[Treatment of osteoporosis with fluoride].
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Bone and Bones↗
Biomedical subjects
D J Baylink
Publications and source records attributed to D J Baylink.
Generalized osteoarthritis associated with increased insulin-like growth factor types I and II and transforming growth factor beta in cortical bone from the iliac crest. Possible mechanism of increased bone density and protection against osteoporosis.
OBJECTIVE: To investigate whether growth factors stored in bone might explain the increased bone density and resistance to osteoporosis in generalized osteoarthritis. METHODS: Levels of insulin-like growth factor (IGF) types I and II and transforming growth factor beta (TGF beta) were measured in extracts of cortical bone from the iliac crest obtained at necropsy from subjects with or without osteoarthritis of the hands. RESULTS: Concentrations of IGF-I, IGF-II, and TGF beta were significantly higher in extracts of bone powder from subjects in the osteoarthritis group than in extracts from subjects in the control group. CONCLUSION: The results suggest that the increased bone density and resistance to osteoporosis in patients with osteoarthritis may be associated with increased skeletal concentrations of IGF-I, IGF-II, and TGF beta and may reflect a generally increased biosynthetic activity of osteoblasts in these patients.
Aged↗
Autocrine regulators of MC3T3-E1 cell proliferation.
MC3T3-E1 cells, a clonal osteoblast-like mouse calvarial cell line, secrete several growth regulating factors. These regulators include insulin-like growth factor (IGF) type I, transforming growth factor beta (TGF-beta), and IGF-II in descending order of abundance. MC3T3-E1 cells in culture also produce two IGF binding proteins (IGFBP), M(r) 25 and 32 kD, having sequence identity with IGFBP-4 and IGFBP-6, respectively. In addition, this is the first observation that osteoblast-like bone cells in culture produce IGFBP-6. To determine if growth factors produced by MC3T3-E1 cells have autocrine actions on these cells, the effects of IGF-I, IGF II, TGF-beta 1, and IGFBP-4 on MC3T3-E1 cell proliferation were determined. Exogenous addition of IGF-I and IGF-II stimulated MC3T3-E1 cell proliferation, but TGF-beta 1 and IGFBP-4 inhibited MC3T3-E1 cell proliferation. Based on these findings, we conclude that MC3T3-E1 cells in culture produce autocrine regulators of MC3T3-E1 cell proliferation and that the actions of IGFs may also be regulated by IGFBPs produced by these same cells.
Amino Acid Sequence↗
Insulin-like growth factor binding protein-4 inhibits both basal and IGF-mediated chick pelvic cartilage growth in vitro.
This laboratory has purified a unique insulin-like growth factor binding protein (IGFBP-4) that was previously demonstrated to be inhibitory to bone cell proliferation. In this study, the hypothesis that IGFBP-4 is inhibitory to insulin-like growth factor (IGF) actions on cartilage was tested using the pelvic cartilages of 10-day-old chick embryos as an in vitro model system. Pelvic leaflets were incubated in serum-free medium for 18 h with effectors (BSA, IGF-I, IGF-II, IGFBP-4, or a combination of IGF and IGFBP-4). After the first 8 h, 1.5 microCi [3H]thymidine per well was added. Cartilage growth was assayed by TCA-insoluble [3H]thymidine incorporation into DNA. Additional experiments were conducted under similar conditions to assess the actions of the effectors on cartilage dry weight over a 72 h time period. In separate experiments, serum-free medium conditioned by chick pelvic cartilages for 72 h was assayed for IGF-II by radioreceptorassay, IGF-I by radioimmunoassay, and IGFBP by western ligand analysis. Exogenous IGF addition increased [3H]thymidine incorporation and dry weight of cartilages compared to controls. IGFBP-4 decreased both parameters in basal cartilage growth and also inhibited IGF-mediated cartilage growth. Pelvic cartilages secreted in vitro both IGF-I and IGF-II and a 32-34 kD IGFBP. In conclusion, the IGFs are stimulatory to cartilage growth in vitro and embryonic chick cartilage in vitro produces both IGF-I and II as well as an IGFBP.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Changes in markers of bone formation and resorption in a bed rest model of weightlessness.
To study the mechanism of bone loss in physical unloading, we examined indices of bone formation and bone resorption in the serum and urine of eight healthy men during a 7 day -6 degrees head-down tilt bed rest. Prompt increases in markers of resorption--pyridinoline (PD), deoxypyridinoline (DPD), and hydroxyproline (Hyp)/g creatinine--during the first few days of inactivity were paralleled by tartrate-resistant acid phosphatase (TRAP) with significant increases in all these markers by day 4 of bed rest. An index of formation, skeletal alkaline phosphatase (SALP), did not change during bed rest and showed a moderate 15% increase 1 week after reambulation. In contrast to SALP, serum osteocalcin (OC) began increasing the day preceding the increase in Hyp, remained elevated for the duration of the bed rest, and returned to pre-bed rest values within 5 days of reambulation. Similarly, DPD increased significantly at the onset of bed rest, remained elevated for the duration of bed rest, and returned to pre-bed rest levels upon reambulation. On the other hand, the other three indices of resorption, Hyp, PD, and TRAP, remained elevated for 2 weeks after reambulation. The most sensitive indices of the levels of physical activity proved to be the noncollagenous protein, OC, and the collagen crosslinker, DPD. The bed rest values of both these markers were significantly elevated compared to both the pre-bed rest values and the post-bed rest values. The sequence of changes in the circulating markers of bone metabolism indicated that increases in serum OC are the earliest responses of bone to head-down tilt bed rest.
Acid Phosphatase↗
Growth factors to stimulate bone formation.
During the past decade we and others have shown that bone is a storehouse for growth factors. Accordingly, bone contains a number of growth factors including insulin-like growth factors I and II (IGF-I, IGF-II) transforming growth factor (TGF-beta 1, TGF-beta 2), platelet-derived growth factor, basic and acidic fibroblast growth factor, and bone morphogenetic proteins (BMPs). Osteoblasts have been shown to produce many of these growth factors, which then act in an autocrine and paracrine fashion. The production of these growth factors is regulated by both systemic hormones and local mechanical stress. Recent studies on the relative distribution of bone growth factors during different physiologic and pathologic situations indicate that the concentration of bone growth factors is not invariant and provide indirect evidence that growth factors deposited in bone have physiologic significance. In addition, many of these bone growth factors have been shown to increase bone formation either systemically or locally in vivo. Based on the past findings, we propose that different growth factors may have a specific role in regulating proliferation and differentiation of different stages of osteoblast lineage cells and play important roles in the local regulation of bone formation.
Bone and Bones↗
Dibutyryl cyclic adenosine monophosphate differentially regulates cell proliferation in low and high alkaline phosphatase SaOS-2 human osteosarcoma cells: evidence for mediation by the insulin-like growth factor-II system.
In the present study, we have sought to determine whether a given signal transduction pathway can have diverse effects on subpopulations of cells of a lineage depending upon the stage of differentiation. To test this hypothesis, we selected the cyclic adenosine monophosphate (cAMP) signal transduction pathway because of its recognized importance in mediating the actions of many hormones, e.g., parathyroid hormone which acts on the bone-forming cells, the osteoblasts. Subpopulations of human osteosarcoma SaOS-2 cells with low (LSaOS) and high (HSaOS) alkaline phosphatase (ALP) content were chosen as model systems for preosteoblasts (pre-OB) and osteoblasts (OB), respectively. Dibutyryl cyclic AMP (DBcAMP) treatment of serum free cultures produced a differential effect on the proliferation of LSaOS cells (40 +/- 5% of control at 1 mM DBcAMP, P < 0.001) compared with HSaOS cells (no statistically significant effect). The finding supports the hypothesis. Next, we sought evidence for mediation, at least in part, by the insulin-like growth factor (IGF)-II regulatory system. We report that the basal expression of IGF-II, IGF binding protein (IGFBP)-3, and IGFBP-4 was higher in LSaOS cells than in HSaOS cells with the opposite true for type I IGF receptor. DBcAMP treatment of LSaOS cells decreased IGF-II and IGFBP-3 but increased IGFBP-4 and type I IGF receptor; no effect was observed for the type II IGF receptors. DBcAMP treatment of HSaOS cells had no detectable effect on IGF-II; IGFBP-3, or type I and type II IGF receptor expression; only IGFBP-4 expression increased with DBcAMP. These observations suggest that the differential regulation of cell proliferation by the cAMP signal transduction pathway may be mediated, at least in part, by the IGF-II regulatory system.
Alkaline Phosphatase↗
Mechanism of mitogenic action of aluminum ion on human bone cells: potential involvement of the insulin-like growth factor regulatory system.
Aluminum ion at micromolar concentrations significantly stimulated the [3H]thymidine incorporation into human TE85 osteosarcoma cell DNA. Cells treated with mitogenic concentrations of aluminum ion for 48 h showed biphasic stimulation in secretion of IGFs (insulin-like growth factors) into the conditioned medium. Treatment of the human osteosarcoma TE85 cells with mitogenic doses of aluminum ion for 24 h also markedly and reproducibly increased the steady-state level of IGF-II mRNA in a dose-dependent, biphasic manner. The effect of aluminum ion on the steady-state level of IGF-I mRNA could not be determined since the IGF-I mRNA in these cells was not detectable with our oligodeoxynucleotide probes. To test whether the mitogenic effects of aluminum ion could be mediated through IGFs, the stimulation of [3H]thymidine incorporation of TE85 cells was evaluated in the presence and the absence of an inhibitory IGF binding protein (i.e., IGFBP-4). The presence of IGFBP-4 significantly reduced the stimulation in thymidine incorporation by a mitogenic concentration of aluminum ion. Western ligand blot analysis revealed that mitogenic concentrations of aluminum ion also inhibited the secretion of IGF-binding proteins, particularly the inhibitory IGFBP-4, which could lead to the potentiation of the overall activity of IGFs. In conclusion, these findings are consistent with the premise that the mitogenic action of aluminum ion on human bone cells is, in part, mediated by an increased local bone cell production and activity of IGFs.
Alkaline Phosphatase↗
Characterization of the IGF regulatory system in bone.
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Animals↗
Effects of calcitonin on bone quality and osteoblastic function.
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Animals↗
Exogenous prostacyclin, but not prostaglandin E2, produces similar responses in both G6PD activity and RNA production as mechanical loading, and increases IGF-II release, in adult cancellous bone in culture.
Cyclic mechanical loading in vivo that leads to new bone formation is also associated in osteocytes and surface bone cells with almost immediate increases in G6PD activity, and later increases in RNA production. Both these early, loading-related, responses can be reproduced in organ culture of adult cancellous bone, and both are abolished by the presence of indomethacin in the culture medium at the time of loading. The implication that prostaglandins (PGs) are involved in the control of loading-related osteogenesis is supported by increases in prostacyclin (PGI2) and PGE2 release from cores of cancellous bone during loading. In the experiments reported here, PGE2 and PGI2 were added exogenously (10(-6) M) to perfusable cores of adult canine cancellous bone to determine whether they would simulate the loading-related responses in G6PD activity and RNA synthesis. PGE2 increased G6PD activity in surface cells and osteocytes within 8 minutes but had no effect on [3H]-uridine incorporation at 6 hours. PGI2 stimulated both G6PD activity and [3H]-uridine incorporation equally in osteocytes and surface cells. Neither PG produced any significant change in medium concentrations of IGF-I, and PGE2 had no effect on IGF-II. In contrast PGI2 elevated the medium concentration of IGF-II threefold. IGF-I and IGF-II were localized immunocytochemically to osteocytes and surface cells in both treated and untreated cores. Prostacyclin, but not PGE2, appears to imitate the early loading-related increases in G6PD activity and RNA synthesis in bone cells in situ. Prostacyclin, but not PGE2, also stimulates the early release of IGF-II.
Animals↗
Evidence that fluoride therapy increases trabecular bone density in a peripheral skeletal site.
We measured the spinal bone density (SBD) and femoral condyle bone density (FCD) in normal and osteoporotic females (n = 219) both before and during fluoride therapy. SBD and FCD in untreated osteoporotics were significantly lower (P < 0.05) than those in the age-matched controls. SBD and FCD were correlated in the untreated (r = 0.62; P < 0.0001) as well as in the fluoride-treated osteoporotics (r = 0.42; P < 0.0001). SBD and FCD were significantly increased (P < 0.05) in response to fluoride therapy. The average rates of increase in FCD and SBD were similar (1.3 +/- 1.3 vs. 1.24 +/- 1.4 mg/cc.month). We conclude that the osteogenic action of fluoride is not limited to the axial skeleton. An increase in trabecular bone density also occurs at peripheral weight-bearing sites such as the femoral condyle.
Aged↗
1,25-Dihydroxyvitamin D3 increases secretion of insulin-like growth factor binding protein-4 (IGFBP-4) by human osteoblast-like cells in vitro and elevates IGFBP-4 serum levels in vivo.
Insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs) are thought to play an important role in the regulation of bone metabolism. In the present study, we investigated the effect of 1,25-dihydroxyvitamin D(3) [1,25-(OH)2D3] on the expression and secretion of IGFBPs in human osteoblast-like osteosarcoma cells (MG63) and untransformed human bone-derived cells in vitro. Northern blot analysis revealed that 1,25-(OH)2D3 (10(-8) mol/L) increased IGFBP-4 messenger RNA maximally 11-fold over control level in MG63 cells (after 24 h treatment) and 2.8-fold in human bone-derived cells (at 10(-10) mol/L). 1,25-(OH)2D3 increased secretion of IGFBP-4 2- and 3-fold, respectively, in MG63 cells and in human bone-derived cells. In normal human bone-derived cells, 1,25-(OH)2D3 also stimulated messenger RNA expression (3.9-fold) and the secretion of IGFBP-3 (2.2-fold). 1,25-(OH)2D3 also increased IGFBP-4 expression in skin fibroblasts but not in hepatocellular carcinoma cells. Consistent with these in vitro findings, treatment of human subjects with high doses of oral 1,25-(OH)2D3 (2-3 micrograms/day) for psoriasis resulted in a significant increase in serum IGFBP-4 concentration compared with pretreatment levels. Our observations present direct evidence that 1,25-(OH)2D3 plays an important role in the regulation of IGFBP secretion in vitro and in vivo.
Adult↗
Galactosyl hydroxylysine and deoxypyridinoline: a methodological comparison.
Galactosyl hydroxylysine and deoxypyridinoline are at present the most promising markers of bone resorption. Various studies have indeed shown that these two markers discriminate with high accuracy subjects with different rates of bone turnover and that their accuracies and discriminate power are very similar. The aim of this paper is to compare the practicality and the reproducibility of the HPLC galactosyl hydroxylysine and deoxypyridinoline assays. In summary, this review shows that the galactosyl hydroxylysine and deoxypyridinoline HPLC assays differ mainly in the need, in using deoxypyridinoline, for an acid hydrolysis and a preextraction of the urine samples. This implies two major problems for deoxypyridinoline: 1) more time is required due to the cumbersome preanalytical procedures; and 2) a lower reproducibility. Our data, in fact, show that both the intra-assay and inter-assay coefficient of variation of the deoxypyridinoline assay are almost 100% higher than those of the galactosyl hydroxylysine assay.
Adult↗
Synthetic peptide-based immunoassay for amino-terminal propeptide of type I procollagen: application for evaluation of bone formation.
Serum biochemical markers are powerful tools for the evaluation of bone turnover. In this study, we developed a radioimmunoassay, using a synthetic peptide for the N-terminal fragment of human type I [alpha 1(I)] procollagen (N-PCP). A 14-amino acid peptide was synthesized from the amino terminus and used to generate antibodies in rabbits. The synthetic peptide was used as standard and tracer in the assay. Both native type I amino procollagen (PINP), which was purified from skin fibroblasts, and human serum displaced tracer binding in parallel with the synthetic peptide. The range for measurement of N-PCP in serum was 0.7 to 30 micrograms/L (0.21-9.18 nmol/L). In a sample of 17 normal adults and 13 children (ages 9-16 years) there was a strong correlation between serum N-PCP determined by this assay and both skeletal alkaline phosphatase isoenzyme and osteocalcin, markers of bone formation. Serum concentrations of N-PCP in a group of normal children were eightfold higher than concentrations in normal adults, with no overlap between the two groups. N-PCP also correlated with C-terminal type I procollagen determined with a commercially available kit (r = 0.92).
Adolescent↗
Phosphotyrosyl protein phosphatases: potential regulators of cell proliferation and differentiation.
Tyrosyl phosphorylated proteins have been associated with the regulation of cellular activities, including proliferation, differentiation, and transformation. The overall cellular levels of tyrosyl phosphorylated proteins are regulated by the balance of the activities of both tyrosyl protein kinases and phosphotyrosyl protein phosphatases. Until recently, it was generally assumed that the kinase reaction was the key regulatory process for determining the level of tyrosyl phosphorylated proteins and that the dephosphorylation reaction was an unregulated event. However, recent evidence strongly suggest a regulatory role for phosphotyrosyl protein phosphatases for determination of the overall level of tyrosyl phosphorylated proteins. This review focuses on the discussion of the properties, the regulation, and the primary structure of phosphotyrosyl protein phosphatases. Evidence that supports an important role for phosphotyrosyl protein phosphatases on cell proliferation and differentiation also is presented.
Amino Acid Sequence↗
Ovariectomy selectively reduces the concentration of transforming growth factor beta in rat bone: implications for estrogen deficiency-associated bone loss.
Previous work showed that production of transforming growth factor beta (TGF-beta) by osteoblast-like rat UMR 106 cells was increased by 17 beta-estradiol at physiological concentrations. To determine whether ovariectomy alters the concentration of TGF-beta in rat long bones, female Sprague-Dawley rats were either sham-operated (n = 19) or ovariectomized (n = 19), pair-fed a semisynthetic diet for 6 weeks, and sacrificed. Tibial and femoral diaphyses were removed and extracted by demineralization. Ovariectomy lowered serum estrogen; did not alter body weight, serum magnesium, or serum 1,25-dihydroxyvitamin D; and produced only modest differences in serum calcium and phosphate concentrations. Hydroxyproline was higher and extractable protein was lower in bones from ovariectomized rats than in bones from sham-operated rats; calcium content did not differ between the two groups of animals. Ovariectomy lowered the concentration of TGF-beta in bone but did not change the concentration of insulin-like growth factors I or II compared with values in bone from control animals. The reduction of bone TGF-beta was evident 6 weeks after surgery but not at 3 weeks. Treatment of ovariectomized rats with estrogen eliminated the TGF-beta deficit. To determine whether 17 beta-estradiol increased TGF-beta production by normal bone cells, mouse osteoblasts were treated for 2 days with 17 beta-estradiol. The production of TGF-beta was increased almost 2-fold by 1 nM 17 beta-estradiol, and short-term treatment stimulated the intracellular accumulation of TGF-beta 1 mRNA. We conclude that ovariectomy reduces deposition of TGF-beta in rat bone and that diminished skeletal TGF-beta could play a role in the pathogenesis of bone loss, fractures, and microfractures that occur in estrogen-deficient states. Our results support the possibility that estrogen and bone TGF-beta may be necessary for normal maintenance of the skeleton in female rats.
Animals↗
Evidence for a lack of functional receptors for nerve growth factor (NGF) in chick bone cells in vitro.
Nerve growth factor (NGF) is essential for the development and differentiation of sympathetic and sensory neurons. Recently, NGF receptors were demonstrated in non-neural cells, and several mesenchymal cell types including lymphocytes and skeletal myotubes were shown to be stimulated to proliferate by NGF. Our purpose was to examine for the presence of functional NGF receptors in osteoblasts. Bone cells from chick calvaria were used as a model; PC-12 cells derived from rat adrenal pheochromocytoma were used as positive controls. NGF was examined for functions in chick bone cells by studying effects on (1) [3H]-thymidine incorporation; (2) alkaline phosphatase (ALP) activity; and (3) protein tyrosine phosphorylation. Effects of NGF on thymidine incorporation and protein tyrosine phosphorylation by PC-12 cells were also measured. A radioreceptor assay was used to test for the presence of receptors. In chick calvarial cells, NGF had no effect on thymidine incorporation, ALP activity or protein tyrosine phosphorylation. Radioreceptor assay with bone cells showed no evidence of NGF receptors. In contrast, in PC-12 cells, NGF (1) decreased thymidine incorporation; (2) increased protein tyrosine phosphorylation; and (3) showed receptor activity by radioreceptor assay. In conclusion, unlike several other mesenchymal cell types, chick bone cells show no evidence of NGF receptors or functional responses to NGF in vitro.
Alkaline Phosphatase↗