Gene expression of glucocorticoid receptor alpha and beta in giant cell tumour of bone: evidence of glucocorticoid-stimulated osteoclastogenesis by stromal-like tumour cells

A 71-Year-Old Female with Myocardial Infarction and Long-Standing Ulcers on the Thigh

Calciphylaxis is most commonly encountered in patients with end-stage renal disease; however, it is increasingly observed in nonuremic patients as well. It is important to consider and diagnose nonuremic calciphylaxis early, as prompt treatment and mitigation of associated risk factors is essential to improve long-term outcomes for these patients. Here, we present the case of a 71-year-old woman with atrial fibrillation on warfarin, but without renal disease, who presented with two long-standing ulcers on her thigh and was diagnosed with the aid of biopsy with calciphylaxis. We review the existing literature on the subject and offer this case as a representative report of a clinicopathologic correlation for this disorder.

Immune-Mediated Muscle Diseases of the Horse

In horses, immune-mediated muscle disorders can arise from an overzealous immune response to concurrent infections or potentially from an inherent immune response to host muscle antigens. Streptococcus equi ss. equi infection or vaccination can result in infarctive purpura hemorrhagica (IPH) in which vascular deposition of IgA-streptococcal M protein complexes produces ischemia and complete focal infarction of skeletal muscle and internal organs. In Quarter Horse–related breeds with immune-mediated myositis, an apparent abnormal immune response to muscle antigens results in upregulation of major histocompatibility complex class (MHC) I and II on muscle cell membranes, lymphocytic infiltration of lumbar and gluteal myofibers, and subsequent gross muscle atrophy. Rarely, an inflammatory event results in myositis with subsequent systemic calcinosis characterized by a pathognomonic hyperphosphatemia and high fatality rate. This review presents an overview of these immune-mediated myopathies and highlights clinical and pathological features as well as the suspected pathophysiology.

Management of glucocorticoids-induced osteoporosis: role of teriparatide

Glucocorticoids (GC)-induced osteoporosis (GIOP) is the most common cause of secondary osteoporosis, which leads to an increased fracture risk in patients. The normal bone turnover depends on a balance between osteoblasts and osteoclasts activity and GC can cause a rapid bone loss, decreasing bone formation and increasing bone resorption. The decreased bone formation is mainly due to the GC-induced apoptosis of both osteoblasts and osteocytes, while the increased bone resorption is due to the increased life-span of pre-existing osteoclasts. Bisphosphonates are clearly effective in preventing and treating GIOP but anabolic therapeutic strategies are the new promising therapeutic alternative. Experimental and clinical studies indicate that teriparatide, the active (1–34) parathyroid hormone (PTH) molecule, is efficacious for the treatment of GIOP, being able to induce an increase in bone mass in these patients. Intermittent administration of human PTH (1–34) stimulates bone formation by increasing osteoblast number. Additionally, human PTH (1–34) modulates the level and/or activity of locally produced growth factors and cytokines. Teriparatide has been demonstrated in several clinical studies to significantly decrease the incidence of fractures in patients affected by GIOP. It has recently received an indication for GIOP and its label indication has also been expanded.

Calciphylaxis from nonuremic causes: a systematic review

BACKGROUND AND OBJECTIVES

Calciphylaxis, or calcific uremic arteriolopathy, is a well-described entity in end-stage kidney disease and renal transplant patients; however, little systematic information is available on calciphylaxis from nonuremic causes. This systematic review was designed to characterize etiologies, clinical features, laboratory abnormalities, and prognosis of nonuremic calciphylaxis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A systematic review of literature for case reports and case series of nonuremic calciphylaxis was performed. Cases included met the operational definition of nonuremic calciphylaxis-histopathologic diagnosis of calciphylaxis in the absence of end-stage kidney disease, renal transplantation, or acute kidney injury requiring renal replacement therapy.

RESULTS

We found 36 cases (75% women, 63% Caucasian, aged 15 to 82 yr) of nonuremic calciphylaxis. Primary hyperparathyroidism, malignancy, alcoholic liver disease, and connective tissue disease were the most common reported causes. Preceding corticosteroid use was reported for 61% patients. Protein C and S deficiencies were seen in 11% of patients. Skin lesions were morphologically similar to calcific uremic arteriolopathy. Mortality rate was 52%, with sepsis being the leading cause of death.

CONCLUSION

Calciphylaxis should be considered while evaluating skin lesions in patients with predisposing conditions even in the absence of end-stage kidney disease and renal transplantation. Nonuremic calciphylaxis is reported most often in white women. Mineral abnormalities that are invoked as potential causes in calcific uremic arteriolopathy are often absent, suggesting that heterogeneous mechanisms may contribute to its pathogenesis. Nonuremic calciphylaxis is associated with high mortality, and there is no known effective treatment.

Sex-specific association of the glucocorticoid receptor gene with extreme BMD

To study the role of the GR gene on BMD regulation in the Chinese, a sex-specific association study was performed. The results indicated that GR variation contributed to the extreme BMD variation in the Chinese.

INTRODUCTION

The glucocorticoid (GC) receptor (GR) gene is an important candidate gene for BMD regulation in GC-induced osteoporosis (GIO). However, no study has explored the genetic effects of the GR gene on BMD variation in the Chinese population.

MATERIALS AND METHODS

Our sample consisted of 800 unrelated subjects (400 women and 400 men) with extreme age-adjusted hip BMD Z-scores selected from a population composed of 1988 normal adult Chinese Han. Four single nucleotide polymorphisms (SNPs) in the GR gene were genotyped. Both single SNP and haplotype association analyses were conducted.

RESULTS

SNP rs1866388 (p(c) = 0.028) was found to be significantly associated with extreme BMD only in men. In both sexes, haplotypes involving rs1866388 and rs2918419 were found to have different frequency distributions in extremely low and high BMD groups (p(p) = 0.024, 0.001, and 0.002 in women and 0.002, 0.003, and 0.003 in men for window sizes of two, three, and four SNPs, respectively). Most shared haplotypes showed opposite effects between women and men.

CONCLUSIONS

For the first time, our study suggested the possible role of the GR gene on BMD regulation and sex specificity in the association of GR with extreme BMD in the Chinese.

Calciphylaxis: natural history, risk factor analysis, and outcome

BACKGROUND

Calciphylaxis is characterized by ischemic cutaneous ulceration, high mortality, and ineffective treatment.

METHODS

We conducted a retrospective study of 64 patients with calciphylaxis (including 49 dialysis patients age- and sex-matched to 98 dialysis controls).

RESULTS

The estimated 1-year survival rate of calciphylaxis was 45.8%. Risk factors for calciphylaxis included obesity, liver disease, systemic corticosteroid use, calcium-phosphate product more than 70 mg(2)/dL(2), and serum aluminum greater than 25 ng/mL. Survival rates were similar for 16 patients who received parathyroidectomy and 47 who did not. An estimated 1-year survival rate of 61.6% was observed for 17 patients receiving surgical debridement compared with 27.4% for the 46 who did not (P = .008).

LIMITATIONS

The study was limited by its retrospective design and there was no control group for the 15 nondialysis cases.

CONCLUSIONS

Calciphylaxis is multifactorial and usually fatal. Prevention of calciphylaxis may include correction of risk factors identified in this study. Surgical debridement was associated with improved survival, but parathyroidectomy was not.

Influence of glucocorticoids on human osteoclast generation and activity

Using human peripheral blood mononuclear cells as osteoclast precursors, we showed that dexamethasone stimulated osteoclast generation at a pharmacological concentration but did not affect the life span of human osteoclasts. Dexamethasone also dose-dependently increased signals for osteoclastogenesis.

INTRODUCTION

Glucocorticoid-induced osteoporosis is a common and serious disease. Glucocorticoids predominantly affect osteoblast proliferation and life span. Much of the bone loss is caused by reduced bone formation, but there is also an element of increased bone resorption.

MATERIALS AND METHODS

Human peripheral blood mononuclear cells were cultured on whale dentine and induced to differentiate to osteoclasts by RANKL and human macrophage-colony stimulating factor (M-CSF). Osteoclast activity was quantified by pit area. RANKL and osteoprotegerin (OPG) expression in osteoblasts were measured by real-time RT-PCR.

RESULTS

In the early phase of osteoclast generation (0-16 days), cultures from two different donors showed that dexamethasone at 10(-8) M increased pit area by 2.5-fold, whereas lower concentrations had no effect. At the highest dexamethasone concentration (10(-7) M), pit area was reduced. In 21-day cultures from three other donors, a similar increase was seen with dexamethasone at 10(-8) M. There was, however, no evidence of increased life span of osteoclasts with dexamethasone. In human primary osteoblasts, dexamethasone dose-dependently reduced OPG and increased RANKL expression as measured by quantitative real time RT-PCR.

CONCLUSION

These data provide some explanation at a cellular and molecular level for the observed increase in bone resorption seen in patients treated with glucocorticoids and indicate that there are clear direct effects of glucocorticoids on bone resorption in human cell systems that may differ from other species.

Characterization of circulating human osteoclast progenitors: development of in vitro resorption assay

Several cell surface markers were used to isolate monocytes as osteoclast progenitors with an immunomagnetic cell separation system. Use of this system with specific monocyte antibodies produced 99% pure monocytes. When purified monocytes were cultured on bovine bone slices in the presence of receptor activator of nuclear factor-kappaB (RANKL), macrophage-colony stimulating factor (M-CSF), tumor necrosis factor alpha (TNF-alpha), and dexamethasone for 14 days, CD14(+) CD11b(+), and CD61(+) monocytes had approximately 90-, 30- and 20-fold higher osteoclast formation capacities/plated cells compared to the control culture. CD15(+) monocytes generated few tartrate-resistant acid phosphatase-positive multinucleated cells (TRACP+ MNC), and CD169(+) monocytes generated no TRACP+ MNC. This suggests, that there are various subsets of monocytes in the blood circulation and that they have different capacities in osteoclast formation. These results show that circulating human osteoclast progenitors can be efficiently purified by immunomagnetic cell separation system using anti-CD14, -CD11b, and -CD61 antibodies. These purified monocyte fractions had different ability to give rise to osteoclasts. CD169 was not found to be suitable for osteoclast progenitor isolation. Optimal concentration of dexamethasone for osteoclast formation and bone resorption was 10 nM. To develop a human resorption assay, osteoclasts were first induced for 7 days, whole media were replaced, cultures were continued for additional 3 days and C-terminal telopeptide of type I collagen was determined from culture media. This assay was shown to be functional, since two well-known resorption inhibitors, bafilomycin A(1) and calcitonin, dose-dependently inhibited the resorption activity of osteoclasts.

Nuclear receptor signaling in macrophages

Macrophages play diverse roles in host defense and in maintenance of homeostasis. Based on their ability to promote inflammatory responses, inappropriate macrophage function also contributes to numerous pathological processes, including atherosclerosis, rheumatoid arthritis and inflammatory bowel disease. Members of the nuclear receptor superfamily of ligand-dependent transcriptions factors have emerged as key regulators of inflammation and lipid homeostasis in macrophages. These include the glucocorticoid receptor (GR), which inhibits inflammatory programs of gene expression in response to natural corticosteroids and synthetic anti-inflammatory ligands such as dexamethasone. Also, in response to endogenous eicosanoids and oxysterols, respectively, peroxisome proliferator-activated receptors (PPARs) and liver X receptors (LXRs) regulate transcriptional programs involved in inflammatory responses and lipid homeostasis. Identification of their mechanisms of action should help guide the development of new therapeutic agents useful in the treatment of diseases in which macrophages play critical pathogenic roles.

Giant cell tumor of bone

Giant cell tumor of bone is an enigmatic osseous neoplasm that is histologically benign but clinically shows local aggression and metastatic potential. The absence of clinical, radiographic, or pathologic features that are predictive of tumor behavior and patient outcome has resulted in recent attention to the pathobiology of giant cell tumor of bone. In this report, the clinicopathologic features of and current treatment approaches to giant cell tumor of bone are reviewed. Recent investigations of the specific role of the cell populations present in giant cell tumor of bone that influence tumor proliferation, bone resorption, and its clinical behavior are described.