SEARCH · PubMed Health

Results for “OSTEOBLASTS”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28Linked to original sources

PubMed1996

Cortisol decreases IGF-I mRNA levels in human osteoblast-like cells.

Excess levels of glucocorticoids are known to cause osteoporosis. It is speculated that the effect of glucocorticoids could be mediated via regulation of IGF-I. The aims of the present study were to detect and quantify the expression of IGF-I and/or IGF-II mRNA transcripts in human osteoblast-like cells and to investigate whether glucocorticoids regulate the expression of IGF-I mRNA transcripts in human osteoblast-like cells. Cultures of human osteoblast-like cells from trabecular bone were established. The IGF-IA and IGF-IB transcripts were detected in human osteoblast-like cells from seven out of nine patients while the IGF-II transcript was detected in human osteoblast-like cells from eight out of nine patients, as determined by RT-PCR assays. Human osteoblast-like cells, as well as human muscle tissue, expressed approximately 1/10 of the IGF-I mRNA levels found in liver, as determined by RNase protection solution hybridization assay. The IGF-I mRNA levels did not decrease with age in the human osteoblast-like cells and no difference was seen between males and females. However, cortisol (10(-6) mol/l) decreased IGF-I mRNA levels. In summary, the present study has shown that human osteoblast-like cells express IGF-I and IGF-II mRNA transcripts and that cortisol down-regulates the IGF-I mRNA levels, indicating that some of the inhibitory effect of glucocorticoids on bone formation in humans is mediated via a reduced autocrine/paracrine expression of IGF-I.

Adolescent↗

PubMed2002

Osteoblast differentiation influences androgen and estrogen receptor-alpha and -beta expression.

Significant levels of estrogen and androgens circulate in men and women, and both play an important role in bone metabolism. While it is well established that either estrogen or androgen replacement therapy is effective at ameliorating bone loss associated with hypogonadism, recent evidence nevertheless suggests that estrogen and androgens have distinct molecular actions on the skeleton. In this study, we have employed normal rat calvarial osteoblast cultures to characterize relative expression profiles of estrogen (ERalpha and ERbeta) and androgen receptors (AR) during osteoblast differentiation. Normal osteoblast cultures can proceed through in vitro differentiation with distinct stages of proliferation, matrix maturation and mineralization in the appropriate differentiation medium containing ascorbic acid. Expression profiles of AR, ERalpha and ERbeta in primary cultures during osteoblast differentiation were characterized both by semi-quantitative relative RT-PCR and by Western analysis. In cultures induced to differentiate by growth in the presence of ascorbic acid, the expression profile for each receptor was unique during the course of differentiation. ERalpha levels were elevated during matrix maturation and then declined during mineralization. ERbeta expression was relatively constant throughout differentiation, exhibiting more constitutive expression. In contrast, AR levels were lowest during proliferation, and then increased throughout differentiation with highest levels in the most mature mineralizing cultures. Since steroid hormone action is generally mediated by specific cognate receptors, these results suggest that androgen actions may target cells during the mineralization stage of osteoblast differentiation, while estrogen action through either receptor isoform is more likely to affect osteoblasts earlier during matrix maturation. Interestingly, sex steroid receptor expression profiles did not exhibit the same patterns of regulation if osteoblast cultures were grown without ascorbic acid in medium that did not support extracellular matrix deposition. Thus, sex steroids may distinctly influence skeletal health by differential modulation of function during osteoblast differentiation.

Animals↗

PubMed2006

Ghrelin and unacylated ghrelin stimulate human osteoblast growth via mitogen-activated protein kinase (MAPK)/phosphoinositide 3-kinase (PI3K) pathways in the absence of GHS-R1a.

Recent studies demonstrate widespread expression of ghrelin among tissues and have uncovered its pleiotropic nature. We have examined gene expression of ghrelin and its two receptor splice variants, growth hormone secretagogue receptors (GHS-R) 1a and 1b, in human bone biopsies and in the human pre-osteoblastic SV-HFO cell line during differentiation. Additionally, we examined proliferative effects of ghrelin and unacylated ghrelin (UAG) in differentiating and non-differentiating cells. We detected GHS-R1b mRNA in human bone and osteoblasts but not ghrelin's cognate receptor GHS-R1a, using two different real-time PCR assays and both total RNA and mRNA. In osteoblasts GHS-R1b mRNA expression remained low during the first 14 days of culture, but increased 300% in differentiating cells by day 21. Both human bone biopsies and osteoblasts expressed ghrelin mRNA, and osteoblasts were found to secrete ghrelin. Overall, ghrelin gene expression was greater in differentiating than non-differentiating osteoblasts, but was not increased during culture in either group. Ghrelin and UAG induced thymidine uptake dose-dependently, peaking at 1 and 10 nM respectively, at day 6 of culture in both non-differentiating and differentiating osteoblasts. The proliferative response to ghrelin and UAG declined with culture time and state of differentiation. The proliferative effects of ghrelin and UAG were suppressed by inhibitors of extracellular-signal-regulated kinase (ERK) and phosphoinositide-3 kinase, and both peptides rapidly induced ERK phosphorylation. Overall, our data suggest new roles for ghrelin and UAG in modulating human osteoblast proliferation via a novel signal transduction pathway.

Alkaline Phosphatase↗

PubMed2006

Requirement of a bone morphogenetic protein for the maintenance and stimulation of osteoblast differentiation.

The requirement of a bone morphogenetic protein for the maintenance and stimulation of an osteoblast phenotype was examined using mouse MC3T3-E1 cell cultures. Cells expressed BMP-4 mRNA, which correlated with the stimulation of the osteoblast phenotype. The addition of a BMP-4 specific antibody reduced bone nodules, suggesting that BMP-4 is required for the osteogenic activity of osteoblasts in an autocrine manner. Exogenously added BMP-7 gradually decreased the expression of BMP-4 with a concurrent stimulation of the osteoblast phenotype. Exogenous BMP-7 can therefore substitute for endogenously produced BMP-4 acting as a paracrine factor on osteoblasts. The addition of 17beta estradiol decreased BMP-4 expression but initiated synthesis of BMP-6 mRNA, an endocrine signal for osteoblasts, which also substituted for the lack of endogenous BMP-4, as evidenced by normal bone nodule formation. The addition of dexamethasone and parathyroid hormone did not affect the BMP-4 expression but induced transcripts for BMP-2 and BMP-3, respectively, suggesting that their effects on bone can be in part achieved via the BMP signaling. These experiments support the requirement of a BMP for osteoblast differentiation and function, demonstrating for the first time that a BMP can functionally substitute for another BMP in an autocrine/paracrine manner or mediate a response to an endocrine action on osteoblasts.

Animals↗

PubMed2001

Proliferation, differentiation and apoptosis in connexin43-null osteoblasts.

Osteoblasts are highly coupled by gap junctions formed primarily by connexin43 (Cx43). We have shown that interference with Cx43 expression or function disrupts transcriptional regulation of osteoblast genes, and that deletion of Cx43 in the mouse causes skeletal malformations, delayed mineralization, and osteoblast dysfunction. Here, we studied the mechanisms by which genetic deficiency of Cx43 alters osteoblast development. While cell proliferation rates were similar in osteoblastic cells derived from calvaria of Cx43-null and wild type mice, camptothecin-induced apoptosis was 3-fold higher in mutant compared to wild type osteoblasts. When grown in mineralizing medium, Cx43-null cells were able to produce mineralized matrix but it took one week longer to reach the same mineralization levels as in normal cells. Likewise, expression of alkaline phosphatase activity per cell--a marker of osteoblast differentiation--was maximal only 2 weeks later in Cx43-null relative to wild-type cells. These observations suggest that Cx43 is important for a normal and timely development of the osteoblastic phenotype. Delayed differentiation and increase programmed cell death may explain the skeletal phenotype of Cx43-null mice.

Alkaline Phosphatase↗

PubMed2004

Development and transplantation of a mineralized matrix formed by osteoblasts in vitro for bone regeneration.

The use of extracellular matrix materials as scaffolds for the repair and regeneration of tissues is receiving increased attention. The current study was undertaken to test whether extracellular matrix formed by osteoblasts in vitro could be used as a scaffold for osteoblast transplantation and induce new bone formation in critical size osseous defects in vivo. Human osteoblasts derived from alveolar bone were cultured in six-well plates until confluent and then in mineralization media for a further period of 3 weeks to form an osteoblast--mineralized matrix complex. Histologically, at this time point a tissue structure with a "connective tissue"-like morphology was formed. Type I collagen was the major extracellular component present and appeared to determine the matrix macrostructure. Other bone-related proteins such as alkaline phosphatase (ALP), bone morphogenetic protein (BMP)-2 and -4, bone sialoprotein (BSP), osteopontin (OPN), and osteocalcin (OCN) also accumulated in the matrix. The osteoblasts embedded in this matrix expressed mRNAs for these bone-related proteins very strongly. Nodules of calcification were detected in the matrix and there was a correlation between calcification and the distribution of BSP and OPN. When this matrix was transplanted into a critical size bone defect in skulls of immunodeficient mice (SCID), new bone formation occurred. Furthermore, the cells inside the matrix survived and proliferated in the recipient sites, and were traceable by the human-specific Alu gene sequence using in situ hybridization. It was found that bone-forming cells differentiated from both transplanted human osteoblasts and activated endogenous mesenchymal cells. This study indicates that a mineralized matrix, formed by human osteoblasts in vitro, can be used as a scaffold for osteoblast transplantation, which subsequently can induce new bone formation.

Animals↗

PubMed1999

Resveratrol pretreatment desensitizes AHTO-7 human osteoblasts to growth stimulation in response to carcinoma cell supernatants.

Resveratrol, a natural phytoestrogen, has been reported to promote differentiation of murine MC3T3-E1 osteoblasts and to inhibit proliferation of prostate cancer cell lines. In the present study we tested the effects of resveratrol on the increased proliferation of human AHTO-7 osteoblastic cell line induced by conditioned media (CM) from a panel of carcinoma cell lines. This compound was found to modulate AHTO-7 proliferation in a tamoxifen-sensitive mechanism at lower concentrations, but failed to induce the osteoblast differentiation marker alkaline phosphatase (ALP) in contrast to vitamin D3. The proliferative response of AHTO-7 cells to conditioned media from carcinoma cell lines was diminished (30-71.4% inhibition) upon pretreatment with 0.5 microM resveratrol. Highest inhibition was demonstrated for pancreas (BxPC3, Panc-1), breast (ZR75-1) and renal (ACHN) carcinoma cell line supernatants whereas the effect on colon carcinoma (SW620, Colo320DM) cell CM and prostate cancer (PC3, DU145 and LNCaP) CM was less pronounced. Direct addition of resveratrol affected only supernatants of cell lines (<25% inhibition) exhibiting growth stimulatory activity for normal WI-38 lung fibroblasts. Resveratrol inhibited proliferation of DU145 and LNCaP cells in concentrations exceeding 5 microM, altered cell cycle distribution of all prostate cancer cell lines in concentrations as low as 0.5 microM, but did not inhibit the production of osteoblastic factors by these lines. In conclusion, resveratrol failed to induce ALP activity as marker of osteoblast differentiation in human osteoblastic AHTO-7 cells, however, inhibited their response to osteoblastic carcinoma-derived growth factors in concentrations significantly lower than those to reduce growth of cancer cells, thus effectively modulating tumor - osteoblast interaction.

Alkaline Phosphatase↗

PubMed2005

Muramyl dipeptide enhances osteoclast formation induced by lipopolysaccharide, IL-1 alpha, and TNF-alpha through nucleotide-binding oligomerization domain 2-mediated signaling in osteoblasts.

Muramyl dipeptide (MDP) is the minimal essential structural unit responsible for the immunoadjuvant activity of peptidoglycan. As well as bone-resorbing factors such as 1alpha,25-dihydroxyvitamin D3 (1alpha,25(OH)2D3) and PGE2, LPS and IL-1alpha stimulate osteoclast formation in mouse cocultures of primary osteoblasts and hemopoietic cells. MDP alone could not induce osteoclast formation in the coculture, but enhanced osteoclast formation induced by LPS, IL-1alpha, or TNF-alpha but not 1alpha,25(OH)2D3 or PGE2. MDP failed to enhance osteoclast formation from osteoclast progenitors induced by receptor activator of NF-kappaB ligand (RANKL) or TNF-alpha. MDP up-regulated RANKL expression in osteoblasts treated with LPS or TNF-alpha but not 1alpha,25(OH)2D3. Osteoblasts expressed mRNA of nucleotide-binding oligomerization domain 2 (Nod2), an intracellular sensor of MDP, in response to LPS, IL-1alpha, or TNF-alpha but not 1alpha,25(OH)2D3. Induction of Nod2 mRNA expression by LPS but not by TNF-alpha in osteoblasts was dependent on TLR4 and MyD88. MDP also enhanced TNF-alpha-induced osteoclast formation in cocultures prepared from Toll/IL-1R domain-containing adapter protein (TIRAP)-deficient mice through the up-regulation of RANKL mRNA expression in osteoblasts, suggesting that TLR2 is not involved in the MDP-induced osteoclast formation. The depletion of intracellular Nod2 by small interfering RNA blocked MDP-induced up-regulation of RANKL mRNA in osteoblasts. LPS and RANKL stimulated the survival of osteoclasts, and this effect was not enhanced by MDP. These results suggest that MDP synergistically enhances osteoclast formation induced by LPS, IL-1alpha, and TNF-alpha through RANKL expression in osteoblasts, and that Nod2-mediated signals are involved in the MDP-induced RANKL expression in osteoblasts.

Acetylmuramyl-Alanyl-Isoglutamine↗

PubMed1999

Transient upregulation of CBFA1 in response to bone morphogenetic protein-2 and transforming growth factor beta1 in C2C12 myogenic cells coincides with suppression of the myogenic phenotype but is not sufficient for osteoblast differentiation.

The bone morphogenetic protein (BMP)-2 is a potent osteoinductive signal, inducing bone formation in vivo and osteoblast differentiation from non-osseous cells in vitro. The runt domain-related protein Cbfa1/PEBP2alphaA/AML-3 is a critical component of bone formation in vivo and transcriptional regulator of osteoblast differentiation. To investigate the relationship between the extracellular BMP-2 signal, Cbfa1, and osteogenesis, we examined expression of Cbfa1 and osteoblastic genes during the BMP-2 induced osteogenic transdifferentiation of the myoblastic cell line C2C12. BMP-2 treatment completely blocked myotube formation and transiently induced expression of Cbfa1 and the bone-related homeodomain protein Msx-2 concomitant with loss of the myoblast phenotype. While induction of collagen type I and alkaline phosphatase (AP) expression coincided with Cbfa1 expression, Cbfa1 mRNA was strikingly downregulated at the onset of expression of osteopontin (OPN) and osteocalcin (OCN) genes, reflecting the mature osteoblast phenotype. TGF-beta1 treatment effectively suppressed myogenesis and induced Cbfa1 expression but was insufficient to support osteoblast differentiation reflected by the absence of ALP, OPN, and OCN. We addressed whether induction of Cbfa1 in response to BMP-2 results in the transcriptional activation of the OC promoter which contains three enhancer Cbfa1 elements. Transfection studies show BMP-2 suppresses OC promoter activity in C2C12, but not in osteoblastic ROS 17/2.8 cells. Maximal suppression of OC promoter activity in response to BMP-2 requires sequences in the proximal promoter (up to nt -365) and may occur independent of the three Cbfa sites. Taken together, our results demonstrate a dissociation of Cbfa1 expression from development of the osteoblast phenotype. Our findings suggest that Cbfal may function transiently to divert a committed myoblast to a potentially osteogenic cell. However, other factors induced by BMP-2 appear to be necessary for complete expression of the osteoblast phenotype.

Animals↗

PubMed2000

Bisphosphonates directly regulate cell proliferation, differentiation, and gene expression in human osteoblasts.

Bisphosphonates are widely used clinically to treat bone diseases in which bone resorption is in excess. However, the mechanism of bisphosphonate action on bone is not fully understood. Studies of direct action of bisphosphonates on bone have been limited mainly to their effects on bone-resorbing osteoclast cells, with implications that some activity may be mediated indirectly through paracrine factors produced by the bone-forming osteoblast cells. Little is known about the direct effects of bisphosphonates on osteoblasts. In this report, the direct actions of several bisphosphonates on cell proliferation, gene expression, and bone formation by cultured human fetal osteoblasts were examined. Osteoblast cell proliferation was decreased, and cytodifferentiation was increased in a dose-dependent manner in cultures treated with the bisphosphonate pamidronate. In addition, pamidronate treatment increased total cellular protein, alkaline phosphatase activity, and type I collagen secretion in osteoblasts. Consistent with the above-mentioned findings, the rate of bone formation was also increased in osteoblasts cultured with pamidronate. The actions of two other bisphosphonates, the weak-acting etidronate and the potent new analogue zoledronate, were also compared with the action of pamidronate on proliferation of immortalized human fetal osteoblast (hFOB) cells and rate of bone formation. Pamidronate and zoledronate decreased hFOB cell proliferation with equal potency, whereas etidronate decreased proliferation only at much higher concentrations. Studies comparing EDTA and etidronate indicate that etidronate may act indirectly on the hFOB cells by reducing free divalent ion concentrations, whereas pamidronate and zoledronate appear to act on the hFOB cells by a direct action. Both pamidronate and zoledronate increase hFOB cell bone formation, whereas no increase is observed with etidronate and EDTA. Taken together, these observations strongly suggest that treatment with pamidronate or zoledronate enhances the differentiation and bone-forming activities of osteoblasts.

Alkaline Phosphatase↗

PubMed2001

Methotrexate (MTX) inhibits osteoblastic differentiation in vitro: possible mechanism of MTX osteopathy.

OBJECTIVE: To clarify the mechanism of impaired bone formation during low dose methotrexate (MTX) therapy. METHODS: The in vitro effects of MTX on the function and differentiation of osteoblastic cells were investigated using (1) a mouse osteogenic cell line (MC3T3-E1) with the capacity to differentiate into osteoblastic or osteocytes, (2) a human osteoblastic osteosarcoma cell line (SaOS-2) with a mature osteoblastic phenotype, and (3) mouse bone marrow stromal cells containing osteoblast precursors. Osteoblast function was assessed by measuring the cellular activity of alkaline phosphatase (ALP) and the mineralization capacity of cultures. RESULTS: MTX suppressed ALP activity dose-dependently in growing MC3T3-E1 cells, but proliferation of these cells was only inhibited by a high concentration of MTX. In contrast, inhibition of ALP activity in MC3T3-E1 cells of mature osteoblastic phenotype was only observed with 10(-8) M and 10(-7) M MTX, and proliferation was not influenced. ALP activity and the proliferation of SaOS-2 cells were not inhibited by MTX, even when growing cells were treated. However, both ALP activity and formation of calcified nodules in bone marrow stromal cell cultures were significantly suppressed by MTX at concentrations between l0(-10) and 10(-7) M. CONCLUSION: These results suggest that MTX suppresses bone formation by inhibiting the differentiation of early osteoblastic cells.

Alkaline Phosphatase↗

PubMed2001

Cytotoxic and antioxidant effects of the water extract of the traditional Chinese herb gusuibu (Drynaria fortunei) on rat osteoblasts.

BACKGROUND AND PURPOSE: Gusuibu (Drynaria fortunei) is a traditional Chinese herb that has been claimed to have therapeutic effects on bone healing; however, a clinical mechanism responsible for this effect has not been identified. This study evaluated the cytotoxic and antioxidant effects of the water extract of gusuibu (WEGSB) on rat osteoblasts. MATERIALS AND METHODS: Osteoblasts were prepared from neonatal Wistar rat calvarias and treated with WEGSB. Cell viability and alkaline phosphatase activity were determined. Intracellular reactive oxygen species were detected using the dye 2',7'-dichlorofluorescin, and mitochondrial membrane potential was detected using the dye 3,3'-dihexyloxacarbocyanine iodide and flow cytometry. RESULTS: WEGSB at 1 and 10 micrograms/mL was not cytotoxic to rat osteoblasts, but WEGSB at 100 micrograms/mL reduced cell viability and alkaline phosphatase activity in a time-dependent manner. Although WEGSB and hydrogen peroxide did not affect the mitochondrial membrane potential of rat osteoblasts, combined treatment with WEGSB (100 micrograms/mL) and hydrogen peroxide lowered the membrane potential of mitochondria and resulted in cell death. The basal level of intracellular reactive oxygen species in rat osteoblasts was significantly suppressed by WEGSB at 10 to 100 micrograms/mL. WEGSB (10 micrograms/mL) specifically inhibited hydrogen peroxide-induced oxidative stress without an effect on nitric oxide-induced stress. Hydrogen peroxide caused concentration-dependent death of rat osteoblasts, but WEGSB significantly protected cells from hydrogen peroxide-induced death. CONCLUSION: This study has shown that WEGSB at 10 micrograms/mL is not cytotoxic to rat osteoblasts in vitro, and also that the extract at 10 micrograms/microL has an antioxidant effect on these cells. The antioxidant activity of WEGSB can protect rat osteoblasts from hydrogen peroxide-induced death and may promote bone recovery under similar pathologic conditions.

Alkaline Phosphatase↗

PubMed1998

Effects of microgravity on osteoblast growth.

Studies from space flights over the past two decades have demonstrated that basic physiological changes occur in humans during space flight. These changes include cephalic fluid shifts, loss of fluid and electrolytes, loss of muscle mass, space motion sickness, anemia, reduced immune response, and loss of calcium and mineralized bone. The cause of most of these manifestations is not known and until recently, the general approach was to investigate general systemic changes, not basic cellular responses to microgravity. Recently analyzed data from the 1973-1974 Skylabs disclose that there is a rise in the systemic hormone, cortisol, which may play a role in bone loss in flight. In two flights where bone growth was measured (Skylabs 3 and 4), the crew members had a significant loss of calcium accompanied by a rise in 24 hour urinary cortisol during the entire flight period. In ground-based work on osteoblasts, we have demonstrated that equivalent amounts of glucocorticoids can inhibit osteoblast cell growth. In addition, this laboratory has recently studied gene growth and activation of mouse osteoblasts (MC3T3-E1) during spaceflight. Osteoblast cells were grown on glass coverslips, loaded in the Biorack plunger boxes 18 hours before launch and activated 19 hours after launch in the Biorack incubator under microgravity conditions. The osteoblasts were launched in a serum deprived state, activated and collected in microgravity. Samples were collected at 29 hours after sera activation (0-g, n=4; 1-g, n=4). The osteoblasts were examined for changes in gene expression and cell morphology. Approximately one day after growth activation, remarkable differences were observed in gene expression in 0-g and 1-g flight samples. The 0-g activated cells had increased c-fos mRNA when compared to flight 1-g controls. The message of immediate early growth gene, cox-2 was decreased in the microgravity activated cells when compared to ground or 1-g flight controls. Cox-1 was not detected in any of the samples. There were no significant differences in the expression of actin mRNA between the 0-g and 1-g samples. These data indicate that quiescent osteoblasts are slower to enter the cell cycle in microgravity, suggesting that the force of gravity itself may be a significant factor in bone loss in spaceflight. Preliminary data from our STS 76 flight experiment support our hypothesis that a basic biological response occurs at the tissue, cellular, and molecular level in 0-g. Here we examine ground-based and space flown data on osteoblast growth in ground-based experiments mimicking space flight conditions and in microgravity to simulate lack of gravity stress to help us understand the mechanism of bone loss by experiments.

Animals↗

PubMed2002

Expression of Na(+)/Ca(2+) exchanger isoforms (NCX1 and NCX3) and plasma membrane Ca(2+) ATPase during osteoblast differentiation.

The ability to deliver calcium to the osteoid is critical to osteoblast function as a regulator of bone calcification. There are two known transmembrane proteins capable of translocating calcium out of the osteoblast, the Na(+)/Ca(2+) exchanger (NCX) and the plasma membrane Ca(2+)-ATPase (PMCA). In this study, we reveal the presence of the NCX3 isoform in primary osteoblasts and examine the expression of NCX1, NCX3, and PMCA1 during osteoblast differentiation. The predominant NCX isoform expressed by osteoblasts is NCX3. NCX1 also is expressed, but at low levels. Both NCX isoforms are expressed at nearly static levels throughout differentiation. In contrast, PMCA expression peaks at 8 days of culture, early in osteoblast differentiation, but declines thereafter. Immunocytochemical co-detection of NCX and PMCA reveal that NCX is positioned along surfaces of the osteoblast adjacent to osteoid, while PMCA is localized to plasma membrane sites distal to the osteoid. The expression pattern and spatial distribution of NCX support a role as a regulator of calcium efflux from osteoblasts required for calcification. The expression pattern and spatial distribution of PMCA makes its role in the mineralization process unlikely and suggests a role in calcium homeostasis following signaling events.

Animals↗

PubMed2002

Metabolic activity of osteoblasts from periprosthetic trabecular bone in failed total hip arthroplasties and osteoarthritis as markers of osteolysis and loosening.

OBJECTIVE: This study explored whether osteoblast metabolism in trabecular bone of failed total hip replacement (fTHR) in primary osteoarthritis (OA) plays a role in differential failure. METHODS: Osteoblast cell cultures were prepared from metaphyseal trabecular bone of normal individuals, OA patients, OA patients with fTHR with massive cavitary osteolysis (fTHR-O) and without massive cavitary osteolysis (fTHR-NO). Osteoblasts were characterized by measuring osteocalcin, cellular alkaline phosphatase (ALP), and urokinase plasminogen activator (uPA) activity. The cellular metabolic activity was also evaluated by measuring the production of interleukin (IL)-1beta, IL-6, and prostaglandin E2 (PGE2). RESULTS: ALP activity was increased in osteoblasts from patients with OA and fTHR-O compared to normal controls and fTHR-NO. Osteocalcin release was increased only in fTHR-O compared to all other groups. uPA activity was highest in the subgroup of "high metabolic OA" and in fTHR-O, while it was lowest in the subgroup of "low metabolic OA" and in fTHR-NO. IL-6 and PGE2 production was higher in the high metabolic OA and fTHR-O compared to fTHR-NO and low metabolic OA patients. CONCLUSION: Osteoblasts from fTHR-O and a subgroup of OA patients present similarly increased osteoblast markers compared to normal subjects, the low metabolic OA subgroup, and fTHR-NO. This information suggests the differential role of osteoblasts in osteolysis pathophysiology in primary THR surgery. The pertinence of the differential high and low metabolic activities of osteoblasts to the pathophysiology of OA remains to be fully established.

Adult↗

PubMed2002

Use of zoledronate to treat osteoblastic versus osteolytic lesions in a severe-combined-immunodeficient mouse model.

Prostate adenocarcinoma is associated with the formation of osteoblastic metastases in bone. It has been hypothesized that osteoclastic bone resorption is a critical component before the development of these osteoblastic lesions in bone. This observation has led researchers to test agents that inhibit osteoclastic activity to prevent or halt the formation of metastatic prostate cancer lesions in bone. Bisphosphonates inhibit osteoclast activity, and previous studies showed that they have the ability to reduce the osteolytic bone resorption associated with multiple myeloma and breast cancer. The objective of this study was to evaluate the efficacy of zoledronate in limiting the formation and/or progression of osteoblastic lesions produced by the injection of known prostate cancer cells (LAPC-9 and PC-3 cells) into the tibia of SCID mice. The mice were treated with either 30- micro g or 150- micro g doses of zoledronate before tumor implantation (pretreatment group), or at weekly intervals after tumor implantation (weekly treatment group), or weekly starting one month after tumor implantation (delayed-treatment group). The zoledronate was very effective in limiting the formation of osteolytic lesions in PC-3 implanted tibias by inhibiting osteoclast activity. Radiographic and histological analysis at weekly intervals revealed that osteolytic lesions developed in the control tibias by 2 weeks, and there was complete destruction of the cortical bone in much of the proximal tibias by 4 weeks. In the treatment groups, there was minimal cortical destruction noted in the weekly treatment groups at both doses, whereas mild cortical erosion was evident in the pretreatment groups, with more cortical destruction noted in the 30- micro g group compared with the 150- micro g group. Tartrate-resistant acid phosphatase (TRAP) staining showed that zoledronate decreased osteoclastic numbers and that there was a dose-dependent response. In tibias implanted with the LAPC-9 cells, the zoledronate was not effective in halting the formation of the osteoblastic lesions. Radiographic and histological analysis revealed that osteoblastic lesions either had formed or were developing in 18 of 18 of the control tibias and 36 of 36 of the treated tibias at 8 weeks regardless of dose or treatment schedule. Furthermore, TRAP staining demonstrated that osteoblastic lesions had formed in the LAPC-9 tibias under conditions in which osteoclast numbers were significantly reduced. These results suggest that osteoclast activity may not be critical for the development of osteoblastic lesions associated with prostate tumor cells. Hence, bisphosphonates may not be ideal agents to prevent the formation of osteoblastic lesions associated with prostate cancer metastases to bone.

Adenocarcinoma↗

PubMed2001

[The effects of leptin on proliferation and function of human osteoblast].

OBJECTIVE: To observe the effect of leptin on osteoblast. METHODS: Human osteoblast primary culture was carried out, and the morphology and function of osteoblast were observed. The effects of different levels of leptin on osteoblast in different days were assessed by MTT colorimetry. Osteocalcin production was measured also. RESULTS: Human osteoblasts were fusiform in shape and were positive for alkaline phosphatase by histochemical staining, positive for osteocalcin by immunofluorescence staining, and positive by Alizarin Reds staining after mineralized upon supplementation with ascorbate and beta-glycerophosphate. On the first, second and third days, the proliferation of osteoblast, cultured with different concentrations of leptin, had no changes. The leptin-stimulated synthesis of osteocalcin of cells was found to be dose-dependent (P < 0.05), but not time-dependent (P > 0.05). CONCLUSION: The above data indicated that there were no evidences for the effects of leptin on the proliferation of human osteoblast, but leptin could enhance the function of human osteoblast.

Ascorbic Acid↗

PubMed2003

[Interaction effects between 1,25-dihydroxyvitamin D3 and transforming growth factor-beta1 on the proliferation and differentiation of human embryonic osteoblasts].

OBJECTIVE: To characterize the interaction effects between 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] and human transforming growth factor-beta1 (hTGF-beta1) on the proliferation and differentiation of human embryonic osteoblasts. METHODS: Human embryonic osteoblasts were cultured. 1,25(OH)(2)D(3), of the concentration of 50 nmol/L, hTGF-beta1 of different concentrations (1 x 10(-8) g/L, 1 x 10(-7) g/L, 1 x 10(-6) g/L, and 1 x 10(-5) g/L), and both hTGF-beta1 of different concentrations and 1,25(OH)(2)D(3) of the concentration of 50 nmol/L were added into the cultures with a stimulation time of 96 hours. 3-(4, 5-dimethylthiazol-2-yl) - 2, 5 - diphenyl - tetrazolium bromide (MTT) was added into the cultures. ELISA technique was used to measure the optical density values so as to observe cell's number and proliferation. Alkaline phosphatase (ALP) activity was tested by King's method. Osteocalcin (OC) was tested by radioimmunoassay. The mRNA expression level of SMAD proteins, the key proteins of the TGF-beta signal transduction passageway, was detected by reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: MTT staining showed an absorbance of 0.086 +/- 0.022 in the 1,25(OH)(2)D(3) group, significantly lower than that of the control group (0.124 +/- 0.031, P < 0.05). The ALP activity in the culture of 1,25(OH)(2)D(3) group, hTGF-beta1 groups, and combined 1,25 (OH)(2)D(3) and hTGF-beta1 groups were 1.3 - 2.0 times that of the control group (all P < 0.05). When the concentration of hTGF-beta1 is 1 x 10(-6) g/L, an interaction effect was found between 1,25(OH)(2)D(3) and hTGF-beta1 on the ALP activity of human embryonic osteoblasts. The OC value in cell medium was 5.3 micro g/L +/- 1.6 micro g/L and 5.4 micro g/L +/- 0.9 micro g/L respectively in the hTGF-beta1 1 x 10(-6) g/L and 1 x 10(-5) g/L combined with 1,25(OH)(2)D(3) (50 nmol/L) groups, significantly higher than that in the control group (P < 0.05), but no interaction effect was found between 1,25(OH)(2)D(3) and hTGF-beta1 on the OC production. hTGF-beta1 of different concentrations and hTGF-beta1 of different concentrations combined with 1,25(OH)(2)D(3) all increased the SMAD3 mRNA expression level in human embryonic osteoblasts (all P < 0.05). When the human embryonic osteoblasts were treated with 1,25(OH)(2)D(3) combined with 1 x 10(-6) g/L hTGF-beta1, its SMAD3 mRNA level reached the peak, about 6-fold that of the control group. 1,25(OH)(2)VD(3) and/or hTGF-beta1 did not influenced the SMAD4 mRNA expression. CONCLUSION: 1,25(OH)(2)D(3) inhibits the proliferation of human embryonic osteoblasts and increases the expression of osteoblastic markers, such as ALP and OC, thus promoting its differentiation. An interaction effect exists between 1,25(OH)(2)D(3) and hTGF-beta1 on the differentiation of human embryonic osteoblasts, which may be partly induced by SMA D(3) protein in the TGF-beta signal transduction passageway.

Alkaline Phosphatase↗