The visualization and evaluation of bone architecture in the rat using three-dimensional X-ray microcomputed tomography

Microcomputed tomography allows the true three-dimensional structure of bone to be assessed by a nondestructive analysis. This article describes how this technique has for the first time been applied to rat bone to determine the effects of aging, ovariectomy, and antiresorptive drugs on bone structure and how these results compare with those determined by histological and histomorphometric techniques. During the procedure, a micro X-ray source is directed toward the bone sample. Modifications in the X-ray beam induced by bone crystals are determined for a range of acquisitions before three-dimensional reconstruction of bone architecture is performed. Morphometric parameters determined were trabecular bone volume/tissue volume, trabecular number, and trabecular thickness. The results show that ovariectomy has a dramatic effect on rat bone structure. Following treatment with the bone resorption inhibitor tiludronate, the morphometric parameters were significantly improved. The results obtained with three-dimensional microcomputed tomography were in agreement with observations made using classical techniques. Microcomputed tomography should prove useful for evaluating the antiresorptive effects of bisphosphonates on bone architecture and in allowing between-drug comparisons.

Calcitonin receptor polymorphism is associated with a decreased fracture risk in post-menopausal women

High bone resorption by the osteoclast results in osteoporosis, a disease affecting 40% of women after the menopause. Calcitonin, used to treat osteoporosis, inhibits bone resorption via receptors located on the osteoclasts. Two alleles of the calcitonin receptor gene ( CTR ) exist: a base mutation T-->C in the third intracellular C-terminal domain changes a proline (CCG) at position 447 to a leucine (CTG). We therefore studied the distribution of these alleles in a cohort of 215 post-menopausal Caucasian women suffering or not from osteoporotic fractures. The region of interest within the point mutation was amplified by PCR and screened for single strand conformation polymorphism. This work was followed by DNA sequencing of the fragments amplified. We found that bone mineral density (BMD) at the femoral neck was significantly higher in heterozygous subjects with the Rr genotype compared with the homozygous leucine (RR) and homozygous proline (rr) genotypes. Also, a decreased fracture risk was observed in heterozygote subjects. In conclusion, our results suggest that polymorphism of CTR could be associated with osteoporotic fractures and BMD in a population of post-menopausal women. CTR heterozygotes could produce both alleles of the receptor. The heterozygous advantage effect of Rr subjects could explain their protection against osteoporosis: higher bone density and decreased fracture risk. Establishing the genotype of the CTR gene in post-menopausal women could be of value in evaluating their risk of developing fractures.

Markers of bone remodelling in metabolic bone disease

New specific markers of bone remodelling have been developed that allow the evaluation of bone formation (plasma levels of osteocalcin and bone alkaline phosphatases) or bone resorption (collagen crosslink levels in urine). These markers can be used to evaluate bone disease. Their best application is currently in renal osteodystrophy, where there is a broad spectrum of bone abnormalities. In patients with this disease, bone markers can obviate the need for bone biopsy. So far, bone alkaline phosphatase is the most sensitive and specific marker for predicting the type of bone disease and therefore for deciding treatment in dialysed patients, although it is not ideal. Bone markers have also allowed a dramatic improvement in the comprehensive approach to bone loss with aging in women. Monitoring of the marked increase in bone turnover, and its persistence, in older women after menopause may help in the design of treatment strategies for osteoporosis. There is some hope that the measurement of urinary levels of collagen crosslinks will help to predict the clinical outcome of osteoporosis with respect to fractures in postmenopausal women. Bone markers could, besides being a measurement of bone density, help to determine the optimal treatment of postmenopausal women. Bone markers could also be used to predict or ascertain the response to treatment of osteoporosis, but few data are currently available to judge the routine usefulness of these new applications.

Estrogen stimulates PTHrP but not PTH/PTHrP receptor gene expression in the kidney of ovariectomized rat

The aim of the present study was to test the hypothesis that the decreased renal tubular reabsorption of calcium observed in estrogen deficiency is associated with a local regulation of either PTHrP or PTH/PTHrP receptor genes in the kidney. Rats were randomly sham-operated (S) or ovariectomized receiving either vehicle (OVX) or 4 microg E2/kg/day (OVX+E4) or 40 microg E2/kg/d (OVX+E40) during 14 days using alzet minipumps. Plasma PTH and calcium levels were lower in untreated OVX animals than in all other groups (P < 0.01). Plasma PTH was higher in OVX+E40 than in OVX+E4 (P < 0.05). PTHrP mRNA expression in the kidney was unaffected by ovariectomy but was increased in OVX+E40 (0.984 +/- 0.452 for PTHrP/GAPDH mRNAs expression vs. 0.213 +/- 0.078 in sham, P < 0.01). PTH/PTHrP receptor mRNA expression and the cAMP response of renal membranes to PTH were unaffected by ovariectomy and estrogen substitution. In conclusion, renal PTHrP and PTH/PTHrP receptor mRNAs are not modified by ovariectomy. However, 17beta-estradiol increases renal expression of PTHrP mRNA without evident changes in its receptor expression and function. This may help to explain the pharmacological action of estrogen in the kidney, especially how it prevents the renal leak of calcium in postmenopausal women.

[Bone remodeling: evaluation methods]

Bone tissue undergoes continual renewal in order to keep the mechanical competence of the bone matrix. This is performed by two cells: osteoclasts which resorb the calcified matrix and osteoblast which synthetize a new bone matrix. Biochemical markers of bone remodelling allow the evaluation of the activity of each type of bone cells. An unbalance in this process induces modifications of the amount of calcified tissue and of the bone microarchitecture. Several technics based on X-ray and ultrasound allow a non invasive evaluation of these modifications.

Pamidronate corrects the down-regulation of the renal parathyroid hormone (PTH)/PTH-related peptide (PTHrP) receptor mRNA in rats bearing Walker tumors

Human hypercalcemia of malignancy (HHM) is generally due to the release into the circulation of parathyroid hormone-related peptide (PTHrP). PTHrP stimulates osteoclastic bone resorption and renal calcium reabsorption through the activation of a receptor similar to that of PTH (PTH-R). However, there is scarce information about the PTH-R regulation in the setting of the hypercalcemia. In the present study, we assessed the molecular basis of renal PTH-R regulation in Walker tumor-bearing rats either treated or not by a bisphosphonate, pamidronate. Twenty-seven 6-week-old rats were randomly divided into three experimental groups: WC- APD- (9 control rats), WC+ APD- (9 Walker tumor-bearing rats), and WC+ APD+ (9 Walker tumor-bearing rats receiving 15 mg/kg/day of sodium pamidronate every day for seven days). Pamidronate induced a significant decrease in the mean tumor weight (9.3+/-0.8 vs 6.3+/-0.6 g). Seven days after the subcutaneous implantation of the Walker cells, plasma total calcium was 10.8+/-0.4, 16.8+/-0.6, and 12.9+/-0.6 mg/dl in WC- APD-, WC+ APD-, and WC+ APD+, respectively. Plasma PTHrP concentration was undetectable, 15.9+/-2.6, and 7.2+/-1.4 pmol/l, respectively. Bone histomorphometric results showed high resorption in WC+ APD-, which returned below the basal level of the WC- APD- with pamidronate treatment. Densitometric analysis of Northern blots revealed that the renal PTH-R mRNA expression in WC+ WPD- rats was a quarter of the levels in the WC- APD- and WC+ APD+ groups. WC+ APD- also had a decreased PTH-stimulated cAMP production in renal membranes. The PTH-R was expressed in the Walker tumor and it was not modified by pamidronate treatment. In conclusion, the expression of PTH-R receptor mRNA is significantly reduced in the kidney of rats bearing Walker carcinoma tumor. Its regulation is tissue-specific: pamidronate, which partially corrected the hypercalcemia and elevated circulating PTHrP, normalized the PTH-R mRNA expression in the kidney but not in the tumor.

Cytokine release from marrow mononuclear cells is negatively correlated to cortical elasticity in non-osteoporotic postmenopausal women

Activation of bone remodeling is likely to be under the control of mechanical factors acting, in part, through soluble local factors. We therefore investigated a relationship between cytokine production by marrow cells and bone elasticity. We studied 36 non-osteoporotic postmenopausal women undergoing hip arthroplasty for hip arthrosis (mean age: 68 +/- 8 years; lumbar BMD Z-score: +0.54 +/- 0.33 SD). Adherent marrow mononuclear cells were cultured for 48 hours with autologous plasma, and supernatants were harvested for PGE2, IL-1, TNF-alpha, and IL-6 measurements. Femoral neck cortical bones were removed during surgery for cortical histomorphometric evaluation and determination of elasticity indices (C33) using ultrasonic transmission method. In this nonosteoporotic population, femoral neck longitudinal elasticity indices were inversely correlated to both cortical thickness (r = -0.58, P < 0.01) and cortical porosity (r = -0.33, P < 0.01). The longitudinal elasticity indices were also negatively correlated to basal IL-1 and TNF-alpha release by adherent mononuclear marrow cells (r = -0.59, P < 0.01; r = -0.60, P < 0.01, respectively). However, no relationship was found between the three cytokines tested and either cortical thickness or porosity. These data show a link between cortical biomechanical properties and local factors involved in bone remodeling. We suggest that increased bone elasticity decreases transmission of strain, which in turn decreases cytokine release from marrow cells. However, whether cytokines influence bone elasticity or vice versa remains to be demonstrated.

Effects of prostaglandins on human hematopoietic osteoclast precursors

The effect of prostaglandin E2 (PGE2) on osteoclast (OC) differentiation is unclear, either stimulator or inhibitor, depending on the in vitro system used. This probably reflects indirect mechanisms through intermediate cells. We have investigated the direct effect of PGE2 on human OC differentiation from cord blood monocytes (CBMs) in the absence of stromal cells. Macrophages and multinucleated cells (MNCs) resembling OCs form in cultures of CBMs stimulated by 1,25-dihydroxyvitamin D3. In the present study, CBMs were cultured for 3 weeks, as previously described, in the presence or absence of PGE2. The number of MNCs was significantly reduced in the presence of PGE2 as was the proliferation of cultured CBMs, assessed on day 7. Immunohistochemistry was performed to evaluate macrophage markers (CD11b and CD14) and OC marker (beta3-chain). PGE2 significantly increased the numbers of CD11b-positive and CD14-positive cells, whereas the number of beta3-chain-positive cells was significantly decreased. beta3-Chain, c-fos, and human calcitonin receptor (h-CTR) messenger RNA (mRNA) expressions were evaluated by reverse transcription-PCR with RNA extracted from cultured CBMs. In the presence of PGE2, expression of beta3-chain and c-fos mRNA was reduced from the first week of culture. h-CTR mRNA expression was also reduced, and only the h-CTR1 isoform was detected in the presence of PGE2. In addition, when PGE2 was added only during the last week of culture, when no CBM proliferation occurred, the number of CD11b- and beta3-positive cells was unchanged compared to that in the control culture, as were the proportion of MNCs, the fusion index, and the expression of c-fos mRNA. In conclusion, our results suggest that PGE2 has an inhibitory effect on human OC differentiation from CBMs, possibly by reducing precursor proliferation in these cultures. We also hypothesize that PGE2 may reduce OC differentiation by increasing the proportion of precursor cells that differentiate into macrophages. In addition, this may be the result of inhibition of the c-fos expression in CBMs.

1,25-dihydroxyvitamin D3 induces NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase in human neonatal monocytes

1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3] induces the differentiation of monocytes into macrophage-like cells in vitro. To identify the genes expressed during this process, we performed differential display polymerase chain reaction on RNA extracted from cord blood monocytes (CBMs) treated with 1,25-(OH)2D3. Treated CBMs expressed type-I 15-hydroxyprostaglandin dehydrogenase (type-I 15-PGDH), the key enzyme of prostaglandin E2 (PGE2) catabolism and a 15-PGDH-related mRNA (15-PGDHr). This newly described 15-PGDH-related mRNA was constitutively expressed in adult monocytes. 15-PGDH gene(s) transcription was accompanied by the appearance of the 15-PGDH activity in treated CBMs. In addition, the cyclooxygenase 2 mRNA level was decreased and PGE2 levels in the culture mediums were lowered (50%). Our results stress that 1,25-(OH)2D3, at least in neonatal monocytes, can exert, directly or indirectly, a dual control on key enzymes of PGE2 metabolism. In conclusion, we suggest that modifications in prostaglandin metabolism, induced by the expression of type-I 15-PGDH and the downregulation of cyclooxygenase 2, could be involved in monocytic differentiation.

Quality of life as outcome in the treatment of osteoporosis: the development of a questionnaire for quality of life by the European Foundation for Osteoporosis

The morbidity of osteoporosis is caused by fractures. Vertebral fractures lead to pain and disability and a decrease in quality of life. A Working Party of the European Foundation for Osteoporosis has developed a specific questionnaire for patients with established vertebral osteoporosis. This questionnaire is intended for use in clinical trials. The questionnaire consists of questions and visual analogue scales in the following domains: pain, activities of daily living, jobs around the house, mobility, leisure and social activities, general health perception and mood. The questionnaire has been translated from English into French, German, Italian, Hebrew, Swedish and Dutch. The questionnaire is currently being validated in a multicentre study involving patients with stable osteoporosis and control subjects. Preliminary results indicate that the reproducibility is sufficient and that the questionnaire is able to discriminate between patients with vertebral osteoporosis and control subjects.

Inhibitory and stimulatory effects of prostaglandins on osteoclast differentiation

The effect of prostaglandins (PGs) on osteoclast differentiation, an important point of control for bone resorption, is poorly understood. After an initial differentiation phase that lasts at least 4 days, murine monocytes, cocultured with UMR106 osteoblastic cells (in the presence of 1,25-dihydroxyvitamin D3) give rise to tartrate-resistant acid phosphatase (TRAP) positive osteoclast-like cells that are capable of lacunar bone resorption. PGE2 strongly inhibits TRAP expression and bone resorption in these cocultures. To examine further the cellular mechanisms associated with this inhibitory effect, we added PGE2 to monocyte/UMR106 cocultures at specific times before, during, and after this initial 4-day differentiation period. To determine whether this PGE2 inhibition was dependent on the type of stromal cell supporting osteoclast differentiation, we also added PGE2 to cocultures of monocytes with ST2 preadipocytic cells. Inhibition of bone resorption was greatly reduced when the addition of PGE2 to monocyte/UMR106 cocultures was delayed until the fourth day of incubation; when delayed until the seventh day, inhibition did not occur. PGE2 inhibition of bone resorption was concentration-dependent and at 10(-6) M was also mediated by PGE1 and PGF2alpha. In contrast to its effects on monocyte/UMR106 cocultures, PGE2 stimulated bone resorption in monocyte/ST2 cocultures. Both ST2 cells and UMR106 cells were shown to express functional receptors for PGE2.These results show that PGs strongly influence the differentiation of osteoclast precursors and that this effect is dependent not only on the type and dose of PG administered, but also on the nature of the bone-derived stromal cell supporting this process.

PTH/PTHrP receptor mRNA is down-regulated in epiphyseal cartilage growth plate of uraemic rats

PTH/PTHrP receptor mRNA is down-regulated in epiphyseal cartilage growth plate of uraemic rats. Growth retardation, hypocalcaemia, hyperphosphataemia, and skeletal resistance to the action of PTH are well known features of advanced chronic renal failure (CRF). It has been suggested that the downregulation of renal and skeletal PTH receptors (PTH/PTHrP-R) could play an important role in the occurrence of these abnormalities. In the present study, four uraemic (4 weeks after 5/6 nephrectomy) and four control (sham-operated) rats were analysed for PTH/PTHrP-R mRNA expression at the proximal femoral and tibial growth plates by in situ hybridization. Uraemic rats had plasma biochemical abnormalities of advanced CRF including high creatinine, phosphate, and PTH, and low calcium and calcitriol levels. The femoral and tibial bones of uraemic animals were shorter in length than those of control rats, and had reduced width and cellularity of the epiphyseal cartilage growth plate. Mean (+/- SD) tibia growth plate width was 152 +/- 30 microns in uraemic rats, compared with 170 +/- 35 microns in control rats. The difference was mostly due to a marked reduction of the zone expressing PTH/PTHrP-R (mature chondrocytes) which was 30 +/- 5 microns in tibias from uraemic versus 44 +/- 10 microns in tibias from control rats. The hybridization signals of PTH/PTHrP-R per individual cell were quantified on dark field images using a computer-assisted image analysis system. The number of grains in PTH/PTHrP-R positive cells was also decreased in uraemic rats, 103 +/- 13 compared with 123 +/- 14 arbitrary units (dark pixel density)/cell in control rats (P < 0.005). In conclusion, these data indicate that rats with severe CRF and secondary hyperparathyroidism have reduced epiphyseal cartilage PTH/PTHrP-R mRNA expression. This alteration may be relevant in the pathogenesis of growth retardation in uraemia.

Dynamics of bone remodelling: biochemical and pathophysiological basis

Renewal of the bone matrix is induced by bone cells called osteoblasts and osteoclasts, which act sequentially on the bone surface. This "remodelling" depends on local factors, such as cytokines and growth factors which play an important role in the bone tissue as mediators of cell-to-cell and matrix-to-cell communication. Growth factors released from the bone matrix during the resorption are responsible for the refilling of the resorption cavity by osteoblasts. Cytokines also mediate locally the effect of several hormones on bone cells. Recent work is concerned with the modulation by oestradiol of osteoblastic cytokines acting on osteoclast differentiation. In mice, an increased production of interleukin-6 production by osteoblasts is responsible for the increased bone resorption occurring after ovariectomy. Other growth factors, such as transforming growth factor-beta, whose secretion is modified by oestradiol, may also be implicated. In women, an increase in cytokine production by blood mononuclear cells is associated with the occurence of menopause and reversed by oestrogen treatment. During osteoporosis and age-related bone changes, changes in the production of insulin-like growth factor I or of one of its binding proteins could be responsible for low bone formation. In addition to their role in bone remodelling, cytokines and growth factors are now implicated in osteoporosis.

Plasma total versus bone alkaline phosphatase as markers of bone turnover in hemodialysis patients

Plasma total versus bone alkaline phosphatase as markers of bone turnover in hemodialysis patients. Plasma bone-specific alkaline phosphatase (bAP) has been demonstrated to be more reliable than total alkaline phosphatases (tAP) in providing information about bone turnover in patients with metabolic bone diseases. This study surveyed 42 hemodialysis patients who underwent a systematic transiliac bone biopsy for histomorphometry study. Plasma bAP was determined by using a new immunoassay (Tandem-R Ostase, Hybritech, Liège, Belgium). Plasma bAP values were compared with those of two other plasma markers of bone metabolism, namely tAP and intact parathyroid hormone (iPTH), for the correlations with bone histomorphometric parameters. Patients with high-turnover bone disease (HTBD) (N = 32) had significantly higher plasma bAP levels than patients with normal or low bone turnover (N/LTBD) (N = 10) (66.9 +/- 63.5 ng/mL versus 10.8 +/- 4.2 ng/mL, respectively). Bone formation and resorption were highly correlated in these patients, and plasma bAP levels were positively correlated with bone resorption parameters, including osteoclast surface (r = 0.39, P < 0.0001) and osteoclast number/mm2 (r = 0.36, P < 0.001), and with bone formation parameters, osteoblast surface (r = 0.50, P < 0.005), and bone formation rate (r = 0.91, P < 0.0001). The bone formation rate was better correlated with plasma bAP levels than with either plasma tAP or iPTH concentrations. Plasma bAP level equal or higher than 20 ng/mL, either alone or combined with plasma iPTH of 200 pg/mL, had the highest sensitivity, specificity, and predictability values for the diagnosis of high-turnover bone disease, and formally excluded patients with normal or LTBD. In conclusion, plasma bAP can be measured with a reliable immunoassay in hemodialysis patients. It represents a highly sensitive and specific biochemical marker of skeletal remodeling in these patients. Therefore, both serum iPTH and bAP are complementary in diagnoses of the type of renal osteodystrophy.

Cytokines and osteoporosis

Bone remodeling is a complex process that involves cells from various lineages, the calcified extracellular bone matrix and a multitude of regulation factors that act at both the tissular and cellular levels. Resorption and formation of bone are regulated at various levels during the series of events that lead from stem cell proliferation to differentiation of mature cells. These events are controlled by calciotropic hormones, whose indirect cellular effects are mediated by the production of local factors. A host of cytokines and growth factors influence the proliferation and differentiation of bone cells, and their activities are modulated by a large number of hormones. Resorption by osteoclasts is regulated at various stages of the differentiation process by cytokines produced by osteoblasts or stromal cells. Experimental studies in mice suggest that these local factors play a role in postoophorectomy bone loss, although their exact mechanisms of action are not known. Evidence that these factors are involved in postmenopausal bone loss is beginning to accumulate, opening up a vast field of investigation.

The development of a European questionnaire for quality of life in patients with vertebral osteoporosis

The complaints of vertebral osteoporosis usually result from wedge or crush fractures and biconcave deformities. These are caused by a decrease of bone mass and deterioration of bone structure leading to loss of strength. Treatment of osteoporosis should result in an increase of bone mass, and the incidence of new vertebral fractures should diminish. However, new vertebral fractures are not always accompanied by pain, and disability does not well correlate with the number of vertebral fractures. Patients with osteoporosis often have other problems e.g. with taking a shower, preparing meals, gardening, walking stairs, visiting friends and attending social activities. In addition, pain and disability may influence mood and lead to depression. The assessment of quality of life should be a primary endpoint in clinical trials in patients with osteoporosis and in individual patients care. Recently, the European Foundation for Osteoporosis (EFFO) has decided a develop a questionnaire for patients with vertebral osteoporosis, i.e. patients with vertebral deformities. The questionnaire is meant for use in clinical trials. A questionnaire was made including 48 questions and 6 visual analogue scales. The questions concern the following domains: pain, activities of daily living, jobs around the house, moving, leisure and social activities, general health perception and mood. The questionnaire ("Qualeffo") has now entered the validation phase. The first study in 8 centres concerns the within-subject reproducibility, the internal coherence, and the specificity by comparing osteoporotic patients with a control group not suffering from osteoporosis or backpain.

Sequence of a novel mRNA coding for a C-terminal-truncated form of human NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase

We amplified, using the polymerase chain reaction (PCR) and NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase (type-I 15-PGDH)-specific primers, RNA extracted from the HL-60 cell line. Two bands, differing in size by approx. 160 bp, were detected with ethidium bromide staining after electrophoresis of amplification products and hybridization with a 15-PGDH-specific probe. Sequencing these DNA bands revealed that the largest corresponded to the 15-PGDH cloned from human placenta [Ensor et al., J. Biol. Chem. 265 (1990) 14888-14891]. The smaller sequence coded for a predicted C-terminal-truncated form of 15-PGDH. This subtype of the type-I 15-PGDH mRNA was also found using RT-PCR in human liver, placenta and a cell line derived from a human medullary thyroid carcinoma (TT cells). Hybridization studies using specific probes indicated that this new mRNA form probably corresponded to the 3.4-kb mRNA, one of the two 15-PGDH mRNAs previously detected in Northern blot analysis.

1,25 dihydroxyvitamin D and dexamethasone decrease in vivo Walker carcinoma growth, but not parathyroid hormone related protein secretion

Parathyroid hormone related protein (PTHrP) is produced by several breast cancers. 1,25 dihydroxyvitamin D (1,25[OH]2D) and Dexamethasone (DEX) have been shown to decrease PTHrP mRNA expression in several cell lines. We therefore tested the in vivo effect of both steroids on PTHrP secretion and tumor development of the Walker carcinoma (WC). WC cells were injected subcutaneously in Fisher rats which were simultaneously treated with either vehicle, or 1,25(OH)2D (0.5 micrograms/kg/d) or DEX (2 mg/kg/d). After 7 days, tumor weight was significantly decreased in the 2 treated-groups as compared to the control group. Vehicle treated-rats developed hypercalcemia, which was also observed in rats treated with 1,25(OH)2D; by contrast, the plasma calcium was significantly decreased in the DEX-treated group compared to vehicle-treated rats. In a dose-effect experiment, this dose of 1,25(OH)2D induced marked hypercalcemia in rats not implanted with WC, but was required to decrease the tumor weight in implanted rats. In both 1,25(OH)2D and DEX-treated groups, plasma PTHrP levels were significantly decreased, but there was a similar correlation between PTHrP plasma level and tumor weight in the three groups. Indeed, the cytosolic PTHrP content/mg tumor was identical in the 3 groups. By contrast, the PTHrP/Actin mRNA in the tumor was significantly decreased in the 1,25(OH)2D group, comparatively to the vehicle and DEX groups. Our results show that Dexamethasone and 1,25(OH)2D decrease WC tumor development in vivo, but do not change the PTHrP secretion by the remaining tumor although steady state PTHrP mRNA content level is decreased by 1,25(OH)2D.

Cytokine-mediated bone resorption in patients with the hyperimmunoglobulin E syndrome

Hyperimmunoglobulin E syndrome (HIES) is a rare immunodeficiency disorder characterized by increased serum immunoglobulin E levels. Bone fragility is part of this syndrome, which has recently been reported to be also associated with an imbalance in cytokine-secreting lymphocyte subpopulation. It has recently been shown that some cytokines can play a role in the bone fragility following menopause. We therefore investigated six patients (mean age 16.5 +/- 8.5 years) affected by this rare syndrome in order to study their bone remodeling and the possible involvement of cytokines in causing the bone fragility associated with this disease. Three of six patients had suffered long bone fractures; in four of six patients the cortical bone mass measured at the distal radius was two standard deviations below that of the aged-matched controls. Urinary pyridinoline excretion, a marker of bone resorption, was markedly increased in the two youngest patients. Adherent mononuclear cells derived from these patients were cultured in vitro and the bone resorbing activity (BRA) of the culture supernatant was measured by means of a fetal rat long bone assay. The BRA was up to 28% above the basal value. We compared the BRA and the cytokine production by the mononuclear cells of these patients to that of postmenopausal women. The BRA, and the IL1 beta, IL6, and TNF alpha levels in the mononuclear cell culture supernatants were identical for both HIES and postmenopausal women. However, the levels of PGE2 were higher and the levels of interferon-gamma were lower in the HIES patients. In conclusion, increased bone resorption in young patients with the HIES is responsible for the cortical bone loss that leads to a higher incidence of fractures. The high BRA secreted by the mononuclear cells of these patients is similar to that found in mononuclear cells from postmenopausal women. These data provide evidence of potent mononuclear cell activation leading to bone loss in HIES, which could be related to IgE-dependent mechanisms.

Osteoclast formation from human cord blood mononuclear cells co-cultured with mice embryonic metatarsals in the presence of M-CSF

Investigating the potentiality of cord monocytes to differentiate toward osteoclast-like cells (OCL) in vitro, we previously reported that in the presence of 1,25(OH)2 vitamin D3 (1,25-(OH)2D3), multinucleated-cells generated by cord monocyte cultures though displaying morphological features of OCL failed to resorb devitalized bones. We thus hypothesized that full differentiation of cord monocytes toward bone-resorbing cells may require the presence of factors released from and/or direct interactions with living osteogenic cells. In the present study, we tested these hypotheses using two culture systems supporting the development of bone-resorbing cells in the presence of bone matrix. First, cord mononuclear cells were co-cultured with murine fetal metatarsals depleted of osteoclast progenitor cells (stripped metatarsals) in the presence of 1,25-(OH)2D3. We found that cord mononuclear cells failed to differentiate toward OCL as indicated by the absence of the release of 45Ca previously incorporated in fetal bones and by the absence of formation of TRAP-positive (TRAP[+]) multinucleated cells which have invaded mineralized cartilage during the co-culture period. In the same model, we then investigated the effect of some soluble factors known as stimulators of osteoclast differentiation. Whereas exogenous rhIL6 and rhIL3 were ineffective in this assay, rhM-CSF consistently increased both the number of TRAP(+) multinucleated cells inside the mineralized cartilage and the release of 45Ca into the culture media. The effects of rhM-CSF were time-dependent reaching the maximum after 3 weeks of culture.(ABSTRACT TRUNCATED AT 250 WORDS)