Biomedical subjects

Z Schwartz

Publications and source records attributed to Z Schwartz.

At least 37 records · Page 2Linked to original sources

PubMed2004

Osteoblast response to bioactive glasses in vitro correlates with inorganic phosphate content.

Inorganic phosphate (Pi) is a physiological regulator of osteoblasts and chondrocytes, suggesting that phosphate may contribute to the biological response of these cells to bioactive glasses like Bioglass 45S5, which is composed of 45% SiO2, 24.5% CaO, 24.5% Na2O, and 6% P2O5. We investigated the effect of varying the Pi content of bioactive glass disks (0%, 3%, 6% and 12% P2O5) using human osteoblast-like MG63 cells as the model. Cell number on 6% Pi disks was comparable to cultures on tissue culture plastic, but was reduced at higher and lower Pi concentrations. Alkaline phosphatase specific activity of isolated cells and cell layer lysates, as well as PGE2, TGF-beta1 and NO levels in conditioned media, were elevated in cultures grown on bioactive glass and varied with the Pi content. The greatest effects were observed in cultures grown on disks with the lowest Pi concentrations. Thus, growth on the bioactive glasses enhances cell function in comparison with tissue culture plastic and lower Pi content favors osteoblast differentiation.

Biocompatible Materials↗

PubMed2004

Mechanisms regulating differential activation of membrane-mediated signaling by 1alpha,25(OH)2D3 and 24R,25(OH)2D3.

Vitamin D metabolites 1alpha,25(OH)(2)D(3) and 24R,25(OH)(2)D(3) regulate endochondral ossification in a cell maturation-dependent manner via membrane-mediated mechanisms. 24R,25(OH)(2)D(3) stimulates PKC activity in chondrocytes from the growth plate resting zone, whereas 1alpha,25(OH)(2)D(3) stimulates PKC in growth zone chondrocytes. We used the rat costochondral growth plate cartilage cell model to study how these responses are differentially regulated. 1alpha,25(OH)(2)D(3) acts on PKC, MAP kinase, and downstream physiological responses via phosphatidylinositol-specific PLC-beta; 24R,25(OH)(2)D(3) acts via PLD. In both cases, diacylglycerol (DAG) is increased, activating PKC. Both cell types possess membrane and nuclear receptors for 1alpha,25(OH)(2)D(3), but the mechanisms that render the 1alpha,25(OH)(2)D(3) pathway silent in resting zone cells or the 24R,25(OH)(2)D(3) pathway silent in growth zone cells are unclear. PLA(2) is pivotal in this process. 1alpha,25(OH)(2)D(3) stimulates PLA(2) activity in growth zone cells and 24R,25(OH)(2)D(3) inhibits PLA(2) activity in resting zone cells. Both processes result in PKC activation. To understand how negative regulation of PLA(2) results in increased PKC activity in resting zone cells, we used PLA(2) activating peptide to stimulate PLA(2) activity and examined cell response. PLAP is not expressed in resting zone cells in vivo, supporting the hypothesis that PLA(2) activation is inhibitory to 24R,25(OH)(2)D(3) action in these cells.

24,25-Dihydroxyvitamin D 3↗

PubMed2004

Changes in daily energy amounts of main milk components (lactose, protein and fat) during the lactation of high-yielding dairy cows.

The aim of this study was to examine the changes of the daily energy amount of lactose, protein and fat throughout the lactations, and compare them to each other. A total of 309 Israeli Holstein-Friesian cows from one kibbutz were investigated in three lactations, and information was given for a period of five years from 1996 to the end of 2000. The distribution of milk components and milk yield during lactation, and changes of the absolute and relative energy amount in the different milk components were calculated and evaluated. The results showed changes in the energy content of milk and its different components throughout the lactation. Each component (fat, lactose and protein) is dominant in different periods during the lactation. The energy amount from fat reaches a peak first, between days 40 and 50. Lactose has a peak at about day 66 of lactation, and protein reaches the peak last, approximately at day 104 of lactation. It seems that this peak sequence is constant and it is considered to be physiological. It might be suggested that there is a regulation governing the secretion of the different components at different times, and only one component is dominant in a given period. Each component exerts negative and positive influences on the secretion of the other components, which interact with each other and are not fully independent.

Animals↗

PubMed2003

Membrane actions of vitamin D metabolites 1alpha,25(OH)2D3 and 24R,25(OH)2D3 are retained in growth plate cartilage cells from vitamin D receptor knockout mice.

1alpha,25(OH)(2)D(3) regulates rat growth plate chondrocytes via nuclear vitamin D receptor (1,25-nVDR) and membrane VDR (1,25-mVDR) mechanisms. To assess the relationship between the receptors, we examined the membrane response to 1alpha,25(OH)(2)D(3) in costochondral cartilage cells from wild type VDR(+/+) and VDR(-/-) mice, the latter lacking the 1,25-nVDR and exhibiting type II rickets and alopecia. Methods were developed for isolation and culture of cells from the resting zone (RC) and growth zone (GC, prehypertrophic and upper hypertrophic zones) of the costochondral cartilages from wild type and homozygous knockout mice. 1alpha,25(OH)(2)D(3) had no effect on [(3)H]-thymidine incorporation in VDR(-/-) GC cells, but it increased [(3)H]-thymidine incorporation in VDR(+/+) cells. Proteoglycan production was increased in cultures of both VDR(-/-) and VDR(+/+) cells, based on [(35)S]-sulfate incorporation. These effects were partially blocked by chelerythrine, which is a specific inhibitor of protein kinase C (PKC), indicating that PKC-signaling was involved. 1alpha,25(OH)(2)D(3) caused a 10-fold increase in PKC specific activity in VDR(-/-), and VDR(+/+) GC cells as early as 1 min, supporting this hypothesis. In contrast, 1alpha,25(OH)(2)D(3) had no effect on PKC activity in RC cells isolated from VDR(-/-) or VDR(+/+) mice and neither 1beta,25(OH)(2)D(3) nor 24R,25(OH)(2)D(3) affected PKC in GC cells from these mice. Phospholipase C (PLC) activity was also increased within 1 min in GC chondrocyte cultures treated with 1alpha,25(OH)(2)D(3). As noted previously for rat growth plate chondrocytes, 1alpha,25(OH)(2)D(3) mediated its increases in PKC and PLC activities in the VDR(-/-) GC cells through activation of phospholipase A(2) (PLA(2)). These responses to 1alpha,25(OH)(2)D(3) were blocked by antibodies to 1,25-MARRS, which is a [(3)H]-1,25(OH)(2)D(3) binding protein identified in chick enterocytes. 24R,25(OH)(2)D(3) regulated PKC in VDR(-/-) and VDR(+/+) RC cells. Wild type RC cells responded to 24R,25(OH)(2)D(3) with an increase in PKC, whereas treatment of RC cells from mice lacking a functional 1,25-nVDR caused a time-dependent decrease in PKC between 6 and 9 min. 24R,25(OH)(2)D(3) dependent PKC was mediated by phospholipase D, but not by PLC, as noted previously for rat RC cells treated with 24R,25(OH)(2)D(3). These results provide definitive evidence that there are two distinct receptors to 1alpha,25(OH)(2)D(3). 1alpha,25(OH)(2)D(3)-dependent regulation of DNA synthesis in GC cells requires the 1,25-nVDR, although other physiological responses to the vitamin D metabolite, such as proteoglycan sulfation, involve regulation via the 1,25-mVDR.

24,25-Dihydroxyvitamin D 3↗

PubMed2003

Osteoblasts generate an osteogenic microenvironment when grown on surfaces with rough microtopographies.

Osteoblasts respond to microarchitectural features of their substrate. On smooth surfaces (tissue culture plastic, tissue culture glass, and titanium), the cells attach and proliferate but they exhibit relatively low expression of differentiation markers in monolayer cultures, even when confluent. When grown on microrough Ti surfaces with an average roughness (Ra) of 4-7 mum, proliferation is reduced but differentiation is enhanced and in some cases, is synergistic with the effects of surface microtopography. In addition, cells on microrough Ti substrates form hydroxyapatite in a manner that is more typical of bone than do cells cultured on smooth surfaces. Osteoblasts also respond to growth factors and cytokines in a surface-dependent manner. On rougher surfaces, the effects of regulatory factors like 1alpha,25(OH)2D3 or 17beta-estradiol are enhanced. The response to the surface is mediated by integrins, which signal to the cell through many of the same mechanisms used by growth factors and hormones. Studies using PEG-modified surfaces indicate that increased differentiation may be related to altered attachment to the surface. When osteoblasts are grown on surfaces with chemistries or microarchitectures that reduce cell attachment and proliferation, and enhance differentiation, the cells tend to increase production of factors like TGF-beta1 that promote osteogenesis while decreasing osteoclastic activity. Thus, on microrough Ti surface, osteoblasts create a microenvironment conducive to new bone formation.

Calcium↗

PubMed2003

1alpha,25(OH)2D3 causes a rapid increase in phosphatidylinositol-specific PLC-beta activity via phospholipase A2-dependent production of lysophospholipid.

1alpha,25(OH)(2)D(3) activates protein kinase C (PKC) in rat growth plate chondrocytes via mechanisms involving phosphatidylinositol-specific phospholipase C (PI-PLC) and phospholipase A(2) (PLA(2)). The purpose of this study was to determine if 1alpha,25(OH)(2)D(3) activates PI-PLC directly or through a PLA(2)-dependent mechanism. We determined which PLC isoforms are present in the growth plate chondrocytes, and determined which isoform(s) of PLC is(are) regulated by 1alpha,25(OH)(2)D(3). Inhibitors and activators of PLA(2) were used to assess the inter-relationship between these two phospholipid-signaling pathways. PI-PLC activity in lysates of prehypertrophic and upper hypertrophic zone (growth zone) cells that were incubated with 1alpha,25(OH)(2)D(3), was increased within 30s with peak activity at 1-3 min. PI-PLC activity in resting zone cells was unaffected by 1alpha,25(OH)(2)D(3). 1beta,25(OH)(2)D(3), 24R,25(OH)(2)D(3), actinomycin D and cycloheximide had no effect on PLC in lysates of growth zone cells. Thus, 1alpha,25(OH)(2)D(3) regulation of PI-PLC enzyme activity is stereospecific, cell maturation-dependent, and nongenomic. PLA(2)-activation (mastoparan or melittin) increased PI-PLC activity to the same extent as 1alpha,25(OH)(2)D(3); PLA(2)-inhibition (quinacrine, oleyloxyethylphosphorylcholine (OEPC), or AACOCF(3)) reduced the effect of 1alpha,25(OH)(2)D(3). Neither arachidonic acid (AA) nor its metabolites affected PI-PLC. In contrast, lysophosphatidylcholine (LPC) and lysophosphatidylethanolamine (LPE) activated PI-PLC (LPE>LPC). 1alpha,25(OH)(2)D(3) stimulated PI-PLC and PKC activities via Gq; GDPbetaS inhibited activity, but pertussis toxin did not. RT-PCR showed that the cells express PLC-beta1a, PLC-beta1b, PLC-beta3 and PLC-gamma1 mRNA. Antibodies to PLC-beta1 and PLC-beta3 blocked the 1alpha,25(OH)(2)D(3) effect; antibodies to PLC-delta and PLC-gamma did not. Thus, 1alpha,25(OH)(2)D(3) regulates PLC-beta through PLA(2)-dependent production of lysophospholipid.

Animals↗

PubMed2003

Pulsed electromagnetic fields affect phenotype and connexin 43 protein expression in MLO-Y4 osteocyte-like cells and ROS 17/2.8 osteoblast-like cells.

Osteocytes, the predominant cells in bone, are postulated to be responsible for sensing mechanical and electrical stimuli, transducing signals via gap junctions. Osteocytes respond to induced shear by increasing connexin 43 (Cx43) levels, suggesting that they might be sensitive to physical stimuli like low-frequency electromagnetic fields (EMF). Immature osteoblasts exhibit decreased intercellular communication in response to EMF but no change in Cx43. Here, we examined long term effects of pulsed EMF (PEMF) on MLO-Y4 osteocyte-like cells and ROS 17/2.8 osteoblast-like cells. In MLO-Y4 cell cultures, PEMF for 8 h/day for one, two or four days increased alkaline phosphatase activity but had no effect on cell number or osteocalcin. Transforming growth factor beta-1 (TGF-beta 1) and prostaglandin E(2) were increased, and NO(2-) was altered. PEMFs effect on TGF-beta1 was via a prostaglandin-dependent mechanism involving Cox-1 but not Cox-2. In ROS 17/2.8 cells, PEMF for 24, 48 or 72 h did not affect cell number, osteocalcin mRNA or osteocalcin protein. PEMF reduced Cx43 protein in both cells. Longer exposures decreased Cx43 mRNA. This indicates that cells in the osteoblast lineage, including well-differentiated osteoblast-like ROS 17/2.8 cells and terminally differentiated osteocyte-like MLO-Y4 cells, respond to PEMF with changes in local factor production and reduced Cx43, suggesting decreased gap junctional signaling.

Alkaline Phosphatase↗

PubMed2003

Pretreatment of bone with osteoclasts affects phenotypic expression of osteoblast-like cells.

Implant surface morphology regulates osteoblast phenotypic expression. Osteoblast sensitivity to non-biologic surfaces suggests that native bone surface features may also affect osteoblast response. To test this, MG63 osteoblast-like cells were grown for 7 days on bovine cortical bone wafers pretreated with rat bone marrow osteoclasts for 0, 10 or 20 days. Response to osteoclast-treated surfaces was compared to the response of MG63 cells to titanium surfaces with smooth and rough microtopographies. Cell number, differentiation (alkaline phosphatase activity and osteocalcin levels), and local factors (PGE(2) and TGF-beta1) were measured in confluent cultures. Compared to culture on plastic, cell number was reduced on all three types of bone wafers; this effect was dose-dependent with increasing resorption of the surface. Alkaline phosphatase specific activity was increased (P<or=0.05) on all three surfaces compared with plastic, but this increase was not dependent on resorption time, indicating this parameter was sensitive to the surface (bovine bone vs. plastic) but not to osteoclast-resorption. There was a direct correlation between the area of the bone surface resorbed and the amount of osteocalcin, TGF-beta1 and PGE(2) (R(2)=0.8025, 0.8689, 0.8896, respectively). With 20 days of osteoclast pretreatment, there was a 20-fold increase in osteocalcin over plastic and a 7-fold increase over cultures on untreated bone wafers. Similar increases were found for TGF-beta1 and PGE(2). Thus, surface changes resulting from osteoclast pretreatment have a strong effect on osteoblast phenotypic expression, and suggest that microtopography may play a role.

Alkaline Phosphatase↗

PubMed2003

Estrogen-dependent rapid activation of protein kinase C in estrogen receptor-positive MCF-7 breast cancer cells and estrogen receptor-negative HCC38 cells is membrane-mediated and inhibited by tamoxifen.

We examined protein kinase C (PKC) in the regulation of breast cancer cells by estrogen. Estrogen receptor (ER)- positive (+) MCF-7 and ER-negative (-) HCC38 cells were treated with 17 beta-estradiol (E(2)) or E(2)-BSA, which cannot enter the cell. E(2) and E(2)-BSA rapidly increased PKC-alpha in both cells via phosphatidylinositol-dependent phospholipase C and G protein, but not phospholipase A(2) or arachidonic acid. In MCF-7 cells, E(2) and E(2)-BSA had comparable effects, maximal at 90 min. In HCC38 cells, PKC was maximal at 9 min, with E(2)-BSA more than E(2). Tamoxifen blocked estrogen-dependent PKC in MCF-7 cells and reduced it in HCC38 cells. ER-antagonist ICI 182780, ER-agonist diethylstilbestrol, and antibodies to ER alpha and ER beta had no effect. E(2) stimulated [(3)H]thymidine incorporation in MCF-7 only; E(2)-BSA had no effect. Tamoxifen did not alter E(2)-dependent increases in MCF-7 cells, whereas ICI 182780 reduced DNA synthesis in control and E(2)-treated cultures. PKC activity was positively correlated with tumor severity in 133 breast cancer specimens and was greater in ER(-) tumors. Tamoxifen treatment reduced recurrence, and recurrent tumors had higher PKC activity. This indicates that E(2) rapidly increases PKC activity via membrane pathways not involving ER alpha or ER beta and suggests that tamoxifen works by reducing PKC activity through non-ER alpha/ER beta-dependent mechanisms.

Adult↗

PubMed2003

Use of orthodontic treatment as an aid to third molar extraction: a method for prevention of mandibular nerve injury and improved periodontal status.

BACKGROUND: Impaction of mandibular third molars predisposes to pathological conditions including periodontal disease. Extraction of these teeth also may lead to damage to the nerve and to periodontal involvement of the second molars. This report describes a series of cases in which the third molars were orthodontically induced to erupt to prevent the sequelae associated with extraction. METHODS: Impacted mandibular third molars in 18 patients were surgically exposed following placement of an orthodontic appliance. Depending on the individual case, 1 of 3 approaches was used: attachment of a bracket, placement of a post in the root canal, or placement of an orthodontic wire through a bucco-lingual canal. After suturing the mucoperiosteal flap, the orthodontic appliance was activated. After the tooth erupted, it was removed and periodontal parameters were measured on the second molar. RESULTS: No damage to the inferior alveolar nerve was found. Probing depths on the second molar were reduced from 7.9 +/- 1.6 mm on the buccal and 7.4 +/- 1.0 mm on the lingual to 1.8 +/- 0.7 mm and 1.9 +/- 0. 7 mm, respectively. There was an average gain of 5.0 mm in attachment. Keratinized tissue increased from 2.9 +/- 0.7 to 3.8 +/- 0.6 mm. CONCLUSIONS: The interdisiplinary use of periodontics and orthodontics results in non-surgical removal of impacted mandibular third molars without damage to the inferior alveolar nerve and iatrogenic periodontal sequelae to the second molars.

Adolescent↗

PubMed2003

[The relationship between osteoporosis, osteopenia and periodontitis].

A review of the literature on the reciprocal influence of osteoporosis and periodontitis. The imbalance in coupling of bone remodeling causes skeletal osteopenia and osteoporosis. Does the remodeling imbalance influence the oral bone? Both diseases are chronic, multifactorial and result at bone loss. In addition, the diseases share common risk factors such genetics, dietary, environmental and systemic factors. Different studies indicate that the skeletal bone loss in osteoporosis accelerate the decrease in bone density in oral bone. Although the differences in etiology between the two diseases some studies showed that treatment of osteoporosis improved the periodontal health. Further investigation of the mechanisms behind the relationship between osteoporosis and periodontitis may lead to common treatment strategies.

Alveolar Bone Loss↗

PubMed2003

[The role of Matrix Metaloproteinases in the progression of periodontitis, and the use of specific inhibitors to these enzymes in the treatment of the periodontal disease].

Matrix Metaloproteinases (MMPs) play a crucial role in the pathogenesis of the periodontal disease. This group of enzymes can degrade most of the proteins that compose the extracellular matrix. Recently a new concept of treatment, the "host modulating therapy" (HMT) was developed. The rationale behind this concept is to inhibit the production of the inflammatory mediators and/or to block the production of the host MMPs and thus inhibiting disease production. In the recent years it was found that Tetracyclines (TC) decrease the levels of TNF-alpha, IL-1, Nitric Oxide, and prostaglandins, and via intra and extra cellular mechanisms inhibit the production and activation of the MMPs. A capsule of 20 mg Doxycycline, called later Low Dose Doxycycline (LDD), was the first HMT in the periodontal disease. In a 9 month study it was found that LDD bid after supragingival scaling statistically increased pocket reduction and attachment gain compared to supragingival scaling alone. However, this improvement was found only in pockets of 7 mm or more, and was not compared yet to periodontal supportive therapy every three month. There is a need for more basic and clinical research in the field of HMT in the treatment of periodontal disease, to expand our knowledge and clinical experience that will enable us to decide when and how to use medications to modulate host response.

Anti-Bacterial Agents↗

PubMed2003

[The role of surface roughness in promoting osteointegration].

Scientific evidence that has been gathered in the past 20 years established that certain endosseous dental implants--primarily screw-type implants made of commercially pure titanium can be successfully utilized as anchorage for dental prostheses. In recent years, an effort has been made to simplify the surgical procedure, in order to modify clinical treatment modalities. One of the trends is to increasingly utilize microrough titanium implants. Roughened implant surfaces have a long history in implant dentistry, and the most prominent surface is titanium plasma-sprayed (TPS). In recent years new implant surfaces have emerged, so-called microrough titanium surfaces produced with reducing techniques such as grit-blasting with Al2O3 or TiO2 particles, sandblasting and acid-etching, or acid-etching alone. These different titanium surfaces have been tested in numerous in-vivo studies utilizing different animal models. Summarizing the results of these studies, it can be concluded that there is currently sufficient evidence that titanium implants with a microrough surfaces achieve a faster bone integration, a higher percentage of Bone implant Contact (BIC), and a higher resistance to shear documented with higher Removal Torque Values (RTV) when compared with titanium implants with a polished or machined surface. In order to understand the mechanism through which surface roughness modulates its effects mentioned above, recent studies used in-vitro experimental methods to study cell response to implant surface topography. These studies have shown that osteoblasts are sensitive to surface roughness, exhibiting decreased proliferation and a more differentiated phenotype on rougher surfaces. PGE2 production is enhanced on rough surfaces, as is the production of TGF beta 1, suggesting that surface roughness can mediate autocrine and paracrine regulation of osteogenesis. Moreover, surface roughness was found to modulate the effect of systemic hormones like 1,25-(OH)2D3 on osteoblasts. The clinical advantages of implants with rough surface were observed in recently conducted clinical trials. It was found, in humans, that roughened titanium implants need shorter healing period before loading, 6-8 (SLA and Osseotite respectively) weeks instead of 12 weeks. The clinical advantages of shorter healing periods are obvious. Moreover, it was found that certain roughened implants can be used in shorter sizes (6-8 mm) then accepted today. The utilization of shorter implants offers the avoidance of extensive surgical procedures such as nerve lateralization in the mandible or sinus grafting in the maxilla. However, sufficient long term documentation is still lacking, and the predictability of such modalities has yet to be examined in long term prospective clinical trials.

Animals↗

PubMed2002

Osteoblast-mediated mineral deposition in culture is dependent on surface microtopography.

Osteoblast phenotypic expression in monolayer culture depends on surface microtopography. Here we tested the hypothesis that mineralized bone nodule formation in response to osteotropic agents such as bone morphogenetic protein-2 (BMP-2) and dexamethasone is also influenced by surface microtopography. Fetal rat calvarial (FRC) cells were cultured on Ti implant materials (PT [pretreated], Ra = 0.6 microm; SLA [course grit blasted and acid etched], Ra = 4.0 microm; TPS [Ti plasma sprayed], Ra = 5.2 microm) in the presence of either BMP-2 (20 ng/ml) or 10(-8) M dexamethasone (Dex). At 14 days post-confluence, a homogenous layer of cells covered the surfaces, and stacks of cells that appeared to be nodules emerging from the culture surface were present in some areas on all three Ti surfaces. Cell proliferation decreased while alkaline phosphatase specific activity (ALPase) and nodule number generally increased with increasing surface roughness in both control and treated cultures. There was no difference in cell number between the control and Dex-treated cultures for a particular surface, but BMP-2 significantly reduced cell number compared with control or Dex-treated cultures. Treatment with Dex or BMP-2 further increased ALPase on all surfaces except for PT cultures with Dex. Dex had no effect on nodule area in cultures grown on PT or SLA disks, yet increased nodule number by more than 100% in cultures on PT disks. Though the effect of BMP-2 on nodule number was the same as Dex, BMP-2 increased nodule area on all surfaces except TPS, where area was decreased. Ca and P content of the cell layers in control cultures did not vary with surface roughness. However, cultures treated with Dex had increased Ca content on all surfaces, but the greatest increase was seen on SLA and TPS. BMP-2 increased Ca content in cultures on all surfaces, with the greatest increase on the PT surface. BMP-2 treatment increased P content on all surfaces, whereas Dex only increased P on rough surfaces. Of all cultures examined, the Ca/P weight ratio was 2:1 only on rough surfaces with BMP-2, indicating the presence of bone-like apatite. This was further validated by Fourier transform infrared (FTIR) imaging showing a close association between mineral and matrix on TPS and SLA surfaces with BMP-2-treated cells, and individual spectra indicated the presence of an apatitic mineral phase comparable to bone. In contrast, mineral on the smooth surface of BMP-2-treated cultures and on all surfaces where cultures were treated with Dex was not associated with the matrix and the spectra, not typical of bone apatite, implying dystrophic mineralization. This demonstrates that interactions between growth factor or hormone and surface microtopography can modulate bone cell differentiation and mineralization.

Alkaline Phosphatase↗

PubMed2002

Shear force modulates osteoblast response to surface roughness.

Previous studies have shown that osteoblasts are sensitive to surface roughness. When cultured on Ti, MG63 osteoblast-like cells exhibit decreased proliferation and increased differentiation with increasing surface roughness. In vivo, osteoblasts also are subjected to shear force during osseointegration. To examine how shear force modulates osteoblast response to surface roughness, MG63 cells were cultured on glass disks or Ti disks with three different R(a) values and topographies (PT: R(a) = 0.60 microm; SLA: R(a) = 3.97 microm; TPS: R(a) = 5.21 microm) in a continuous flow device, resulting in shear forces of 0, 1, 5, 14, and 30 dynes/cm(2). Confluent cultures were exposed to fluid flow for 1 h. After an additional 23 h, cell number, alkaline-phosphatase-specific activity, and levels of osteocalcin, TGF-beta1, and PGE2 in the conditioned media were determined. Cell numbers on smooth surfaces (glass and PT) were unaffected by shear force. In contrast, shear force caused a dose-dependent reversal of the decrease in cell numbers seen on rough SLA and TPS surfaces. Alkaline-phosphatase-specific activity was unaffected on glass or PT, but shear force caused a biphasic reduction in the roughness-dependent increase on SLA and TPS that was maximal at 14 dynes/cm(2). There was a similar effect seen with TGF-beta1 levels. Osteocalcin was unaffected on smooth surfaces; shear force caused a dose-dependent reduction in the roughness-stimulated increase seen on SLA and TPS. PGE2 production was increased by shear force on all surfaces. There was a twofold increase in PGE2 levels in the media of MG63 cells cultured on glass and PT in response to 14 dynes/cm(2), but on SLA and TPS, 14 dynes/cm(2) shear force caused a 9-10-fold increase. These results show that osteoblastic response to shear force is modulated by surface topography. The shear-force-mediated decrease in osteoblast differentiation seen in cultures on rough surfaces may be due to increased production of PGE2.

Alkaline Phosphatase↗

PubMed2002

Response of normal female human osteoblasts (NHOst) to 17beta-estradiol is modulated by implant surface morphology.

Titanium (Ti) surfaces with rough microtopographies enhance osteogenic differentiation, local factor production, and response to osteogenic agents in vitro and increase pullout strength of dental implants in vivo. Estrogens regulate bone formation, resorption, and remodeling in females and may be important in implant success. Here, we tested the hypothesis that estrogen modulates osteoblast response to implant surface morphology. Primary female human osteoblasts were cultured to confluence on three Ti surfaces (pretreatment, PT - R(a) 0.60 microm; sandblasted and acid-etched, SLA - R(a) 3.97 microm; and Ti plasma-sprayed, TPS - R(a) 5.21 microm) and treated for 24 h with 10(-7) or 10(-8) M 17beta-estradiol (E(2)). Cell number decreased with increasing surface roughness, but was not sensitive to E(2). Alkaline phosphatase specific activity of isolated cells and cell layer lysates was lower on rough surfaces. E(2) increased both parameters on smooth surfaces, whereas on rough surfaces, the stimulatory effect of E(2) on alkaline phosphatase was evident only when measuring cell layer lysates. Osteocalcin levels were higher in the conditioned media of cells grown on rough surfaces; E(2) had no effect in cultures on the plastic surfaces, but increased osteocalcin production on all Ti surfaces. TGF-beta1 and PGE(2) production was increased on rough surfaces, and E(2) augmented this effect in a synergistic manner; on smooth surfaces, there was no change in production with E(2). The response of osteoblasts to surface topography was modulated by E(2). On smooth surfaces, E(2) affected only alkaline phosphatase, but on rough surfaces, E(2) increased levels of osteocalcin, TGF-beta1, and PGE(2). These results show that normal adult human female osteoblasts are sensitive to surface microtopography and that E(2) can alter this response.

Alkaline Phosphatase↗

PubMed2002

Tamoxifen elicits its anti-estrogen effects in growth plate chondrocytes by inhibiting protein kinase C.

17 beta-Estradiol (E(2)) regulates growth plate cartilage cells via classical nuclear receptor mechanisms, as well as by direct effects on the chondrocyte membrane. These direct effects are stereospecific, causing a rapid increase in protein kinase C (PKC) specific activity, are only found in cells from female rats and are mimicked by E(2)-bovine serum albumin (BSA), which cannot penetrate the cell membrane. E(2) and E(2)-BSA stimulate alkaline phosphatase specific activity and proteoglycan sulfation in female rat costochondral cartilage cell cultures, but traditional nuclear receptors do not appear to be involved. This study examined the effect of the anti-estrogen tamoxifen on these markers of chondrocyte differentiation; the gender-specificity of tamoxifen's effect on PKC, if tamoxifen has an effect on vitamin D metabolite-stimulated PKC, which is mediated via specific membrane receptors (1,25-mVDR; 24,25-mVDR) and whether the effect of tamoxifen is mediated by nuclear estrogen receptors. Tamoxifen dose-dependently inhibited the effect of E(2)-BSA on PKC, alkaline phosphatase and proteoglycan sulfation in confluent cultures of female resting zone (RC) cells and growth zone (GC) (prehypertrophic/upper hypertrophic zones) cells, suggesting that its action is at the membrane and not cell maturation-dependent. Neither the estrogen receptor (ER) antagonist ICI 182780 nor the ER agonist diethylstilbesterol affected E(2) or E(2)-BSA-stimulated PKC in female chondrocytes. Tamoxifen also inhibited the increase in PKC activity due to 1 alpha,25-(OH)(2)D(3) or 24R,25-(OH)(2)D(3) in growth plate cells derived from either female or male rats. Inhibition of PKC by tamoxifen may be a general property of membrane receptors involved in rapid responses to hormones.

Alkaline Phosphatase↗

PubMed2002

Rat costochondral chondrocytes produce 17beta-estradiol and regulate its production by 1alpha,25(OH)(2)D(3).

Prior studies have shown that 17beta-estradiol (17beta-E(2)) regulates growth plate chondrocyte maturation and differentiation. This study examines the hypothesis that 17beta-E(2) is a local regulator of rat costochondral growth plate chondrocytes by determining whether these cells express aromatase mRNA and enzyme activity, produce 17beta-E(2), and regulate 17beta-E(2) production by vitamin D(3) metabolites in a gender-specific and cell-maturation-dependent manner. Aromatase gene expression was assessed by reverse transcription-polymerase chain reaction (RT-PCR) and northern analysis of total RNA from male and female chondrocytes. Aromatase specific activity was measured in cell layer lysates of confluent male and female rat costochondral resting zone (RC) and growth zone (GC) cartilage cells that had been treated for 24 h with 1alpha, 25(OH)(2)D(3), 24R,25(OH)(2)D(3), or transforming growth factor (TGF)-beta1. 17beta-E(2) released into the culture media of treated cells was measured by radioimmunoassay (RIA). Female RC cells expressed the highest levels of aromatase mRNA compared with male RC cells and both male and female GC cells. Aromatase activity was present in male and female cells and was 1.6 times greater in female RC cells than female GC cells; male RC and GC cells displayed comparable levels. All cultures produced 17beta-E(2), with a 2.5-fold greater production by female RC cells than female GC cells or either cell type from male rats. Treatment of cultures with 1alpha,25(OH)(2)D(3) caused a dose-dependent increase in 17beta-E(2) production by female RC (1.5-fold greater than control cells) and female GC (threefold greater than control cells) cells. In contrast, 1alpha,25(OH)(2)D(3) had no effect on male GC cells and increased production in male RC cells by only 10% at the highest concentration of 1alpha,25(OH)(2)D(3) used. Neither 24R, 25(OH)(2)D(3) nor TGF-beta1 had an effect on 17beta -E(2) production. These results support our hypothesis and indicate that 17beta-E(2) is most likely a local regulator of rat costochondral growth plate chondrocytes.

24,25-Dihydroxyvitamin D 3↗