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Biomedical subjects

C R Dunstan

Publications and source records attributed to C R Dunstan.

At least 55 records · Page 3Linked to original sources
PubMed1997

Osteoprotegerin: a novel secreted protein involved in the regulation of bone density.

A novel secreted glycoprotein that regulates bone resorption has been identified. The protein, termed Osteoprotegerin (OPG), is a novel member of the TNF receptor superfamily. In vivo, hepatic expression of OPG in transgenic mice results in a profound yet nonlethal osteopetrosis, coincident with a decrease in later stages of osteoclast differentiation. These same effects are observed upon administration of recombinant OPG into normal mice. In vitro, osteoclast differentiation from precursor cells is blocked in a dose-dependent manner by recombinant OPG. Furthermore, OPG blocks ovariectomy-associated bone loss in rats. These data show that OPG can act as a soluble factor in the regulation of bone mass and imply a utility for OPG in the treatment of osteoporosis associated with increased osteoclast activity.

Amino Acid Sequence↗
PubMed1997

Mitogenic lectin concanavalin A induces calvarial bone formation in vivo via indomethacin-sensitive pathway.

Natural products such as plant lectins have not been extensively surveyed for their potential as anabolic agents. Wlodarski (1991) observed that the lectin Concanavalin A (ConA) has chondrogenic and osteogenic activity following local injection over the mouse tibia. To gain more insight into the mechanism of ConA in bone, we investigated and quantitated the effects of ConA injected locally over the mouse calvaria in vivo. ConA was injected subcutaneously over the calvaria of mice at 2, 10, and 20 microg per injection, four times a day, for three consecutive days. By day fourteen, a layer of new woven bone 30 microm thick had been laid down on the periosteal surface, resulting in a 36% increase in calvarial thickness (as compared with 2% in vehicle-treated controls). ConA also increased periosteal width and osteoblast surface in a dose-dependent manner. Concurrent administration of indomethacin (30 microg) with ConA (20 microg), four times a day for 3 days, strongly inhibited new bone formation. With a single injection of ConA (80 microg) over the calvaria, osteoclastic bone resorption and proliferation of osteoblast precursors and periosteum increased at day four, but showed a decrease at later times (14 and 28 days after injection). Except at the earliest time, there was little evidence of osteoclastic bone resorption. New bone width increased linearly over 28 days. In summary, ConA induced new bone formation in a pattern comparable with that of aFGF and bFGF, potent stimulators of calvarial bone formation (Dunstan, 1993), and this osteogenic effect was caused by an indomethacin-sensitive pathway.

Animals↗
PubMed1997

Effects of human tumor cell lines on local new bone formation in vivo.

Although some tumors cause osteolytic lesions, there are some that stimulate new bone formation. This is an important phenomenon because the responsible mechanisms probably represent an aberration of normal physiological bone formation, and identifying the factors involved in the process may lead to new therapies for various bone diseases. To clarify our understanding of the potential mechanism responsible, we compared and quantitated the extent of new bone formation stimulated by human tumors (HeLa, Hep-2, AV-3, FL, WISH and KB), some of which have osteogenic activity in vivo [2]. Tumor cells were injected over the calvaria of nude mice to examine formation of new bone. The tumor cells produced three histologically distinct patterns of new bone growth: (1) WISH and KB stimulated appositional bone growth adjacent to periosteal bone surfaces; (2) HeLa and Hep2 induced new bone growth over calvarial surface even when distant from the tumor mass; (3) FL stimulated bone formation adjacent to periosteum as well as ectopic bone formation in sites distant from bone. All tumors except AV3 induced mean new bone thickness >100 microm, and Hep-2 cells produced bone 330 microm thick. PCR and Northern blot analysis of mRNA isolated from cultured tumor cells revealed that all cell lines expressed mRNA for TGFbeta, (fibroblast growth factor) FGF-1, FGF-2, and IGF-I, and most cell lines produced mRNA for PDGF. Only FL expressed large amounts of mRNA for BMP2. In serum-free conditioned media from Hep2 and HeLa cells purified by heparin affinity chromatography, we have identified FGF-I, FGF-2, and PDGF by immunodetection with specific antibodies. Our results show that new bone growth caused by these tumors is likely due to the production of bone growth factors by the tumor cells, and that the overall effects on bone may be due to several factors working in concert.

Animals↗
PubMed1997

Bone morphogenetic protein 2 (BMP-2) enhances BMP-3, BMP-4, and bone cell differentiation marker gene expression during the induction of mineralized bone matrix formation in cultures of fetal rat calvarial osteoblasts.

Normal bone formation is a prolonged process that is carefully regulated and involves sequential expression of growth regulatory factors by osteoblasts as they proliferate and ultimately differentiate. Since this orderly sequence of gene expression by osteoblasts suggests a cascade effect, and BMP-2 is capable of initiating and maintaining this effect, we examined the effects of BMP-2 on expression of other BMPs and compared these effects with the expression pattern of bone cell differentiation marker genes in primary cultures of fetal rat calvarial (FRC) osteoblasts. To examine the gene expression profile during bone cell differentiation and bone formation, we also examined the effects of rBMP-2 on bone formation in vivo and in vitro. rBMP-2 stimulated bone formation on the periosteal surface of mice when 500 ng/day rBMP-2 was injected subctaneously. When rBMP-2 was added to primary cultures of FRC osteoblasts, it accelerated mineralized nodule formation in a time and concentration-dependent manner (10-40 ng/ml). rBMP-2 (40 ng/ml) enhanced BMP-3 and -4 mRNA expression during the mineralization phase of primary cultures of FRC osteoblasts. Enhancement of BMP-3 and -4 mRNA expression by rBMP-2 was associated with increased expression of bone cell differentiation marker genes, alkaline phosphatase (ALP), type I collagen, osteocalcin (OC), osteopontin (OP), and bone sialoprotein (BSP). These results suggest that BMP-2 enhances expression of other BMP genes during bone cell differentiation. BMP-2 may act in a paracrine fashion in concert with other BMPs it induces to stimulate bone cell differentiation and bone formation during remodeling.

Amino Acid Sequence↗
PubMed1996

E-cadherin expression in human breast cancer cells suppresses the development of osteolytic bone metastases in an experimental metastasis model.

The molecular mechanisms by which human cancer cells spread to bone are largely unexplored. The process likely involves cell adhesion molecules (CAMs) that are responsible for homophilic and heterophilic cell-cell interactions. One relevant CAM may be the calcium-dependent transmembrane glycoprotein E-cadherin. To investigate the involvement of E-cadherin in breast cancer metastasis to bone, we used an in vivo model in which osteolytic bone metastases preferentially occur after injections of cancer cells directly into the arterial circulation through the left ventricle of the hearts of nude mice. We have found that E-cadherin-negative human breast cancer cells MDA-MB-231 (MDA-231) develop radiographically detectable multiple osteolytic bone metastases and cachexia in this model. However, MDA-231 breast cancer cells that were transfected with E-cadherin cDNA showed a dramatically impaired capacity to form osteolytic metastases and induce cachexia. Histological and histomorphometrical analyses of bones of mice bearing mock-transfected MDA-231 revealed aggressive metastatic tumor, whereas metastatic tumor burden was significantly decreased in the bones of mice bearing E-cadherin-expressing MDA-231. Nude mice bearing E-cadherin-transfected MDA-231 breast cancer cells survived longer than mice bearing mock-transfected MDA-231 breast cancer cells. Anchorage-dependent and -independent growth in culture and tumor enlargement in the mammary fat pad of nude mice were unchanged between mock-transfected and E-cadherin-expressing MDA-231, suggesting that these differences in metastatic behavior are not due to an impairment of cell growth and tumor-igenicity. Our results show the suppressive effects of E-cadherin expression on bone metastasis by circulating breast cancer cells and suggest that the modulation of expression of this CAM may reduce the destructive effects of breast cancer cells on bone.

Animals↗
PubMed1993

Measurement of osteoclasts and bone resorption by automated image analysis.

An automated image analysis method is described for measurement of osteoclasts and resorbing surface in calcified bone. Osteoclasts, osteoid, and mineralized bone were measured in a single section, reacted for acid phosphatase activity, and then stained with orange G and light green stain. Three images were acquired of each field with a monochromatic camera at illuminating wavelengths of 635, 540, and 480 nm (selected using a stage monochromator). These wavelengths were chosen according to the absorption spectra of the different image components to maximize absorption differences between osteoclasts (red), mineralized bone (blue/green), and osteoid (orange). These components were then discriminated according to operator-defined ranges of color density (mineralized bone) or color fraction (osteoid and osteoclasts). A gray level coded segmented image was produced, from which was determined the area, perimeter, and number of each component and the length of contact zones with the marrow and between these components. The method was evaluated by twice measuring 10 bone sections from patients with end-stage liver failure awaiting liver transplantation. The method was quite reproducible, with coefficients of variation varying between 4% for bone volume (% tissue volume) and 22% for osteoid surface (% bone surface). The sections were also measured using a previously established semiautomated method. Coefficients of variation between methods were higher varying between 4% for bone volume (% tissue volume) and 56% for osteoid volume (% bone volume). The automated method gave a substantial time saving compared to the semiautomated method. An interactive technique was used in adjacent sections to evaluate tetracycline labeling and osteoblast surfaces.

Adolescent↗
PubMed1993

The effect of low-dose cyclical etidronate and calcium on bone mass in early postmenopausal women.

This 2-year study was carried out in 36 healthy women of mean age 53.9 +/- 3.8 (SD) years and 3.4 +/- 2.3 years postmenopausal. Bone mineral density (BMD) in the spine, measured by single-energy quantitative computed tomographic scanning, gave a mean initial value of 110 +/- 26 mg/ml. The women were divided randomly into group 1 (n = 11), calcium 600 mg/day; group 2 (n = 15), calcium plus etidronate sodium 400 mg/day for 14 days every 3 months; and group 3 (n = 10), calcium plus etidronate plus phosphate, the 14-day etidronate course being preceded by phosphate 1 g twice daily for 3 days. During the first year of the study BMD decreased by 6.0 +/- 5.8% (p < 0.005) in group 1 subjects and increased by 4.5 +/- 7.8% (p < 0.005) in the combined etidronate-treated groups (difference between control and treated p < 0.001). Inclusion of phosphate in the regimen did not affect the response to etidronate. In the second year there was no significant mean change in BMD in any of the three groups. However, whilst there was little change in BMD values for most of the group 1 subjects, there was considerable variation in individual response within the etidronate-treated groups, with some subjects gaining and some losing bone. The change in BMD during the second year in the subjects as a whole was highly correlated with the change in plasma calcium after 3 months of treatment (r = 0.60, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Bone Density↗
PubMed1993

Osteocyte death and hip fracture.

The viability of osteocytes can be demonstrated in sawn decalcified sections of bone by their lactate dehydrogenase activity. In the cancellous bone of the femoral head, the proportion of lacunae containing viable osteocytes decreased from 88 +/- 7% (mean +/- SD) at 10-29 years to 58 +/- 12% (P < 0.001) by 70-89 years. Viability in the second lumbar vertebra was 88 +/- 3% in subjects aged 25-90 years and did not decrease with age. Mean osteocyte viability in the femoral head of 21 hip fracture patients aged 72-94 years was 58 +/- 21%, similar to controls of a similar age, though there was greater variation and, in five patients, osteocyte viability was less than 25%. In hip fracture patients, microfracture callus incidence correlated positively with osteocyte viability, with little or no fracture callus observed if the bone viability was low. Ultimate compressive strength did not correlate with osteocyte viability. In the femoral head there is gradual, age-related reduction in osteocyte viability that can be more pronounced in hip fracture. Osteocyte death may affect bone quality by impairing repair of fatigue damage.

Adolescent↗
PubMed1992

Bone death in transient regional osteoporosis.

A 48-year-old man developed transient regional osteoporosis, with hip and later knee pain. He responded well to lumbar sympathectomy. The femur and tibia adjacent to the painful knee were osteoporotic, while the medial femoral condyle showed increased uptake in a bone scan. In the femoral condyle, bone histology showed areas of dead bone undergoing osteoclastic resorption, and increased bone formation. The tibial bone was histologically normal. The partial bone death in the distal femur suggests that the disorder may be related to both avascular necrosis of bone and reflex sympathetic dystrophy.

Bone Resorption↗
PubMed1992

Metabolic studies in kidney stone disease.

Patients with kidney stones (n = 59) and healthy controls (n = 31) collected a 24-hour urine sample and later underwent a 6-hour 'fast and load' test in which an oral calcium load was taken after 2 hours. In the 24-hour urine sample, mean calcium excretion was higher in patients than controls, while mean urate, oxalate and citrate levels were similar. The patients had higher levels of fasting plasma calcium, serum calcitriol and fasting urinary calcium, and lower levels of plasma phosphate than did the controls. Following the calcium load, plasma and urinary calcium increased similarly in both groups. Serum parathyroid hormone (PTH) levels were similar in both groups and decreased similarly following the calcium load. Multiple linear regression, relating the presence or absence of stone formation to all variables, found the only variables significantly related to stone formation to be plasma levels of calcium (p less than 0.001) and phosphate (p = 0.001) and fasting urinary urea (p less than 0.001), and 24-hour urinary calcium excretion (p less than 0.05). Urinary oxalate and citrate were not related to stone formation. The data do not support the hypothesis that primary stimulation by calcitriol produces a normal fasting plasma calcium level, with an exaggerated increase after an oral calcium load. The findings instead suggest an abnormality of parathyroid cell 'set point', such that PTH secretion continues until the plasma calcium level is a little higher and the phosphate a little lower than in controls.

Adult↗
PubMed1991

Treatment of Paget's disease of bone with a combination of intranasal salmon calcitonin and oral calcium and thiazide.

The purpose of this study was to establish the smallest dose of nasally administered salmon calcitonin (SCT) which, if given in conjunction with a previously published calcium/thiazide treatment, would be as effective as parenteral SCT in the treatment of Paget's disease of bone. Forty patients suffering from symptomatic Paget's disease were treated with 0.5 g calcium three times daily, 10 mg/day clopamide, and 400 IU nasally administered salmon calcitonin given once or twice weekly. This regimen was given for 5 months, after which all treatment was ceased for 4 months. Parenteral SCT (100 IU) was then given three times weekly for 5 months to 25 of the patients. With the oral/nasal treatment, the plasma alkaline phosphatase level (AP) decreased by 30 +/- 15 (SD)% when the SCT was given once weekly and by 39 +/- 11% (P less than 0.05) when the SCT was given twice weekly. There were similar decreases in the fasting urinary hydroxyproline:creatinine ratios. The parenteral SCT reduced the AP by 33 +/- 23%. Though reduction in bone pain was similar with both treatments, most patients preferred the oral/nasal treatment. It is concluded that the oral/nasal treatment, when the SCT is given twice weekly, has similar efficacy to parenteral SCT, and is a well tolerated, effective initial treatment for Paget's disease of bone.

Administration, Intranasal↗
PubMed1991

Bone loss after liver transplantation.

We studied 35 adult patients (mean age = 43 yr) referred for orthotopic liver transplantation. Spinal bone mineral density was measured by quantitative computed tomography scanning before transplantation (n = 35) and at 3 mo (n = 21) and 12 mo (n = 11) after orthotopic liver transplantation. The readings were corrected to age 50 yr, using the regression equations derived from normal control subjects. Quantitative bone histological studies were performed in 17 patients before orthotopic liver transplantation and 3 mo after orthotopic liver transplantation. Before orthotopic liver transplantation, the corrected spinal bone mineral density in men was 108 +/- 20 mg/cm3, less than in male control subjects (129 +/- 22 mg/cm3, p less than 0.005). In women patients the value was 117 +/- 27 mg/cm3, and in female control subjects 126 +/- 19 mg/cm3 (NS). However, women patients with primary biliary cirrhosis had lower spinal bone mineral density (106.5 +/- 14.8) than female control subjects (p less than 0.005). Histologically, the resorbing surface was near the normal mean, whereas the osteoblast surface, tetracycline surface and bone formation rate was lower in men (p less than 0.05) but not women. Spinal bone mineral density decreased by 24% in the first 3 mo after orthotopic liver transplantation with no further decrease at 12 mo. Five patients had vertebral fractures within 6 mo of orthotopic liver transplantation. One patient fractured a wrist and three had osteonecrosis of the hip or knee.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Bone death in hip fracture in the elderly.

We examined femoral head bone from 50 cadavers and from 21 patients who had suffered pathologic fracture of the femoral neck. We used a histochemical technique for lactate dehydrogenase (LDH) activity to demonstrate osteocyte viability. The femoral heads were removed within 36 hours of death or fracture, as LDH activity persists in the cytoplasm of viable cells for this time at 37 degrees after interruption of the blood supply. In the controls, there was an age-related reduction in mean osteocyte viability, from 88 +/- 7% (mean +/- SD) at age 10-29 years to 58 +/- 12% at age 70-89 years. In the hip fracture patients, mean osteocyte viability was 58 +/- 21% but there was much variability in both osteocyte viability and bone mass. In 5 fracture patients, there was extensive osteocyte death, suggesting that most of the femoral head bone was nonviable; these patients had little microfracture callus. Others had predominantly viable bone which was usually osteoporotic, and their bone frequently showed microfracture callus. Osteomalacia was not seen in any patient. It is suggested that bone death, in addition to osteoporosis, may sometimes contribute to hip fracture in the elderly.

Aged↗
PubMed1989

Measurement of bone in the os calcis: a clinical evaluation.

Bone mineral content (BMC) was measured in the os calcis of 232 normal subjects aged 17-82 years. The mean reproducibility (coefficient of variation) of the measurement was 1.8%. Substantial bone loss occurred between the ages of 20 and 50 years, and in females the menopause was associated with additional bone loss. There was no significant difference in the rate of bone loss in females and males, but the mean BMC was greater at all ages in males than in females. We also compared os calcis BMC with spinal bone mineral density (BMD), measured by quantitative computed tomographic (CT) scanning, in 85 subjects: 33 were normal controls, 19 had osteoporosis defined by the presence of one or more pathological fractures, and in the remainder the CT examination was performed at the patient's request. Os calcis BMC correlated with spinal BMD in both females (r = 0.69, p less than 0.001) and males (r = 0.84, p less than 0.001). However, the os calcis BMC did not reliably predict spine values around the CT "fracture threshold" of 90-100 mg/cm3 and did not correlate with osteoporotic fracture as well as did spinal BMD. It is concluded that measurement of the os calcis BMC is of limited clinical usefulness for the early diagnosis of osteoporosis.

Adolescent↗
PubMed1989

Bone histology in young adult osteoporosis.

Bone histology was quantitated in 10 osteoporotic patients aged between 17 and 51 years and in six healthy subjects aged between 23 and 43 years. The osteoporosis was of varying aetiology and was clinically stable. All patients were given tetracycline before biopsy and double tetracycline labelling was used in seven patients. Bone forming and resorbing surfaces were defined by the presence of osteoblasts and osteoclasts, respectively, which were identified by histochemical techniques. The associations between bone forming and resorbing surfaces were similar in patients and controls, though the range of values was wider in the patients than in the controls. Mineral apposition rate was normal in the osteoporotic patients, but there was a reduction in mineralising (tetracycline) surface, whether related to osteoid surface or to osteoblast surface. This did not indicate osteomalacia as the directly and indirectly measured mineralisation lag times were normal. The osteoid seams were thinner in osteoporotic patients than in controls. The data suggest that osteoclast and osteoblast numbers were normal in this group of osteoporotic patients but that the metabolic activity of osteoblasts was impaired.

Adolescent↗
PubMed1988

The effectiveness of a soluble calcium preparation as a gut phosphate binder.

We determined the phosphate binding capacity of a soluble commercial calcium preparation by carrying out metabolic balances on four normal subjects and by administering it for 4 weeks to six patients treated by maintenance hemodialysis. Each tablet of Sandocal 1000 (Sandoz, Australia) contained 1 g of elemental calcium as calcium lactate-gluconate 5.23 g and calcium carbonate 0.8 g. The metabolic balance study was performed over two consecutive nine-day periods. A constant, normal diet was consumed throughout, but in the second period one Sandocal 1000 tablet was added to each of the three major daily meals. Each period consisted of four days of equilibrium, then five days of collection of urine and feces. Polyethylene glycol 4,000 was used as a continuous fecal marker and carmine red was used to indicate gut transit time. Calcium supplementation increased fecal phosphate excretion by 11.2 +/- 2.3 mmol/d (SD), and decreased urinary phosphate by 8.4 +/- 2.6 mmol/d. Plasma calcium levels were unchanged, while plasma phosphate levels rose slightly. The increase in fecal phosphate was similar to that previously reported when calcium carbonate 8 g/d or aluminum hydroxide 6.4 g/d were administered. In the patients treated by maintenance hemodialysis, the reduction in plasma phosphate induced by Sandocal 1000, three tablets daily, was similar to that obtained with aluminum hydroxide 1.8 +/- 1.2 g/d. Hence, this calcium preparation appears to have a phosphate binding capacity similar to that of standard doses of aluminum hydroxide.

Adult↗