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Biomedical subjects

M Grano

Publications and source records attributed to M Grano.

At least 19 recordsLinked to original sources
PubMed1995

Biomaterials in orthopaedic surgery: effects of different hydroxyapatites and demineralized bone matrix on proliferation rate and bone matrix synthesis by human osteoblasts.

The effects of different biomaterials, used in orthopaedic surgery for bone substitution and/or prosthesis coating to improve fixation and durability of prosthetic implants, have been studied in vitro on cell growth and bone matrix synthesis by human osteoblasts. The materials were a bovine collagen matrix (Osteovit, B. Braun Melsungen AG, Melsungen, Germany) and two hydroxyapatite (Ceros 80, Robert Mathys Co, Instrumentenfabrik Bettlach, Germany and Ostilit, Howmedica International, Staines House, UK). Cell proliferation and bone matrix synthesis were assessed by incorporation of [3H]thymidine and [3H]proline, respectively. Cell viability in the presence of the materials was also morphologically controlled using phase-contrast microscopy. Exposure to Osteovit caused increased proliferation of human osteoblasts, whereas both Ostilit and Ceros 80 induced a decreased cell growth. Osteoblast bone matrix synthesis was increased by all the materials tested.

Biocompatible Materials↗
PubMed1994

New model for bone resorption study in vitro: human osteoclast-like cells from giant cell tumors of bone.

Cells harvested from 12 human giant cell tumors of bone and kept in culture for several passages were characterized for bone-resorbing capability, total and tartrate-resistant acid phosphatase activity, response to the calciotropic hormone calcitonin, cell proliferation, multinucleation after passages, and presence of calcium sensing. Cells obtained from three tumors presented a complete panel of osteoclast characteristics and maintained their multinuclearity after several passages. Cells from four other tumors increased their cAMP levels after treatment with calcitonin, and the other five apparently consisted of cells of stromal origin. These human cell populations with osteoclast characteristics may provide valid in vitro models for the investigation of osteoclastic differentiation and activity.

Acid Phosphatase↗
PubMed1994

Extracellular Ca2+ sensing is modulated by pH in human osteoclast-like cells in vitro.

Osteoclasts are polarized cells with a basolateral and an apical membrane exposed to different extracellular Ca2+ ([Ca2+]o) and H+ (pHe) concentrations. Osteoclast bone resorption is inhibited in vitro by increases of [Ca2+]o slightly above physiological levels, detected by a [Ca2+]o sensing causing elevations of the intracellular signal, [Ca2+]i. Nevertheless, during bone resorption the apical membrane is exposed to [Ca2+]o severalfold higher than physiological without apparent inhibition of osteoclast functions. Because pHe facing the apical membrane is acidic, in this single-cell [Ca2+]i and intracellular pH study we addressed the question of whether the responses of human osteoclast-like cells from a giant cell tumor of bone to elevated [Ca2+]o are altered by reducing pHe. We first observed that low pHe stimulated Ca2+ efflux and cell acidification. We then demonstrated that the amplitude of the [Ca2+]o-dependent [Ca2+]i "spikes" is downregulated by low pHe, with approximately 70-fold higher [Ca2+]o required to induce significant responses at pHe 6.0 compared with pHe 7.4. Similar downregulation was observed in authentic freshly isolated rat osteoclasts. Finally, we observed that occupancy of the [Ca2+]o sensing by Ca2+ prompted rapid and transient cell acidification partially counteracted by a Na(+)-dependent amiloride derivative-sensitive H+ transport. These results demonstrate that the cascade of events triggered by activation of the [Ca2+]o sensing is affected by environmental pH and in turn influences cellular H+ transport. Such pH-related features of the [Ca2+] o sensing mechanism might be relevant for the regulation of osteoclast-like function.

Calcium↗
PubMed1993

Human osteoclast-like cells recognize laminin via an RGD independent mechanism.

Interactions between cells from human giant cell tumors of bone and the extracellular matrix protein laminin were studied. Cells were capable of recognizing this substratum via a RGD-independent mechanism. Recognition induces adhesion and spreading onto laminin. This protein triggered the release of cellular FN which in turn enhanced recruitment of the beta 1 chain-containing integrin receptor.

Amino Acid Sequence↗
PubMed1992

Protein kinase C affects microfilaments, bone resorption, and [Ca2+]o sensing in cultured osteoclasts.

The effects of protein kinase C (PKC) in the control of osteoclast activity are still unknown. We investigated the role of the enzyme in the control of microfilament organization, podosome assembly, bone resorption, and extracellular Ca2+ sensing in chicken and rabbit osteoclasts treated with agents known to affect PKC activity. Cells were treated for 20 min with a PKC activator [phorbol 12-myristate 13-acetate (PMA)], a PKC inhibitor (staurosporine), a protein kinase A (PKA) inhibitor (H-9), a guanosine 3',5'-cyclic monophosphate-dependent protein kinase-PKA-PKC inhibitor (H-7), or with the inactive phorbol, 4 alpha-phorbol, to examine microfilaments by decoration with rhodamine-phalloidin. In PMA-treated osteoclasts, the number of microfilament-containing adhesion structures (podosomes) per cell decreased. However, enlarged microfilamentous cores in podosomes and stress fiber-like filaments, otherwise absent in controls, appeared. Whereas H-7 induced increase of the number of podosomes, staurosporine, H-9, and 4 alpha-phorbol failed to change microfilament organization. Chicken osteoclasts received also long-term treatment with the agents in the presence of [3H]proline-prelabeled chicken or rat bone particles to measure bone resorption. PMA, as well as staurosporine and H-7, stimulated the resorbing activity, whereas cells were insensitive to H-9 and 4 alpha-phorbol. Measurement of cytosolic free calcium concentration in PMA-treated fura-2-loaded single osteoclasts demonstrated a synergistic effect of PKC activation on the inhibitory extracellular calcium concentration-sensing mechanism, which was, by contrast, blocked by H-7, staurosporine, and H-9 and was insensitive to 4 alpha-phorbol. These results indicate that PKC regulates osteoclast activity inducing both morphological and functional modifications.

Actin Cytoskeleton↗
PubMed1992

Cells from human bone giant cell tumors show a [Ca2+]o-sensing.

Giant cells from a human giant cell tumor of bone, showing several osteoclast features were tested for their capability of detecting the [Ca2+]o by a receptor like [Ca2+]o sensing. We found that cultured cells responded to elevation of [Ca2+]o, obtained adding 4 mM Ca2+ to the 2 mM Ca2+ containing buffer, by a transient increase of [Ca2+]i. Proliferative cells induced to differentiate by treatment with 10(-8) M 1,25 dihydroxyvitamin D3, were upregulated in their capability of responding to elevated [Ca2+]o. In fact, in this circumstance, the peak of [Ca2+]o-induced [Ca2+]i rise was increased compared to untreated cells. This suggests that 1,25 dihydroxyvitamin D3 induces a more efficient regulation of osteoclast activity.

Bone Neoplasms↗
PubMed1992

Protein kinase C-dependent phosphorylation regulates osteoclast calcium-sensing.

Osteoclasts display a membrane Ca(2+)-sensing mechanism capable of detecting the extracellular calcium concentration ([Ca2+]o), and to induce increase of [Ca2+]i and inhibition of bone resorption. The ultimate result of the stimulation of such sensing is probably the activation of protein kinase C (PKC). To demonstrate whether PKC plays a role in the control of the osteoclast activity, we treated rabbit single osteoclasts with agents known to activate or to inhibit the enzyme. We measured [Ca2+]i in single fura 2-loaded single cells and found that activation of PKC by phorbol esters doubled the [Ca2+]o-induced [Ca2+]i elevation, whereas inhibition of the enzyme by H7, staurosporine or sphingosine, completely blocked the ability of the cell to respond to elevated [Ca2+]i. By contrast, a control inactive agent, 4Aphorbol, failed to modify the cellular response to elevated [Ca2+]o. We conclude that PKC plays a synergistic role in the regulation of osteoclast Ca(2+)-sensing. Since we have previously demonstrated that activation of PKA up-regulates the Ca(2+)-sensing as well, we hypothesize that such mechanism is positively fed-back by both PKA and PKC-dependent threonine/serine phosphorylations.

Animals↗
PubMed1992

Functional and biochemical characterization of osteoclast-like cells derived from giant cell tumours of bone.

Cells harvested from human giant cell tumours of bone were characterized on the basis of morphological features, proliferative capacity, total(AP) and tartrate resistant acid phosphatase (TRAP) activity, and hormonal response. Culture were formed by mononucleated and multinucleated cells. Mononucleated cells showed fibroblastic morphology, whereas multinucleated cells showed osteoclastic phenotype. We conclude that in these cultures mature osteoclasts and their mononuclear precursors are present.

Bone Neoplasms↗
PubMed1992

Integrin expression and adhesion property of osteoclast-like cells from giant cell tumours of bone.

Cells cultured from human giant cell tumours of bone were used to study interactions with different extracellular matrix proteins as Collagen, Fibronectin, Osteocalcin, Thrombospondin and Bone Sialoprotein II. Cells were capable of recognizing these substrata; beta 3 integrin subunit was distributed in focal adhesions, together with beta 1 on BSPII, FN, and in presence of serum, whereas and presented a diffuse organization onto the other substrate. beta 1 alone was expressed over collagen coated coverslips.

Bone Neoplasms↗
PubMed1991

Recognition of osteopontin and related peptides by an alpha v beta 3 integrin stimulates immediate cell signals in osteoclasts.

We have investigated the nature of immediate cell signals produced by occupancy of the chicken osteoclast alpha v beta 3 integrin. Synthetic osteopontin and peptides from the osteopontin and bone sialoprotein sequences containing Arg-Gly-Asp stimulated immediate reductions in osteoclast cytosolic Ca2+. The changes in cytosolic Ca2+ required the Arg-Gly-Asp sequence and were blocked by a monoclonal antibody to the alpha v beta 3 integrin, LM609. Osteoclast stimulation by the proteins through the integrin did not require immobilization since soluble peptides produced changes in cytosolic Ca2+ and inhibited osteoclast binding to bone particles and bone resorption. The decrease in cytosolic Ca2+ stimulated by osteopontin and related peptides appeared to be due to activation of a plasma membrane Ca(2+)-ATPase by calmodulin. Thus, the data suggest that ligand binding to the osteoclast alpha v beta 3 integrin results in calmodulin-dependent reduction in cytosolic Ca2+ which participates in regulation of osteoclast function.

Amino Acid Sequence↗
PubMed1991

Osteoblast-osteoclast relationships in bone resorption: osteoblasts enhance osteoclast activity in a serum-free co-culture system.

Osteoblast-osteoclast relationships in bone resorption are unclear. We investigated whether osteoblasts constitutively influence osteoclast activity. We employed a serum-free co-culture system in which chicken osteoclasts and chick calvaria or, alternatively, isolated chick osteoblasts were cultured in two different compartments separated by a 0.45 micron porous membrane permeable to soluble molecules. Osteoclastic bone resorption, evaluated by release of 3H-proline from prelabeled bone fragments, was significantly enhanced by bone cells resident in the calvaria, as well as by isolated osteoblasts. Stimulation was specific, since periosteal cells, or skin fibroblasts, failed to mimic osteoblast activity. Conditioned medium from osteoblast cultures stimulated osteoclast function in a similar manner, indicating that paracrine signals, capable of crossing the porous membrane separating the two compartments, are released by the bone forming cells.

Alkaline Phosphatase↗
PubMed1991

Effects of calcium-phosphate-based materials on proliferation and alkaline phosphatase activity of newborn rat periosteal cells in vitro.

The effects of dental materials, intended for bone substitution, on cell growth and alkaline phosphatase activity of newborn rat periosteal cells have been studied in vitro. Confluent periosteal cells were exposed to three apatite-based materials (400 micrograms/mL) with different physico-chemical properties. The materials were a beta-tricalcium phosphate with a microporous granular structure obtained by sinterization (Synthograft, Johnson & Johnson, East Windsor, NY), a 40-60-mesh microporous durapatite ceramic (Periograf, Sterling Drug, Inc., Rensselaer, NY), and a 1-2-mm-diameter hydroxyapatite ceramic (Osprovit, Feldmuhle Aktiengeselschaft, Plochingen, Germany) with macropores larger than 100 microns. Cell proliferation and alkaline phosphatase activity were assessed by incorporation of 3H-thymidine into trichloroacetic-acid-precipitable material and by a fluorimetric method, respectively. Cell viability and compatibility with the materials were determined by morphology in phase-contrast microscopy. Periosteal cells showed increased proliferation following exposure to Synthograft, but were unaffected by Osprovit, whereas Periograf caused significantly reduced cell growth. Alkaline phosphatase activity was unaffected by Osprovit, but was decreased by both Synthograft and Periograf. The results indicated a differential response of periosteal cells to bone-substituting materials with heterogeneous physico-chemical characteristics.

Alkaline Phosphatase↗
PubMed1990

Osteoclast bone resorption is enhanced in the presence of osteoblasts.

Bone resorption activity by osteoclasts has been evaluated in a co-culture system in which osteoclasts have been plated in the presence of osteoblasts. The system prevents cell-cell contact but permits diffusion of molecules through the pores of a millipore membrane that separates the two compartments in which the two cell types have been plated. Results demonstrated that osteoblasts exert a stimulatory effect over osteoclast bone resorption due to soluble molecules capable of passing through the membrane pores. The effect is specific since periosteal cells, which do not express osteoblastic characteristics, fail to induce changes in the osteoclast activity. PTH does not affect osteoblast-mediated enhancement of bone resorption, indicating that the stimulatory effect that the hormone exert in vivo occurs via a different cellular system.

Animals↗
PubMed1990

The role of protein kinase C in the osteoclast activity.

Isolated chicken osteoclasts in culture have been treated with 100 nM PMA for 20 minutes, and processed for the decoration of the microfilaments with fluorescent phalloidin. Results demonstrated that this phorbol ester, which activates the protein kinase C, induces the assembly of microfilaments in stress-fibers, and enlarges the microfilamentous core of podosomes. This results indicate that the protein kinase C mediates specific arrangement of microfilaments in osteoclasts. The substratum for protein kinase C-mediated phosphorylation is however still unknown.

Actin Cytoskeleton↗
PubMed1990

Cytosolic free calcium dependent regulation of osteoclast bone resorbing activity.

Osteoclasts are sensitive to KCl-induced depolarization and to increased extracellular calcium concentration, and respond to these treatments with cytosolic calcium increase. In this study we evaluated the possibility that these experimental conditions could affect osteoclast bone resorption. We found that, incubating osteoclasts with 3H-proline previously labeled bone particles the resorbing activity was inhibited by both depolarization and extracellular calcium concentration increase. The released radioactivity was, in fact, 48% and 52% respectively compared to the untreated cultures. These data demonstrated that cytosolic calcium increase is one of the messengers of the pathway that inhibits, in this condition, bone resorption. Furthermore, as in parathyroid cells, extracellular calcium acts with a negative direct feedback mechanism that controls osteoclast activity.

Animals↗
PubMed1990

Osteoblast-osteoclast interaction in bone resorption. Preliminary results.

Osteoclastic bone resorption has been evaluated in vitro by release of tritiated collagen fragments from 3H-proline prelabeled bone particles incubated for 48 hours in presence of avian isolated osteoclasts. Cells were co-incubated with periosteum-free chick calvarial fragments by interposition of 0.4 micron millipore membrane transwells, in presence or absence of 10(-8) M 1.34 bovine parathyroid hormone (PTH). Results demonstrated that i) calvaria exert a stimulating effect over osteoclastic bone resorption which was 1.8 fold enhanced with respect to controls (p less than 0.001). ii) the stimulating effect is exerted by calvarium-derived soluble molecules capable of crossing the 0.4 micron millipore membrane interposed between calvarial fragments and osteoclasts, iii) in this experimental system no further enhancement of calvarial stimulating effect is operated by PTH treatment.

Animals↗
PubMed1989

Immunocytochemical distribution of extracellular matrix receptors in human osteoclasts: a beta 3 integrin is colocalized with vinculin and talin in the podosomes of osteoclastoma giant cells.

Human osteoclasts (OCLs) obtained from cell suspensions of surgically excised giant cell bone tumors (osteoclastomas) were attached to glass coverslips and analyzed by immunofluorescence with antibodies to integrins and cytoskeletal proteins. It was found that in OCLs (i) podosomes, identified by their F-actin core and by interference reflection microscopy, were predominantly found in a peripheral belt as described in avian OCLs; (ii) each F-actin core was surrounded by a ring of vinculin and talin; (iii) beta 1 integrin was diffuse in the ventral membrane; (iv) beta 3 integrin was distributed in intensely fluorescent rings surrounding F-actin cores; (v) beta 2 integrin was absent; (vi) beta 4 integrin was absent. The macrophages detected in the same coverslips displayed podosomes containing beta 2 but not beta 3, fibroblasts showed adhesion plaques positive for beta 1 and beta 3 but not for beta 2, and platelets were intensely positive for beta 3. These results indicate that OCLs produce an integrin complex that is absent in the monocyte-macrophage lineage.

Actins↗