摘要:

AbstractWe investigated the expression of cytokine transcripts in osteoblast‐like cells derived from explants of pagetic and normal bone. A reverse transcription‐linked PCR was used that allowed the simultaneous analysis of a range of cytokines. Normal osteoblast‐like cells were found to contain the transcripts for IL‐1β, IL‐6, and TGF‐β1. For the first time we detected in bone cells the two other mammalian isoforms of TGF‐β, β2, and β3. Furthermore, we have also identified mRNA for IL‐3 and the novel chemotactic factor, IL‐8. Using this sensitive technique it was not possible to detect mRNA for IL‐1α, IL‐2, IL‐4, IL‐5, IL‐7, TNF‐α, or interferon‐γ. The human osteosarcoma cell line Saos‐2 also showed a similar pattern of expression of these cytokines to primary osteoblast‐like cells, with the exception that TNF‐α was also identified. Cells isolated from pagetic bone showed essentially the same profile of cytokine expression as normal bone except that TNF‐α was also detected in two of four samples. The cytokine profile of successive populations of cells harvested from one explant culture at 9, 22, and 57 days showed a consistent pattern of cytokine expression, demonstrating the phenotypic stability o

ISSN:0884-0431    

DOI:10.1002/jbmr.5650081002

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

年代:1993

数据来源: WILEY

摘要:

AbstractPTH and other hormones that stimulate resorption affect osteoclasts indirectly by modulating cytokine production by osteoblasts. However, the identity and role of the osteoblast‐derived cytokines involved in this process are unclear. To examine which cytokines are regulated by PTH, we assessed cytokine mRNA levels in osteoblasts using the reverse transcription‐polymerase chain reaction technique. Of the 16 cytokines we examined, unstimulated MC3T3‐E1 osteoblastic cells expressed mRNA for interleukins 5, 6, and 7, macrophage and granulocyte‐macrophage colony‐stimulating factors, transforming growth factor β1and leukemia inhibitory factor. PTH specifically increased expression of interleukin‐6 (approximately 50‐fold) and leukemia inhibitory factor (approximately 10‐fold). Levels of both IL‐6 and LIF mRNA peaked 30–60 minutes after addition of PTH and returned to baseline by 4–6 h. This rapid and transient mRNA response, which resembles that of immediate early genes, was also observed in primary rat osteoblasts. The transient mRNA response was accompanied by increased secretion of IL‐6 protein. Lipopolysaccharide, another stimulator of resorption, increased mRNA levels of a group of cytokines that were not induced by PTH, namely interleukin‐1α, tumor necrosis factor α, and granulocyte‐macrophage and granulocyte colony‐stimulating factors. We conclude that osteoblasts produce complex networks of cytokines that (1) are regulated by bone‐resorptive agents and (2) may be invol

ISSN:0884-0431    

DOI:10.1002/jbmr.5650081003

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

年代:1993

数据来源: WILEY

摘要:

AbstractNeonatal pig bone marrow stromal cells (PBMSC) were tested in vivo and in vitro to establish their use as a large‐animal model for the study of skeletogenesis. When implanted in diffusion chambers in athymic mice for 6–8 weeks, both freshly isolated pig bone marrow and passage 2 PBMSC formed partially mineralized cartilage, bone‐like material, and fibrous tissue. The cartilage showed metachromatic, perilacunar staining with toluidine blue and safronin O, alcian blue staining for chondroitin and keratan sulfate, and intense immunostaining for type II collagen. Osteocalcin was immunolocalized to the mineralized regions, consistent with the formation of bone. Alkaline phosphatase was primarily observed in cell layers at boundaries between tissue types. Unstimulated monolayer cultures of PBMSC produced type I but not type II collagen, responded to dexamethasone (10−8M) with a 1.7‐fold increase in alkaline phosphatase activity, and were stimulated to divide by basic fibroblast growth factor (1.5‐fold; EC501 ng/ml). Transforming growth factor β (TGF‐β) blocked both dexamethasone‐induced alkaline phosphatase expression (EC50, 1 ng/ml of TGF‐β) and the mitogenic effects of bFGF (EC500.06 ng/ml of TGF‐β). When incubated for 10–14 days in medium containing dexamethasone, β‐glycerophosphate and ascorbate PBMSC formed mineralized nodules. Calcification occurred in the middle of the aggregates and was associated with intensely alkaline phosphatase positive cells and a dense type I collagen‐rich matrix. PBMSC also displayed colony‐forming unit‐fibroblastic activity, with approximately 1 in 80 of the plated cells formed colonies>128 cells over 14–21 days. PBMSC therefore mimic the known activities of stromal cells from other species, including the human, suggesting that they are

ISSN:0884-0431    

DOI:10.1002/jbmr.5650081004

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe effects of different amounts of salt intake on urinary calcium and hydroxyproline (OHP) excretion were studied in oophorectomized (O) and sham‐operated (S) rats on normal calcium diet. Groups of O and S rats were given either tap water or 2, 6, or 18 g/liter of NaCl to drink. Urinary excretion of sodium, calcium, and OHP was monitored at 0, 2, and 4 months. Urinary excretion of calcium and OHP increased with increasing salt intake (P<0.001 by ANOVA) in S and O groups. Oophorectomy did not have any additional effect on calcium or OHP excretion. We conclude that increased salt intake causes increased excretion of calcium and OHP and oophorectomy does not further aggravate the los

ISSN:0884-0431    

DOI:10.1002/jbmr.5650081005

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

年代:1993

数据来源: WILEY

摘要:

AbstractTumor necrosis factor (TNF‐α) has been shown to play an important role in local control of bone remodeling. The interaction of TNF‐α and PTH was evaluated in UMR‐106–01 cells, a phenotypic osteoblastic osteosarcoma cell line. We examined the influence of TNF‐α on the two signal transduction systems triggered by PTH in UMR‐106–01 cells, adenylate cyclase and free cytosolic calcium ([Ca2+]i). cAMP generation was inhibited in TNF‐α‐pretreated cells by 69, 61, 34, and 21% at PTH concentrations of 0.1, 1, 10, and 100 nM, respectively. Inhibition was seen at TNF‐α doses of 100–1500 units/ml after a minimum incubation time of 12 h. TNF‐α inhibition of the PTH‐stimulated increase in [Ca2+], was even more pronounced: treated cells showed no change in baseline [Ca2+]i, after stimulation with 40 nM PTH. Treatment with TNF‐α was also found to inhibit both arms of the PTH response in the nontransformed osteoblastic cell line, MC3T3‐El. TNF‐α treatment did not alter cAMP generation in response to PGE2. TNF‐α inhibition of the PTH‐stimulated cAMP response was reversed completely by addition of cholera toxin (5 μg/ml) and partially by forskolin (10 μM) but not pertussis toxin (100 and 500 ng/ml). Scatchard analysis using PTHrP revealed that TNF‐α treatment reduced the number of receptors but had no effect onKD. These findings suggest that TNF‐α inhibits the osteoblastic response to PTH at least in part because of a reduction in receptor number. Further investigation is indicated to provide insight into the intera

ISSN:0884-0431    

DOI:10.1002/jbmr.5650081006

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

年代:1993

数据来源: WILEY

摘要:

AbstractTo determine whether rat osteoblasts synthesize proteins of the annexin family and to evaluate the extent to which glucocorticoids modulate the expression of annexins by these cells, osteoblasts were grown in primary cultures in the absence or presence of dexamethasone, and the expression of annexins was evaluated by immunoblotting using polyclonal antibodies against human annexins. Four different annexins (I, II, V, and VI) were found to be expressed by rat osteoblasts. The expression of annexin I, but not the other annexins studied, was increased in osteoblasts cultured in the presence of dexamethasone (173 ± 33% increase comparing untreated cells and cells treated for 10 days with 5 × 10−7M dexamethasone). Increased expression of annexin I was observed after the third day of exposure to dexamethasone and rose thereafter until day 10; annexin I expression increased with dexamethasone concentrations above 10−10M throughout the range of concentrations studied. The increase in annexin I protein was associated with an increase in annexin I mRNA and was completely blocked by the concomitant addition of the glucocorticoid receptor antagonist RU 38486. The increase in annexin I content following dexamethasone treatment was associated with an increase in alkaline phosphatase activity and PTH‐induced cAMP stimulation, whereas phospholipase A2activity in the culture medium was reduced to undetectable levels. The finding that four annexins are expressed in rat osteoblasts in primary culture raises the possibility that these proteins could play an important role in bone formation by virtue of their ability to bind calcium and phospholipids, serve as Ca2+channels, interact with cytoskeletal elements, and/or regulate phospholipase A2activity. In addition, the dexamethasone‐induced increase in annexin I may represent a mechanism by which glucocorticoids modify osteoblast

ISSN:0884-0431    

DOI:10.1002/jbmr.5650081007

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

年代:1993

数据来源: WILEY

摘要:

AbstractBased on engineering principles, geometric measurements of femoral size should be related to femoral strength and the risk for hip fracture. To evaluate whether a simple measurement of femoral geometry is associated with hip fracture risk, we obtained dual x‐ray absorptiometry scans of the proximal femur on 8074 white women age 67 or older. During an average of 1.6 years of follow‐up, 64 participants suffered hip fractures. In all fracture cases and in a random sample of 134 women who did not subsequently suffer a hip fracture, we measured hip axis length (the distance from greater trochanter to inner pelvic brim), neck width, and the neck/shaft angle on the scan printout, with the observer blinded to subsequent fracture status of the participant. Results were analyzed using multiple logistic models, and odds ratios were determined. After adjustment for age, each standard deviation decrease in femoral neck bone mineral density increased hip fracture risk 2.7‐fold (95% confidence interval 1.7, 4.3), and each standard deviation increase in hip axis length nearly doubled the risk of hip fracture (odds ratio = 1.8; 95% CI 1.3, 2.5). The relationship between hip axis length and fracture risk persisted even after adjustment for age, femoral neck density, height, and weight. A longer hip axis length was associated with an increased risk of both femoral neck (OR = 1.9; 95% CI 1.3, 3.0) and trochanteric fractures (1.6; 1.0, 2.4). We found no significant association between the neck width (1.1; 0.8, 1.5) or the neck/shaft angle (1.4; 0.9, 2.2) and risk of hip fracture. In a combined analysis of the control group with an additional population of younger volunteers, no significant relationship was found between the hip axis length and age (r= 0.04,P= 0.60) or femoral neck density (r= 0.01,P= 0.84) in 225 women from 41 to 92 years of age. We conclude that hip axis length predicts hip fractures independently of age and bone mineral density in elderly women. If verified by additional studies, this simple measurement can improve the assessment of hip fracture risk compared to a measurement of femoral neck bone density

ISSN:0884-0431    

DOI:10.1002/jbmr.5650081008

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

年代:1993

数据来源: WILEY

摘要:

AbstractRecombinant human interleukin‐1 (rhIL‐1) can induce an elevation in calcium that has been ascribed exclusively to the stimulation of bone resorption. In the present study, we investigated whether rhIL‐1 could also enhance the renal tubular reabsorption of calcium. The chronic influence of recombinant human rhIL‐1 on renal calcium transport was investigated in thyroparathyroidectomized rats. Administration of rhIL‐1 at the dose of 1.5 μg/day sc for 6 days induced a significant elevation in plasma calcium that was associated with a slight but significant decrease in the urinary excretion of calcium. Recording of the urinary calcium excretion expressed per ml glomerular filtrate at various plasma calcium levels, as achieved by acutely infusing calcium gluconate, indicates that rhIL‐1 enhanced the tubular reabsorption of calcium. The calculated index of the tubular reabsorption of calcium (TRCal) was significantly increased by rhIL‐1 (2.18 ± 0.14 versus 1.79 ± 0.07 mmol/l GFR,p<0.05, in vehicle‐treated rats). The change in the renal handling of calcium was not associated with stimulation of the tubular reabsorption of magnesium. Acute administration of a large dose (24 μg given in a bolus IV injection) of rhIL‐1 enhanced within minutes the urinary excretion of prostaglandin E2. This effect was followed by a significant increase in urinary cAMP excretion and associated with a lower urinary calcium excretion. In conclusion, the results presented in this study indicate that rhIL‐1 administered chronically selectively stimulated the tubular reabsorption of calcium. Experimental evidence suggests that this effect is mediated by prostaglandin‐induced cAMP generation. These data strongly suggest that changes in the tubular handling of calcium could contribute to rhI

ISSN:0884-0431    

DOI:10.1002/jbmr.5650081009

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

年代:1993

数据来源: WILEY

摘要:

AbstractBone mineral density (BMD) was measured at the lumbar spine and cervical and intertrochanteric regions of the proximal femur by dual‐photon absorptiometry and bone mineral content was assessed at the distal and midradius by single‐photon absorptiometry in an age‐stratified random sample of 304 Rochester, Minnesota women aged 30–94 years. Over follow‐up extending to 10 years (median 8.3 years), 93 women experienced 163 new fractures. After adjusting for age, these bone mineral measurements predicted the likelihood of any incident fracture due to moderate trauma, with relative hazards varying from 1.4 to 1.6 per SD decrease in baseline bone mineral. A 1 SD decrease in lumbar spine BMD increased the risk of a new vertebral fracture comparably to a 17 year increase in age; a 1 SD decrease in femoral BMD was comparable to a 13–14 year increase in age on the risk of a hip fracture. We conclude that bone mineral measurements made at a variety of skeletal sites can predict the occurrence for at least 8–10 years of moderate trauma fractures of the sort that might be related to

ISSN:0884-0431    

DOI:10.1002/jbmr.5650081010

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

年代:1993

数据来源: WILEY

摘要:

AbstractWe report here that osteoblasts and osteoblast‐like osteosarcoma cells express PMCA1b, an alternatively spliced transcript of plasma membrane Ca2+‐ATPase. Synthetic oligonucleotide pairs were designed based upon unique regions of the cDNA encoding known PMCA isoforms (PMCA1–3) and used as primers in PCR‐mediated amplification of cDNA synthesized from ROS 17/2.8 osteosarcoma cell RNA. A product was observed only when PMCA1‐specific primers were present; no products were seen with PMCA2 or PMCA3 primers unless cDNA synthesized from rat brain RNA was present. Examination of the cDNA encoding the C terminus of PMCA1 from ROS 17/2.8 cells revealed that the mRNA is spliced to yield the PMCA1b isoform, a Ca2+‐ATPase containing a consensus phosphorylation site for cAMP‐dependent protein kinase A and a modified calmodulin binding domain. PMCA1b was also detected in UMR‐106–01 osteosarcoma cells and unpassaged primary rat calvarial osteoblasts. These results suggest that the regulation of osteoblast function by agents that act via cAMP‐mediated pathways may involve alterations in the activity of the plasma m

ISSN:0884-0431    

DOI:10.1002/jbmr.5650081011

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

年代:1993

数据来源: WILEY