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Biomedical subjects

E Canalis

Publications and source records attributed to E Canalis.

At least 37 records · Page 2Linked to original sources
PubMed2000

Transcriptional regulation of connective tissue growth factor by cortisol in osteoblasts.

Glucocorticoids have important effects on osteoblastic function. Connective tissue growth factor (CTGF)/insulin-like growth factor binding protein-related protein 2 (IGFBP-rP2) plays a role in cell adhesion and function. We examined the regulation of CTGF/IGFBP-rP2 synthesis in cultures of osteoblast-enriched cells from 22-day fetal rat calvariae (Ob cells). Cortisol caused a time- and dose-dependent increase in CTGF/IGFBP-rP2 mRNA levels in Ob cells. Cycloheximide did not preclude the effect, indicating that it was not protein synthesis dependent. Cortisol increased the rate of CTGF/IGFBP-rP2 transcription and, in transcriptionally arrested Ob cells, did not modify the decay of the transcript. Parathyroid hormone decreased, whereas transforming growth factor-beta and, to a lesser extent, bone morphogenetic protein 2 increased CTGF/IGFBP-rP2 mRNA levels, but other hormones and growth factors had no effect. In conclusion, cortisol stimulates CTGF/IGFBP-rP2 transcription in Ob cells. Because CTGF/IGFBP-rP2 binds IGFs, its increased expression could be relevant to the actions of cortisol in bone.

Animals↗
PubMed2000

Osteopenia and decreased bone formation in osteonectin-deficient mice.

Bone continuously remodels in response to mechanical and physiological stresses, allowing vertebrates to renew bone as adults. Bone remodeling consists of the cycled synthesis and resorption of collagenous and noncollagenous extracellular matrix proteins, and an imbalance in this process can lead to disease states such as osteoporosis, or more rarely, osteopetrosis. There is evidence that the extracellular matrix glycoprotein osteonectin or secreted protein acidic and rich in cysteine (BM-40) may be important in bone remodeling. Osteonectin is abundant in bone and is expressed in areas of active remodeling outside the skeleton. In vitro studies indicate that osteonectin can bind collagen and regulate angiogenesis, metalloproteinase expression, cell proliferation, and cell-matrix interactions. In some osteopenic states, such as osteogenesis imperfecta and selected animal models for bone fragility, osteonectin expression is decreased. To determine the function of osteonectin in bone, we used contact x-ray, histomorphometry, and Northern blot analysis to characterize the skeletal phenotype of osteonectin-null mice. We found that osteonectin-null mice have decreased bone formation and decreased osteoblast and osteoclast surface and number, leading to decreased bone remodeling with a negative bone balance and causing profound osteopenia. These data indicate that osteonectin supports bone remodeling and the maintenance of bone mass in vertebrates.

Animals↗
PubMed2000

Bone morphogenetic proteins induce gremlin, a protein that limits their activity in osteoblasts.

Bone morphogenetic proteins (BMP) induce the differentiation of cells of the osteoblastic lineage and enhance the function of the osteoblast. Growth factor activity is regulated by binding proteins, and we previously showed that BMPs induce noggin, a glycoprotein that binds and blocks BMP action. Recently, additional BMP antagonists, such as gremlin, have been described, but there is no information about their expression or function in osteoblasts. We tested for the expression of gremlin and studied its induction by BMPs in cultures of osteoblast-enriched cells from 22-day-old fetal rat calvariae (Ob cells). BMP-2 caused a time- and dose-dependent increase in gremlin messenger RNA and polypeptide levels, as determined by Northern and Western blot analyses. The effects of BMP-2 on gremlin transcripts were independent of new protein synthesis. BMP-2 increased the rate of gremlin transcription as determined by nuclear run-on assays. Fibroblast growth factor-2 and platelet-derived growth factor BB also induced gremlin, but other hormones and growth factors had no effect. Gremlin prevented the stimulatory effects of BMP-2 on DNA, collagen, noncollagen protein synthesis, and alkaline phosphatase activity in Ob cells. In conclusion, BMPs induce gremlin transcription in Ob cells, a mechanism that probably limits BMP action in osteoblasts.

Animals↗
PubMed2000

Basic fibroblast growth factor stimulates collagenase-3 promoter activity in osteoblasts through an activator protein-1-binding site.

Basic fibroblast growth factor (bFGF) stimulates collagenase-3 synthesis in fetal rat osteoblast-enriched (Ob) cells. In this study we examined the mechanism of collagenase-3 regulation in Ob cells. bFGF at 0.6 nM or more increased the transcriptional rate of collagenase-3 by 3- to 7-fold. bFGF at 0.6 nM increased the activity of collagenase-3 promoter-luciferase reporter deletion constructs from -721 to -53 nucleotides transiently transfected into Ob cells by 3- to 5-fold. The minimal bFGF response was retained within the -53 to +28 sequence. Mutational analysis revealed that the bFGF effect was mediated through an activator protein-1 (AP-1)-binding site located at -48 to -42 nucleotides in the promoter. bFGF stimulated the binding of nuclear factors to the collagenase AP-1 site by 3- to 4-fold, as determined by electrophoretic mobility shift assays. Supershift analysis of nuclear extracts revealed that bFGF stimulates the occupancy of AP-1 site by c-Jun, JunB, JunD, c-Fos, FosB, and Fra2. In conclusion, bFGF increases collagenase-3 gene transcription, an effect mediated through an AP-1 site, due to the induction or activation of Jun and Fos family transcription factors. The stimulation of collagenase-3 synthesis by bFGF may be critical in mediating the actions of this growth factor in bone remodeling.

Animals↗
PubMed2000

Alendronate stimulates collagenase 3 expression in osteoblasts by posttranscriptional mechanisms.

Bisphosphonates inhibit bone resorption by reducing osteoclastic cell number and activity. Alendronate is a nitrogen-containing bisphosphonate analog used in the treatment of postmenopausal osteoporosis. The effects of alendronate in osteoclasts are well documented; however, there is limited information on the actions of alendronate in osteoblasts (Ob's). In this study, we investigated the effects of alendronate at concentrations of 1-100 microM on the synthesis of collagenase 3 or matrix metalloproteinase 13 (MMP-13) and tissue inhibitors of MMPs (TIMPs) 1, 2, and 3 in primary Ob-enriched cells from 22-day-old fetal rat calvariae. Alendronate at concentrations higher than 10 microM markedly stimulated the synthesis of collagenase messenger RNA (mRNA) and immunoreactive protein in Ob's. Alendronate did not stimulate the transcriptional rate of the collagenase 3 gene. However, in transcriptionally arrested cells, alendronate prolonged the half-life of collagenase transcripts. Alendronate did not alter the expression of TIMP 1 and 2, but modestly stimulated the expression of TIMP 3. The actions of alendronate in Ob's suggest potential additional effects in bone remodeling.

Alendronate↗
PubMed1999

Platelet-derived growth factor induces interleukin-6 transcription in osteoblasts through the activator protein-1 complex and activating transcription factor-2.

Platelet-derived growth factor (PDGF) BB, a mitogen that stimulates bone resorption, increases the expression of interleukin-6 (IL-6), a cytokine that induces osteoclast recruitment. The mechanisms involved in IL-6 induction by PDGF BB are poorly understood. We examined the effect of PDGF BB on IL-6 expression in cultures of osteoblasts from fetal rat calvariae (Ob cells). PDGF BB increased IL-6 mRNA and heterogeneous nuclear RNA levels, the rate of transcription, and the activity of base pairs (bp) -2906 to +20 IL-6 promoter fragments transiently transfected into Ob cells. Deletion analysis revealed two responsive regions, one containing an activator protein-1 (AP-1) site located between bp -276 and -257, and a second, less well defined, downstream of -257. Targeted mutations of a cyclic AMP-responsive element (CRE), and nuclear factor-IL-6 and nuclear factor-kappaB binding sites in a bp -257 to +20 IL-6 construct that was transfected into Ob cells, revealed that the CRE also contributed to IL-6 promoter induction by PDGF BB. Electrophoretic mobility shift assay revealed AP-1 and CRE nuclear protein complexes that were enhanced by PDGF BB. Supershift assays revealed binding of Jun and Fos to AP-1 and CRE sequences and binding of activating transcription factor-2 to CRE. In conclusion, PDGF BB induces IL-6 transcription in osteoblasts by regulating nuclear proteins of the AP-1 complex and activating transcription factor-2.

Activating Transcription Factor 2↗
PubMed1999

Leukemia inhibitory factor and oncostatin M stimulate collagenase-3 expression in osteoblasts.

Leukemia inhibitory factor (LIF) and oncostatin M (OSM) have multiple effects on skeletal remodeling. Although these cytokines modestly regulate collagen synthesis in osteoblasts, their effects on collagenase expression and collagen degradation are not known. We tested whether LIF and OSM regulate the expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in osteoblast-enriched cells isolated from fetal rat calvariae. LIF and OSM increased collagenase-3 (MMP-13) mRNA and immunoreactive protein levels in a time- and dose-dependent manner. LIF and OSM enhanced the rate of transcription of the collagenase gene and stabilized collagenase mRNA in transcriptionally arrested cells. LIF and OSM failed to regulate the expression of gelatinase A (MMP-2) and B (MMP-9). LIF and OSM modestly stimulated the expression of TIMP-1 but did not alter the expression of TIMP-2 and -3. In conclusion, LIF and OSM stimulate collagenase-3 and TIMP-1 expression in osteoblasts, and these effects may be involved in mediating the bone remodeling actions of these cytokines.

Animals↗
PubMed1999

Triiodothyronine induces collagenase-3 and gelatinase B expression in murine osteoblasts.

Triiodothyronine (T3) increases bone resorption, but its effects on matrix metalloprotease (MMP) expression in bone are unknown. We tested the effects of T3 on collagenase-3 and gelatinase A and B expression in MC3T3 osteoblastic cells. T3 at 1 nM to 1 microM for 24-72 h increased collagenase-3 and gelatinase B mRNA levels, but it did not increase gelatinase A transcripts. In addition, T3 increased immunoreactive collagenase and gelatinase activity. Cycloheximide prevented the stimulatory effect of T3 on collagenase-3 but not on gelatinase B transcripts. Indomethacin did not prevent the effect of T3 on either MMP. T3 did not alter the decay of collagenase-3 or gelatinase B mRNA in transcriptionally arrested MC3T3 cells, and it increased the rate of collagenase-3 and gelatinase B gene transcription. Although T3 enhanced the expression of the tissue inhibitor of metalloproteinase-1 in MC3T3 cells, it increased collagen degradation in cultured intact rat calvariae. In conclusion, T3 increases collagenase-3 and gelatinase B synthesis in osteoblasts by transcriptional mechanisms. This effect may contribute to the actions of T3 on bone matrix remodeling.

3T3 Cells↗
PubMed1999

Cortisol enhances the expression of mac25/insulin-like growth factor-binding protein-related protein-1 in cultured osteoblasts.

Glucocorticoids inhibit the synthesis of insulin-like growth factor I (IGF-I) and regulate the expression of IGF-binding proteins (IGFBPs) in osteoblast cultures. IGFBP-related protein-1 (IGFBP-rP1), the product of the mac25 gene, binds IGF-I, IGF-II, and insulin, and we postulated that glucocorticoids regulate IGFBP-rP1 synthesis in osteoblasts. We tested the expression of mac25/IGFBP-rP1 in cultures of osteoblast-enriched cells from 22-day-old fetal rat calvariae (Ob cells). Cortisol treatment at 10 nM to 1 microM for 24-48 h caused a time- and dose-dependent increase in mac25/IGFBP-rP1 messenger RNA (mRNA) levels in Ob cells. Cycloheximide at 3.6 microM did not alter mac25/IGFBP-rP1 transcripts in control or cortisol-treated cells. Cortisol did not modify the decay of mac25/IGFBP-rP1 mRNA in transcriptionally arrested Ob cells and increased the rate of IGFBP-rP1 transcription as determined by nuclear run-on assays. Retinoic acid also increased mac25/IGFBP-rP1 mRNA levels, but 17beta-estradiol, testosterone, 5alpha-dihydrotestosterone, progesterone, and 1,25-dihydroxyvitamin D3 did not. In conclusion, cortisol stimulates mac25/IGFBP-rP1 expression in Ob cells by transcriptional mechanisms. As IGFBP-rP1 binds and possibly modifies the effects of IGFs and insulin, its increased expression could be relevant to the inhibitory actions of cortisol in bone.

Animals↗
PubMed1999

Skeletal bone morphogenetic proteins suppress the expression of collagenase-3 by rat osteoblasts.

Bone morphogenetic proteins (BMPs) are secreted by skeletal cells, induce the differentiation of mesenchymal cells into cells of the osteoblastic lineage, and increase their differentiated function. BMPs also decrease collagenase-3 expression by the osteoblast. We tested the autocrine role of BMPs on collagenase-3 expression in osteoblast-enriched cells from fetal rat calvariae (Ob cells) by examining the effects of noggin, a specific inhibitor of BMP binding and function. Although collagenase-3 transcript expression declined in untreated Ob cells in culture over a 24-h period, BMP-2, -4, and -6 decreased collagenase-3 messenger RNA levels in cells treated for 2-24 h. The addition of noggin prevented the decrease of collagenase-3 transcripts in control cultures, opposed the inhibitory actions of BMP-2, and increased the levels of the protease in the culture medium. Noggin did not alter the decay of collagenase-3 messenger RNA in transcriptionally arrested cells, and it increased the levels of collagenase-3 heterogeneous nuclear RNA in Ob cells. In conclusion, noggin enhances the synthesis of collagenase-3 in osteoblasts, supporting the notion that BMPs act as autocrine suppressors of collagenase-3 in skeletal cells, an effect that may contribute to the maintenance of the bone matrix.

Animals↗
PubMed1999

Fibroblast growth factor-2 induces hepatocyte growth factor/scatter factor expression in osteoblasts.

Hepatocyte growth factor/scatter factor (HGF/SF) is a multifunctional growth factor with a major role in tissue morphogenesis and repair. It stimulates the proliferation of cells of the osteoblast and osteoclast lineages. Mitogenic factors playing a role in fracture repair may act by regulating HGF/SF expression or activity in bone-forming cells. We investigated the effect of fibroblast growth factor-2 (FGF-2) on the expression of HGF/SF and its receptor, encoded by c-met, in the MC3T3-E1 osteoblastic cell line. MC3T3-E1 cells expressed low levels of HGF/SF messenger RNA (mRNA), which were markedly increased by FGF-2 in a dose- and time-dependent manner. FGF-2 also induced HGF/SF polypeptide synthesis. The stimulation of HGF/SF mRNA expression by FGF-2 was blocked by cycloheximide, a protein synthesis inhibitor, but not by DNA or prostaglandin synthesis inhibitors. FGF-2 increased the rate of HGF/SF gene transcription by approximately 2-fold, as determined by nuclear run-on assays, and did not modify the decay of HGF/SF mRNA in transcriptionally arrested cells. FGF-2 also caused a dose- and time-dependent stimulation of c-met mRNA. In conclusion, FGF-2 induces HGF/SF expression in osteoblasts and may promote HGF/SF activity by increasing the expression of its receptor. Through these mechanisms, HGF/SF could mediate FGF actions on bone repair.

Animals↗
PubMed1999

Parathyroid hormone increases mac25/insulin-like growth factor-binding protein-related protein-1 expression in cultured osteoblasts.

PTH induces the synthesis of insulin-like growth factor I (IGF-I) and regulates the expression of IGF-binding proteins (IGFBP) in osteoblast cultures. IGFBP-related protein-1 (IGFBP-RP-1), the product of the mac25 gene, binds IGF-I, IGF-II, and insulin. We tested the actions of PTH on the expression of mac25/IGFBP-RP-1 in cultures of osteoblast-enriched cells from 22-day-old fetal rat calvariae (Ob cells). PTH at 0.1-10 nM for 6-48 h increased mac25/IGFBP-RP-1 messenger RNA (mRNA) levels in Ob cells, an effect not altered by cycloheximide. PGE2 increased mac25/IGFBP-RP-1 mRNA levels, but indomethacin did not modify basal or PTH-stimulated mac25/IGFBP-RP-1 expression. The decay of mac25/IGFBP-RP-1 mRNA in transcriptionally arrested Ob cells was not modified by PTH, and PTH increased the rate of IGFBP-RP-1 transcription. GH, insulin, bone morphogenetic protein-2, fibroblast growth factor-2, platelet-derived growth factor BB, IGF-I, and IGF-II did not modify mac25/IGFBP-RP-1 expression, whereas transforming growth factor-beta1 was modestly stimulatory. In conclusion, PTH stimulates mac25/IGFBP-RP-1 transcription in osteoblasts, an effect that could be relevant to the actions of PTH in bone.

Animals↗
PubMed1998

Bone morphogenetic proteins induce the expression of noggin, which limits their activity in cultured rat osteoblasts.

Bone morphogenetic proteins (BMPs) induce the differentiation of cells of the osteoblastic lineage and enhance the function of the osteoblast. Growth factors are regulated by binding proteins, but there is no information about binding proteins for BMPs in skeletal cells. Noggin specifically binds BMPs, but its expression by cells of the osteoblastic lineage has not been reported. We tested for the expression of noggin and its induction by BMP-2 in cultures of osteoblast-enriched cells from 22-d-old fetal rat calvariae (Ob cells). BMP-2 caused a time- and dose-dependent increase in noggin mRNA and polypeptide levels, as determined by Northern and Western blot analyses. The effects of BMP-2 on noggin transcripts were dependent on protein, but independent of DNA synthesis. BMP-2 increased the rates of noggin transcription as determined by nuclear run-on assays. BMP-4, BMP-6, and TGF-beta1 increased noggin mRNA in Ob cells, but basic fibroblast growth factor, platelet- derived growth factor BB, and IGF-I did not. Noggin decreased the stimulatory effects of BMPs on DNA and collagen synthesis and alkaline phosphatase activity in Ob cells. In conclusion, BMPs induce noggin transcription in Ob cells, a probable mechanism to limit BMP action in osteoblasts.

Animals↗
PubMed1998

Regulation of insulin-like growth factors I and II and their binding proteins in human bone marrow stromal cells by dexamethasone.

Glucocorticoids inhibit the proliferation, but induce the differentiation, of bone marrow stromal cells into osteoblast-like cells. The mechanisms, however, are still conjectural. Since insulin-like growth factors (IGFs) have profound effects on osteoblast growth and differentiation, it is possible that glucocorticoids exert their effects on bone marrow stromal cells in part via regulation of IGFs. Therefore, we analyzed the effects of dexamethasone (Dex) on the expression of IGF I and IGF II in cultured preosteoblastic normal human bone marrow stromal cells (HBMSC). Whereas Dex decreased the concentration of IGF I in the conditioned medium since early in the treatment, the concentration of IGF II was increased progressively as culture period lengthened. As the activities of IGF I and IGF II are regulated by the IGF binding proteins (IGFBPs), we analyzed the effects of Dex on the expression of IGFBPs. Dex increased IGFBP-2 in a time-dependent manner. The increase in IGFBP-2, however, was only to the same extent as that of IGF II at most, depending on the length of treatment. Therefore, the increase in IGFBP-2 would dampen, but not eliminate, the increased IGF II activities. By contrast, Dex decreased IGFBP-3 levels, the latter increasing the bioavailability of IGF II. Although IGFBP-4 mRNA levels were stimulated by Dex, IGFBP-4 concentration in the conditioned medium was unchanged as measured by RIA. IGFBP-5 and IGFBP-6 mRNA levels were decreased by Dex in a time-dependent fashion. IGFBP-5 protein level was also decreased 1-4 days after Dex treatment. IGFBP-1 mRNA was not detectable in HBMSC. These accumulated data indicate that Dex regulates IGF I and IGF II and their binding proteins differentially in normal human bone marrow stromal cells. The progressive increase in IGF II may contribute to Dex-induced cell differentiation.

Blotting, Northern↗
PubMed1998

Dual regulation of stromelysin-3 by fibroblast growth factor-2 in murine osteoblasts.

Osteoblasts express stromelysin-3, a matrix metalloproteinase associated with normal remodeling processes and with stromal fibroblasts surrounding many invasive carcinomas. Fibroblast growth factors (FGFs) play an important role in skeletal development, fracture repair, and osteoblast function. The osteoblastic cell line MC3T3 was used to study the regulation of stromelysin-3 by FGF-2. Acutely, FGF-2 decreased stromelysin-3 mRNA levels, whereas prolonged treatment caused an induction of stromelysin-3 mRNA. RNA stability studies and nuclear run-off assays indicated that acute treatment with FGF-2 decreased stromelysin-3 mRNA stability but did not alter gene transcription. However, the induction of stromelysin-3 after prolonged treatment with FGF-2 resulted from increased gene transcription, with no effect on RNA stability. The stimulatory effect was protein synthesis-dependent, whereas the inhibitory effect was not. This study demonstrates dual regulation of stromelysin-3 by FGF-2: acute destabilization of stromelysin-3 mRNA, followed by induction of gene transcription. This complex regulation may be important in the function of stromelysin-3 in bone and in remodeling processes, such as wound and fracture repair.

Animals↗
PubMed1998

[Our experience in treating obstructive lesions of the main airway by Nd-Yag laser resection].

We performed 164 laser resections with a neodymiumyttrium-aluminum-garnet (Nd-Yag) laser in 116 patients between January 1992 and December 1997. Seventy-eight patients had malignant neoplasms, 5 had neoplasms of intermediate malignancy and 33 had inflammatory tracheal lesions. Eighteen resections were emergency procedures. All resections were performed with the patient under general anesthesia and preferably breathing spontaneously. Immediate results varied according to the nature and location of the lesion. Treatment was palliative for tumors showing intraluminal proliferation, providing successful reopening of the airway as shown endoscopically in 70% of patients. Mean survival of the 44 patients with malignant lesions who could be followed was 29 weeks, with a median of 15.19 (range, 1-120). The tracheas of patients with inflammatory stenosis were reopened rapidly and emergency tracheostomy was avoided in all cases. One patient with malignant tracheal tumors died during the procedure due to asphyxia related to tracheal hemorrhage.

Adult↗