The viral etiology of Paget's disease of bone: a new perspective

Paget's disease of bone and quality of life

Little is known about how Paget's disease of bone affects quality of life. To better understand the relative impact of factors on quality of life, we mailed a brief survey to 2000 people randomly selected from the Paget's Foundation mailing list. The sample was geographically stratified to examine the effects of specialist availability. Nine hundred and fifty-eight persons responded to the questionnaire (53% response rate after adjustment for death, incorrect addresses, and nondeliverable mailings). The sample had equal proportions of males and females, with a mean age of 74 years (SD = 9.0). Most (97%) were white, with high levels of education (mean 13 years; SD 3.7) and income (60% earned more than $20,000 annually). They reported pagetic bone in the skull (34%), spine (35%), pelvis (49%), and leg (48%). The most frequently mentioned complications were hearing loss (37%) and bowed limbs (31%). Comorbidity included arthritis (64%), hypertension (32%), and heart problems (28%). Nearly half (47%) reported feelings of depression, and 42% said that their health was fair or poor. Only 21% reported that quality of life was very good or excellent. In multiple partial F-test regression analyses, variables were divided into four domains (social, psychological, care, and biomedical). The psychological domain explained 19% of the variance beyond that explained by all other variables; the social domain explained 3%, the biomedical domain explained 3% and the care domain explained 1%. The importance of the psychological aspects of Paget's disease suggests that treatment protocols should include psychological intervention to improve quality of life.

Viral behavior of paracrystalline inclusions in osteoclasts of Paget's disease of bone

Fresh tissues from six patients with Paget's disease of bone were examined ultrastructurally to investigate whether the characteristic paracrystalline inclusions in pagetic osteoclasts revealed viral behavior. These inclusions appeared as microfilamentous aggregates in both nuclei and cytoplasm of the osteoclasts in all six cases. The filamentous elements of the inclusions with a diameter of 11-15 nm showed tubular structures with a central electron-lucent zone measuring 5-7 nm in diameter. Viral budding-like structures containing these inclusions were found at the peripheral cytoplasm or cell processes in the ruffled border of some pagetic osteoclasts in two cases. The inclusions in the budding-like structures were often arrayed in a parallel fashion on the cytoplasmic side of the cell membranes of extruded cytoplasm or cell processes. Virion-like particles were also found in the extracellular spaces of the ruffled border. Marked nuclear degeneration was often seen in pagetic osteoclasts of three cases, although other nuclei in the same osteoclasts appeared normal. The degenerated nuclei showed nuclear ring formation where destroyed nuclear membranes were seen and disappearance of nuclear matrices was noted. Since the modifications were always associated with the accumulation of abundant inclusions, they were probably caused by the inclusions. These findings suggested that the inclusions showed viral behavior in pagetic osteoclasts, and that the nuclear modifications were caused by virus infection.

Canine bone marrow cell cultures infected with canine distemper virus: an in vitro model of Paget's disease

We have previously shown that the canine paramyxovirus, canine distemper virus (CDV), is a possible aetiologic agent in Paget's disease of bone and in the canine bone disorder, metaphyseal osteopathy. More recently, we have examined the effects of CDV on the formation of multinucleated, tartrate resistant acid phosphatase positive, calcitonin receptor positive, osteoclast-like cells in cultures of canine bone marrow mononuclear cells, and shown that both in vitro and in vivo infection with CDV produced a dose dependent increase in the number and size of osteoclast-like cells. We have now extended these results to show that CDV infection induces interleukin-6 and c-Fos mRNA in these cells, similar to our recent findings in pagetic bone cells. These results further support the hypothesis that CDV might be involved in the aetiopathogenesis of Paget's disease and metaphyseal osteopathy and suggest that canine marrow culture systems will prove useful as an in vitro model to examine the disease processes in more detail.

Generation of multinucleated osteoclast-like cells from canine bone marrow: effects of canine distemper virus

Recent evidence has implicated canine distemper virus (CDV) as a possible aetiologic agent in Paget's disease of bone and the canine bone disorder, metaphyseal osteopathy. We have therefore examined the effects of CDV on the formation of multinucleated osteoclast-like cells in cultures of canine bone marrow mononuclear cells. Marrow cells from a distemper-infected dog and from five uninfected dogs were cultured in the presence of 1 alpha, 25-(OH)2 vitamin D3 and the number of tartrate resistant acid phosphatase positive multinucleated cells (MNCs) was determined. The presence of calcitonin (CT) receptors was confirmed by autoradiography with 125I-labeled human CT. Cultures from the distemper-infected dog contained a higher level of MNCs than those from the normal dogs. The in vitro addition of CDV to the cultures from all the dogs produced a dose-dependent increase in the number of MNCs, and an increase in size of these cells in the cultures from the infected dog. Cells infected with CDV were hyperresponsive to 1 alpha,25-(OH)2 vitamin D3. The presence of the virus in the relevant samples was confirmed using molecular techniques. In situ hybridization studies also revealed a significant increase in the level of infection following in vitro addition of the virus to the culture from the distemper-infected dog, suggesting that further infection had taken place. Resorption pits were formed on bone slices, although the number of pits was not significantly altered by viral infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Mandibular deformity associated with Paget's disease. Case report

Paget's disease (osteitis deformans) and osteoporosis represent the commonest systemic bone disorders. Clinically Paget's disease may be mono-, or polyostotic, and is characterized by excessive and disorganized formation and resorption of bone. It may affect any of the facial bones, most notably the skull and the jaws. A case is described in which the only symptomatic manifestation of Paget's disease was mandibular prognathism. The pathogenesis, aetiology, and management are discussed.

Paget's disease of bone: current concepts in pathogenesis and treatment

Recent advances have been made in understanding the aetiology, diagnosis and treatment of Paget's disease of bone (osteitis deformans). The role of viruses in the pathogenesis of the disease has been extensively investigated, although no causative link has yet been demonstrated between infective agents and Paget's disease. Recent advances in the diagnosis of the disease have been made with increasing usage of radionucleotide imaging to determine the extent and distribution of the lesions. Treatment options have been extended with the emergence of the biphosphonates as potential main line therapeutic agents.

Drugs used in the treatment of metabolic bone disease. Clinical pharmacology and therapeutic use

Osteoporosis is the most important metabolic bone disease and places an increasing burden on the healthcare system. The condition can be prevented by the early introduction of hormone replacement therapy. The role of bisphosphonates in achieving the same result is being actively explored. The attraction of preventing bone loss is that it preserves the micro-architecture of bone, and therefore its mechanical integrity. The great problem of treating the established condition is that substantial bone loss is accompanied by architectural disintegration. Replacing lost bone may not necessarily restore mechanical integrity and protect against fractures. The management of Paget's disease has been quite revolutionised by the introduction of the bisphosphonates. The condition is a result of a primary increase in osteoclastic bone resorption which can be corrected by bisphosphonates, with considerable symptomatic improvement. The increasing potency and safety margin of the newer agents has meant that the threshold for treatment has fallen. There is now potential for long term control of bone turnover with the hope of preventing late complications. Hypercalcaemia of malignancy is usually the result of both increased bone destruction and decreased urinary calcium excretion. These two components of hypercalcaemia demand different approaches to management. The general availability of an ever-expanding range of increasingly potent bisphosphonates has resulted in a dramatic improvement in the treatment of increased bone resorption associated with malignancy. Many types of tumour, either directly or indirectly, compromise the ability of the kidney to eliminate a calcium load derived from increased bone destruction. Calcitonin is the only agent which is currently available to counter this process.

Extracellular protein secretion of cultured normal and Pagetic osteoblasts

Two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) has been used to map the extracellular secretory activity of normal osteoblasts. The proteins osteonectin, bone sialoprotein, and both the C-telopeptide of collagen I together with collagen I have now been positionally identified. In addition the secretory differences which exist between normal and Pagetic osteoblasts have been mapped with the Pagetic osteoblasts shown to consistently secrete an altered 30 kDa C-telopeptide of collagen type I. The use of the diphosphonate Pamidronate in the treatment of Paget's disease of bone has beneficial effects with suppression of the bone isoenzyme marker alkaline phosphatase. It has been reported that diphosphonates directly inhibit human osteoblast secretory function as well as osteoclast metabolism. The effects of Pamidronate on the secretory activity of normal and Pagetic osteoblast cultures was also investigated. The extracellular protein secretion of normal and Pagetic osteoblasts was not affected by Pamidronate treatment as assessed by 2-D PAGE. This technique allows a comprehensive multiparameter assessment of extracellular secretory activity in normal and diseased states. The findings show that the Pagetic osteoblasts cultured in vitro are functionally abnormal and they support the hypothesis that the underlying problem in Paget's disease is characterised by disorder of osteoblast and osteoclast interactions.

Paramyxovirus-like nuclear inclusions identical to those of Paget's disease of bone detected in giant cells of primary oxalosis

Nuclear inclusions, identical to those characteristic of Paget's disease of bone, were observed in giant cells in four of eight cases of primary oxalosis. The giant cells containing nuclear inclusions were directly involved in phagocytosis of large oxalate crystals in the context of typical foreign body granulomas in the bone marrow. Cytochemically, all of them exhibited strong tartrate-resistant acid phosphatase activity, and a proportion of them also tartrate-resistant acid ATPase. The inclusions consisted of typical arrays of filamentous material as described in Paget's disease, admixed with variable proportions of electron-dense material closely reminiscent of nucleolar pars fibrillaris and fibrillary centres. These data indicate: (a) the occurrence of Paget-like inclusions in a bone disease unrelated to Paget's disease, not causally related to viral infection, and resulting from an inborn metabolic derangement; and (b) the occurrence of Paget-like inclusions in foreign body giant cells as opposed to osteoclasts. We suggest that the occurrence of paramyxovirus-like nuclear inclusions in either osteoclasts or giant cells may represent an epiphenomenon of cell fusion and giant cell formation whenever appropriate stimuli act on latently infected precursor cells. Furthermore, our data suggest that nucleoli may represent the specific site of virus-like inclusion formation.