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At least 793 records · Page 44Linked to original sources

PubMed2000

Collagen type I-coating of Ti6Al4V promotes adhesion of osteoblasts.

The initial contact of osteoblasts with implant surfaces is an important event for osseointegration of implants. Osseointegration of Ti6Al4V may be improved by precoating of its surface with collagen type I. In this study, the adhesion of rat calvarial osteoblasts to uncoated and collagen type I-coated titanium alloy was investigated over a period of 24 h. Collagen type I-coating accelerates initial adhesion of osteoblasts in the presence of fetal calf serum. One hour after plating, no differences in the percentage of adherent cells between the surfaces investigated were found. Adhesion of osteoblasts to uncoated surfaces was reduced by the GRGDSP peptide by about 70%, whereas adhesion to collagen type I-coated surfaces remained unaffected by treatment of the cells with the peptide. Cell adhesion to coated materials was reduced by about 80% by anti-integrin beta1 antibody. The integrin beta1 antibody did not influence the adhesion to uncoated titanium alloy. The results suggest that osteoblasts adhere to collagen type I-coated materials via integrin beta1 but not by interacting with RGD peptides, whereas adhesion to uncoated titanium alloy is mediated by RGD sequences but not via integrin beta1. Fibronectin does not seem to be involved in the adhesion of osteoblasts to either coated or uncoated titanium alloy.

Adsorption↗

PubMed2000

Integrin-mediated signaling in osteoblasts on titanium implant materials.

The intracellular signaling pathway for osteoblast adhesion to the orthopedic implant material Ti6Al4V (TIV) was investigated and compared to integrin-mediated adhesion to extracellular matrix proteins. Primary osteoblasts from fetal rat calvaria were plated onto TIV, fibronectin (FN), and poly-L-lysine (PLL) and the levels of focal adhesion kinase (FAK), mitogen-activated protein kinase (MAPK), and AP-1 transcription factors, c-fos and c-jun, were compared by Western and Northern blots. Cells on all substrates showed maximum FAK phosphorylation within 60 min and then a decrease at 2 and 24 h. However, the subsequent signal transduction pathway differed on PLL compared to TIV and FN. MAPK was phosphorylated similarly in osteoblasts attached to FN and TIV, whereas cells on PLL demonstrated no MAPK phosphorylation. On TIV and FN, c-fos and c-jun mRNA levels were maximal within 1 h and then plateaued or declined by 2 h. On PLL, they increased at 2 h. Within 1 h, c-fos protein was stimulated in cells attached to TIV and FN and decreased in cells on PLL. c-jun protein increased on all substrates compared to unplated cells. Cytoskeletal changes visualized by phalloidin fluorescence microscopy at 4 h of culture were delayed on TIV compared to FN. In addition, approximately 50% fewer cells adhered to TIV compared to FN or PLL. By 24 h, a well-spread cytoskeleton with focal adhesion sites was apparent on TIV and FN, but cells on PLL were rounded with minimal cell spreading. During 6 days of culture, cells on FN and TIV proliferated, whereas the number of cells on PLL remained the same or decreased, depending on the initial plating density. We conclude that osteoblast adhesion to TIV implants is similar to osteoblast adhesion to FN and leads to osteoblast proliferation. These data provide evidence for the biocompatibility of TIV at a molecular level.

Alloys↗

PubMed1983

Bone formation by isolated calvarial osteoblasts in syngeneic and allogeneic transplants: light microscopic observations.

Taking advantage of recently developed methods for osteoblast isolation, we used these cells to study bone morphogenesis in syngeneic and allogeneic intramuscular transplants. Syngeneic osteoblasts from fetal rat calvaria produced small islands of bone by the third day after transplantation. These islands increased in size and began to fuse after about 14 days. At the surface of the woven bone laid down first, lamellar bone developed. The amount of this bone increased, and in 56-day-old transplants solid blocks of bone were present. Osteoclasts were scarce, and the woven bone remained unresorbed. Bone marrow was absent. The structure of bone in transplants differed from that of mature calvarial bones in which only remnants of woven bone remained and bone marrow was well developed. The scarcity of osteoclasts in transplants could be caused by their relative paucity among the injected cells, since these cells responded strongly to added parathyroid hormone by increased production of cyclic adenosine monophosphate (cAMP) but only weakly to calcitonin. Osteoblasts isolated from the surface of calvarial lamellar bone of 28-day-old rats formed woven bone similar to the bone formed by fetal cells. This suggests that the type of bone produced does not depend on the intrinsic properties of the osteoblasts. Bone formed in an allogeneic system was surrounded by infiltrations containing lymphocytes, macrophages, and osteoclastlike cells in 14-day-old transplants. Osteoblasts at the bone periphery were destroyed and bone matrix was resorbed by infiltrating cells. Numerous bone lacunae were enlarged, suggesting the occurrence of osteocytic osteolysis. Isolated osteoblasts cultured for three population doublings or longer did not form bone after transplantation, although they retained some reactivity toward parathyroid hormone.

Alcian Blue↗

PubMed1988

Lifetime of the osteoblast in mouse periodontium.

The kinetics of osteoblasts and osteocytes on appositional and resorptive surfaces of mouse alveolar bone were examined using 3H-thymidine and 3H-proline radioautography. Our results show that the osteoblasts at the appositional surface of the mouse periodontium are recruited from a progenitor population in the G1 phase of the cell cycle that goes through a single S-phase before differentiating into osteoblasts and that the active lifetime of the osteoblast on the periodontal surface is approximately 20 days. The lifetime of the osteoblasts on periosteal and endosteal surfaces is 10 days. The active lifetime of an osteoblast appears to be independent of the amount of matrix produced.

Alveolar Process↗

PubMed2001

Osteoblastic differentiation of periosteum-derived cells is promoted by the physical contact with the bone matrix in vivo.

The periosteum contains osteoprogenitors that differentiate to osteoblasts in bone growth or repair. Our previous studies suggested the hypothesis that the physical contact of the periosteum with the bone matrix is requisite for the differentiation of osteoblasts. To test the hypothesis, the present study was designed to investigate how the contact between the periosteum and the bone matrix influences the osteoblastic differentiation of periosteal cells with establishing a new experimental model in vivo. Differentiation of osteoblasts was assessed by gene expression of type I collagen, osteocalcin and bone sialoprotein using in situ hybridization. A barrier was designed to prevent periosteal cells from contacting the bone matrix using the membrane filter. The membrane filter was inserted surgically between the surface of rat parietal bone and the periosteum after being punched out with pin holes. Periosteal cells were allowed to contact with the bone surface only through the pin holes. The pin hole was filled with cells derived from the periosteum 1 week after inserting the filter. Differentiation of osteoblasts in week 2 and noticeable bone formation in week 3 were identified on the bone surface only under the pin hole but not under the filter. The present study demonstrated that the physical contact with the bone matrix promotes osteoblastic differentiation of periosteum-derived cells in vivo.

Animals↗

PubMed2005

Osteoblasts engulf apoptotic bodies during alveolar bone formation in the rat maxilla.

During bone formation, as in other tissues and organs, intense cellular proliferation and differentiation are usually observed. It has been described that programmed cell death, i.e., apoptosis, takes place in the control of the cellular population by removing of the excessive and damaged cells. Although it is generally accepted that apoptotic bodies are engulfed by professional phagocytes, the neighboring cells can also take part in the removal of apoptotic bodies. In the present study, regions of initial alveolar bone formation of rat molars were examined with the aim to verify whether osteoblasts are capable of engulfing apoptotic bodies, such as professional phagocytes. Rats aged 11-19 days were sacrificed and the maxillary fragments containing the first molar were removed and immersed in the fixative solution. The specimens fixed in glutaraldehyde-formaldehyde were processed for light microscopy and transmission electron microscopy. For the detection of apoptosis, the specimens were fixed in formaldehyde, embedded in paraffin, and submitted to the TUNEL method. The results revealed round/ovoid structures containing dense bodies on the bone surface in close contact to osteoblasts and in conspicuous osteoblast vacuoles. These round/ovoid structures showed also positivity to the TUNEL method, indicating that bone cells on the bone surface are undergoing apoptosis. Ultrathin sections showed images of apoptotic bodies being engulfed by osteoblasts. Occasionally, the osteoblasts exhibited large vacuoles containing blocks of condensed chromatin and remnants of organelles. Thus, these images suggest that osteoblasts are able to engulf and degrade apoptotic bodies.

Alveolar Process↗

PubMed2005

Visualizing levels of osteoblast differentiation by a two-color promoter-GFP strategy: Type I collagen-GFPcyan and osteocalcin-GFPtpz.

A 3.9 kb DNA fragment of human osteocalcin promoter and 3.6 kb DNA fragment of the rat collagen type1a1 promoter linked with visually distinguishable GFP isomers, topaz and cyan, were used for multiplex analysis of osteoblast lineage progression. Three patterns of dual transgene expression can be appreciated in primary bone cell cultures derived from the transgenic mice and by histology of their corresponding bones. Our data support the interpretation that strong pOBCol3.6GFPcyan alone is found in newly formed osteoblasts, while strong pOBCol3.6GFPcyan and hOC-GFPtpz are present in osteoblasts actively making a new matrix. Osteoblasts expressing strong hOC-GFPtpz and weak pOBCol3.6GFPcyan are also present and may or may not be producing mineralized matrix. This multiplex approach reveals the heterogeneity within the mature osteoblast population that cannot be appreciated by current histological methods. It should be useful to identify and isolate populations of cells within an osteoblast lineage as they progress through stages of differentiation.

Animals↗

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

Novel osteoblast-adhesive peptides for dental/orthopedic biomaterials.

Next generation dental/orthopedic biomaterials must be designed to enhance and support osteoblast adhesion. The osteoblasts use different ways to adhere, that is, integrin- and proteoglycan-mediated mechanisms. The present study reports on the synthesis and osteoblast-adhesive properties of peptides carrying RGD motifs and of sequences mapped on human vitronectin. Our data suggest that osteoblast adhesion on polystyrene plates modified with a linear peptide, in which the GRGDSP sequence is repeated four times, was significantly higher when compared to the adhesion obtained using branched peptides, interestingly containing the same motif. Osteoblast adhesion assays on acellular bone matrix using this active peptide gave very promising results. We also demonstrated that a novel peptide, carrying the X-B-B-B-X-B-B-X motif (where B is a basic amino acid and X is a nonbasic residue), promotes proteoglycan-mediated osteoblast adhesion more efficiently with respect to the KRSR sequence that was recently proposed as heparan-sulfate binding peptide.

Amino Acid Sequence↗

PubMed2002

Gene expression analysis of osteoblastic cells contacted by orthopedic implant particles.

Particles generated from orthopedic implants through years of wear play an essential role in the aseptic loosening of a prosthesis. We have investigated the biocompatibility of these orthopedic particles on different osteoblast-like cells representative of different stages of osteoblast maturation. We found the particles induced a caspase-dependent apoptosis of osteoblasts, with less mature osteoblasts being the most susceptible. An analysis of gene expression was performed on the less mature osteoblasts, which were in contact with the particles. We found that the particles had a profound impact on genes that code for inflammatory cytokines and genes involved in controlling the nuclear architecture. Results from this study suggest that the peri-implant osteolysis after a total joint replacement can be due in part to a decrease of bone formation and not solely to an overstimulation of bone resorption as is generally proposed. Development of new drugs that promote normal bone formation and osteoblast survival would possibly control peri-implant osteolysis, resulting in a better prognosis for patients with orthopedic implants.

Animals↗

PubMed2002

A jet impingement investigation of osteoblastic cell adhesion.

When designing dental and orthopedic implants, it is important to consider phenomena occurring at the microscopic level, particularly at the bone-implant interface. The presence of hard tissue at this interface is essential to implant viability. The integrity of this tissue-biomaterial interface is dependent on appropriate osteoblast functions (adhesion, matrix deposition, etc.) in the immediate area. Researchers have modified various materials with cell-adhesive peptides with the ultimate goal of controlling osteoblast functions. This study used microjet impingement to compare the strength of adhesion of osteoblastic cells (at varying populations) and fibroblasts to peptide-modified substrates in the presence and absence of fetal bovine serum. In the presence of the serum, there was no significant difference in cellular adhesion strength between substrates. In the absence of serum, all cells tested adhered more strongly to underlying substrates, and the strength of cellular adhesion was greater on modified surfaces than on plain glass surfaces. In the absence of serum, second-passage osteoblastic cells generally adhered to substrates more strongly than first-passage osteoblastic cells; fibroblasts adhered similarly to second-passage osteoblastic cells. Fundamental studies such as the present increase the understanding of cell adhesion to various substrates--knowledge that may be ultimately useful in creating an optimal bone-implant interface.

Animals↗

PubMed2002

Hydroxylapatite with substituted magnesium, zinc, cadmium, and yttrium. II. Mechanisms of osteoblast adhesion.

The present in vitro study investigated osteoblast adhesion on hydroxylapatite (HA) doped with either cadmium (Cd), zinc (Zn), magnesium (Mg), or yttrium (Y). Compared with any other dopant tested in the present study, osteoblast adhesion was significantly (p < 0.05) greater on HA doped with Y after 4 h; in addition, osteoblast adhesion increased with concentration (2-7 mol%) of Y in HA. The findings that HA doped with greater amounts of Y adsorbed higher concentrations of calcium and, subsequently, of vitronectin and collagen (proteins known to mediate osteoblast adhesion), but not of albumin, laminin, and fibronectin, may explain the observed enhanced adhesion of osteoblasts on these substrates. Interactions (i.e., adsorption and configuration/bioactivity) of vitronectin and collagen may have been promoted by increased porosity of doped HA. Through doping with Y, the present study provided the first evidence that HA can be synthesized and processed with improved cytocompatibility properties for osteoblast adhesion, and thus offered essential information for the design of novel proactive bioceramics. Proactive bioceramics which elicit specific, timely, and desired responses from surrounding cells and tissues are necessary for improving bonding of orthopaedic/dental implants to juxtaposed bone; such osseointegration will, undoubtedly, enhance implant efficacy.

Adsorption↗

PubMed2003

Osteoblast function on nanophase alumina materials: Influence of chemistry, phase, and topography.

Alumina is a material that has been used in both dental and orthopedic applications. It is with these uses in mind that osteoblast (bone-forming cell) function on alumina of varying particulate size, chemistry, and phase was tested in order to determine what formulation might be the most beneficial for bone regeneration. Specifically, in vitro osteoblast adhesion, proliferation, intracellular alkaline phosphatase activity, and calcium deposition was observed on delta-phase nanospherical, alpha-phase conventional spherical, and boehmite nanofiber alumina. Results showed for the first time increased osteoblast functions on the nanofiber alumina. Specifically, a 16% increase in osteoblast adhesion over nanophase spherical alumina and a 97% increase over conventional spherical alumina were found for nanofiber alumina after 2 h. A 29% increase in cell number after 5 days and up to a 57% greater amount of calcium was found on the surface of the nanofiber alumina compared with other alumina surfaces. Some of the possible explanations for such enhanced osteoblast behavior on nanofiber alumina may be attributed to chemistry, crystalline phase, and topography. Increased osteoblast function on nanofiber alumina suggests that it may be an ideal material for use in orthopedic and dental applications.

Alkaline Phosphatase↗

PubMed2004

Osteoblasts respond to hydroxyapatite surfaces with immediate changes in gene expression.

Bone mineral contains hydroxyapatite (HA). This is the surface that mature osteoblasts and osteocytes interact with. Synthetic HA is widely used in orthopedic surgeries as an implant or implant coating. The bone-like HA surfaces increase implant union and bone formation; however, the mechanisms accounting for this effect on osteoblasts are not known. In this study, we compared gene expression profiles of osteoblasts responding to HA or plastic surfaces for 24 h. Expression profiles were also compared between HA discs processed with gravity-sieved compared with combined gravity and air-jet-sieved HA powders. The latter, composed of smaller HA particles, exhibits an increase in grain boundary surface area. Discs made with either HA powder similarly up-regulated osteoblast expression of 10 genes (including proliferin 3, Glvr-1, DMP-1, and tenascin C) and down-regulated 15 genes (such as osteoglycin) by more than 2-fold compared with plastic surfaces. The overall changes are indicative of an immediate (24-h) response to the HA surface and a trend toward osteoblast differentiation. In addition, subsets of modulated genes exist that are unique to each HA subtype. Taken together, we identified HA responsive genes evident within 24 h of surface contact, indicating a critical role for extracellular mineral surfaces in the regulation of osteoblast gene expression and phenotype.

3T3 Cells↗

PubMed2006

Effects of 58S sol-gel glasses on the temporal expression of bone markers during mouse osteoblastic differentiation.

Previous studies have shown that bioactive glasses can support osteoblastic growth and differentiation in vitro as well as in vivo. More recently, a new category of sol-gel glasses has been developed with enhanced bioactivity and open pores enclosed in a mesoporous matrix. In our study, we investigated the effect of 58S sol-gel glasses on the growth and differentiation of mouse calvaria osteoblasts. Two types of granules were used: 58S sol-gel granules and 60S inert glasses used as control. Phase contrast microscopy showed that cells proliferated and formed mineralized bone nodules in both cultures. However, this phenomenon occurred earlier and to a higher degree in cultures with 58S sol-gel glasses. Northern blot analysis of the expression of osteoblastic markers revealed that osteoblasts retained their phenotype in both types of cultures. Interestingly, stimulation of alkaline phosphatase, bone sialoprotein, and osteocalcin was noticed at day 18 in sol-gel cultures when compared with that in control. These data confirm that 58S bioactive glasses are capable of supporting the growth and maturation of primary mouse osteoblasts. In addition, it was shown that 58S glasses affected the gene-expression profile, causing an up-regulation of the major bone markers. These results indicated that 58S sol-gel glasses appeared as suitable candidates for osteoblast scaffolds in the field of bone tissue engineering.

Animals↗

PubMed2006

Osteoblast response to plasma-spray porous Ti6Al4V coating on substrates of identical alloy.

We have evaluated the in-vitro biocompatibility of Ti6Al4V alloy coated by plasma spraying with an identical alloy. These surfaces are widely used in cementless prosthetic components, although osteoblasts behavior on this treated alloy has not been evaluated to date. Cross sectional examination revealed a thick and rough coating of identical composition without sign of delamination. Within the coating, small discontinuities and nonconnected pores were observed. Osteoblast response was evaluated by assessing cell adhesion, proliferation, and differentiation of primary cultures of human osteoblastic cells. Compared to the polished alloy, osteoblast adhesion measured as cell attachment and actin network reorganization was delayed on the plasma-sprayed surface. Cell proliferation and viability were also impaired on the rough surface. Several informative markers of osteoblastic differentiation such as procollagen I peptide, alkaline phosphatase, osteocalcin, osteoprotegerin, and mineralized nodule formation were evaluated and indicated that the plasma-sprayed alloy favored a more differentiated phenotype than polished alloy. Taken together, our in vitro results indicate that successful osseointegration of plasma spraying of Ti6Al4V with an identical alloy is mediated by modulation of osteoblastic differentiation and mineralization.

Aged↗

PubMed2007

Increased osteoblast adhesion on nanograined Ti modified with KRSR.

Peptide sequences such as lysine-arginine-serine-arginine (KRSR) selectively bind transmembrane proteoglycans (e.g. heparin sulfate) of osteoblasts (bone-forming cells) and are, therefore, actively being investigated for orthopedic applications. Further, nanophase materials (or materials with grain or particle sizes less than 100 nm) are promising new materials that promote new bone growth more than compared to conventional (that is, micron grain or particle size) materials. To combine the above two promising approaches for improving orthopedic implants, the objective of this in vitro study was to functionalize titanium (Ti) surfaces (both nanophase and conventional) with KRSR peptides and study their osteoblast cell adhesive properties. Materials were characterized by X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. Results of this in vitro study provided evidence of increased osteoblast adhesion on nanophase compared to conventional Ti whether functionalized with KRSR or not. Results further showed that the immobilization of KRSR onto Ti (both nanophase and conventional) increased osteoblast adhesion compared to respective nonfunctionalized Ti and those functionalized with the negative control peptide KSRR. Most importantly, osteoblast adhesion on nonfunctionalized nanophase Ti increased compared to conventional Ti functionalized with KRSR. Further, select initial osteoblast adhesion was observed to occur at particle boundaries for any type of nanophase and conventional Ti formulated in this study. In summary, results provided evidence that not only should nonfunctionalized nanophase Ti be further studied for improved orthopedic applications but so should nanophase Ti functionalized with KRSR.

Biocompatible Materials↗

PubMed2006

Characterization of human primary osteoblast response on bioactive glass (BaG 13-93)- coated poly-L,DL-lactide (SR-PLA70) surface in vitro.

Bioabsorbable polylactide-based polymers are commonly used for bone reconstruction. Although these polymers have proven successful in many applications, they do not have the capacity to induce osteoconduction. Therefore, several strategies have been developed to manufacture osteoconductive polylactide-based composites. In this study, we have investigated in vitro response of human primary osteoblasts for self-reinforced poly-L,DL-lactide 70/30 (SR-PLA70) plates coated with spheres of bioactive glass 13-93 (SR-PLA70 + BaG). Osteoblasts were cultured on SR-PLA70 and SR-PLA70 + BaG plates for 2, 7, or 14 days. By day 7, both materials induced a reduction in total cell population. However, by day 14 the proliferative response of osteoblasts on SR-PLA70 + BaG surface was such that the cell population had regained similar levels as that of day 2 controls. Alkaline phosphatase activity was higher on SR-PLA70 at day 7 but declined to control levels by day 14. There were no significant time-dependent variations in alkaline phosphatase activity on SR-PLA70 + BaG. After in vitro hydrolysis for 7 days, the elemental analysis of SR-PLA70 + BaG surface showed the presence of mineral precipitates that were confirmed as crystalline hydroxyapatite. This was accompanied by osteoblast spreading, protrusions of microvilli adhered to BaG 19-39 surface, cuboidal phenotype and cell surface associated formation of hydroxyapatite microspheres. In conclusion, the SR-PLA70 + BaG composite is capable of inducing a proliferative response of human primary osteoblasts, and appears to support the development of mature osteoblast phenotype. Therefore, the SR-PLA70 + BaG composites appear as promising osteoconductive scaffold candidates for reconstruction and regeneration of bone matrix.

Cell Adhesion↗