Van Buchem's Disease

Anti-sclerostin antibodies: a new frontier in fragility fractures treatment

Bone fragility is the determinant of the increased risk of minimal trauma fracture and must be treated with a multimodal approach that includes pharmacological therapy, physical exercise, and adequate nutrition. Pharmacological therapy, to date based on the administration of antiresorptive drugs, such as bisphosphonates and denosumab, or osteoanabolic drugs, such as teriparatide and abaloparatide, has shown to be effective in reducing the risk of fracture in osteoporotic patients. In the context of the cellular and molecular mechanisms that regulate bone metabolism, the discovery of the Wnt signaling pathway and its role in bone tissue homeostasis has allowed the identification of sclerostin as an inhibitor of osteoblastic activity and simultaneously as a stimulator of osteoclastic activity. Therefore, the use of a monoclonal antibody, romosozumab, against this protein has been tested as a potential drug with a dual action, stimulating bone neo-apposition and inhibiting bone resorption. The efficacy of romosozumab has been demonstrated in numerous clinical trials against both placebo and other drugs commonly used in the treatment of patients affected by osteoporosis. The advantages of this drug lie above all in its rapid action which makes it particularly suitable in clinical situations where it is necessary to improve bone strength very quickly due to the imminent risk of fragility fracture. Clinical studies and guidelines suggest romosozumab as an initial drug in an ideal sequential approach from osteoanabolic to antiresorptive drugs. Some aspects of cardiovascular safety remain to be fully investigated, therefore its use in osteoporotic patients at high cardiovascular risk should be avoided until further data become available.

Hereditary Metabolic Bone Diseases: A Review of Pathogenesis, Diagnosis and Management

Hereditary metabolic bone diseases are characterized by genetic abnormalities in skeletal homeostasis and encompass one of the most diverse groups among rare diseases. In this review, we examine 25 selected hereditary metabolic bone diseases and recognized genetic variations of 78 genes that represent each of the three groups, including sclerosing bone disorders, disorders of defective bone mineralization and disorder of bone matrix and cartilage formation. We also review pathophysiology, manifestation and treatment for each disease. Advances in molecular genetics and basic sciences has led to accurate genetic diagnosis and novel effective therapeutic strategies for some diseases. For other diseases, the genetic basis and pathophysiology remain unclear. Further researches are therefore crucial to innovate ways to overcome diagnostic challenges and develop effective treatment options for these orphan diseases.

Wnt Antagonists in Hematopoietic and Immune Cell Fate: Implications for Osteoporosis Therapies

PURPOSE OF REVIEW

We reviewed the current literature on the roles of the Wnt antagonists sclerostin (Sost) and sclerostin-containing domain protein 1 (Sostdc1) on bone homeostasis, the relationship of the hypoxia-inducible factor (Hif) and von Hippel-Lindau (Vhl) pathways on Sost expression, and how changes in bone induced by depletion of Sost, Sostdc1, and Vhl affect hematopoietic cells.

RECENT FINDINGS

B cell development is adversely affected in Sost-knockout mice and is more severely affected in Vhl-knockout mice. Inflammation in the Sost^-/- bone microenvironment could alter hematopoietic stem cell behavior. Sostdc1^-/- mice display defects in natural killer cell development and cytotoxicity. Depletion of Sost and Sostdc1 have effects on immune cell function that warrant investigation in patients receiving Wnt antagonist-depleting therapies for treatment of bone diseases. Additional clinical applications for manipulation of Wnt antagonists include cancer immunotherapies, stem cell transplantation, and directed differentiation to immune lineages.

Mouse Models and Online Resources for Functional Analysis of Osteoporosis Genome-Wide Association Studies

Osteoporosis is a complex genetic disease in which the number of loci associated with the bone mineral density, a clinical risk factor for fracture, has increased at an exponential rate in the last decade. The identification of the causative variants and candidate genes underlying these loci has not been able to keep pace with the rate of locus discovery. A large number of tools and data resources have been built around the use of the mouse as model of human genetic disease. Herein, we describe resources available for functional validation of human Genome Wide Association Study (GWAS) loci using mouse models. We specifically focus on large-scale phenotyping efforts focused on bone relevant phenotypes and repositories of genotype-phenotype data that exist for transgenic and mutant mice, which can be readily mined as a first step toward more targeted efforts designed to deeply characterize the role of a gene in bone biology.