Quantitative metrics of bone quality determined at the distal radius using photon-counting CT.

OBJECTIVE: To determine the accuracy of photon-counting-detector CT (PCD-CT) at deriving bone morphometric indices and demonstrate utility in vivo in the distal radius. METHODS: Ten cadaver wrists were scanned using PCD-CT and high-resolution peripheral quantitative CT (HRpQCT). Correlation between PCD-CT and HRpQCT morphometric indices was determined. Agreement was assessed by Lin's concordance correlation coefficient (Lin's CCC). Wrist PCD-CTs of patients between 02/2022 and 08/2023 were also evaluated for clinical utility. Morphometric indices of the in vivo distal radii were extracted and compared between patients with or without osteoporosis. RESULTS: In cadavers, strong correlation between PCD-CT and HRpQCT was observed for cortical thickness (Spearman correlation, ρ, 0.85), trabecular spacing (ρ = 0.98), and trabecular bone volume fraction (ρ = 0.68). Moderate negative correlation (ρ = - 0.49) was observed for trabecular thickness. PCD-CT shows good agreement to HRpQCT for cortical thickness, trabecular spacing, and trabecular bone volume fraction (Lin's CCC = 0.80, 0.94, and 0.86, respectively) but poor agreement (Lin's CCC = - 0.1) for trabecular thickness. In forty participants (31 adults and 9 pediatric), bone morphometrics indices for cortical thickness, trabecular thickness, trabecular spacing, and trabecular bone volume fraction were 0.99 mm (IQR, 0.89-1.06), 0.38 mm (IQR, 0.25-0.40), 0.82 mm (IQR, 0.72-1.05), and 0.28 (IQR, 0.25-0.33), respectively. Patients with osteoporosis had statistically significantly larger trabecular spacing (p = 0.025) and lower trabecular volumetric bone mineral density (p = 0.042). CONCLUSION: This study demonstrates the agreement of PCD-CT to HRpQCT in cadavers of most cortical and bone morphometrics examined and provide in vivo quantitative metrics of bone microarchitecture from routine clinical PCD-CT images of the distal radius.

Grandmaternal allergen sensitization reprograms epigenetic and airway responses to allergen in second-generation offspring.

Asthma susceptibility is influenced by environmental, genetic, and epigenetic factors. DNA methylation is one form of epigenetic modification that regulates gene expression and is both inherited and modified by environmental exposures throughout life. Prenatal development is a particularly vulnerable time period during which exposure to maternal asthma increases asthma risk in offspring. How maternal asthma affects DNA methylation in offspring and what the consequences of differential methylation are in subsequent generations are not fully known. In this study, we tested the effects of grandmaternal house dust mite (HDM) allergen sensitization during pregnancy on airway physiology and inflammation in HDM-sensitized and challenged second-generation mice. We also tested the effects of grandmaternal HDM sensitization on tissue-specific DNA methylation in allergen-naïve and -sensitized second-generation mice. Descendants of both allergen- and vehicle-exposed grandmaternal founders exhibited airway hyperreactivity after HDM sensitization. However, grandmaternal allergen sensitization significantly potentiated airway hyperreactivity and altered the epigenomic trajectory in second-generation offspring after HDM sensitization compared with HDM-sensitized offspring from vehicle-exposed founders. As a result, biological processes and signaling pathways associated with epigenetic modifications were distinct between lineages. A targeted analysis of pathway-associated gene expression found that Smad3 was significantly dysregulated as a result of grandmaternal allergen sensitization. These data show that grandmaternal allergen exposure during pregnancy establishes a unique epigenetic trajectory that reprograms allergen responses in second-generation offspring and may contribute to asthma risk.NEW & NOTEWORTHY Asthma susceptibility is influenced by environmental, genetic, and epigenetic factors. This study shows that maternal allergen exposure during pregnancy promotes unique epigenetic trajectories in second-generation offspring at baseline and in response to allergen sensitization, which is associated with the potentiation of airway hyperreactivity. These effects are one mechanism by which maternal asthma may influence the inheritance of asthma risk.

Illuminating Airway Nerve Structure and Function in Chronic Cough.

Airway nerves regulate vital airway functions including bronchoconstriction, cough, and control of respiration. Dysregulation of airway nerves underlies the development and manifestations of airway diseases such as chronic cough, where sensitization of neural pathways leads to excessive cough triggering. Nerves are heterogeneous in both expression and function. Recent advances in confocal imaging and in targeted genetic manipulation of airway nerves have expanded our ability to visualize neural organization, study neuro-immune interactions, and selectively modulate nerve activation. As a result, we have an unprecedented ability to quantitatively assess neural remodeling and its role in the development of airway disease. This review highlights our existing understanding of neural heterogeneity and how advances in methodology have illuminated airway nerve morphology and function in health and disease.

Identification and characterisation of spontaneous mutations causing deafness from a targeted knockout programme.

BACKGROUND: Mice carrying targeted mutations are important for investigating gene function and the role of genes in disease, but off-target mutagenic effects associated with the processes of generating targeted alleles, for instance using Crispr, and culturing embryonic stem cells, offer opportunities for spontaneous mutations to arise. Identifying spontaneous mutations relies on the detection of phenotypes segregating independently of targeted alleles, and having a broad estimate of the level of mutations generated by intensive breeding programmes is difficult given that many phenotypes are easy to miss if not specifically looked for. Here we present data from a large, targeted knockout programme in which mice were analysed through a phenotyping pipeline. Such spontaneous mutations segregating within mutant lines may confound phenotypic analyses, highlighting the importance of record-keeping and maintaining correct pedigrees. RESULTS: Twenty-five lines out of 1311 displayed different deafness phenotypes that did not segregate with the targeted allele. We observed a variety of phenotypes by Auditory Brainstem Response (ABR) and behavioural assessment and isolated eight lines showing early-onset severe progressive hearing loss, later-onset progressive hearing loss, low frequency hearing loss, or complete deafness, with vestibular dysfunction. The causative mutations identified include deletions, insertions, and point mutations, some of which involve new genes not previously associated with deafness while others are new alleles of genes known to underlie hearing loss. Two of the latter show a phenotype much reduced in severity compared to other mutant alleles of the same gene. We investigated the ES cells from which these lines were derived and determined that only one of the 8 mutations could have arisen in the ES cell, and in that case, only after targeting. Instead, most of the non-segregating mutations appear to have occurred during breeding of mutant mice. In one case, the mutation arose within the wildtype colony used for expanding mutant lines. CONCLUSIONS: Our data show that spontaneous mutations with observable effects on phenotype are a common side effect of intensive breeding programmes, including those underlying targeted mutation programmes. Such spontaneous mutations segregating within mutant lines may confound phenotypic analyses, highlighting the importance of record-keeping and maintaining correct pedigrees.

Unique Allergic Asthma Phenotypes in Offspring of House Dust Mite-exposed Mice.

Asthma is a heterogeneous inflammatory airway disease that develops in response to a combination of genetic predisposition and environmental exposures. Patients with asthma are grouped into phenotypes with shared clinical features and biomarker profiles to help tailor specific therapies. However, factors driving development of specific phenotypes are poorly understood. Prenatal exposure to maternal asthma is a unique risk factor for childhood asthma. Here we tested whether maternal asthma skews asthma phenotypes in offspring. We compared airway hyperreactivity and inflammatory and neurotrophin lung signatures before and after allergen challenge in offspring born to mice exposed to house dust mite (HDM) or vehicle during pregnancy. Maternal HDM exposure potentiated offspring responses to HDM allergen, significantly increasing both airway hyperreactivity and airway eosinophilia compared with control mice. Maternal HDM exposure broadly skewed the offspring cytokine response from a classic allergen-induced T-helper cell type 2 (Th2)-predominant signature in HDM-treated offspring of vehicle-exposed mothers, toward a mixed Th17/Th1 phenotype in HDM-treated offspring of HDM-exposed mothers. Morphologic analysis determined that maternal HDM exposure also increased airway epithelial sensory nerve density and induced distinct neurotrophin signatures to support airway hyperinnervation. Our results demonstrate that maternal allergen exposure alters fetal lung development and promotes a unique inflammatory phenotype at baseline and in response to allergen that persists into adulthood.

Proceedings of the 2022 Santa Fe Bone Symposium: Current Concepts in the Care of Patients with Osteoporosis and Metabolic Bone Diseases.

The 22nd Annual Santa Fe Bone Symposium (SFBS) was a hybrid meeting held August 5-6, 2022, with in-person and virtual attendees. Altogether, over 400 individuals registered, a majority of whom attended in-person, representing many states in the USA plus 7 other countries. The SFBS included 10 plenary presentations, 2 faculty panel discussions, satellite symposia, Bone Health & Osteoporosis Foundation Fracture Liaison Service Boot Camp, and a Project ECHO workshop, with lively interactive discussions for all events. Topics of interest included fracture prevention at different stages of life; how to treat and when to change therapy; skeletal health in cancer patients; advanced imaging to assess bone strength; the state of healthcare in the USA; osteosarcopenia; vitamin D update; perioperative bone health care; new guidelines for managing primary hyperparathyroidism; new concepts on bone modeling and remodeling; and an overview on the care of rare bone diseases, including hypophosphatasia, X-linked hypophosphatemia, tumor induced osteomalacia, osteogenesis imperfecta, fibrodysplasia ossificans progressiva, and osteopetrosis. The SFBS was preceded by the Santa Fe Fellows Workshop on Osteoporosis and Metabolic Bone Diseases, a collaboration of the Endocrine Fellows Foundation and the Osteoporosis Foundation of New Mexico. From the Workshop, 4 participating fellows were selected to give oral presentations at the bone symposium. These proceedings represent the clinical highlights of 2022 SFBS presentations and the discussions that followed, all with the aim of optimizing skeletal health and minimizing the consequences of fragile bones.

Airway Sensory Nerve Density Is Increased in Chronic Cough.

Rationale: Chronic cough is characterized by frequent urges to cough and a heightened sensitivity to inhaled irritants. Airway sensory nerves trigger cough. We hypothesized that sensory nerve density is increased in chronic cough, which may contribute to excessive and persistent coughing.Objectives: To measure airway nerve density (axonal length) and complexity (nerve branching, neuropeptide expression) in humans with and without chronic cough.Methods: Bronchoscopic human airway biopsies were immunolabeled for nerves and the sensory neuropeptide substance P. Eosinophil peroxidase was also quantified given previous reports showing associations between eosinophils and nerve density. Three-dimensional image z-stacks of epithelium and subepithelium were generated using confocal microscopy, and from these z-stacks, total nerve length, the number of nerve branch points, substance P expression, and eosinophil peroxidase were quantified within each airway compartment.Measurements and Main Results: Nerve length and the number of branch points were significantly increased in epithelium, but not subepithelium, in chronic cough compared with healthy airways. Substance P expression was scarce and was similar in chronic cough and healthy airways. Nerve length and branching were not associated with eosinophil peroxidase nor with demographics such as age and sex in either group.Conclusions: Airway epithelial sensory nerve density is increased in chronic cough, suggesting sensory neuroplasticity contributes to cough hypersensitivity.

Approach to echocardiography in ARDS patients in the prone position: A systematic review.

Echocardiography is commonly utilized in patients with acute respiratory distress syndrome (ARDS) for assessment of cardiac function, volume status, and the potential development of acute cor pulmonale. In severe ARDS, prone positioning is frequently used, which imposes technical challenges during transthoracic echocardiography (TTE) image acquisition. Moreover, prone positioning can affect cardiopulmonary function in ways that are reflected on the echocardiographic findings in this position. Historically, a transesophageal approach was recommended when a patient is prone, with few studies reporting utility of TTE in this setting. However, recent publications have begun to address this knowledge gap. This review explores recent literature addressing the use of TTE in prone patients with ARDS, with a special focus on the cardiopulmonary effects of proning and potential solutions to the technical difficulties that arise in this position.

Tumour-induced osteomalacia: a rare cause of chronic pain and weakness.

Tumor-induced osteomalacia is a rare and often misdiagnosed condition that presents with progressively worsening unexplained chronic pain and proximal muscle weakness. The osteomalacia leads to multiple stress fractures which do not heal properly, leading to progressive disability. It is caused by chronic hypophosphatemia due to inappropriate urinary phosphate wasting. This is due to a typically benign mesenchymal tumor that over-secretes a phospaturic hormone. Neurologists need to appreciate the relevance of chronic hypophosphatemia in people with chronic unexplained pain, as timely diagnosis and treatment of tumour-induced osteomalacia can be curative.

Treatment of multiple myeloma-related bone disease: recommendations from the Bone Working Group of the International Myeloma Working Group.

In this Policy Review, the Bone Working Group of the International Myeloma Working Group updates its clinical practice recommendations for the management of multiple myeloma-related bone disease. After assessing the available literature and grading recommendations using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) method, experts from the working group recommend zoledronic acid as the preferred bone-targeted agent for patients with newly diagnosed multiple myeloma, with or without multiple myeloma-related bone disease. Once patients achieve a very good partial response or better, after receiving monthly zoledronic acid for at least 12 months, the treating physician can consider decreasing the frequency of or discontinuing zoledronic acid treatment. Denosumab can also be considered for the treatment of multiple myeloma-related bone disease, particularly in patients with renal impairment. Denosumab might prolong progression-free survival in patients with newly diagnosed multiple myeloma who have multiple myeloma-related bone disease and who are eligible for autologous stem-cell transplantation. Denosumab discontinuation is challenging due to the rebound effect. The Bone Working Group of the International Myeloma Working Group also found cement augmentation to be effective for painful vertebral compression fractures. Radiotherapy is recommended for uncontrolled pain, impeding or symptomatic spinal cord compression, or pathological fractures. Surgery should be used for the prevention and restoration of long-bone pathological fractures, vertebral column instability, and spinal cord compression with bone fragments within the spinal route.

TLR7 is expressed by support cells, but not sensory neurons, in ganglia.

BACKGROUND: Toll-like receptor 7 (TLR7) is an innate immune receptor that detects viral single-stranded RNA and triggers the production of proinflammatory cytokines and type 1 interferons in immune cells. TLR7 agonists also modulate sensory nerve function by increasing neuronal excitability, although studies are conflicting whether sensory neurons specifically express TLR7. This uncertainty has confounded the development of a mechanistic understanding of TLR7 function in nervous tissues. METHODS: TLR7 expression was tested using in situ hybridization with species-specific RNA probes in vagal and dorsal root sensory ganglia in wild-type and TLR7 knockout (KO) mice and in guinea pigs. Since TLR7 KO mice were generated by inserting an Escherichia coli lacZ gene in exon 3 of the mouse TLR7 gene, wild-type and TLR7 (KO) mouse vagal ganglia were also labeled for lacZ. In situ labeling was compared to immunohistochemistry using TLR7 antibody probes. The effects of influenza A infection on TLR7 expression in sensory ganglia and in the spleen were also assessed. RESULTS: In situ probes detected TLR7 in the spleen and in small support cells adjacent to sensory neurons in the dorsal root and vagal ganglia in wild-type mice and guinea pigs, but not in TLR7 KO mice. TLR7 was co-expressed with the macrophage marker Iba1 and the satellite glial cell marker GFAP, but not with the neuronal marker PGP9.5, indicating that TLR7 is not expressed by sensory nerves in either vagal or dorsal root ganglia in mice or guinea pigs. In contrast, TLR7 antibodies labeled small- and medium-sized neurons in wild-type and TLR7 KO mice in a TLR7-independent manner. Influenza A infection caused significant weight loss and upregulation of TLR7 in the spleens, but not in vagal ganglia, in mice. CONCLUSION: TLR7 is expressed by macrophages and satellite glial cells, but not neurons in sensory ganglia suggesting TLR7's neuromodulatory effects are mediated indirectly via activation of neuronally-associated support cells, not through activation of neurons directly. Our data also suggest TLR7's primary role in neuronal tissues is not related to antiviral immunity.

Onset of Skin, Gut, and Genitourinary Prodromal Parkinson's Disease: A Study of 1.5 Million Veterans.

BACKGROUND: Prodromal Parkinson's disease of skin, genitourinary, and gastrointestinal systems offers a unique window for understanding early disease pathogenesis and developing disease modifying treatments. However, prior studies are limited by incomplete timing information, small sample size, and lack of adjustment for known confounders. Verifying prodromal timing and identifying new disorders in these accessible organs is critically important given their broad use. OBJECTIVE: We aimed to measure onset timing for gastrointestinal, genitourinary, and skin disorders in a large, nationwide clinically characterized cohort of 1.5 million participants. METHODS: Patients with Parkinson's disease (n = 303,693) were identified using diagnostic codes in the medical records database of the United States Veterans Affairs healthcare system and were compared 4:1 with matched controls. Disorder prevalence and estimated onset times were assessed for 20 years preceding diagnosis. RESULTS: The earliest significantly increased prodromal disorders were gastroesophageal reflux, sexual dysfunction, and esophageal dyskinesia at 17, 16, and 15 years before diagnosis. Estimated onset times for each disorder occurred 5.5 ± 3.4 years before the first measured increase. The earliest estimated onset times were smell/taste, upper gastrointestinal tract, and sexual dysfunction at 20.9, 20.6, and 20.1 years before diagnosis. Onset times for constipation and urinary dysfunction were notably longer by 7 and 9 years compared to prior studies in sleep disorder patients. Dermatophytosis and prostatic hypertrophy were identified as new high prevalence prodromal disorders. CONCLUSIONS: Gastrointestinal, genitourinary, and skin disorders manifest decades before diagnosis of Parkinson's disease, reiterating their potential as sites for developing early diagnostic testing and understanding pathogenesis.

Preoperative Imaging in Renal Transplant Patients with Tertiary Hyperparathyroidism.

BACKGROUND: Tertiary hyperparathyroidism following kidney transplantation is most commonly characterized by 4-gland hyperplasia, but single and double adenomatous disease has been demonstrated in this population as well. It is unknown whether preoperative imaging can assist in identifying patients who may qualify for focused surgery for adenomatous disease. MATERIALS AND METHODS: We performed a retrospective review of our patient database from 1998-2018 for patients with tertiary hyperparathyroidism following renal transplant. Patient charts were reviewed for patient demographics, laboratory values, preoperative imaging, operative findings, pathology, and complications. RESULTS: We identified 113 patients with tertiary hyperparathyroidism following renal transplant who underwent parathyroidectomy. There were 51 females and 62 males with a mean age of 53.4 ± 13.4 years. Median preoperative calcium and PTH were 10.9 mg/dl (IQR 10.3-11.2) and 228 pg/ml (IQR 118-305). Preoperative ultrasound was performed in 60 patients. Of these, 11 (18%) were negative, 38 (63%) showed 1-2 adenomas, and 11 (18%) showed ≥ 3 adenomas. 99mTc-sestamibi parathyroid scintigraphy was performed in 101/113 patients. Of these, 11 (11%) were negative, 62 (61%) showed 1-2 areas of discordant sestamibi uptake, and 28 (28%) showed ≥ 3 areas of discordant uptake. Ultimately, 19 (17%) patients had a single adenoma removed, 16 (14%) had 2 adenomas removed, and (69%) had multi-gland disease. There were 26 ectopic glands found in 21 patients, 42.3% of which were identified on preoperative imaging. 94.1% of patients were eucalcemic at last follow-up, mean (± SD) 5.8 ± 3.6 years. Adenomas that were visualized on ultrasound were larger on pathology than those non-visualized (997 ± 120 mg (mean ± SE) vs. 388 ± 109 mg, p = 0.0003). This was also true for parathyroid scintigraphy (647 ± 41 mg vs. 355 ± 51 mg, p = 0.0001). CONCLUSION: In patients with tertiary hyperparathyroidism, preoperative imaging can aid in predicting which patients will have 1-2 gland disease. In patients with 1-2 gland disease on congruent ultrasound and nuclear medicine imaging studies, the accuracy increases to 59%. Preoperative imaging can help identify ectopic glands. Larger adenomas are more likely to be identified on both imaging modalities.

IL-5 Exposure In Utero Increases Lung Nerve Density and Airway Reactivity in Adult Offspring.

Asthma is characterized by airway hyperreactivity and inflammation. In the lungs, parasympathetic and sensory nerves control airway tone and induce bronchoconstriction. Dysregulation of these nerves results in airway hyperreactivity. Humans with eosinophilic asthma have significantly increased sensory nerve density in airway epithelium, suggesting that type 2 cytokines and inflammatory cells promote nerve growth. Similarly, mice with congenital airway eosinophilia also have airway hyperreactivity and increased airway sensory nerve density. Here, we tested whether this occurs during development. We show that transgenic mice that overexpress IL-5, a cytokine required for eosinophil hematopoiesis, give birth to wild-type offspring that have significantly increased airway epithelial nerve density and airway hyperreactivity that persists into adulthood. These effects are caused by in utero exposure to maternal IL-5 and resulting fetal eosinophilia. Allergen exposure of these adult wild-type offspring results in severe airway hyperreactivity, leading to fatal reflex bronchoconstriction. Our results demonstrate that fetal exposure to IL-5 is a developmental origin of airway hyperreactivity, mediated by hyperinnervation of airway epithelium.

Transient receptor potential ankyrin-1 causes rapid bronchodilation via nonepithelial PGE2.

Transient receptor potential ankyrin-1 (TRPA1) is a ligand-gated cation channel that responds to endogenous and exogenous irritants. TRPA1 is expressed on multiple cell types throughout the lungs, but previous studies have primarily focused on TRPA1 stimulation of airway sensory nerves. We sought to understand the integrated physiological airway response to TRPA1 stimulation. The TRPA1 agonists allyl isothiocyanate (AITC) and cinnamaldehyde (CINN) were tested in sedated, mechanically ventilated guinea pigs in vivo. Reproducible bronchoconstrictions were induced by electrical stimulation of the vagus nerves. Animals were then treated with intravenous AITC or CINN. AITC and CINN were also tested on isolated guinea pig and mouse tracheas and postmortem human trachealis muscle strips in an organ bath. Tissues were contracted with methacholine, histamine, or potassium chloride and then treated with AITC or CINN. Some airways were pretreated with TRPA1 antagonists, the cyclooxygenase inhibitor indomethacin, the EP2 receptor antagonist PF 04418948, or tetrodotoxin. AITC and CINN blocked vagally mediated bronchoconstriction in guinea pigs. Pretreatment with indomethacin completely abolished the airway response to TRPA1 agonists. Similarly, AITC and CINN dose-dependently relaxed precontracted guinea pig, mouse, and human airways in the organ bath. AITC- and CINN-induced airway relaxation required TRPA1, prostaglandins, and PGE2 receptor activation. TRPA1-induced airway relaxation did not require epithelium or tetrodotoxin-sensitive nerves. Finally, AITC blocked airway hyperreactivity in two animal models of allergic asthma. These data demonstrate that stimulation of TRPA1 causes bronchodilation of intact airways and suggest that the TRPA1 pathway is a potential pharmacological target for bronchodilation.

International myeloma working group consensus recommendations on imaging in monoclonal plasma cell disorders.

Recent advances in the treatment of multiple myeloma have increased the need for accurate diagnosis of the disease. The detection of bone and bone marrow lesions is crucial in the investigation of multiple myeloma and often dictates the decision to start treatment. Furthermore, detection of minimal residual disease is important for prognosis determination and treatment planning, and it has underscored an unmet need for sensitive imaging methods that accurately assess patient response to multiple myeloma treatment. Low-dose whole-body CT has increased sensitivity compared with conventional skeletal survey in the detection of bone disease, which can reveal information leading to changes in therapy and disease management that could prevent or delay the onset of clinically significant morbidity and mortality as a result of skeletal-related events. Given the multiple options available for the detection of bone and bone marrow lesions, ranging from conventional skeletal survey to whole-body CT, PET/CT, and MRI, the International Myeloma Working Group decided to establish guidelines on optimal use of imaging methods at different disease stages. These recommendations on imaging within and outside of clinical trials will help standardise imaging for monoclonal plasma cell disorders worldwide to allow the comparison of results and the unification of treatment approaches for multiple myeloma.

Lung tumor cells inhibit bone mineralization and osteoblast activity.

Patients with non-small cell lung cancer (NSLC) often develop skeletal complications and fractures. To understand mechanisms of bone loss, we developed a murine model of non-metastatic NSLC. Decreased bone mineral density, trabecular thickness and mineralization, without an increase in bone resorption, were observed in vivo in mice injected with Lewis lung adenocarcinoma (LLC1) cells in the absence of tumor cell metastases. A decrease in trabecular bone mineral density was observed in mice injected with cell-free LLC1 CM. Plasma osteoblast biomarkers and PTH-related peptide (PTHrP) were reduced, and parathyroid hormone (PTH), 1,25-dihydroxyvitamin D, calcium and phosphate concentrations were normal in tumor-bearing mice. LLC1 cell conditioned medium (CM) inhibited alkaline phosphatase activity, osteoblast mineralization, and expression of Alpl and Ocn/Bglap mRNA in MC3T3 osteoblast cultures, whereas non-CM or CM from NIH/3T3 fibroblasts did not induce similar changes. LLC1 CM reduced Wnt3a-stimulated Tcf/Lef reporter plasmid activity and Wnt5A, Tcf1 and Lef1 mRNA expression in MC3T3 cells. Although concentrations of the Wnt inhibitor, DKK2, were increased in LLC1 CM compared to non-CM, depletion of DKK2 from LLC1 CM did not completely restore Wnt3a activity in MC3T3 cultures, and recombinant DKK2 failed to inhibit osteoblast mineralization. The data indicate that in a model of lung adenocarcinoma without bone metastases, tumor cells elaborate a secreted factor(s) that reduces bone mass, bone formation and osteoblast Wnt signaling without increases in bone resorption or calcium-regulating hormone concentrations. The factor(s) mediating this inhibition of osteoblast mineralization require further characterization.

The skeletal impact of cancer therapies.

Both cancer and therapies used in the treatment of cancer can have significant deleterious effects on the skeleton, increasing the risks for both bone loss and fracture development. While advancements in cancer therapies have resulted in enhanced cancer survivorship for patients with many types of malignancies, it is increasingly recognized that efforts to reduce bone loss and limit fractures must be considered for nearly all patients undergoing cancer therapy in order to diminish the anticipated future skeletal consequences. To date, most studies examining the impact of cancer therapies on skeletal outcomes have focused on endocrine-associated cancers of the breast and prostate, with more recent advances in our understanding of bone loss and fracture risk in other malignancies. Pharmacologic efforts to limit the adverse effects of cancer therapies on bone have nearly universally employed anti-resorptive approaches, although studies have frequently relied on surrogate outcomes such as changes in bone mineral density or bone turnover markers, rather than on fractures or other skeletal-related events, as primary study endpoints. Compounding current deficiencies for the provision of optimal care is the recognition that despite clearly written and straightforward society-based guidelines, vulnerable eligible patients are very often neither identified nor provided with appropriate treatments to limit the skeletal impact of their cancer therapies.

Pharmacology of bisphosphonates.

The biological effects of the bisphosphonates (BPs) as inhibitors of calcification and bone resorption were first described in the late 1960s. In the 50 years that have elapsed since then, the BPs have become the leading drugs for the treatment of skeletal disorders characterized by increased bone resorption, including Paget's disease of bone, bone metastases, multiple myeloma, osteoporosis and several childhood inherited disorders. The discovery and development of the BPs as a major class of drugs for the treatment of bone diseases is a paradigm for the successful journey from "bench to bedside and back again". Several of the leading BPs achieved "blockbuster" status as branded drugs. However, these BPs have now come to the end of their patent life, making them highly affordable. The opportunity for new clinical applications for BPs also exists in other areas of medicine such as ageing, cardiovascular disease and radiation protection. Their use as inexpensive generic medicines is therefore likely to continue for many years to come. Fifty years of research into the pharmacology of bisphosphonates have led to a fairly good understanding about how these drugs work and how they can be used safely in patients with metabolic bone diseases. However, while we seemingly know much about these drugs, a number of key aspects related to BP distribution and action remain incompletely understood. This review summarizes the existing knowledge of the (pre)clinical and translational pharmacology of BPs, and highlights areas in which understanding is lacking.