Cytokine accumulation in osteitis fibrosa of renal osteodystrophy

Case Report: Effects of Secondary Hyperparathyroidism Treatment on Improvement of Juvenile Nephronophthisis-Induced Pancytopenia and Myelofibrosis

Secondary hyperparathyroidism (HPT) is a common complication of end-stage renal disease (ESRD) and may be an important precipitating factor for the development of myelofibrosis. However, there have been only a few reports on myelofibrosis caused by secondary HPT in children. We describe a case of a 15-year-old boy with myelofibrosis due to secondary HPT who was successfully treated with hemodialysis, erythropoietin, phosphate binders, and activated vitamin D agents. The patient had no past medical history and had been admitted to the hospital for abdominal pain. Routine blood examination revealed pancytopenia combined with renal impairment. Hyperphosphatemia, decreased 1,25-dehydroxyvitamin D, decreased serum calcium, and increased parathyroid hormone (PTH) levels were observed. Bone marrow biopsy confirmed myelofibrosis and renal biopsy revealed nephronophthisis (NPHP). The possibility of renal osteodystrophy and myelofibrosis due to secondary HPT was considered. Hemodialysis and erythropoietin were initiated and combined therapy with a phosphate binder and an active vitamin D agent achieved greater reduction of PTH levels, along with improvement of pancytopenia. As medical treatment for secondary HPT can lead to a reversal of myelofibrosis and avoid parathyroidectomy in children, prompt recognition of this condition has major implications for treatment. Therefore, despite its rarity, pediatricians should consider myelofibrosis due to secondary HPT as a cause of pancytopenia in patients with chronic kidney disease.

TGF-Beta Signaling in Bone with Chronic Kidney Disease

Transforming growth factor (TGF)-β signaling is not only important in skeletal development, but also essential in bone remodeling in adult bone. The bone remodeling process involves integrated cell activities induced by multiple stimuli to balance bone resorption and bone formation. TGF-β plays a role in bone remodeling by coordinating cell activities to maintain bone homeostasis. However, mineral metabolism disturbance in chronic kidney disease (CKD) results in abnormal bone remodeling, which leads to ectopic calcification in CKD. High circulating levels of humoral factors such as parathyroid hormone, fibroblast growth factor 23, and Wnt inhibitors modulate bone remodeling in CKD. Several reports have revealed that TGF-β is involved in the production and functions of these factors in bone. TGF-β may act as a factor that mediates abnormal bone remodeling in CKD.

Anaemia in kidney disease: harnessing hypoxia responses for therapy

Improved understanding of the oxygen-dependent regulation of erythropoiesis has provided new insights into the pathogenesis of anaemia associated with renal failure and has led to the development of novel therapeutic agents for its treatment. Hypoxia-inducible factor (HIF)-2 is a key regulator of erythropoiesis and iron metabolism. HIF-2 is activated by hypoxic conditions and controls the production of erythropoietin by renal peritubular interstitial fibroblast-like cells and hepatocytes. In anaemia associated with renal disease, erythropoiesis is suppressed due to inadequate erythropoietin production in the kidney, inflammation and iron deficiency; however, pharmacologic agents that activate the HIF axis could provide a physiologic approach to the treatment of renal anaemia by mimicking hypoxia responses that coordinate erythropoiesis with iron metabolism. This Review discusses the functional inter-relationships between erythropoietin, iron and inflammatory mediators under physiologic conditions and in relation to the pathogenesis of renal anaemia, as well as recent insights into the molecular and cellular basis of erythropoietin production in the kidney. It furthermore provides a detailed overview of current clinical experience with pharmacologic activators of HIF signalling as a novel comprehensive and physiologic approach to the treatment of anaemia.

Role of TGF-β in a mouse model of high turnover renal osteodystrophy

Altered bone turnover is a key pathologic feature of chronic kidney disease-mineral and bone disorder (CKD-MBD). Expression of TGF-β1, a known regulator of bone turnover, is increased in bone biopsies from individuals with CKD. Similarly, TGF-β1 mRNA and downstream signaling is increased in bones from jck mice, a model of high-turnover renal osteodystrophy. A neutralizing anti-TGF-β antibody (1D11) was used to explore TGF-β's role in renal osteodystrophy. 1D11 administration to jck significantly attenuated elevated serum osteocalcin and type I collagen C-telopeptides. Histomorphometric analysis indicated that 1D11 administration increased bone volume and suppressed the elevated bone turnover in a dose-dependent manner. These effects were associated with reductions in osteoblast and osteoclast surface areas. Micro-computed tomography (µCT) confirmed the observed increase in trabecular bone volume and demonstrated improvements in trabecular architecture and increased cortical thickness. 1D11 administration was associated with significant reductions in expression of osteoblast marker genes (Runx2, alkaline phosphatase, osteocalcin) and the osteoclast marker gene, Trap5. Importantly, in this model, 1D11 did not improve kidney function or reduce serum parathyroid hormone (PTH) levels, indicating that 1D11 effects on bone are independent of changes in renal or parathyroid function. 1D11 also significantly attenuated high-turnover bone disease in the adenine-induced uremic rat model. Antibody administration was associated with a reduction in pSMAD2/SMAD2 in bone but not bone marrow as assessed by quantitative immunoblot analysis. Immunostaining revealed pSMAD staining in osteoblasts and osteocytes but not osteoclasts, suggesting 1D11 effects on osteoclasts may be indirect. Immunoblot and whole genome mRNA expression analysis confirmed our previous observation that repression of Wnt/β-catenin expression in bone is correlated with increased osteoclast activity in jck mice and bone biopsies from CKD patients. Furthermore, our data suggest that elevated TGF-β may contribute to the pathogenesis of high-turnover disease partially through inhibition of β-catenin signaling.

Serum transforming growth factor-beta levels in patients with vitamin D deficiency

BACKGROUND

Transforming growth factor-beta 1 (TGF-β1) contributes to tissue repair by promoting tissue fibrosis, and elevations have been reported in patients with bone marrow fibrosis. The aim of this study was to evaluate the relationship between TGF-β1 levels and vitamin D deficiency.

METHODS

All patients presenting to the outpatient Endocrinology and Metabolic Diseases clinic between June and September of 2008 were approached, and consenting patients who were deemed suitable candidates were enrolled. Hematological parameters were measured, along with serum levels of total and ionized calcium, phosphorus, parathyroid hormone, iron, folic acid vitamin B12 levels, 25 OH vitamin D3 (25OHD(3)) and TGF-β1.

RESULTS

A total of 132 patients were included in the study. Patients were divided into 4 groups based on levels of 25OHD(3) [group 1 (<5 ng/ml), 20 patients; group 2 (5-15 ng/ml), 38 patients; group 3 (16-30 ng/ml); and group 4 (>30 ng/ml), 28 patients]. TGF-β1 levels were higher in patients in group 1 compared to the other groups. Transforming growth factor-beta levels correlated negatively with vitamin D3 and positively with leukocyte count, platelet count, of MCV and MCH. Multiple regression analyses revealed TGF-β1 levels to be associated with 25OHD(3) as well as with platelet count.

CONCLUSIONS

Results of this study are suggestive of the presence of a significant relationship between TGF-β and vitamin D deficiency. Increased TGF-β1 and platelet count may be an early indicator of bone marrow fibrosis in patients with vitamin D deficiency.

The impact of inflammation on bone mass in children

Bone is a dynamic tissue. Skeletal bone integrity is maintained through bone modeling and remodeling. The mechanisms underlying this bone mass regulation are complex and interrelated. An imbalance in the regulation of bone remodeling through bone resorption and bone formation results in bone loss. Chronic inflammation influences bone mass regulation. Inflammation-related bone disorders share many common mechanisms of bone loss. These mechanisms are ultimately mediated through the uncoupling of bone remodeling. Cachexia, physical inactivity, pro-inflammatory cytokines, as well as iatrogenic factors related to effects of immunosuppression are some of the common mechanisms. Recently, cytokine signaling through the central nervous system has been investigated for its potential role in bone mass dysregulation in inflammatory conditions. Growing research on the molecular mechanisms involved in inflammation-induced bone loss may lead to more selective therapeutic targeting of these pathological signaling pathways.

Dietary-induced hyperparathyroidism affects serum and gingival proinflammatory cytokine levels in rats

BACKGROUND

Poor diet and inadequate nutrition are suggested to affect the periodontium as well as impair the systemic health. This study investigated the systemic and periodontal effects of dietary-induced hyperparathyroidism (dHPT) by evaluating serum and gingival proinflammatory cytokine levels.

METHODS

Twenty-four Sprague-Dawley rats were used in the study. dHPT was induced in 12 rats by calcium/phosphorus imbalance, and 12 rats were fed a standard diet (SD). Afterward, endotoxin-induced periodontitis was induced on the right mandibular molar teeth (mmt). Four study groups were created: dHPT + mmt without periodontitis (group 1), dHPT + mmt with periodontitis (group 2), SD + mmt with periodontitis (group 3), and SD + mmt without periodontitis (group 4). Interleukin (IL)-1beta and tumor necrosis factor-alpha (TNF-alpha) levels were measured by enzyme-linked immunosorbent assay to evaluate the proinflammatory cytokine profiles. Serum cytokines were analyzed in the blood samples collected prior to periodontitis induction, whereas gingival cytokines were analyzed in the gingival supernatants of the four groups.

RESULTS

Serum cytokines were higher in dHPT rats than in SD rats (P <0.001), with a positive correlation between parathormone and the cytokines (P <0.001). Gingival cytokines were highest in group 2 and lowest in group 4 (group 2 > group 3 > group 1) (P <0.001). There was a positive correlation between parathormone and the gingival cytokines in group 1 (P <0.001 for IL-1beta; P <0.01 for TNF-alpha).

CONCLUSION

The results suggested that increased serum proinflammatory cytokine production may be a complication of dHPT, and this may affect healthy and diseased periodontia by increasing gingival proinflammatory cytokine levels.

Usefulness of a quick decalcification of bone sections embedded in methyl methacrylate[corrected]: an improved method for immunohistochemistry

Immunohistochemistry of undecalcified bone sections embedded in methyl methacrylate (MMA) is not commonly employed because of potential destruction of tissue antigenicity by highly exothermic polymerization. The aim of the present study was to describe a new technique in which a quick decalcification of bone sections embedded in MMA improves the results for immunohistochemistry. The quality of interleukin 1alpha (IL-1alpha) immunostaining according to the present method was better than the conventional one. Immunostaining for osteoprotegerin (OPG) and the receptor activator of NF-kappaB ligand (RANKL) in bone sections of chronic kidney disease patients with mineral bone disorders (CKD-MBD) was stronger than in controls (postmortem healthy subjects). The present study suggested that this method is easy, fast, and effective to perform both histomorphometry and immunohistochemistry in the same bone fragment, yielding new insights into pathophysiological aspects and therapeutic approaches in bone disease.

Pancytopenia and secondary myelofibrosis could be induced by primary hyperparathyroidism

Hyperparathyroidism may be a precipitating factor important to the development of myelofibrosis: however, there has been only a few reports regarding myelofibrosis secondary to primary hyperparathyroidism. Recently, a rare case of pancytopenia caused by myelofibrosis in a 41-year-old woman who complained of general weakness and arthralgia presented to our clinical service. The patient was diagnosed with primary hyperparathyroidism with pancytopenia. Bone marrow biopsy revealed myelofibrosis. Right parathyroidectomy was performed and a parathyroid adenoma was totally excised. After surgery, the CBC counts and other clinical abnormalities gradually improved without further intervention. We concluded that the pancytopenia was because of bone marrow fibrosis resulting from primary hyperparathyroidism. Therefore, physicians should consider myelofibrosis secondary to primary hyperparathyroidism as a cause of pancytopenia in hypercalcemic patients, even though it is rare.

Glycosaminoglycan, collagen, and glycosidase changes in human osteoblasts treated with interleukin 1, and osteodystrophy

Normal bone homeostasis involves a balance between osteoblast and osteoclast action, regulated by hormones and cytokine stimuli. Hemodialysis patients appear to have increased production of interleukin-1 (IL-1), interleukin-6 (IL-6) and glycosaminoglycans (GAG) in serum. IL-1 plays a role in the synthesis, degradation and degree of sulphatation of ECM components such as glycosaminoglycans. Also, continuous changes in the ECM involve enzymes such as beta-N-acetyl-d-glucosaminidase (beta-NAG) and beta-d-glucuronidase (beta-GLU) which act on different GAG classes and collagen fibers. We examined the effects of IL-1alpha on ECM synthesis and the related enzymes in human uremic osteoblast cultures. We also measured the levels of IL-1beta, and IL-6 and alkaline phosphatase activity. In biopsies of uremic bone there was less ECM deposition than resorption associated with changes in osteoblast morphology. In vitro osteoblast proliferation was higher (P< or =0.01), and extracellular GAG lower (P< or =0.01) than in controls. The enzyme beta-NAG was high (P< or =0.05) but there were no noteworthy changes in beta-GLU. ELISA of the medium indicated spontaneous production of IL-1beta and IL-6, which significantly increased after IL-1alpha treatment compared to controls. IL-1alpha reduced alkaline phosphatase activity (P< or =0.01) in uremic osteoblast cultures. IL-1 acts on osteoblasts with decreases in GAG synthesis and alkaline phosphatase activity, while beta-NAG increases. This lead to a reduction in the organic component in ECM and its mineralization, and to changes in the regulation of cytokine activity by GAG. The enzymatic breakdown might be facilitated by metabolic acidosis and failed osteoblast differentiation; these factors could be correlated with different degrees of osteodystrophy.

Benign parathyroid adenoma presenting with unusual parathyroid crisis, anemia and myelofibrosis

Although the clinical symptoms of patients with benign parathyroid adenoma are usually nonspecific and benign, a malignant presentation of the benign disease may sometimes occur. Here, we report a case of a 58-year-old woman who presented with aggravated sacrum pain, general malaise, and polydipsia. Initial laboratory findings revealed hypercalcemia, normocytic anemia, and impaired renal function. Acute hypercalcemic crisis manifested and primary hyperparathyroidism was diagnosed together with myelofibrosis on account of the result of bone marrow biopsy. Excision of a parathyroid adenoma was performed, and the anemia and bone marker regressed later. These findings suggested that benign parathyroid adenoma may mimic the clinical presentation of parathyroid carcinoma, releasing excess parathyroid hormone and resulting in hyperparathyroid crisis. In addition, primary hyperparathyroidism can be associated with anemia and myelofibrosis.

In vitro human osteoblast and extracellular matrix changes after transforming growth factor beta 1 treatment

AIMS

Normal bone tissue is characterised by a balancing of osteoblast and osteoclast activity. The activity and differentiation of these cells are regulated by vitamins, hormones and cytokines. The action of these factors on bone tissue cells depends on the composition and mineralisation of extracellular bone matrix. In particular, transforming growth factor beta 1 (TGFbeta1) acts on collagen fibres, glycosaminoglycan secretion and on the enzymes correlated to the turnover of glycosaminoglycans. The normal functions of bone tissue also depend on its mineralisation, which is highly altered in the process of uraemia.

METHODS

In this study, we analysed in vitro the effect of transforming growth factor beta on osteoblast proliferation, collagen synthesis and glycosaminoglycan secretion with 3H-thymidine, 3H-proline or 3H-glucosamine incorporation, and on enzymes, such as beta-N-acetyl-D-glucosaminidase and beta-glucuronidase, involved in extracellular matrix turnover. Moreover, phosphatase alkaline activity and osteocalcin related to mineralisation of extracellular matrix were determined.

RESULTS

Our data show that TGFbeta1 significantly decreases 3H-thymidine and 3H-proline incorporation and increases (p < or = 0.01) extracellular sulphated glycosaminoglycan synthesis. It also increases osteocalcin levels, phosphatase alkaline, beta-N-acetyl-D-glucosaminidase and beta-glucoronidase activities.

CONCLUSION

TGFbeta1 changes the synthesis of extracellular matrix components by osteoblasts. These variations favour the action of cytokine and osteoclasts. Since the TGFbeta1 accumulates in bone tissue and increases during uraemia, with due limitations this action leads to an imbalance between synthesis and degradation and could explain bone alterations in uraemic patients.

IL-1beta, TNF-alpha, TGF-beta, and bFGF expression in bone biopsies before and after parathyroidectomy

BACKGROUND

There is growing evidence pointing to an involvement of cytokines and growth factors in renal osteodystrophy. In this study, the expression of interleukin-l beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-beta (TGF-beta), and basic fibroblast growth factor (bFGF) in bone biopsies taken from uremic patients before and 1 year after parathyroidectomy (PTX) was evaluated. Biochemical features and histomorphometric outcome were also studied.

METHODS

Iliac bone biopsies were taken before and 1 year after PTX in nine uremic patients with severe hyperparathyroidism (HPT). Immunohistochemical techniques were used to identify the expression of IL-1 beta, TNF-alpha, TGF-beta, and bFGF in these bone samples.

RESULTS

At the time of the second bone biopsy, the mean serum total alkaline phosphatase activity was normal, whereas mean serum intact parathyroid hormone (iPTH) level was slightly above the upper limit of normal values. Histomorphometric analysis showed a decrease in resorption parameters and static bone formation parameters after PTX. Dynamically, mineral apposition rate (MAR) and mineralization surface (MS/BS) decreased significantly. There was a marked local expression of IL-1beta, TNF-alpha, TGF-beta, and bFGF in bone biopsies before PTX, particularly in fibrous tissue and resorption areas. One year after PTX, IL-1beta decreased from 23.6 +/- 7.5% to 9.9 +/- 3.1%, TNF-alpha from 4.5 +/- 1.5% to 0.7 +/- 0.8%, TGF-beta from 49.6 +/- 9.8% to 15.2 +/- 4.6%, and bFGF from 50.9 +/- 12.7% to 12.9 +/- 7.9% (P < 0.001). A significant correlation was documented between cytokines and growth factors expression in bone with iPTH levels before and after PTX (P < 0.05).

CONCLUSIONS

Based on these results, we suggest that IL-1beta, TNF-alpha, TGF-beta, and bFGF are involved in bone remodeling regulation, acting as local effectors, possibly under the control of PTH.