Long-term management and outcome of parathyroidectomy for sporadic primary multiple-gland disease.

HYPOTHESIS: For a specific subset of patients with sporadic primary multiple-gland parathyroid disease, subtotal parathyroidectomy results in long-term normocalcemia in the majority of patients, with a minimal complication rate. DESIGN: Retrospective analysis of outcomes in patients undergoing parathyroidectomy performed by a single surgeon (A.E.G.) between 1984 and 1999. SETTING: A multidisciplinary endocrine service based at a tertiary referral center. PATIENTS: Patients undergoing subtotal parathyroidectomy for primary hyperparathyroidism due to sporadic multiple-gland disease identified from a single surgeon's operative records (A.E.G.). MAIN OUTCOME MEASURES: Data analyzed included demographic factors, operative and pathologic findings, and postoperative and long-term clinical and laboratory results, including calcium and intact parathyroid hormone levels. RESULTS: Of 379 patients undergoing parathyroidectomy for hyperparathyroidism between 1984 and 1999, 49 (13%) had sporadic multiple-gland disease. Median preoperative calcium and intact parathyroid hormone (iPTH) levels were 2.7 mmol/L (10.8 mg/dL) and 11.79 pmol/L, respectively. Postoperative calcium and iPTH levels were available in 39 patients, and median values were 2.28 mmol/L (9.1 mg/dL) and 2.84 pmol/L, respectively. Long-term follow-up was available for 36 patients (73%), and duration ranged from 6 to 180 months (median, 44 months). Median calcium and iPTH levels at follow-up were 2.3 mmol/L (9.2 mg/dL) and 3.26 pmol/L, respectively, with 3 (8%) of 36 patients having evidence of persistent or recurrent hyperparathyroidism. No patient had biochemical evidence of hypoparathyroidism at long-term follow-up. Five patients (14%) had persistent elevated iPTH levels (range, 8.11-10.95 pmol/L) and normal calcium levels. CONCLUSIONS: Subtotal parathyroidectomy for sporadic primary multiple-gland disease resulted in a long-term normocalcemia rate of 92%, with minimal complications. Selective subtotal parathyroidectomy can yield excellent long-term results in patients with multiple-gland disease.

Bisphosphonate treatment inhibits the growth of prostate cancer cells.

The presence of skeletal metastases in patients suffering from cancer leads to a variety of clinical complications. Bisphosphonates are a class of drugs with a potent bone resorption inhibition activity that have found increasing utility in treating and managing patients with metastatic bone disease. Several clinical trials have demonstrated that bisphosphonates have clinical value in the treatment and management of skeletal metastases derived from advanced prostate cancer. Currently, the mechanism(s) through which bisphosphonates exert their activity is only beginning to be understood. We have studied the effects of bisphosphonate treatment on the growth of prostate cancer cell lines in vitro. Treatment of PC3, DU145, and LNCaP cells with pamidronate or zoledronate significantly reduced the growth of all three cell lines. Using flow cytometry, pamidronate treatment (100 microM) was shown to induce significant amounts of cell death in all three cell lines studied. In contrast, treatment with zoledronate (100 microM) did not induce cell death, instead exerting dramatic effects on cell proliferation, as evidenced by a major increase in cells present in the G0-G1 and S phase. Although both drugs reduced prostate cancer cell growth in the presence of serum, zoledronate was more potent under these conditions, disrupting growth at doses as low as 25 microM in the presence of 5% fetal bovine serum. These results raise the intriguing possibility that the observed clinical utility of bisphosphonates in managing skeletal metastases may in part derive from direct inhibition of prostate cancer cell growth in the bone microenvironment.

Enhanced RANK ligand expression and responsivity of bone marrow cells in Paget's disease of bone.

Paget's disease is characterized by highly localized areas of increased osteoclast (OCL) activity. This suggests that the microenvironment in pagetic lesions is highly osteoclastogenic, or that OCL precursors in these lesions are hyperresponsive to osteoclastogenic factors (or both). To examine these possibilities, we compared RANK ligand (RANKL) mRNA expression in a marrow stromal cell line developed from a pagetic lesion (PSV10) with that in a normal stromal cell line (Saka), and expression in marrow samples from affected bones of Paget's patients with that in normal marrow. RANKL mRNA was increased in PSV10 cells and pagetic marrow compared with Saka cells and normal marrow, and was also increased in marrow from affected bones compared with uninvolved bones from Paget's patients. Furthermore, pagetic marrow cells formed OCLs at much lower RANKL concentrations than did normal marrow. Anti-IL-6 decreased the RANKL responsivity of pagetic marrow to normal levels, whereas addition of IL-6 to normal marrow enhanced RANKL responsivity. Thus, RANKL expression and responsivity is increased in pagetic lesions, in part mediated by IL-6. These data suggest that the combination of enhanced expression of RANKL in affected bones and increased RANKL sensitivity of pagetic OCL precursors may contribute to the elevated numbers of OCLs in Paget's disease.

Cell biology of Paget's disease.

Paget's disease is characterized by markedly increased osteoclast formation and bone resorption followed by excessive new bone formation. Osteoclasts in Paget's disease are increased both in number and size, contain paramyxoviral-like nuclear inclusions, and can have up to 100 nuclei per cell. Marrow culture studies have identified several abnormalities in osteoclast formation in Paget's disease. Osteoclast-like multinucleated cells formed more rapidly in marrow cultures from patients with Paget's disease, produced increased levels of interleukin-6 (IL-6), and expressed high levels of IL-6 receptors compared to normals. IL-6 levels were also increased in bone marrow and peripheral blood of patients with Paget's disease. In addition, osteoclast precursors from patients with Paget's disease are hyperresponsive to 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and calcitonin. The increased sensitivity of osteoclast precursors to 1,25(OH)2D3 is mediated through the vitamin D receptor (VDR), since 24-hydroxylase activity is also up-regulated at concentrations of 1,25(OH)2D3 that are one log less than that needed to induce 24-hydroxylase activity in osteoclast precursors from normals. However, VDR numbers and affinity for 1,25(OH)2D3 do not differ in osteoclast precursors from Paget's patients compared to those from normals. Synergistic interactions between cytokines such as IL-6 and 1,25(OH)2D3 also cannot explain the enhanced sensitivity of osteoclast precursors from patients with Paget's disease to 1,25(OH)2D3. Interestingly, coculture studies of osteoclast precursors and cells from the marrow microenvironment of patients with Paget's disease and normals have demonstrated that the marrow microenvironment is more osteoclastogenic than normal. Thus, studies of the cell biology of osteoclasts in Paget's disease have demonstrated an increased rate of osteoclast formation and abnormalities in both osteoclast precursors and the marrow microenvironment. Enhanced IL-6 production by osteoclasts in Paget's disease may further amplify the increased osteoclast formation already ongoing in the pagetic lesion, and may explain the increased bone turnover at uninvolved sites distant from the pagetic lesion.

Measles virus nucleocapsid transcript expression is not restricted to the osteoclast lineage in patients with Paget's disease of bone.

Abundant evidence supports a viral etiology for Paget's disease of bone (PD), however, an infectious virus has not been isolated from PD patients. Thus, it is unclear how the virus is maintained for the many years that the disease persists in patients. We considered if a primitive multipotential hematopoietic stem cell (HSC), which is self-renewing, passes the virus to its differentiated progeny and serves as a reservoir for the pathogen. If a primitive stem cell harbored measles virus (MV), then other hematopoietic lineages derived from this stem cell in PD patients should also express MV transcripts. Therefore, because the human hematopoietic stem cell has not been clearly identified or isolated in large numbers, we isolated RNA from highly purified erythroid and multipotential hematopoietic progenitors that are the precursors for erythroid, granulocyte, megakaryocyte and macrophages (CFU-GEMM), and used RT-PCR to determine if MV nucleocapsid transcripts were present. MV transcripts were detected in PD patients in early erythroid (BFU-E) and more primitive multipotential myeloid progenitors (CFU-GEMM). Nonhematopoietic stromal cells from PD patients did not express MV transcripts. The expression of MV transcripts in erythroid progenitors was further confirmed by in situ hybridization using antisense riboprobes to MV nucleocapsid transcripts. Thus, our findings suggest that the pluripotent HSCs may be a potential reservoir for the virus. We propose that when HSCs, which contain MV, divide they produce a second HSC that serves as a reservoir for the virus and also transmit the virus to their more differentiated progeny in the erythroid and myeloid lineages. This mechanism would permit a defective virus to persist in HSCs of PD patients for many years, since HSCs are usually in G0 phase, and then be transmitted to more differentiated cells. This model further suggests that a mature complete virus that affects cell function could only act pathogenetically in the osteoclast lineage, which offers a permissive milieu.

In vivo morphologic changes in the rat osteoclast induced by gallium nitrate: the result of toxicity or other effects?

Gallium nitrate, an approved antitumor drug, has found clinical application in the treatment of cancer-related hypercalcemia and of Paget's disease; the exact mechanism of its action, however, remains unknown. The present study utilized rats in a 7-day exposure to gallium at doses similar to those used clinically. Quantitative histomorphometry and ultrastructural examination of osteoclast fine structure were carried out on specimens from animals with documented hypocalcemia. Gallium exposure produced striking changes in the osteoclast. The number of nuclei/osteoclast increased, and the ruffled borders of the osteoclasts were markedly decreased along the length of the Howship's lacunar cavity. The absence of a decrease in osteoclast number and the types of changes seen in ultrastructure suggest that the mechanism of action of gallium seen here may differ from that of calcitonin, a nontoxic, reversible antiresorbing agent. Results underscore the difficulty in assessing the toxicity of agents such as gallium on the osteoclast, a mature differentiated cell which does not divide and which does not produce a characteristic extracellular matrix component.

Evidence for a novel osteosarcoma tumor-suppressor gene in the chromosome 18 region genetically linked with Paget disease of bone.

Paget disease of bone, or "osteitis deformans," is a bone disorder characterized by rapid bone remodeling resulting in abnormal bone formation. It is the second most common metabolic bone disease after osteoporosis, affecting 3%-5% of subjects aged >40 years. Recent evidence suggests that predisposition to Paget disease may have a genetic component. Genetic linkage analysis of families with multigenerational Paget disease shows linkage to a region of chromosome 18q near the polymorphic locus D18S42. Approximately 1% of Paget patients develop osteosarcoma, which represents an increase in risk that is several thousandfold over that of the general population. Osteosarcoma in Paget patients is the underlying basis for a significant fraction of osteosarcomas occurring after age 60 years. Our analysis of tumor-specific loss of constitutional heterozygosity (LOH) in 96 sporadic osteosarcomas has identified a putative tumor-suppressor locus that maps to chromosome 18q. We have localized this tumor-suppressor locus between D18S60 and D18S42, a region tightly linked to familial Paget disease. Analysis of osteosarcomas from patients with Paget disease revealed that these tumors also undergo LOH in this region. These findings suggest that the association between Paget disease and osteosarcoma is the result of a single gene or two tightly linked genes on chromosome 18.

Pagetic osteoclasts formed in vitro: absence of paracrystalline inclusions.

In Paget's disease of bone, osteoclasts are increased in number and size and contain intracellular paramyxoviral-like inclusions which cross-react with antibody against measles, respiratory syncytial, and canine distemper viral nucleocapsid antigens. Moreover, measles virus nucleocapsid transcripts are present in pagetic osteoclasts and their mononuclear precursors formed in vitro. The present study was undertaken to morphologically assess pagetic osteoclasts formed in culture; special attention has been directed towards the ultrastructural identification of nuclear and cytoplasmic inclusions. Pagetic osteoclasts were produced in long-term cultures of non-adherent bone marrow mononuclear cells derived from involved bone of patients with Paget's disease. These cultured osteoclasts had many of the ultrastructural features of pagetic osteoclasts in vivo. Of interest, no viral-like inclusions were observed in either the multinucleated osteoclasts or mononuclear cell precursors in these cultures. These data suggest that other factors in the bone microenvironment are required for viral nucleocapsid formation in pagetic osteoclasts.

Evidence that serum NTx (collagen-type I N-telopeptides) can act as an immunochemical marker of bone resorption.

Previous studies have shown that immunoassay of urinary NTx (cross-linked N-telopeptides of type I collagen) provides a responsive index of human bone resorption. Here we report by a sensitive immunoassay that NTx is present in serum and is suppressed appropriately in patients with Paget disease of bone by bisphosphonate antiresorptive therapy. The monoclonal antibody (1H11) developed against urinary NTx was applied in a sensitive chemiluminescence format. Results for human serum and urine showed parallel inhibition curves. The NTx concentrations in paired serum and urine samples from individual patients correlated well when urinary concentrations were normalized to creatinine concentrations (in premenopausal and postmenopausal women and Paget disease patients, r = 0.90, n = 60). The percentage of NTx suppression from baseline values for Paget disease patients on bisphosphonate therapy was similar for serum and urine. Blood samples drawn from bone marrow at the site of Pagetic lesions in three patients with active disease had as much as 10-fold higher concentrations of NTx than did peripheral blood samples drawn at the same time. The latter finding is consistent with other evidence showing that immunoreactive NTx originates directly during the proteolytic cleavage of bone collagen by osteoclasts rather than, e.g., by degradative processes occurring later in the liver and kidney.

Detection of measles virus nucleocapsid transcripts in circulating blood cells from patients with Paget disease.

Paget disease of bone is characterized by abnormalities in all phases of bone remodeling, but the fundamental cellular abnormality resides in the osteoclast (OCL). Osteoclasts in bone involved by Paget disease contain viral-like nuclear and cytoplasmic inclusions that react with antibodies directed against paramyxovirus nucleocapsid proteins, such as measles virus, respiratory syncytial virus, or canine distemper virus. However, the identity of the virus or the mechanisms responsible for its persistence or pathologic role in Paget disease is unclear. Furthermore, although Paget disease persists for many years, it remains a highly localized process with new lesions rarely if ever developing in previously unaffected bones. Since osteoclasts are formed by fusion of mononuclear precursors derived from colony forming unit-granulocyte macrophage (CFU-GM), the granulocyte-macrophage progenitor, we used reverse transcriptase polymerase chain reaction (RT-PCR) analysis to determine if CFU-GM, more differentiated osteoclast precursors, and peripheral blood cells derived from CFU-GM express measles virus nucleocapsid (MV-N) transcripts. We found that osteoclast precursors, as well as peripheral blood mononuclear cells, express MV transcripts in 9 of 13 patients. Sequence analysis of the PCR amplified products confirmed nucleotide identity of MV-N transcripts expressed in peripheral blood and bone marrow-derived cells from the same patient. In contrast, MV-N transcripts were not detected in OCL precursors or the peripheral blood from 10 normal subjects. In situ hybridization studies using 35S-labeled antisense riboprobes to MV-N transcripts further confirmed the expression of MV transcripts in these cells. Sequence analysis of the PCR amplified product from one of these patients also identified a novel mutation that converted lysine441 to glutamic acid441 in the MV-N transcript. These data demonstrate that OCL precursors and circulating peripheral blood cells also express MV transcripts in patients with Paget disease and suggest that the pagetic marrow microenvironment plays a critical role in maintaining the highly localized nature of the lesions in Paget disease.

Bone marrow mononuclear cells from patients with Paget's disease contain measles virus nucleocapsid messenger ribonucleic acid that has mutations in a specific region of the sequence.

Ultrastructural, immunocytochemical, and in situ hybridization studies have suggested that paramyxoviruses, such as measles virus (MV), are present in Pagetic osteoclasts and may contribute to the abnormality in osteoclast function. However, little additional information is known about potential viruses present in Pagetic osteoclasts. As there are increased numbers of osteoclast precursors among the marrow mononuclear cells of Paget's patients, we used the reverse transcriptase-polymerase chain reaction to amplify the nucleocapsid sequence of MV from freshly isolated bone marrow-derived mononuclear cells to examine the potential role of these viruses in cells in the osteoclast lineage. We detected MV nucleocapsid transcripts in 5 of 6 individual Paget's patients' marrow samples. MV transcripts were not detected in marrow samples from 10 normal subjects. Sequence analysis of the PCR products revealed that 1 patient had the same sequence as the Edmonston strain of MV. The remaining 4 patients had point mutations clustered between position 1360-1371 base pairs. Two of the patients exhibited identical mutations at this region. In total, 3 different point mutations were identified that resulted in amino acid substitutions. These data show that 1) unlike those from normal subjects, marrow mononuclear cells from Paget's patients express MV nucleocapsid messenger ribonucleic acid; and 2) mutations of a specific region of the MV nucleocapsid gene were present in 4 of 5 patients and suggest a persistent MV infection in Pagetic osteoclast precursors. These data further suggest that osteoclasts are infected by fusion with infected precursors.

Bisphosphonates in the treatment of disorders of mineral metabolism.

Bisphosphonates are analogues of inorganic pyrophosphate, a naturally occurring chemical in bone. In vitro and animal experiments demonstrated that these agents were effective inhibitors of bone resorption. Subsequently they were applied to a variety of clinical problems in which increased bone resorption was an underlying feature of the pathology. In 1971 etidronate became the first bisphosphonate shown to inhibit bone resorption in humans when it was given to patients with Paget's disease. Subsequently this agent was also found to be useful in treating the hypercalcemia of malignancy. At the present time cyclic etidronate therapy is also used for the prevention of bone loss in patients with osteoporosis and for the prevention of heterotopic ossification in spinal cord-injured patients and in patients after hip replacement. Newer bisphosphonates are generally more potent than etidronate and do not produce a severe mineralization defect as do higher doses of etidronate. Pamidronate and clodronate are highly effective in the management of Paget's disease, hypercalcemia due to malignancy and immobilization, metastatic bone disease, and hematologic malignancies affecting bone. They are also promising agents for the prevention of osteoporosis. Alendronate, risedronate, and CGP 42446 are highly potent bisphosphonates that look very promising for the treatment of all disorders of bone resorption. It is fortunate that adverse reactions are not a prominent feature of bisphosphonate use. The main side effects are nausea and abdominal discomfort, mainly with oral use, a transient increase in bone pain in patients with Paget's disease, and an acute-phase reaction (fever, myalgia, mild leukopenia) in patients receiving aminobisphosphonates. The evolution of bisphosphonate therapy should be considered one of the major therapeutic events of the past 25 years. Future research should define the optimum use of these agents.

Multinucleated cells formed in vitro from Paget's bone marrow express viral antigens.

Paget's disease of bone is characterized by large numbers of osteoclasts that have viral-like nuclear and/or cytoplasmic inclusions. Pagetic osteoclasts express respiratory syncytial viral (RSV) and measles viral (MV) nucleocapsid antigens. The data suggest a possible viral etiology for Paget's disease. However, studies to characterize further the putative viral inclusions in Paget's osteoclasts have been severely hampered by the extreme difficulty in isolating large numbers of osteoclasts from pagetic bone. The recent demonstration that osteoclast-like multinucleated cells (MNC), that had certain characteristics of pagetic osteoclasts formed in marrow cultures from Paget's patients, may permit studies to describe this virus further. Therefore, we have cultured marrow samples from involved and uninvolved bones from Paget's patients and from normal subjects to determine if the MNC formed in these cultures express viral antigens. RSV and/or MV antigens were expressed in the mononuclear cells and/or the MNC formed in 12 of 12 marrow cultures from active lesions of patients with Paget's disease, with 40-50% of the cells expressing viral antigens. In contrast, less than 5% of cells isolated from cultures from normal subjects expressed RSV and/or MV. These results suggest that MNC formed in long-term marrow cultures from patients with Paget's disease frequently express paramyxoviral antigens and are very similar to pagetic osteoclasts. Thus, these marrow cultures may be useful for further characterizing the virus in Paget's disease.

Abnormalities in osteoclast precursors and marrow accessory cells in Paget's disease.

Paget's disease of bone is characterized by increased numbers of abnormal osteoclasts. To determine if osteoclast precursors were increased or abnormal in this disease, we examined CFU-GM, the committed granulocyte-macrophage progenitor and the most likely precursor for osteoclasts. In cultures of unfractionated marrow mononuclear cells, CFU-GM colony formation was significantly increased in Paget's marrow cultures compared to that in normal cells (356 +/- 44 vs. 271 +/- 15/10(5) cells; P < 0.05). However, when we enriched hematopoietic precursors from Paget's and normal marrow samples using an antibody that recognizes the CD34 antigen present on most hematopoietic precursors, we found that similar numbers of CFU-GM colonies were formed (87 +/- 13/10(4) cells plated vs. 83 +/- 13). Coculture experiments with highly purified hematopoietic precursors (CD34+ cells) and nonhematopoietic marrow accessory cells (CD34- cells) revealed that the growth of Paget's precursors was significantly enhanced above expected levels by normal or Pagetic CD34- cells (P < 0.05). CFU-GM colony formation was also significantly enhanced when normal CD34+ cells were cocultured with Pagetic, but not with normal, CD34- cells. In addition, CFU-GM colony-derived cells from Paget's patients were hyperresponsive to 1,25-dihydroxyvitamin D3 and could form osteoclast-like multinucleated cells with 1,25-dihydroxyvitamin D3 concentrations one tenth of that required for normal multinucleated formation (10(-11) vs. 10(-10) M). These data suggest that osteoclast precursors may be abnormal in Paget's disease, and other cells in the Pagetic marrow microenvironment may further enhance the growth and differentiation of these abnormal precursors.

Giant cell tumor arising in Paget's disease of bone. Recurrences after 36 years.

A 96-year-old woman had both Paget's disease and a giant cell tumor of the same bone, the left scapula. Despite five surgical procedures, a full course of radiation therapy, and treatment with salmon calcitonin, human calcitonin, and finally disodium etidronate, the tumor has recurred over a 36-year period. The characteristic viral-like nuclear and cytoplasmic inclusions found in the osteoclasts of Paget's disease were found in the tumor giant cells, in specimens excised over an eight-year period, and in specimens obtained during orthopedic procedures on her other pagetic bone lesions over 12 years.

A specific immunoassay for monitoring human bone resorption: quantitation of type I collagen cross-linked N-telopeptides in urine.

Peptides of low molecular weight that contain pyridinoline cross-links were isolated from adolescent human urine. A fraction was selected that was enriched in the N-telopeptide-to-helix intermolecular cross-linking domain of bone type I collagen. Mouse monoclonal antibodies were generated against these urinary peptides conjugated to a carrier protein as immunogen. A high-affinity antibody was identified that specifically bound to the trivalent peptides derived from the N-telopeptide-to-helix pyridinoline cross-linking site in type I collagen of human bone. This was confirmed by the direct isolation from human bone collagen of similar fragments recognized selectively by the antibody. A sensitive inhibition ELISA was established on microtiter plates that could quantify the bone-derived peptides in human urine. The assay, which can be run directly on untreated urine, was thoroughly tested against samples from normal subjects and from patients with metabolic bone disease. For example, strong correlations with urinary hydroxyproline and total pyridinoline cross-links were found in patients with Paget's disease of bone. The method shows considerable promise as a rapid and specific index of human bone resorption rates, with greatly improved specificity and convenience over total pyridinoline analysis. Potential applications include the study of normal metabolism, the diagnosis and monitoring of bone disease, and evaluating the effectiveness of antiresorption therapies.