摘要:

Abstract1α,25‐Dihydroxyvitamin D3[1α,25‐(OH)2D3] rapidly increases cytosolic calcium in a variety of cell types. Although these rapid effects do not appear to directly involve genome activation, the requirement for the classic vitamin D receptor is unclear. Clonal rat osteosarcoma cells, ROS 17/2.8, respond to 1α,25‐(OH)2D3with an increase in osteocalcin message but ROS 24/1 cells do not. The lack of the receptor for vitamin D in the ROS 24/1 cells has been confirmed by the absence of any detectable vitamin D‐receptor complex binding to the vitamin D‐responsive element (VDRE) of the osteocalcin gene and the absence of vitamin D receptor mRNA in the cells. Quin‐2‐loaded ROS 17/2.8 and ROS 24/1 cells were treated with 1α,25‐(OH)2D3in the presence and absence of extracellular calcium and with the inactive epimer, 1β,25‐dihydroxyvitamin D3[1β,25‐(OH)2D3]. The 1α,25‐(OH)2D3increased cytosolic calcium in the ROS 17/2.8 and 24/1 cells after 5 minutes in a dose‐responsive manner and in the presence and absence of extracellular calcium. Pretreatment of both cell lines with 1β,25‐(OH)2D3for 30 s blocked the hormone‐induced rise in cytosolic calcium. The rapid effects of 1α,25‐(OH)2D3on ROS cells with and without the vitamin D receptor and the ability of the inactive epimer to inhibit these effects indicate that the signaling system mediating the hormone's rapid actions

ISSN:0884-0431    

DOI:10.1002/jbmr.5650061202

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1991

数据来源: WILEY

摘要:

AbstractWe recently showed that leukemia inhibitory factor (LIF) stimulates45Ca release from neonatal mouse calvariae in vitro and that it increases DNA and protein synthesis in this model. To elucidate further the actions of LIF on bone we now report the effects of this cytokine on DNA synthesis and cell proliferation in isolated fetal rat osteoblasts and in the osteogenic sarcoma cell line, UMR‐106. In both actively growing and growth‐arrested rat osteoblasts, LIF stimulated [3H]thymidine incorporation in a dose‐dependent manner. The increase in DNA synthesis was time dependent, was associated with an increase in the number of osteoblasts, and was not blocked by indomethacin. LIF‐treated cells showed reduced [3H]thymidine incorporation in comparison with control, as they approached confluence, possibly because of the increased cell density in the LIF‐treated cultures.In UMR‐106 cells, treatment with LIF inhibited [3H]thymidine incorporation in both actively growing and growth‐arrested cultures. The effect was dose dependent and sustained with time. There was a corresponding decrease in cell numbers. It is concluded that although LIF causes an early stimulation of proliferation in isolated osteoblasts, it has opposing effects on UMR‐106 cells. It is not possible to determine which of these effects is more relevant to the actions of LIF in vivo. The demonstration of a LIF effect on both these cell types, however, provides further evidence that this cytokine acts directly

ISSN:0884-0431    

DOI:10.1002/jbmr.5650061203

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1991

数据来源: WILEY

摘要:

AbstractRecent evidence suggests that cytokines, in addition to regulating hematopoiesis and immune functions, may be important paracrine regulators of bone turnover. Interleukin‐1 (IL‐1) and IL‐6 are cytokines that are produced by and affect both hematopoietic and nonhematopoietic cell types. IL‐1 stimulates bone resorption and inhibits osteoblast proliferation and collagen production. Previous reports that IL‐6 was secreted in murine osteoblast and bone organ cultures in response to IL‐1 and PTH suggested that IL‐6 has paracrine effects on bone resorption or formation. To determine whether IL‐6 has a paracrine function in human bone, IL‐6 expression in cells isolated from normal human bone was investigated. IL‐6 mRNA levels in untreated cultures were low and variable, and IL‐6 secretion was undetectable. PTH had no effect on IL‐6 mRNA levels or IL‐6 secretion. IL‐1β increased IL‐6 mRNA levels, maximally 40‐fold at 12 h. IL‐1β increased IL‐6 secretion to 0.13 nM, more than 80‐fold that of untreated controls at 12 h. IL‐1β also increased IL‐1β mRNA levels, maximally 9‐fold at 12 h, but did not increase cellular levels or secretion of IL‐1β protein. Recombinant human IL‐6 at 0.5–5 nM stimulated resorption in neonatal mouse calvarial organ cultures but had no effect on human bone‐derived cell DNA synthesis or type I procollagen mRNA levels. The results suggest that IL‐6 production by human osteoblasts may function to enhance osteolytic activity of IL‐1 but does not affect proliferative and matrix biosynthetic aspects of bone formation that were tested. Because osteoblasts and bone marrow cells are in close proximity, IL‐6 produced by osteoblasts may also function to amplify IL‐1

ISSN:0884-0431    

DOI:10.1002/jbmr.5650061204

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1991

数据来源: WILEY

摘要:

AbstractEstrogen stimulates osteoblastic collagen production in vitro, but whether the same stimulation takes place in vivo is still unknown. To test the stimulatory effects of a combined estrogen‐gestagen regimen in vivo we monitored serum levels of the carboxy‐terminal propeptide of human type I procollagen (S‐PICP) in a group of 12 osteoporotic women over a 150 week treatment period. Spinal bone mineral content (BMC) increased to a maximum of 5% over pretreatment values around week 90. Serum alkaline phosphatase (S‐AP) and serum bone gla protein (S‐BGP) both fell from initial values of 220 U/liter and 39 ng/ml, respectively, to 146 U/liter (p<0.01) and 27.2 ng/ml (NS) around week 60 and remained reduced over the remaining treatment period. S‐PICP also fell from 117 to 68 μg/liter at week 60 and 70 μg/ml at week 150 (P<0.01). This is equal to a reduction to 32 ± 10% pretreatment levels. The reduction in S‐PICP was not significantly different from that of the other two markers of bone formation (S‐AP and S‐BGP). Thus, provided the metabolic clearance of PICP remains unaltered after hormone replacement therapy, no major stimulation of osteoblastic collagen type I synthesis was demonstrable during estrogen‐gestagen treatment in this population of osteoporotic women. The changes in bone markers seen in this study are therefore consistent with an estrogen‐mediated reduction in the frequency of remodeling activation. Because of the reduction in bone turnover and methodologic limitations of bone marker assays, however, smaller increases in the amount of bone formed per activation c

ISSN:0884-0431    

DOI:10.1002/jbmr.5650061205

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1991

数据来源: WILEY

摘要:

AbstractWe tested acid and basic fibroblast growth factor (aFGF and bFGF), members of the heparin binding FGF family, for their ability to stimulate bone resorption as measured by the release of previously incorporated45Ca from cultured fetal rat long bones in the presence and absence of heparin. Purified low‐molecular‐weight heparin (LMW heparin) at 5–125 μg/ml had no direct stimulatory effect. There was little effect from aFGF (10−11‐10−8M) alone, but increased resorption was observed in the presence of LMW heparin. With bFGF, increased bone resorption was observed at 10−9M but not at 10−8M. The stimulatory effects of aFGF and bFGF in the presence of LMW heparin were not blocked by the addition of indomethacin (10−6M), which blocks prostaglandin production, or hydroxyurea (10−3M), which blocks DNA synthesis. However, pretreatment with aphidicolin (3 × 10−5M), a potent inhibitor of DNA synthesis, blocked the effect of acid FGF and diminished the effect of bFGF. These results indicate that both aFGF and bFGF can stimulate bone resorption by a prostaglandin‐independent mechanism, particularly in the presence of heparin. The activation of FGF‐mediated bone resorption by heparin could play a role in producing the osteoporosis that has been described with hepar

ISSN:0884-0431    

DOI:10.1002/jbmr.5650061206

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1991

数据来源: WILEY

摘要:

AbstractThe actions of a novel vitamin D3analog calcipotriol (MC 903), on human bone‐derived cells were compared to those of 1,25‐dihydroxyvitamin D3[1,25‐(OH)2D3]. Both calcipotriol and 1,25‐(OH)2D3inhibited the proliferation of human osteoblast‐like cells in a dose‐dependent manner (10−10‐10−6M), an effect observed at different cell densities. Lower concentrations of either agent exerted no marked effect on the growth of the cells compared to untreated cultures. Calcipotriol and 1,25‐(OH)2D3were equipotent in stimulating the activity of alkaline phosphatase and the synthesis of osteocalcin in human osteoblast‐like cells. The stimulation of alkaline phosphatase activity and osteocalcin synthesis by both compounds was evident by 24 h and was increased progressively up to 96 h in a dose‐dependent manner over the concentration range of 10−10‐10−6M. The increment in both proteins was dependent on cell density and was attenuated at higher cell densities. In contrast to these actions, neither calcipotriol nor 1,25‐(OH)2D3(10−14‐10−6M) affected the synthesis of prostaglandin E2. These studies indicate that calcipotriol and 1,25‐(OH)2D3exhibit a similar spectrum of activity

ISSN:0884-0431    

DOI:10.1002/jbmr.5650061207

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1991

数据来源: WILEY

摘要:

AbstractWe Evaluated Spinal And Femoral Bone Mass And Density Utilizing Dual‐Energy X‐Ray Absorptiometry (Dexa) In Rats In Which Severe Hyperparathyroidism Was Produced By The Expression Of The Gene For Human Pth‐(1–84) (Hpth). This Gene Was Incorporated Into A Retroviral Vector That Was Transfected Into Fibroblasts Which Were Subsequently Injected Into Their Peritoneal Cavities. Further, We Examined The Effect Of The Administration Of Pamidronate On Bone Mass And Density In The Presence Of Extremely High Concentrations Of Hpth. Three Groups Of Rats Were Studied. Groups 1 And 2 Receive The Hpth‐Secreting Fibroblasts; Group 2 Subsequently Received Pamidronate (2.5 Mg/Kg Iv) 18 And 27 Days After Receiving The Fibroblasts. These Animals Developed Levels Of Hpth>1.0 μg/Liter And Became Hypercalcemia Within 20 Days. These Animals Became Lethargic And Were Significantly Lower In Weight Than Age‐Matched Controls (Group 3,P<0.05). After Accounting For The Animal Weight There Was A Further Significant Decrease In Bone Mineral Content And Density (Bmc And Bmd) On Day 29 Attributable To Hpth‐Mediated Bone Loss. Treatment With Pamidronate Resulted In A Higher Bmc Of The Lumbar Spine Than In The Untreated Animals, With Elevated Concentrations Of Hpth. The Bmd Was Significantly Higher At Both The Lumbar Spine And Femur In The Pamidronate‐Treated Animals (P<0.05). The Cv Of Paired Measurements Of Bmd Was 2.7% At The Spine And 1.5% Of A Femur, Respectively. The Bmc Of The Lumbar Spine And Femur Was Closely Correlated With The Ashed Weight Of The Same Bones (R= 0.92 And 0.8

ISSN:0884-0431    

DOI:10.1002/jbmr.5650061208

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1991

数据来源: WILEY

摘要:

AbstractFractional Whole‐Body Retention Of47Ca (retention fraction) in 58 healthy postmenopausal women participating in a calcium supplementation trial was examined for seasonal variation and for relationships to rates of bone loss and plasma vitamin D levels. Retention fraction was measured after 18 months in the trial. Bone mineral densities of the radius, femoral neck, and lumbar spine were measured at baseline, 12 months, and 24 months in the trial, and plasma 1,25‐dihydroxyvitamin D [1,25‐(OH)2D] and 25‐hydroxyvitamin D (25‐OHD) at 12, 18, and 24 months. The adjusted retention (retention fraction adjusted for total calcium intake, smoking status, and log years since menopause) was significantly higher in women evaluated in the months of August through October (mean ± SD, 19.8 ± 4.1%,n= 13) than in March through May (mean ± SD, 17.0 ± 4.7%,n= 18,p= 0.05). Plasma 25‐OHD was associated with retention fraction only in women with low calcium intakes (partialr= 0.69 controlling for total calcium intake and log body mass index,n= 14,p= 0.01). Plasma 1,25‐(OH)2D was not related to retention fraction. Adjusted retention, independent of total calcium intake, log years since menopause, smoking status, and season, explained 8% of the variability in the annual change in radius density (partialr= 0.29,p<0.05). No significant associations were seen at the spine and femur. These results indicate there is seasonal variation in calcium retention, that calcium retention is positively correlated with plasma 25‐OHD levels in women with low calcium intakes, and that an increased level of retained calcium is associated with a lower rate of bone l

ISSN:0884-0431    

DOI:10.1002/jbmr.5650061209

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1991

数据来源: WILEY

摘要:

AbstractWe have devised a new method for measurement of final depth of erosion in cancellous bone with an intra‐individual precision of 4.3% and applied it to determine the mechanism of continuing reduction in trabecular thickness after menopause. Mean erosion depth (SD) was 40.8 (2.0) μm in 10 healthy postmenopausal women and 41.4 (2.1) μm in 10 age‐matched patients with postmenopausal osteoporosis; the difference was not statistically significant. In contrast, wall thickness, using a method based on density differences between new and old bone, was 39.5 (2.0) μm in the normal subjects and 35.3 (2.0) μm in the patients with osteoporosis (p<0.0001). The balance per remodeling cycle (ΔBMU) was −1.34 (2.49) μm in the normal subjects and −6.11 (1.95) μm in the patients with osteoporosis. This difference was also highly significant (p<0.001). Indirect estimations of erosion depth and ΔBMU, based on the fall in trabecular thickness from an assumed premenopausal value of 147 μm and the number of remodeling cycles accumulated since menopause, agreed closely with the measured values. Erosion depth measured by the Eriksen method also showed no significant difference between the two groups, but because the values were substantially higher ΔBMU was improbably high in both groups, did not differ significantly between groups, and was inconsistent with the observed difference in trabecular thickness. We conclude that (1) the more rapid continuing loss of cancellous bone in patients with postmenopausal osteoporosis than in age‐matched control subjects is due entirely to a difference in wall thickness, not to a difference in erosion depth; and (2) defective recruitment and/or function of osteoblasts is the major cellular mechanism of trabecular thinning in patients with postmenopausal osteoporosis and probably also in normal subjects. We emphasize that these conclusions do not speak to the mechanism of complete removal of trabeculae in the early ye

ISSN:0884-0431    

DOI:10.1002/jbmr.5650061210

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1991

数据来源: WILEY

摘要:

Abstract1,25‐Dihydroxyvitamin D3[1,25‐(OH)2D3] was tested for its effects on prostaglandin E2(PGE2) production and bone resorption in cultured mouse parietal bones. We found that at 24 h 1,25‐(OH)2D3increased45Ca release but did not affect PGE2production. However, at 48 h 1,25‐(OH)2D3produced a dose‐related increase in PGE2production. PGE2production was increased with 1,25‐(OH)2D3at 10−10‐10−8M, and45Ca release was increased with 1,25‐(OH)2D3at 10−11‐10−8M. The effects of 1,25‐(OH)2D3on PGE2production persisted in the presence of cortisol (10−8M), and the effects were greater in the presence of arachidonic acid (10−5M) or fetal bovine serum (10%). Human interleukin‐1α (IL‐1, 1 ng/ml) and bovine parathyroid hormone‐(1–34) (PTH, 10 ng/ml) increased PGE2production earlier and to a greater extent than 1,25‐(OH)2D3. The PGE2response to IL‐1 and PTH was not affected by 1,25‐(OH)2D3at 24 h, but at 48 h 1,25‐(OH)2D3(10−8M) increased the PGE2response to both IL‐1 and PTH. The stimulation of45Ca release at 48 h by high concentrations of 1,25‐(OH)2D3, PTH, or IL‐1 was similar, and there was no evidence for an additive effect. To test for an effect of 1,25‐(OH)2D3on endogenous IL‐1 production, experiments were performed in the presence of an IL‐1 receptor antagonist (IL‐1Ra, 1000 ng/ml), which has been found to block selectively IL‐1 effects on bone resorption and PG production. We found that IL‐1Ra blocked the stimulatory effect of 1,25‐(OH)2D3(10−8M) on PGE2production but not on45Ca release. We conclude that 1,25‐(OH)2D3at high concentrations is a stimulator of PGE2release from bone and can enhance the response to PTH and IL‐1. Its effect is smaller and occurs later than that of PTH and IL‐1. Th

ISSN:0884-0431    

DOI:10.1002/jbmr.5650061211

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1991

数据来源: WILEY