energy distal radius fractures (DRFs) are the most common upper arm fractures correlated with bone fragility. Vitamin D deficiency is an important risk factor associated with DRFs. However, the relationship between DRF severity and vitamin D deficiency is not elucidated. Therefore, this study aimed to identify the correlation between DRF severity and serum 25-hydroxyvitamin-D level, which is an indicator of vitamin D deficiency. Methods. This multicentre retrospective observational study enrolled 122 female patients aged over 45 years with DRFs with extension deformity. DRF severity was assessed by three independent examiners using 3D CT. Moreover, it was categorized based on the AO classification, and the degree of articular and volar cortex comminution was evaluated. Articular comminution was defined as an articular fragment involving three or more fragments, and volar cortex comminution as a fracture in the volar cortex of the distal fragment. Serum 25-hydroxyvitamin-D level, bone metabolic markers, and bone mineral density (BMD) at the lumbar spine, hip, and wrist were evaluated six months after injury. According to DRF severity, serum 25-hydroxyvitamin-D level, parameters correlated with bone metabolism, and BMD was compared. Results. The articular comminuted group (n = 28) had a significantly lower median serum 25-hydroxyvitamin-D level than the non-comminuted group (n = 94; 13.4 ng/ml (interquartile range (IQR) 9.8 to 17.3) vs 16.2 ng/ml (IQR 12.5 to 20.4); p = 0.005). The AO classification and volar cortex comminution were not correlated with the serum 25-hydroxyvitamin-D level. Bone metabolic markers and BMD did not significantly differ in terms of DRF severities. Conclusion. Articular comminuted DRF, referred to as AO C3 fracture, is significantly associated with low serum 25-hydroxyvitamin-D levels. Therefore, vitamin D. 3. supplementation for vitamin D deficiency might prevent articular comminuted DRFs. Nevertheless, further studies must be conducted to validate the results of the current study. Cite this article: Bone Jt Open 2022;3(3):261–267

Previous studies have described an age-dependent distortion of bone microarchitecture for α-CGRP-deficient mice (3). In addition, we observed changes in cell survival and activity of osteoblasts and osteoclasts isolated from young wildtype (WT) mice when stimulated with α-CGRP whereas loss of α-CGRP showed only little effects on bone cell metabolism of cells isolated from young α-CGRP-deficient mice. We assume that aging processes differently affect bone cell metabolism in the absence and presence of α-CGRP. To further explore this hypothesis, we investigated and compared cell metabolism of osteoblasts and bone marrow derived macrophages (BMM)/osteoclast cultures isolated from young (8–12 weeks) and old (9 month) α-CGRP-deficient mice and age matched WT controls. Isolation/differentiation of bone marrow macrophages (BMM, for 5 days) to osteoclasts and osteoblast-like cells (for 7/14/21 days) from young (8–12 weeks) and old (9 month) female α-CGRP−/− and WT control (both C57Bl/6J) mice according to established protocols. We analyzed cell migration of osteoblast-like cells out of femoral bone chips (crystal violet staining), proliferation (BrdU incorporation) and caspase 3/7-activity (apoptosis rate). Alkaline phosphatase (ALP) activity reflects osteoblast bone formation activity and counting of multinucleated (≥ 3 nuclei), TRAP (tartrate resistant acid phosphatase) stained osteoclasts reflects osteoclast differentiation capacity. We counted reduced numbers of BMM from young α-CGRP−/− mice after initial seeding compared to young WT controls but we found no differences between old α-CGRP−/− mice and age-matched controls. Total BMM number was higher in old compared to young animals. Migration of osteoblast-like cells out of bone chips was comparable in both, young and old α-CGRP−/− and WT mice, but number of osteoblast-like cells was lower in old compared to young animals. Proliferation of old α-CGRP−/− BMM was higher when compared to age-matched WT whereas proliferation of old α-CGRP−/− osteoblasts after 21 days of osteogenic differentiation was lower. No differences in bone cell proliferation was detected between young α-CGRP−/− and age-machted WT mice. Caspase 3/7 activity of bone cells from young as well as old α-CGRP−/− mice was comparable to age-matched controls. Number of TRAP-positive multinucleated osteoclasts from young α-CGRP−/− mice was by trend higher compared to age-matched WT whereas no difference was observed in osteoclast cultures from old α-CGRP−/− mice and old WT. ALP activity, as a marker for bone formation activity, was comparable in young WT and α-CGRP−/− osteoblasts throughout all time points whereas ALP activity was strongly reduced in old α-CGRP−/− osteoblasts after 21 days of osteogenic differentiation compared to age-matched WT. Our data indicate that loss of α-CGRP results in a reduction of bone formation rate in older individuals caused by lower proliferation and reduced activity of osteogenic cells but has no profound effects on bone resorption rate. We suggest that the osteopenic bone phenotype described in aged α-CGRP-deficient mice could be due to an increase of dysfunctional matured osteoblasts during aging resulting in impaired bone formation

In the past the prevailing view believed that there was an inverse relationship between osteoarthritis and osteoporosis; a recent study showed that elderly women with advanced osteoarthritis requiring total hip replacement had an evidence of osteoporosis and vitamin-D deficiency. An altered metabolic bone status as induced by low level of vitamin D could be one of the major causes of aseptic bone loosening and consequently failure of the implant. We studied the bone mineral metabolism of thirty elderly women with osteoarthritis undergoing total hip replacement in order to identify whether or not there were a bone metabolic alterations. All the subjects included in the study were over than 70 years old (mean age 74 ± 2.5). The results showed that six (20%) subjects had a hypovitaminosis D status and eighteen (60%) had a vitamin D deficiency status. Five subjects (16%) had a secondary iperparathyroidism. The bone mineral metabolism of elderly women with osteoarthritis undergoing total hip replacement is characterised by a high prevalence of vitamin D deficiency and in a less percentage of the cases by a secondary iperparathyroidism. Both of these metabolic conditions could compromise the bone integration of the implant and lead to aseptic bone loosening

Aims

Despite the interest in the association of gut microbiota with bone health, limited population-based studies of gut microbiota and bone mineral density (BMD) have been made. Our aim is to explore the possible association between gut microbiota and BMD.

Previously, we have demonstrated reduced biomechanical bone strength and matrix quality in Tachykinin (Tac)1-deficient mice lacking the sensory neuropeptide substance P (SP). A similar distortion of bone microarchitecture was described for α-calcitonin gene-related pepide (α-CGRP)-deficient mice. In previous studies we observed alterations in cell survival and differentiation capacity of bone cells isolated from wildtype mice when stimulated with SP and α-CGRP. We assume that changes in sensory neurotransmitter balance modulate bone cell metabolism thereby possibly contributing to inferior bone quality. In order to explore this hypothesis, we investigated and compared metabolic parameters in osteoblasts and osteoclasts isolated from SP- and α-CGRP-deficient mice and wildtype (WT) controls. Bone marrow-derived macrophages (BMMs) and osteoblast-like cells from female C57Bl/6J (WT-control), Tac1-deficient (Tac1-/−) and α-CGRP-deficient (α-CGRP-/−) mice were isolated and differentiated according to established protocols (Niedermair et al., 2014). Cell metabolism studies were performed for enzyme activity and cell survival. We observed reduced numbers of BMM from Tac1-/− and α-CGRP-/− mice after initial seeding compared to WT but no changes in viability. Osteoblast-like cells from Tac1-/− mice tend to migrate out faster from bone chips compared to WT-controls whereas migration of osteoblast-like cells from α-CGRP-/− mice was not affected. Osteoblasts and osteoclast/BMM cultures from WT mice endogenously synthesize and secrete SP as well as α-CGRP at a picomolar range. We found no changes regarding BMM or osteoblast proliferation from both, Tac1-/− and α-CGRP-/− mice when compared to WT-controls. Caspase 3/7-activity was reduced by trend in osteoclast/BMM cultures of α-CGRP-/− mice and significantly reduced in osteoclast/BMM cultures of Tac1-/− mice compared to WT-controls. We found significantly higher Caspase 3/7-activity in osteoblasts of Tac1-/− mice after 14 days of osteogenic culture conditions when compared to WT-controls whereas osteoblasts of α-CGRP-/− mice were unaffected. Cathepsin K enzyme activity was significantly reduced in osteoclast/BMM cultures of Tac1-/− and α-CGRP-/− mice compared to WT-controls. ALP activity of Tac1-/− osteoblasts was higher after 7 days and reduced after 21 days of osteogenic culture compared to WT-controls whereas ALP activity of osteoblasts of α-CGRP-/− mice was unchanged. Acccording to our in vitro observations, we suggest some reduction in bone resorption rate but concomitantly a reduction in bone formation rate in Tac1-/− mice compared to WT-controls resulting in a net bone loss in these mice as bone resorption is faster than bone formation. Furthermore, we assume that bone resorption rate is slightly reduced in α-CGRP-/− mice but bone formation rate seems to be unchanged. Therefore we hypothesize that additional conditions present in vivo might contribute to the inferior bone properties of α-CGRP-/− mice

Osteoporosis (OP) is a chronic metabolic bone disease characterized by the decrease of bone tissue per unit volume under the combined action of genetic and environmental factors, which leads to the decrease of bone strength, makes the bone brittle, and raises the possibility of bone fracture. However, the exact mechanism that determines the progression of OP remains to be underlined. There are hundreds of trillions of symbiotic bacteria living in the human gut, which have a mutually beneficial symbiotic relationship with the human body that helps to maintain human health. With the development of modern high-throughput sequencing (HTS) platforms, there has been growing evidence that the gut microbiome may play an important role in the programming of bone metabolism. In the present review, we discuss the potential mechanisms of the gut microbiome in the development of OP, such as alterations of bone metabolism, bone mineral absorption, and immune regulation. The potential of gut microbiome-targeted strategies in the prevention and treatment of OP was also evaluated. Cite this article: Bone Joint Res 2020;9(8):524–530

Aims. Currently, the effect of drug treatment for osteoporosis is relatively poor, and the side effects are numerous and serious. Melatonin is a potential drug to improve bone mass in postmenopausal women. Unfortunately, the mechanism by which melatonin improves bone metabolism remains unclear. The aim of this study was to further investigate the potential mechanism of melatonin in the treatment of osteoporosis. Methods. The effects of melatonin on mitochondrial apoptosis protein, bmal1 gene, and related pathway proteins of RAW264.7 (mouse mononuclear macrophage leukaemia cells) were analyzed by western blot. Cell Counting Kit-8 was used to evaluate the effect of melatonin on cell viability. Flow cytometry was used to evaluate the effect of melatonin on the apoptosis of RAW264.7 cells and mitochondrial membrane potential. A reactive oxygen species (ROS) detection kit was used to evaluate the level of ROS in osteoclast precursors. We used bmal1-small interfering RNAs (siRNAs) to downregulate the Bmal1 gene. We established a postmenopausal mouse model and verified the effect of melatonin on the bone mass of postmenopausal osteoporosis in mice via micro-CT. Bmal1 lentiviral activation particles were used to establish an in vitro model of overexpression of the bmal1 gene. Results. Melatonin promoted apoptosis of RAW264.7 cells and increased the expression of BMAL1 to inhibit the activation of ROS and phosphorylation of mitogen-activated protein kinase (MAPK)-p38. Silencing the bmal1 gene weakened the above effects of melatonin. After that, we used dehydrocorydaline (DHC) to enhance the activation of MAPK-p38, and the effects of melatonin on reducing ROS levels and promoting apoptosis of RAW264.7 cells were also blocked. Then, we constructed a mouse model of postmenopausal osteoporosis and administered melatonin. The results showed that melatonin improves bone loss in ovariectomized mice. Finally, we established a model of overexpression of the bmal1 gene, and these results suggest that the bmal1 gene can regulate ROS activity and change the level of the MAPK-p38 signalling pathway. Conclusion. Our study confirmed that melatonin promotes the apoptosis of RAW264.7 cells through BMAL1/ROS/MAPK-p38, and revealed the therapeutic effect and mechanism of melatonin in postmenopausal osteoporosis. This finding enriches BMAL1 as a potential target for the treatment of osteoporosis and the pathogenesis of postmenopausal osteoporosis. Cite this article: Bone Joint Res 2023;12(11):677–690

The clinical success of posterior lumbar interbody fusion (PLIF) may be limited by pseudarthrosis, defined as the absence of solid fusion 1 year after surgery. Currently, CT is used to diagnose pseudarthrosis but is not able to be conclusive earlier than 1 year after surgery. No non-invasive technique is available to reliably assess bone graft incorporation in the early phase after PLIF. Positron Emission Tomography (PET) is a nuclear imaging modality that is able to identify changes at the cellular and molecular level in an early stage, well before manifestation of anatomical changes. PET/CT with the bone seeking tracer . 18. F-fluoride allows localization and quantification of bone metabolism. This study investigates whether an . 18. F-fluoride PET/CT scan early after PLIF is able to predict the fusion status at 1 year postoperative on CT. Twenty patients after PLIF were enrolled after written informed consent. At 6 weeks and at 1 year after PLIF, intravenous injection of . 18. F-fluoride was followed by a static scan at 60 minutes (Philips, Gemini TF PET/CT). Processing of images resulted in a bone metabolism parameter i.e. standardized uptake value (SUV). This parameter was determined for 3 regions of interest (ROIs): the intervertebral disc space (IDS) and the upper and lower endplate (UE and LE, respectively) of the operated segment. Interbody fusion was scored on a diagnostic CT scan made 1 year postoperatively and was defined as the amount of complete bony bridges between vertebrae, i.e 0, 1 or 2. Based on these scores, patients were divided in either the pseudarthrosis group (score 0) or the fusion group (scores 1 and 2). Differences between groups were analyzed using the independent samples Mann-Whitney U-test. Ten patients were classified as pseudarthrosis (0 bridges: n=10) and 10 patients as fused (1 bridge: n=5, 2 bridges: n=5). Patients in the pseudarthrosis group showed significantly lower bone metabolism values in the IDS on the 6 weeks PET/CT scan compared to patients in the fusion group (SUV. IDS,6w. 13.3±5.62 for pseudarthrosis and 22.6±6.42 for the fusion group, p=0.003), whereas values at the endplates were similar (SUV. UE,6w. 20.3±5.85 for pseudarthrosis and 21.6±4.24 for the fusion group, p=0.282). Furthermore, only in the pseudarthrosis group, bone metabolism in the IDS was significantly lower than at the endplates (p=0.006). In the fusion group, bone metabolism in the IDS and at the endplates was similar (p=0.470). The PET/CT scan at 1 year postoperative showed that in the pseudarthrosis group, bone metabolism of the IDS remained lower compared to the endplates (SUV. IDS,1y. 13.2±4.37, SUV. UE,1y. 16.4±5.33, p=0.004), while in the fusion group, IDS and endplate bone metabolism was similar (SUV. IDS,1y. 13.6±2.91, SUV. UE,1y. 14.4±3.14, p=0.397). This study shows that low bone metabolism values in the IDS of the operated segment as seen on . 18. F-fluoride PET/CT 6 weeks after PLIF, is related to development of pseudarthrosis 1 year postoperatively. These results suggest that . 18. F-fluoride PET/CT might be an early diagnostic tool to identify patients prone to develop pseudarthrosis after PLIF

Hip and knee arthroplasty (HKA) are two of the most successful orthopaedic procedures. However, one major complication necessitating revision surgery is osteolysis causing aseptic loosening of the prosthesis. JAK-STAT has been demonstrated to influence bone metabolism and can be regulated by microRNA (miRNA). Adult patients with osteolysis or aseptic loosening undergoing revision HKA were recruited. Age and gender matched patients undergoing primary hip or knee arthroplasty were our controls. Samples of bone, tissue and blood were collected and RNA isolation was performed. The best quality samples were used for RNA-sequencing. Data analysis was performed using RStudio and Galaxy to identify differentially expressed genes. Western blotting of IL6 was used to confirm protein expression. Five circulating miRNA were identified which had 10 differentially expressed genes in bone and 11 differentially expressed genes in tissue related to the JAK-STAT pathway. IL6 in bone and EpoR in bone were highly significant and IL6 in tissue, MPL in bone, SOCS3 in tissue, JAK3 in bone and SPRED1 in bone were borderline significant. Western blot results demonstrated up-expression of IL6 in bone tissue of revision patients. Periprosthetic osteolysis and aseptic loosening can be attributed to miRNA regulation of the JAK-STAT pathway in osteoblasts and osteoclasts, leading to increased bone resorption. These findings can be used for further experiments to determine utility in the clinical setting for identifying diagnostic markers or therapeutic targets

Osteoporosis is a progressive, chronic disease of bone metabolism, characterized by decreased bone mass and mineral density, predisposing individuals to an increased risk of fractures. The use of animal models, which is the gold standard for the screening of anti-osteoporosis drugs, raises numerous ethical concerns and is highly debated because the composition and structure of animal bones is very different from human bones. In addition, there is currently a poor translation of pre-clinical efficacy in animal models to human trials, meaning that there is a need for an alternative method of screening and evaluating new therapeutics for metabolic bone disorders, in vitro. The aim of this project is to develop a 3D Bone-On-A-Chip that summarizes the spatial orientation and mutual influences of the key cellular components of bone tissue, in a citrate and hydroxyapatite-enriched 3D matrix, acting as a 3D model of osteoporosis. To this purpose, a polydimethylsiloxane microfluidic device was developed by CAD modelling, stereolithography and replica molding. The device is composed by two layers: (i) a bottom layer for a 3D culture of osteocytes embedded in an osteomimetic collagen-enriched matrigel matrix with citrate-doped hydroxyapatite nanocrystals, and (ii) a upper layer for a 2D perfused co-culture of osteoblasts and osteoclasts seeded on a microporous PET membrane. Cell vitality was evaluated via live/dead assay. Bone deposition and bone resorption was analysed respectively with ALP, Alizarin RED and TRACP staining. Osteocytes dendrite expression was evaluated via immunofluorescence. Subsequently, the model was validated as drug screening platform inducing osteocytes apoptosis and administrating standard anti-osteoporotic drugs. This device has the potential to substitute or minimize animal models in pre-clinical studies of osteoporosis, contributing to pave the way for a more precise and punctual personalized treatment

Introduction and Objective. Klinefelter Syndrome (KS, karyotype 47,XXY) is the most frequent chromosomal aneuploidy in males, as well as the most common cause of infertility in men. Patients suffer from a lack of testosterone, i.e. hypergonadotropic hypogonadism provoking infertility, but KS men also show an increased predisposition to osteoporosis and a higher risk of bone fracture. In a mouse model for human KS, bone analysis of adult mice revealed a decrease in bone mass that could not be rescued by testosterone replacement, suggesting a gene dosage effect originating from the supernumerary X-chromosome on bone metabolism. Usually, X chromosome inactivation (XCI) compensates for the dosage imbalance of X-chromosomal genes between sexes. Some studies suggested that expression of genes that escape silencing of the supernumerary X-chromosome (e.g. androgen receptor) has an impact on sex differences, but may also cause pathological changes in males. As a promising new such candidate for a musculoskeletal escape gene, we identified the integral membrane protein (ITM) 2a, which is encoded on the X-chromosome and related to enchondral ossification. The aim of the project was to characterize systemic bone loss in the course of aging in our KS mouse model, and whether the supernumerary X-chromosome causes differences in expression of genes related to bone development. Materials and Methods. Bone structure of 24 month (=aged) old male wild type (WT) and 41, XXY mice (B6Ei.Lt-Y) were analysed by μCT. Afterwards bones were paraffin embedded and cut. In addition, tissue of brain, liver, kidney, lung and heart were also isolated and embedded for IHC staining. Using an anti-ITM2a antibody, expression and cellular localization of ITM2a was evaluated. IHC was also performed on musculoskeletal tissue of WT embryos (E18.5) and neonatal mice to determine possible age-related differences. Results. In 24 month old mice, the analysis of the lumbar vertebrae revealed a significantly lower BV/TV, trabecular bone volume and trabecular number in the XXY- group compared to WT. Trabecular thickness appeared lower but did not reach significance, with the cortical thickness being significantly higher in the XXY- group. High expression of ITM2a was detected in bone slices of both karyotypes in the chondrocytes inside the growth plate, as well as in megakaryocytes and leucocytes as well as endothelial cells of blood vessels inside the bone marrow. Osteocytes, along with erythrocytes and erythropoetic stem cells were negative for ITM2a. Other organs that showed ITM2a positive staining were kidney (blood vessels), heart (muscle) and brain (different structures). Liver and lung tissue were negative for ITM2a. No obvious difference in the intensity of the ITM2a-expression was observed between the WT and the XXY-karyotype. Analyses of embryotic bone tissue (WT) showed high expression of ITM2a in proliferating, hypertrophic and resting chondrocytes in the growth plates of tibia and femur. In comparison, the neonatal animals (WT) did not show any protein-expression in chondrocytes. Furthermore, within the metaphysis of both, embryotic and neonatal bones, endothelial cells and osteoblasts were ITM2a-positive. Further analyses of bones and tissues from young mice (4–6 month) are ongoing. Conclusions. Bone analyses revealed a significant reduction in trabecular bone mass along with fewer and thinner trabeculae in XXY mice compared to the WT, especially in the spine. ITM2a expression was visible in different cell types inside the bone, and in addition, different expression patterns at different stages of development (embryonic/neonatal) were observed. However, we have not found a significant difference in the quantity of ITM2a between tissues of XXY-karyotypes and WT. Further analyses of X-chromosomal encoded and therefore dysregulated modulators in XXY-karyotype mice and patients may reveal new sex chromosomal effector proteins in bone metabolism

Nitric oxide is a free radical which in vivo is solely produced during the conversion of the amino acid arginine into citrulline by nitric oxide synthase enzymes. Recently, the importance of nitric oxide on inflammation and bone metabolism has been investigated. However, the knowledge regarding possible in vitro effects of arginine supplementation on chondrogenic differentiation is limited. ATDC5, a cell line which is derived from mouse teratocarcinoma cells and which is characterized as chondrogenic cell line, were proliferated in Dulbecco's Modified Eagle Medium (DMEM)/F12 and subsequently differentiated in proliferation medium supplemented with insulin, transferrin and sodium-selenite and where arginine was added in four different concentrations (0, 7.5, 15 and 30 mM). Samples were harvested after 7 or 10 days and were stored at −80 °C for subsequent RNA isolation for qPCR analysis. To determine chondrogenic differentiation, Alcian Blue staining was performed to stain the proteoglycan aggrecan, which is secreted by differentiated ATDC5 cells. All measurements were performed in triplo. Alcian Blue staining showed a qualitative increase of proteoglycan aggrecan secretion in differentiated ATDC5 cells after treatment with 7 and 15 mM arginine, with additional increased expression of ColII, ColX, Bmp4 and Bmp6. Treatment with 30 mM arginine inhibited chondrogenic differentiation and expression of aforementioned genes, however, Cox-2 and Vegfa gene expression were increased in these samples. Bmp7 was not significantly expressed in any experimental condition. The obtained results are suggestive for a dose-dependent effect of arginine supplementation on chondrogenic differentiation and associated gene expression, with 7.5 and 15 mM as most optimal concentrations and implications for apoptosis after incubation with 30 mM arginine. A future recommendation would be to investigate the effects of citrulline in a similar experiment, as this shows even more promising results to enhance the nitric oxide metabolism in sepsis and bone healing

Introduction. The identification of biological markers associated to implant failure in THA (total hip arthroplasty) patients remains a challenge in orthopedic surgery. In this search, previous studies have been mainly focused on typical mediators associated to bone metabolism and inflammation. Our group has evaluated changes in serum levels of insulin-like growth factor binding protein-1 (IGFBP-1), a protein which is not directly related to bone homeostasis, in patients undergoing THA. Method. We assessed IGFBP-1 levels in serum obtained from 131 patients (58% female, 42 % male; age: 68 ± 13 years) who underwent THA in the Orthopedic Surgery and Traumatology Department of our institution. In this cohort, 57% of patients had metal on polyethylene (MoP) as hip-bearing surface combination, 17 % had ceramic on ceramic (CoC) and 26% of them did not have any prosthesis. A test based on an enzyme-linked immunosorbent assay (ELISA) was used to determine IGFBP-1 levels in serum obtained from these patients. Result. Our results showed a significant increase in IGFBP- 1 levels in MoP group as compared to CoC and control groups, in which no differences in quantified levels were detected. Further analysis revealed no significant differences in IGFBP-1 between cemented and non-cemented MoP bearings. We performed a ROC curve to evaluate the accuracy of serum IGFBP-1 in discriminating MoP from the rest of patients (area under the curve: 0.7; 95% confidence interval: 0,6-0.8; p<0.05) and established a cut-off value of 10.2 ng/ml, according to the Youden´s Index. Logistic regression analysis showed that patients with MoP bearing surfaces had a higher risk of increased IGFBP- 1 levels in serum (p<0.05, Odds Ratio: 6.7, 95% Confidence Interval 3.1 to 14.8). Conclusion. IGFBP- 1 levels are significantly elevated in THA patients with MoP bearing surfaces, suggesting that this protein might be a reliable biomarker for the outcome of patients implanted with MoP

Nuclear factor erythroid 2–related factor 2 (Nrf2) is a crucial transcription factor to maintain cellular redox homeostasis, but is also affecting bone metabolism. As the association between Nrf2 and osteoporosis in elderly females is not fully elucidated, our aim was to shed light on the potential contribution of Nrf2 to the development of age-dependent osteoporosis using a mouse model. Female wild-type (WT, n=18) and Nrf2-knockout (KO, n=12) mice were sacrificed at different ages (12 weeks=young mature adult, and 90 weeks=old), morphological cortical and trabecular properties of femoral bone analyzed by micro-computed tomography (µCT), and compared to histochemistry. Mechanical properties were derived from quasi-static compression tests and digital image correlation (DIC) used to analyze full-field strain distribution. Bone resorbing cells and aromatase expression by osteocytes were evaluated immunohistochemically and empty osteocyte lacunae counted in cortical bone. Wilcoxon rank sum test was used for data comparison and differences considered statistically significant at p<0.05. When compared to old WT mice, old Nrf2-KO mice revealed a significantly reduced trabecular bone mineral density (BMD), cortical thickness (Ct.Th), cortical area (Ct.Ar), and cortical bone fraction (Ct.Ar/Tt.Ar). Surprisingly, these parameters were not different in skeletally mature young adult mice. Metaphyseal trabeculae were thin but present in all old WT mice, while no trabecular bone was detectable in 60% of old KO mice. Occurrence of empty osteocyte lacunae did not differ between both groups, but a significantly higher number of osteoclast-like cells and fewer aromatase-positive osteocytes were found in old KO mice. Furthermore, female Nrf2-KO mice showed an age-dependently reduced fracture resilience when compared to age-matched WT mice. Our results confirmed lower bone quantity and quality as well as an increased number of bone resorbing cells in old female Nrf2-KO mice. Additionally, aromatase expression in osteocytes of old Nrf2-KO mice was compromised, which may indicate a chronic lack of estrogen in bones of old Nrf2-deficient mice. Thus, chronic Nrf2 loss seems to contribute to age-dependent progression of female osteoporosis