Paget's Disease: Skeletal Manifestations and Effect of Bisphosphonates

Signaling Dynamics in Osteogenesis: Unraveling Therapeutic Targets for Bone Generation

Diseases affecting bone encompass a spectrum of disorders, from prevalent conditions such as osteoporosis and Paget's disease, collectively impacting millions, to rare genetic disorders including Fibrodysplasia Ossificans Progressiva (FOP). While several classes of drugs, such as bisphosphonates, synthetic hormones, and antibodies, are utilized in the treatment of bone diseases, their efficacy is often curtailed by issues of tolerability and high incidence of adverse effects. Developing therapeutic agents for bone diseases is hampered by the fact that numerous pathways regulating bone metabolism also perform pivotal functions in other organ systems. Consequently, the selection of an appropriate target is a complicated process despite the significant demand for novel medications to address bone diseases. Research has shown the role of various cell signaling pathways, including Wnt, PTHR1, CASR, BMPRs, OSCAR, and TWIST1, in the regulation of osteogenesis, bone remodeling, and homeostasis. Disruptions in bone homeostasis can result in decreased bone density and the onset of osteoporosis. There remains a need for the development of drugs that can enhance bone remodeling with improved side effects profiles. The exploration of promising targets to stimulate bone formation has the potential to significantly advance the field of bone-related medical care, thereby improving the quality of life for millions. Additionally, a deeper understanding of anabolic and catabolic pathway mechanisms could enable future studies to explore synergistic effects between unrelated pathways. Herein, we explore potential drug targets that may be exploited therapeutically using small molecule agonists or antagonists to promote bone remodeling and discuss their advantages and limitations.

Artroplastia total de cadera en paciente con enfermedad de Paget: presentación de un caso

Introducción: La enfermedad de Paget es un trastorno metabólico de etiología desconocida, secundario a un incremento en la función de los osteoclastos y la consecuente respuesta de los osteoblastos a la formación exagerada de hueso. Compromete con mayor frecuencia el fémur proximal y, a menudo, se diagnostica incidentalmente. Se presenta el caso de una mujer con antecedente de enfermedad de Paget y pseudoartrosis de cadera izquierda, con indicaciones de prótesis total de cadera izquierda y un episodio único de luxación, sin complicaciones posteriores y una adecuada evolución. Conclusión: El manejo quirúrgico en casos de fractura de cadera permite restablecer la marcha y mejorar la calidad de vida de los pacientes con enfermedad de Paget. A pesar de ser una patología que dificulta el manejo de los pacientes, la enfermedad de Paget no es una contraindicación para la artroplastia total de cadera y permite mejorar el dolor y recuperar la funcionalidad

Updates on Paget's Disease of Bone

Paget's disease of the bone is a prevalent bone disease characterized by disorganized bone remodeling; however, it is comparatively uncommon in East Asian countries, including China, Japan, and Korea. The exact cause still remains unknown. In genetically susceptible individuals, environmental triggers such as paramyxoviral infections are likely to cause the disease. Increased osteoclast activity results in increased bone resorption, which attracts osteoblasts and generates new bone matrix. Fast bone resorption and formation lead to the development of disorganized bone tissue. Increasing serum alkaline phosphatase or unique radiographic lesions may serve as the diagnostic indicators. Common symptoms include bone pain, bowing of the long bones, an enlarged skull, and hearing loss. The diagnosis is frequently confirmed by radiographic and nuclear scintigraphy of the bone. Further, bisphosphonates such as zoledronic acid and pamidronate are effective for its treatment. Moreover, biochemical monitoring is superior to the symptoms as a recurrence indicator. This article discusses the updates of Paget's disease of bone with a clinical case.

Stress Fracture of the Femoral Shaft in Paget's Disease of Bone: A Case Report

Paget’s disease of bone (PDB) is a progressive bone disorder characterized by increased osteoclast-mediated bone resorption and abnormal bone formation. Incomplete atypical femoral fracture, appearing radiographically as a stress fracture at the lateral aspect of the femur, is an uncommon low-trauma fracture frequently seen in association with long-term bisphosphonate therapy. We describe the case of a 61-year-old female patient with PDB who developed a stress fracture at the lateral femoral cortex after 5 doses of intravenous bisphosphonate. The conservative treatment plan included discontinuation of bisphosphonate, a continuation of calcium and vitamin D supplementation, and limited weight-bearing for 3 months. The patient’s pain level gradually improved after switching to the new treatment plan. At the latest follow-up, approximately 5 years after the initiation of conservative treatment, the patient remained pain-free, and her PDB was well-controlled. However, the fracture line was still visible on the most recent radiograph. Although it remains unclear whether a stress fracture at the lateral femoral cortex occurred due to bisphosphonate therapy or PDB, this case highlights the importance of careful evaluation of any lesion that appears in PDB patients receiving bisphosphonate therapy.

Pelvic Insufficiency Fractures in Cervical Cancer After Radiation Therapy: A Meta-Analysis and Review

AIM

The aim of the study was to estimate the prevalence of pelvic insufficiency fractures (PIFs) after radiation therapy (RT) in patients with cervical cancer.

PATIENTS AND METHODS

A total of 3,633 patients from 15 cohort studies were included. Proportion meta-analysis was performed to estimate prevalence and subgroup analysis was performed according to imaging modalities for diagnosis of PIF. For continuous variables (age and length of follow-up), meta-regression analysis was performed.

RESULTS

Pooled prevalence estimate of PIF was 14% (95% CI=10-19). Incidence of PIF was higher in studies that used MRI as a diagnostic tool (17%, 95% CI=12-22) than non-MRI (8%, 95% CI=2-14). In meta-regression, we found a significant association of prevalence of PIF with age (p=0.021) but not with length of follow-up (p=0.118).

CONCLUSION

PIF after RT in patients with cervical cancer is not rare. Physicians need to pay attention to PIFs, especially in patients with high-risk factors for osteoporotic fracture.

Bisphosphonates, Old Friends of Bones and New Trends in Clinics

Bisphosphonates, used for a long time in osteoporosis management, are currently the target of intensive research, from pre-formulation studies to more advanced stages of clinical practice. This review presents an overview of the contributions of this family of compounds to human health, starting with the chemistry and clinical uses of bisphosphonates. Following this, their pharmacology is described, highlighting administration-borne handicaps and undesirable effects. The last three sections of the review describe the research efforts that seek to curb delivery-related issues and expand bisphosphonate use. Innovative routes and strategies of administration, such as nano-encapsulation for oral intake or injectable cements for local or in-bone delivery are presented, as well as the latest results of case studies or preclinical studies proposing new therapeutic indications for the clinically approved bisphosphonates. Finally, a selection of anti-infectious bisphosphonate new drug candidates is shown, with focus on the molecules reported in the last two decades.

Paget's Disease of Bone Affecting Peripheral Limb: Difficulties in Diagnosis: A Case Report

In terms of management of Paget's disease of bone (PDB), early diagnosis and proper management achieving remission is essential with lifelong specialist follow-up. We present the case of a 40-year-old woman with PDB affecting mainly the distal extremities (ankle and wrist). The patient visited our hospital in 2012 with heel pain. Plain radiography revealed osteoporosis, and a bone scan revealed hot uptake. Initial laboratory investigations showed normal serum calcium, 25-hydroxy-vitamin D, and parathyroid hormone levels; however, osteocalcin, C-terminal telopeptide of type I collagen, and bone alkaline phosphatase levels were elevated. A bone mineral density scan showed T- and Z-scores of −2.5 and −2.7, respectively, and bisphosphonate treatment was initiated. Biopsy performed on the calcaneal lateral wall revealed inconclusive findings. Follow-up biopsy on the left distal radius was performed 7 years later to investigate wrist pain, and this examination led to a final diagnosis as PDB. We suggest inconclusive biopsy result during the early phase of PDB and highly recommend follow-up evaluation in osteoporosis with atypical behavior.

Paget's Disease of Bone: Diagnosis and Treatment

Paget's disease of bone is a common bone disorder characterized by disorganized bone remodeling. The most likely etiology is a slow paramyxoviral infection in genetically susceptible individuals; however, the exact cause is unknown. Enhanced bone resorption due to an increased activity of osteoclasts recruits numerous osteoblasts to resorption sites, with large quantities of new bone matrix produced as a result. The accelerated bone resorption and formation are not as closely coupled as in a healthy bone; a disorganized bone tissue is formed. Many patients are asymptomatic; rising serum alkaline phosphatase or incidental finding of characteristic radiographic lesions are often the only diagnostic clues. Common clinical manifestations include bone pain, bowing of long bones, enlarged skull, and hearing loss. An elevated serum alkaline phosphatase level correlates with the disease activity. The diagnosis is confirmed by characteristic radiographic findings and by nuclear scintigraphy of the bone (the most sensitive test). Bisphosphonates, such as zoledronic acid, pamidronate, alendronate, and risedronate, are the mainstay of treatment. Patients who do not tolerate bisphosphonates can be treated with calcitonin.

Atypical femur fracture in a woman with osteogenesis imperfecta and multiple myeloma

Use of intravenous bisphosphonates has been demonstrated to improve clinical outcomes in children with osteogenesis imperfecta (OI). However, efficacy and safety of bisphosphonates in adults with OI remains unclear. Atypical femur fractures (AFF) are rare insufficiency fractures associated with long-term bisphosphonate use. We report on a 56 year old woman with OI type 1 and long-term bisphosphonate use who was diagnosed with multiple myeloma (MM) following a severe vertebral fracture. During workup, an asymptomatic incomplete AFF of the left femur diaphysis was noted. Multiple factors may have contributed to the occurrence of AFF, including bisphosphonate exposure, bowing of the proximal femur, as well as the intrinsic collagen defect of OI. To reduce the risk of skeletal complications from MM, intravenous pamidronate was administered in addition to chemotherapy, though in reduced dose and frequency. Orthopedic consultant recommended against prophylactic surgery for the AFF. Follow-up radiograph showed no progression of the AFF, though delayed healing was present. This case highlights the importance of close monitoring of patients on long-term bisphosphonate therapy who have additional risk factors for developing AFF, such as underlying genetic bone disorders or lower limb deformities. A multidisciplinary approach is recommended for optimal management of such complex patients.

The Effects of Systemic Therapy of PEGylated NEL-Like Protein 1 (NELL-1) on Fracture Healing in Mice

Fractures are common, with an incidence of 13.7 per 1000 adults annually. Systemic agents have been widely used for enhancing bone regeneration; however, the efficacy of these therapeutics for the management and prevention of fracture remains unclear. NEL-like protein 1 (NELL-1) is a potent pro-osteogenic cytokine that has been modified with polyethylene glycol (PEG)ylation [PEGylated NELL-1 (NELL-PEG)] to enhance its pharmacokinetics for systemic therapy. Our aim was to investigate the effects of systemic administration of NELL-PEG on fracture healing in mice and on overall bone properties in uninjured bones. Ten-week-old CD-1 mice were subjected to an open osteotomy of bilateral radii and treated with weekly injections of NELL-PEG or PEG phosphate-buffered saline as control. Systemic injection of NELL-PEG resulted in improved bone mineral density of the fracture site and accelerated callus union. After 4 weeks of treatment, mice treated with NELL-PEG exhibited substantially enhanced callus volume, callus mineralization, and biomechanical properties. NELL-PEG injection significantly augmented bone regeneration, as confirmed by high expression of bone turnover rate, bone formation rate, and mineral apposition rate. Consistently, the immunohistochemistry results also confirmed a high bone remodeling activity in the NELL-PEG-treated group. Our findings suggest that weekly injection of NELL-PEG may have the clinical potential to accelerate fracture union and enhance overall bone properties, which may help prevent subsequent fractures.