Advances and Unmet Needs in the Therapeutics of Bone Fragility

Single-Cell Integration of BMD GWAS Results Prioritize Candidate Genes Influencing Age-Related Bone Loss

The regulation of bone mineral density (BMD) is highly influenced by genetics and age. Although genome-wide association studies (GWAS) for BMD have uncovered many genes through their proximity to associated variants (variant nearest-neighbor [VNN] genes), the cell-specific mechanisms of each VNN gene remain unclear. This is primarily due to the inability to prioritize these genes by cell type and age-related expression. Using age-related transcriptomics, we found that the expression of many VNN genes was upregulated in the bone and marrow from aged mice. Candidate genes from GWAS were investigated using single-cell RNA-sequencing (scRNA-seq) datasets to enrich for cell-specific expression signatures. VNN candidate genes are highly enriched in osteo-lineage cells, osteocytes, hypertrophic chondrocytes, and Lepr+ mesenchymal stem cells. These data were used to generate a "blueprint" for Cre-loxp mouse line selection for functional validation of candidate genes and further investigation of their role in BMD maintenance throughout aging. In VNN-gene-enriched cells, Sparc, encoding the extracellular matrix (ECM) protein osteonectin, was robustly expressed. This, along with expression of numerous other ECM genes, indicates that many VNN genes likely have roles in ECM deposition by osteoblasts. Overall, we provide data supporting streamlined translation of GWAS candidate genes to potential novel therapeutic targets for the treatment of osteoporosis. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Real-World Effectiveness of Anti-Resorptive Treatment in Patients With Incident Fragility Fractures-The STORM Cohort-A Swedish Retrospective Observational Study

Results from real-world evidence (RWE) from the largest healthcare region in Sweden show low uptake of antiresorptive (AR) treatment, but beneficial effect in those receiving treatment, especially for the composite outcome of hip fracture or death. For RWE studies, Sweden is unique, with virtually complete coverage of electronic medical records (EMRs) and both regional and national registries, in a universal publicly funded healthcare system. To our knowledge, there is no previous RWE study evaluating the efficacy of AR treatment compared to no AR treatment after fragility fracture, including data on parenteral treatments administered in hospital settings. The Stockholm Real World Management (STORM) study cohort was established in the healthcare region of Stockholm to retrospectively assess the effectiveness of AR treatment after first fragility fracture using the regional EMR system for both hospital and primary care. Between 2012 and 2018, we identified 69,577 fragility fracture episodes among 59,078 patients, men and women, 50 years and older. Of those, 21,141 patients met inclusion and exclusion criteria (eligible cohort). From these, the final matched study cohort comprised 9840 fragility fractures (cases receiving AR treatment [n = 1640] and controls not receiving AR treatment [n = 8200]). Propensity scores were estimated using logistic regression models with AR treatment as outcome and confounders as independent variables followed by analysis using Cox proportional hazard models. Real world evidence from Sweden's largest healthcare region, comprising a quarter of the Swedish population, show that only 10% of patients receive AR treatment within 1 year after a fragility fracture. Factors associated with not receiving treatment include having a diagnosis of cardiovascular disease. In those treated, AR have positive effects particularly on the composite of fracture and death (any fracture/death and hip fracture/death) in individuals matched for all major confounders. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Risk factors and new diagnostic index for deep venous thrombosis of lower extremities in elderly patients with traumatic femoral neck fracture

Purpose

To determine the incidence and risk factors of deep vein thrombosis (DVT) of lower extremities at admission in elderly Chinese patients with femoral neck fracture, and to establish and evaluate a new DVT predictor based on these risk factors.

Methods

Patients who were hospitalized from January 2018 to December 2020 at three independent centers were reviewed. According to the results of lower extremities vascular ultrasound at admission, they were divided into DVT group and non-DVT group. Single and multivariate logistic regression analysis were applied to identify independent risk factors for DVT occurrence, and then a prediction formula for DVT based on the risk factors was developed. The new predictive index of DVT was calculated by the formula. Receiver operating characteristic (ROC) curve analysis was used to determine the diagnostic value of different factors and the new predictive index.

Results

There were 203 elder patients were included in the final analysis after application of the exclusion criteria. Thirty seven patients (18.2%) were diagnosed as DVT by ultrasound, including 33 patients (89.2%) of peripheral type, 1 patient (2.7%) of central type and 3 patients (8.1%) of mixed type.Multivariate logistic regression analysis showed that four factors including injured side, hemoglobin, fibrinogen, d-dimer were the independent risk factors for the incidence of DVT. On this basis, a new formula for DVT predictive factor was constructed: New predictive index = 0.895 * injured side (right = 1, left = 0) + 0.899 * hemoglobin (<109.5 g/L = 1, > 109.5 g/L = 0) + 1.19 * fibrinogen (>4.24 g/L = 1, < 4.24 g/L = 0) + 1.221* d-dimer (>2.4 mg/L = 1, < 2.4 mg/L = 0). The AUC value of this new developed index was 0.735.

Conclusions

This work showed that the incidence of DVT in elderly patients with femoral neck fracture in China was high at admission. New DVT predictive value can be used as an effective diagnosis strategy for evaluation of thrombosis at admission.

Postmenopausal osteoporosis: risk evaluation and treatment options

Postmenopausal osteoporosis is a chronic progressive condition characterized by reduced bone mass and impaired bone quality, leading to an increased risk of fragility fractures. Osteoporotic fractures reduce quality of life and are associated with high morbidity, mortality and economic burden. Primary and secondary prevention interventions are always recommended starting from the premenopausal age, in women after menopause, however, it is essential to develop a long-term intervention strategy that allows to identify patients at high risk of fracture and the choice of therapy based on the estimated risk. This narrative review described the tools for layering the management approach in relation to low, high and very high fracture risk. Several medications are now available for the treatment of osteoporosis and the prevention of fractures; the knowledge of the efficacy, safety and additional benefits profile of the individual preparations allows an appropriate choice between the different drugs available and the possibility of adapting the prescription to the lifetime fracture risk spectrum. From the literature it emerges that menopausal hormone therapy (MHT), TSEC combination and SERMs can be drugs of choice to counteract postmenopausal bone loss in younger women or at low risk of fracture, while bisphosphonates and denosumab are appropriate for women with high risk or at an older age. Therapy with denosumab and anabolic agents such as teriparatide and romosozumab is particularly indicated for subjects with very high risk of fracture.

Morphological and immunohistochemical features of tooth extraction sites in rats treated with alendronate, raloxifene, or strontium ranelate

OBJECTIVE

The aim of this study was to evaluate morphological and immunohistochemical features of tooth extraction sites in rats subjected to different antiresorptive drugs.

MATERIALS AND METHODS

Wistar rats were allocated into 4 groups according to the treatment: (1) alendronate, (2) raloxifene, (3) strontium ranelate, and (4) control. The animals underwent tooth extraction (60th day of treatment) and afterwards were euthanized (90th day of treatment). Tooth extraction sites were analyzed by means of scanning electron microscopy (SEM), hematoxylin-eosin staining (H&E), and immunohistochemical staining (RANKL and OPG).

RESULTS

On H&E analysis, the alendronate group showed greater amounts of non-vital bone, biofilm, inflammatory infiltrate and root fragment, and smaller amount of vital bone. The strontium ranelate group showed great amount of non-vital bone. This group also had lower levels of OPG, while the alendronate group showed lower OPG and RANKL than the other groups. On SEM analysis, the alendronate group showed a considerable number of microcracks on the alveolar bone surface and few Howship lacunae and lack of bone cells as well. The raloxifene, strontium ranelate, and control groups showed a large number of bone cells and Howship lacunae on the bone surface and few microcracks.

CONCLUSION

Alendronate therapy is associated with macro- and microscopic features of medication-related osteonecrosis of the jaw at tooth extraction sites, whereas raloxifene therapy is not, and strontium ranelate therapy is associated with non-vital bone.

CLINICAL RELEVANCE

Osteonecrosis of the jaws is a serious side effect of alendronate therapy, where tooth extraction is a major risk factor. Considering the significant number of patients undergoing antiresorptive therapies worldwide, the present study investigated whether raloxifene and strontium ranelate interfere with bone repair after tooth extraction in a similar way to bisphosphonates.

Malic Enzyme Couples Mitochondria with Aerobic Glycolysis in Osteoblasts

The metabolic program of osteoblasts, the chief bone-making cells, remains incompletely understood. Here in murine calvarial cells, we establish that osteoblast differentiation under aerobic conditions is coupled with a marked increase in glucose consumption and lactate production but reduced oxygen consumption. As a result, aerobic glycolysis accounts for approximately 80% of the ATP production in mature osteoblasts. In vivo tracing with 13C-labeled glucose in the mouse shows that glucose in bone is readily metabolized to lactate but not organic acids in the TCA cycle. Glucose tracing in osteoblast cultures reveals that pyruvate is carboxylated to form malate integral to the malate-aspartate shuttle. RNA sequencing (RNA-seq) identifies Me2, encoding the mitochondrial NAD-dependent isoform of malic enzyme, as being specifically upregulated during osteoblast differentiation. Knockdown of Me2 markedly reduces the glycolytic flux and impairs osteoblast proliferation and differentiation. Thus, the mitochondrial malic enzyme functionally couples the mitochondria with aerobic glycolysis in osteoblasts.

Old Mice Have Less Transcriptional Activation But Similar Periosteal Cell Proliferation Compared to Young-Adult Mice in Response to in vivo Mechanical Loading

Mechanical loading is a potent strategy to induce bone formation, but with aging, the bone formation response to the same mechanical stimulus diminishes. Our main objectives were to (i) discover the potential transcriptional differences and (ii) compare the periosteal cell proliferation between tibias of young-adult and old mice in response to strain-matched mechanical loading. First, to discover potential age-related transcriptional differences, we performed RNA sequencing (RNA-seq) to compare the loading responses between tibias of young-adult (5-month) and old (22-month) C57BL/6N female mice following 1, 3, or 5 days of axial loading (loaded versus non-loaded). Compared to young-adult mice, old mice had less transcriptional activation following loading at each time point, as measured by the number of differentially expressed genes (DEGs) and the fold-changes of the DEGs. Old mice engaged fewer pathways and gene ontology (GO) processes, showing less activation of processes related to proliferation and differentiation. In tibias of young-adult mice, we observed prominent Wnt signaling, extracellular matrix (ECM), and neuronal responses, which were diminished with aging. Additionally, we identified several targets that may be effective in restoring the mechanoresponsiveness of aged bone, including nerve growth factor (NGF), Notum, prostaglandin signaling, Nell-1, and the AP-1 family. Second, to directly test the extent to which periosteal cell proliferation was diminished in old mice, we used bromodeoxyuridine (BrdU) in a separate cohort of mice to label cells that divided during the 5-day loading interval. Young-adult and old mice had an average of 15.5 and 16.7 BrdU+ surface cells/mm, respectively, suggesting that impaired proliferation in the first 5 days of loading does not explain the diminished bone formation response with aging. We conclude that old mice have diminished transcriptional activation following mechanical loading, but periosteal proliferation in the first 5 days of loading does not differ between tibias of young-adult and old mice. © 2020 American Society for Bone and Mineral Research.

Both aerobic glycolysis and mitochondrial respiration are required for osteoclast differentiation

Excessive bone resorption over bone formation is the root cause for bone loss leading to osteoporotic fractures. Development of new antiresorptive therapies calls for a holistic understanding of osteoclast differentiation and function. Although much has been learned about the molecular regulation of osteoclast biology, little is known about the metabolic requirement and bioenergetics during osteoclastogenesis. Here, we report that glucose metabolism through oxidative phosphorylation (OXPHOS) is the predominant bioenergetic pathway to support osteoclast differentiation. Meanwhile, increased lactate production from glucose, known as aerobic glycolysis when oxygen is abundant, is also critical for osteoclastogenesis. Genetic deletion of Glut1 in osteoclast progenitors reduces aerobic glycolysis without compromising OXPHOS, but nonetheless diminishes osteoclast differentiation in vitro. Glut1 deficiency in the progenitors leads to osteopetrosis due to fewer osteoclasts specifically in the female mice. Thus, Glut1-mediated glucose metabolism through both lactate production and OXPHOS is necessary for normal osteoclastogenesis.

Diet-Induced Metabolic Dysregulation in Female Mice Causes Osteopenia in Adult Offspring

Bone mass and quality in humans are controlled by numerous genetic and environmental factors that are not fully understood. Increasing evidence has indicated that maternal metabolic dysregulation impairs multiple physiological processes in the adult offspring, but a similar effect on bone health is yet to be established. Here, we have analyzed the bones of first-generation offspring from murine dams that present metabolic syndrome due to a high-fat and high-sugar (HF/HS) diet. Micro-CT analyses show that the long bones of HF/HS offspring possess lower cortical bone mass and weaker mechanical strength than normal, even though the trabecular bone is not affected. Histomorphometry and serum biochemistry indicate that both bone formation and resorption are diminished in the HF/HS offspring. In vitro, both osteoblast and osteoclast progenitors from the HF/HS offspring are deficient in differentiation, likely due to impairment of mitochondrial respiration. The study, therefore, identifies maternal metabolic health as an important environmental factor influencing bone volume and strength.

Uncertainty managing patients treated with antiresorptive drugs: a cross-sectional study of attitudes and self-reported behavior among dentists in Sweden

Objective: To evaluate the level of knowledge and attitudes among Swedish general dentists regarding the behavior and management of patients treated with bisphosphonates and denosumabMaterials and Methods: A questionnaire was sent to 656 dentists. The web-based survey included questions on demographics, risk perception of osteonecrosis of the jaws (ONJ), the experience of managing patients treated with bisphosphonates and denosumab and requests to acquire new knowledge. Independence and associations were tested using Fisher's exact test and the chi-square test function.Results: The overall response rate was 57.6%. Most of the dentists, 69.7%, had been in the profession for more than 5 years. The criteria for ONJ were not known by 43.2% and 86.9% did not feel comfortable with their current level of knowledge when managing the patients in question. The rest of the respondents felt uncertain and more than 70% were unaware of the different stages of ONJ, when to refer a patient to a specialist and when to prescribe antibiotics.Conclusion: Dentists practicing in Sweden express a strong need for an improved level of knowledge when managing patients treated with bisphosphonates and denosumab. The results demonstrate a need for the necessary advancement of education and clinical training at dental schools in order to prepare dentists to provide safe, modern care within the healthcare sector.

Inducible expression of Wnt7b promotes bone formation in aged mice and enhances fracture healing

There remain unmet clinical needs for safe and effective bone anabolic therapies to treat aging-related osteoporosis and to improve fracture healing in cases of nonunion or delayed union. Wnt signaling has emerged as a promising target pathway for developing novel bone anabolic drugs. Although neutralizing antibodies against the Wnt antagonist sclerostin have been tested, Wnt ligands themselves have not been fully explored as a potential therapy. Previous work has demonstrated Wnt7b as an endogenous ligand upregulated during osteoblast differentiation, and that Wnt7b overexpression potently stimulates bone accrual in the mouse. The earlier studies however did not address whether Wnt7b could promote bone formation when specifically applied to aged or fractured bones. Here we have developed a doxycycline-inducible strategy where Wnt7b is temporally induced in the bones of aged mice or during fracture healing. We report that forced expression of Wnt7b for 1 month starting at 15 months of age greatly stimulated trabecular and endosteal bone formation, resulting in a marked increase in bone mass. We further tested the effect of Wnt7b on bone healing in a murine closed femur fracture model. Induced expression of Wnt7b at the onset of fracture did not affect the initial cartilage formation but promoted mineralization of the subsequent bone callus. Thus, targeted delivery of Wnt7b to aged bones or fracture sites may be explored as a potential therapy.

Pharmacological Therapy of Osteoporosis: What's New?

Osteoporosis and fragility fractures are relevant health issues because of their impact in terms of morbidity, mortality, and socioeconomic burden. Despite this alarming scenario, both underdiagnosis and undertreatment are common features of osteoporotic patients, particularly those who have already sustained a fragility fracture. Pharmacotherapy of osteoporosis is the main treatment option for these patients because of strong evidence about the efficacy of available drugs targeting bone metabolism. However, several issues can interfere with the effectiveness of anti-osteoporotic drugs in clinical practice, such as lack of awareness of both healthcare providers and patients, poor adherence to therapy, and safety in long-term treatment. Therefore, new therapeutic strategies have been proposed to overcome these problems, such as sequential therapy or emerging molecules mainly targeting the stimulation of bone formation. In particular, abaloparatide has been demonstrated to reduce major nonvertebral fracture risk compared with both placebo and teriparatide, although the European Medicines Agency (EMA) refused the marketing authorization because the benefits of this drug did not outweigh its risks. On the other side, EMA has recently approved romosozumab, a monoclonal antibody directed against sclerostin and the only available therapeutic option targeting Wnt signaling, as both bone-forming and antiresorptive intervention to treat osteoporosis and fragility fractures.

Metabolism and pharmacological activities of the natural health-benefiting compound diosmin

Diosmin is a famous natural flavonoid for treating chronic venous insufficiency and varicose veins.

"Bridging the Gap" Everything that Could Have Been Avoided If We Had Applied Gender Medicine, Pharmacogenetics and Personalized Medicine in the Gender-Omics and Sex-Omics Era

Gender medicine is the first step of personalized medicine and patient-centred care, an essential development to achieve the standard goal of a holistic approach to patients and diseases. By addressing the interrelation and integration of biological markers (i.e., sex) with indicators of psychological/cultural behaviour (i.e., gender), gender medicine represents the crucial assumption for achieving the personalized health-care required in the third millennium. However, ‘sex’ and ‘gender’ are often misused as synonyms, leading to frequent misunderstandings in those who are not deeply involved in the field. Overall, we have to face the evidence that biological, genetic, epigenetic, psycho-social, cultural, and environmental factors mutually interact in defining sex/gender differences, and at the same time in establishing potential unwanted sex/gender disparities. Prioritizing the role of sex/gender in physiological and pathological processes is crucial in terms of efficient prevention, clinical signs’ identification, prognosis definition, and therapy optimization. In this regard, the omics-approach has become a powerful tool to identify sex/gender-specific disease markers, with potential benefits also in terms of socio-psychological wellbeing for each individual, and cost-effectiveness for National Healthcare systems. “Being a male or being a female” is indeed important from a health point of view and it is no longer possible to avoid “sex and gender lens” when approaching patients. Accordingly, personalized healthcare must be based on evidence from targeted research studies aimed at understanding how sex and gender influence health across the entire life span. The rapid development of genetic tools in the molecular medicine approaches and their impact in healthcare is an example of highly specialized applications that have moved from specialists to primary care providers (e.g., pharmacogenetic and pharmacogenomic applications in routine medical practice). Gender medicine needs to follow the same path and become an established medical approach. To face the genetic, molecular and pharmacological bases of the existing sex/gender gap by means of omics approaches will pave the way to the discovery and identification of novel drug-targets/therapeutic protocols, personalized laboratory tests and diagnostic procedures (sex/gender-omics). In this scenario, the aim of the present review is not to simply resume the state-of-the-art in the field, rather an opportunity to gain insights into gender medicine, spanning from molecular up to social and psychological stances. The description and critical discussion of some key selected multidisciplinary topics considered as paradigmatic of sex/gender differences and sex/gender inequalities will allow to draft and design strategies useful to fill the existing gap and move forward.

Therapeutic Irradiation: Consequences for Bone and Bone Marrow Adipose Tissue

Radiotherapy continues to be one of the most accepted medical treatments for cancer. Localized irradiation is the most common treatment for prostate, pancreatic, rectal, cervical and endometrial malignancies. Conventional localized fractions are total doses of 30-62Gy at 1.8-2Gy per fraction, with administration of ~60Gy often used for tumor ablation. However, even the lowest dose of localized irradiation exposure can result in adverse complications to adjacent organs, tissues, and vessels, which absorb a portion of the treatment. Skeletal complications are common amongst cancer patients undergoing these localized treatments. Irradiation exposure causes deterioration to the overall quantity and quality of bone by interfering with the trabecular architecture through increased osteoclast activity and decreased osteoblast activity. Irradiation-induced bone damage parallels adipocyte infiltration of the bone marrow (BM) resulting in compositional alterations of the microenvironment that may further affect bone quality and disease state. There may also be direct effects of irradiation on the BM adipocyte/pre-adipocyte, although in vitro findings do not always agree and cellular response is dependent on irradiation dosage. Hematopoietic cells also become apoptotic upon irradiation, which causes a range of skeletal effects. Bone loss leaves patients at a greater risk for osteopenia, osteoporosis, osteonecrosis, and skeletal fractures that drastically reduce quality of life. Osteoanabolic agents stimulate bone formation and reduce fracture risk in patients with low bone density; thus, osteoanabolic or anti-resorptive agents may be useful co-treatments with irradiation. This review discusses these topics and proposes further research directions using novel or combination therapies to enhance bone health during irradiation.