Differential effects of different forms of hydroxyapatite and hydroxyapatite/tricalcium phosphate particulates on human monocyte/macrophages in vitro

Novel titanium-apatite hybrid scaffolds with spongy bone-like micro architecture intended for spinal application: In vitro and in vivo study

Titanium alloy scaffolds with novel interconnected and non-periodic porous bone-like micro architecture were 3D-printed and filled with hydroxyapatite bioactive matrix. These novel metallic-ceramic hybrid scaffolds were tested in vitro by direct-contact osteoblast cell cultures for cell adhesion, proliferation, morphology and gene expression of several key osteogenic markers. The scaffolds were also evaluated in vivo by implanting them on transverse and spinous processes of sheep's vertebras and subsequent histology study. The in vitro results showed that: (a) cell adhesion, proliferation and viability were not negatively affected with time by compositional factors (quantitative MTT-assay); (b) the osteoblastic cells were able to adhere and to attain normal morphology (fluorescence microscopy); (c) the studied samples had the ability to promote and sustain the osteogenic differentiation, matrix maturation and mineralization in vitro (real-time quantitative PCR and mineralized matrix production staining). Additionally, the in vivo results showed that the hybrid scaffolds had greater infiltration, with fully mineralized bone after 6 months, than the titanium scaffolds without bioactive matrix. In conclusion, these novel hybrid scaffolds could be an alternative to the actual spinal fusion devices, due to their proved osteogenic performance (i.e. osteoinductive and osteoconductive behaviour), if further dimensional and biomechanical optimization is performed.

Effect of Ta2O5 content on the osseointegration and cytotoxicity behaviors in hydroxyapatite-Ta2O5 coatings applied by EPD on superelastic NiTi alloys

In the present study, the different contents of tantalum pentoxide (Ta₂O₅: 10, 15, 20 and 30 wt%) nanoparticles were introduced into the natural hydroxyapatite (nHA) coating structure on NiTi substrate through electrophoretic deposition (EPD) method. The phase compositions of coatings were perused before and after the sintering at 800 °C for 1 h by XRD. The incorporation of 30wt%Ta₂O₅ into nHA matrix induced the formation of undesirable soluble Ca₃(PO₄)₂ phase in composite coating. The FESEM images showed that the density of continuous nHA coating increased by compositing with Ta₂O₅. The maximum adhesion strength of 28.3 ± 0.7 MPa accomplished from the nHA-20 wt%Ta₂O₅ composite coating. The Ni ions concentration measurement results from the passivated-NiTi with nHA and nHA-(10, 15 and 20)wt%Ta₂O₅ coatings during 30 days of immersion in PBS clarified the positive role of Ta₂O₅ in decreasing the Ni leaching due to the lowering the open porosities of nHA structure. The biological response of the coating surfaces was assessed in vitro by cell culturing and MTS assay. By considering the morphology and density of adsorbed cells on each coating, the improved biocompatibility of nHA coating in the presence of Ta₂O₅ was justified by scrutinizing the surface roughness, wettability and charge. The highest cell attachment and proliferation on nHA-20 wt%Ta₂O₅ coating was related to owning the lowest roughness, wetting angle of 34^o ± 0.5 and the highest negative surface charge density. Also, the concentration of the highest negative charge density on nHA-20 wt%Ta₂O₅ coating surface in the SBF solution caused to the enhancement of the amount of the apatite nuclei through providing more sites to calcium absorption.

Calcium supplementation decreases BCP-induced inflammatory processes in blood cells through the NLRP3 inflammasome down-regulation

Interaction of host blood with biomaterials is the first event occurring after implantation in a bone defect. This study aimed at investigating the cellular and molecular consequences arising at the interface between whole blood and biphasic calcium phosphate (BCP) particles. We observed that, due to calcium capture, BCP inhibited blood coagulation, and that this inhibition was reversed by calcium supplementation. Therefore, we studied the impact of calcium supplementation on BCP effects on blood cells. Comparative analysis of BCP and calcium supplemented-BCP (BCP/Ca) effects on blood cells showed that BCP as well as BCP/Ca induced monocyte proliferation, as well as a weak but significant hemolysis. Our data showed for the first time that calcium supplementation of BCP microparticles had anti-inflammatory properties compared to BCP alone that induced an inflammatory response in blood cells. Our results strongly suggest that the anti-inflammatory property of calcium supplemented-BCP results from its down-modulating effect on P2X7R gene expression and its capacity to inhibit ATP/P2X7R interactions, decreasing the NLRP3 inflammasome activation. Considering that monocytes have a vast regenerative potential, and since the excessive inflammation often observed after bone substitutes implantation limits their performance, our results might have great implications in terms of understanding the mechanisms leading to an efficient bone reconstruction.

STATEMENT OF SIGNIFICANCE

Although scaffolds and biomaterials unavoidably come into direct contact with blood during bone defect filling, whole blood-biomaterials interactions have been poorly explored. By studying in 3D the interactions between biphasic calcium phosphate (BCP) in microparticulate form and blood, we showed for the first time that calcium supplementation of BCP microparticles (BCP/Ca) has anti-inflammatory properties compared to BCP-induced inflammation in whole blood cells and provided information related to the molecular mechanisms involved. The present study also showed that BCP, as well as BCP/Ca particles stimulate monocyte proliferation. As monocytes represent a powerful target for regenerative therapies and as an excessive inflammation limits the performance of biomaterials in bone tissue engineering, our results might have great implications to improve bone reconstruction.

Controlled laser texturing of titanium results in reliable osteointegration

We have developed a laser-textured superhydrophilic Ti-6Al-4V surface with unique surface chemistry and topography that substantially promotes osteoblast adhesion in culture. Here we investigate the osteointegration of laser-textured implants in an ovine model. Our hypothesis was that laser-textured implants, without any surface coating (LT), would encourage comparable amounts of bone-implant contact and interfacial strength when compared with widely accepted hydroxyapatite (HA) coated implants. Additionally, we hypothesized that LT would significantly increase bony integration compared with machine-finished (MF) and grit-blasted (GB) implants. Forty-eight tapered transcortical pins were implanted into six sheep. Four experimental groups (LT, HA, MF, and GB) were investigated (n = 12) and implants remained in vivo for 6 weeks. Bone apposition rates, interfacial shear strength, and bone-implant contact (BIC) were quantified. The interfacial strength of LT and HA implants were found to be significantly greater than GB (p = 0.032 and p = 0.004) and MF (p = 0.004 and p = 0.004, respectively), but no significant difference between LT and HA implants was observed. Significantly increased BIC was measured adjacent to HA implants when compared with both LT and GB implant surfaces (p = 0.022 and p = 0.006, respectively). No significant difference was found when LT and GB implants were compared. However, all surface finishes encouraged significantly increased BIC when compared with the MF surface. Maximizing implant fixation to host bone is vital for its long-term success. The production of an LT surface is a simple and cheap manufacturing process and this study demonstrated that laser-textured implants are a very promising technical development that warrants further research. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:820-828, 2017.

Effects of Bio-Oss® and Cerasorb® dental M on the expression of bone-remodeling mediators in human monocytes

In contribution to diverse techniques of bone reconstruction involving biomaterials in contemporary dentistry, this study aimed to evaluate the effect of the bone-grafting materials Bio-Oss^® and Cerasorb^® Dental M on the expression of cytokines associated with bone remodeling by human monocytes in vitro. Bio-Oss^® and Cerasorb^® Dental M were incubated in separate culture media, and their supernatants were added to mononuclear cells of human peripheral blood, some of which had been stimulated with Porphyromonas gingivalis. The frequency of total monocytes and CD14⁺ monocytes producing cytokines interleukin 6 (IL-6), IL-8, IL-10, IL-12, and tumor necrosis factor alpha (TNF-α) were determined by flow cytometry. One-way analysis of variance with repeated measures, followed by Tukey's post hoc test, revealed that stimulation with P. gingivalis increased the expression of IL-6 and IL-8 and reduced the expression of TNF-α compared to effects demonstrated in the control group (p < 0.05). Adding biomaterial supernatants did not significantly affect the expression of any cytokine evaluated, however, either in the absence or in the presence of bacterial stimulation. Our data suggest that Bio-Oss^® and Cerasorb^® Dental M neither stimulate cytokine production in human monocytes nor interfere with mechanisms of cell communication mediated by cytokines evaluated during stimulation with P. gingivalis. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2066-2073, 2017.

POLYMER-ASSISTED DEPOSITION OF HYDROXYAPATITE COATINGS USING ELECTROPHORETIC TECHNIQUE

Hydroxyapatite (HA) finds use as powder, scaffold, paste, and coatings for orthopedic and dental applications. Plasma spraying is the most commonly used technique to coat HA on metallic implants. However, undesirable phase changes at high temperatures encourage to adopt ambient temperature deposition techniques such as dip coating, electrophoretic, and physical vapor deposition (PVD). Electrophoretic technique is being used extensively to deposit HA, however sintering is required after the deposition to enhance adhesion of coatings to the substrate. In the present work, polyethylene glycol (PEG) modified HA was deposited on 316L Stainless Steel plates using electrophoretic deposition (EPD), which improved the binding strength of the HA to the substrate with increased packing density of HA particles without the need of sintering. PEG is a biocompatible and soluble polymer that helps HA to bond well with the substrate and in addition, prevents the agglomeration and precipitation of HA. Phase identification and crystal structure of the coatings were determined using X-ray diffraction (XRD). The stability of the coatings was assessed by Fourier transform infrared spectroscopy (FTIR), whereas scanning electron microscopy (SEM) was utilized in order to investigate the morphological properties of the deposited coatings. The mechanical properties of the coatings were investigated using the indentation testing that depicted an enhanced level of adhesion of coatings to the substrate.

Evaluating the toxicity of hydroxyapatite nanoparticles in catfish cells and zebrafish embryos

The toxicity of needle-(nHA-ND) and rod-shaped (nHA-RD) hydroxyapatite (HA) nanoparticles is evaluated in vitro on catfish B-cells (3B11) and catfish T-cells (28s.3) and in vivo on zebrafish embryos to determine if biological effects are similar to the effects seen in mammalian in vitro systems. Neither nHA-ND nor nHA-RD affect cell viability at concentrations of 10 to 300 μg mL(-1) . However, 30 μg mL(-1) needle-shaped nHA lower metabolic activity of the cells. Axial deformations are seen in zebrafish exposed to 300 μg mL(-1) needle shaped nHA after 120 h. For the first time, nHA is reported to cause zebrafish hatching delay. The lowest concentration (3 μg mL(-1) ) of both types of nHA cause the highest hatching inhibition and needle-shaped nHA exposed zebrafish exhibit the lowest hatch at 72 h post fertilization.

Secretion of growth factors from macrophages when cultured with microparticles

The aim of this study is to investigate the influence of macrophages on osteoblast (OB) performance and differentiation. In this regard, we studied the secretion of growth factors including bone morphogenetic proteins (BMPs) from before and after activation of macrophages. We also evaluated osteogenic markers in the co-culture of macrophages and OBs. The macrophages were seeded on microparticles (MPs) based on chitosan (CS). Two types of MPs were fabricated including CS MPs and 10% calcium phosphate (CaHPO4 )-incorporated CS MPs. Macrophage seeded on MPs was activated using lipopolysaccharide (LPS). The expression of BMP-2, BMP-6, BMP-7, and transforming growth factor beta (TGF-β) from macrophages seeded and cultured on hybrid MPs before and after activation of LPS at predetermined times was quantified using a quantitative reverse transcription-polymerase chain reaction (RT-PCR). All of the above growth factors were expressed from MP-macrophage cultures before LPS activation. Osteogenic markers such as alkaline phosphatase (ALP), osteocalcin (OCN), and collagen I (COL-I) in the cultures of MP-OB-macrophage were quantified using a quantitative RT-PCR at days 2, 4, and 7. We found an elevation of gene expression of ALP and COL-1 in the co-cultures of OB-macrophage on MPs compared to OB on MP cultures. These data suggest that macrophages enhance expression of osteogenic markers in OBs, and demonstrate the importance of the role of macrophages in bone regeneration.

The effect of the DLTIDDSYWYRI motif of the human laminin α2 chain on implant osseointegration

Considerable effort has been directed towards replacing lost teeth using tissue-engineering methods such as titanium implants. A number of studies have tried to modify bioinert titanium surfaces by coating them with functionally bioactive molecules for faster and stronger osseointegration than pure titanium surfaces. Recently, peptides have been recognized as valuable scientific tools in the field of tissue-engineering. The DLTIDDSYWYRI motif of the human laminin-2 α2 chain has been previously reported to promote the attachment of various cell types; however, the in vivo effects of the DLTIDDSYWYRI motif on new bone formation have not yet been studied. To examine whether a laminin-2-derived peptide can promote osseointegration by accelerating new bone formation in vivo, we applied titanium implants coated with the DLTIDDSYWYRI motif in a rabbit tibia model. The application of the DLTIDDSYWYRI motif-treated implant to tibia wounds enhanced collagen deposition and alkaline phosphatase expression. It significantly promoted implant osseointegration compared with treatment with scrambled peptide-treated implants by increasing the bone-to-implant contact ratio and bone area. These findings support the hypothesis that the DLTIDDSYWYRI motif acts as an effective osseointegration accelerator by enhancing new bone formation.

Inflammatory cell response to calcium phosphate biomaterial particles: an overview

Bone is a metabolically active and highly organized tissue consisting of a mineral phase of hydroxyapatite (HA) and amorphous calcium phosphate (CaP) crystals deposited in an organic matrix. One objective of bone tissue engineering is to mimic the chemical and structural properties of this complex tissue. CaP ceramics, such as sintered HA and beta-tricalcium phosphate, are widely used as bone substitutes or prosthesis coatings because of their osteoconductive properties. These ceramic interactions with tissues induce a cell response that can be different according to the composition of the material. In this review, we discuss inflammatory cell responses to CaP materials to provide a comprehensive overview of mechanisms governing the integration or loosening of implants, which remains a major concern in tissue engineering. A focus on the effects of the functionalization of CaP biomaterials highlights potential ways to increase tissue integration and limit rejection processes.

The influence of genetic factors on the osteoinductive potential of calcium phosphate ceramics in mice

The efficacy of calcium phosphate (CaP) ceramics in healing large bone defects is, in general, not as high as that of autologous bone grafting. Recently, we reported that CaP ceramics with osteoinductive properties were as efficient in healing an ilium defect of a sheep as autologous bone graft was, which makes this subclass of CaP ceramics a powerful alternative for bone regeneration. Although osteoinduction by CaP ceramics has been shown in several large animal models it is sporadically reported in mice. Because the lack of a robust mouse model has delayed understanding of the mechanism, we screened mice from 11 different inbred mouse strains for their responsiveness to subcutaneous implantation of osteoinductive tricalcium phosphate (TCP). In only two strains (FVB and 129S2) the ceramic induced bone formation, and in particularly, in FVB mice, bone was found in all the tested mice. We also demonstrated that other CaP ceramics induced bone formation at the same magnitude as that observed in other animal models. Furthermore, VEGF did not significantly increase TCP induced bone formation. The mouse model here described can accelerate research of osteoinductive mechanisms triggered by CaP ceramics and potentially the development of therapies for bone regeneration.

Synthetical bone-like and biological hydroxyapatites: a comparative study of crystal structure and morphology

Phase composition, crystal structure and morphology of biological hydroxyapatite (BHAp) extracted from human mandible bone, and carbonated hydroxyapatite (CHAp), synthesized by the chemical precipitation method, were studied by x-ray powder diffraction (XRD), Fourier transform infrared (FTIR) and Raman (R) spectroscopy techniques, combined with transmission electron microscopy (TEM). Structural and microstructural parameters were determined through Rietveld refinement of recorded XRD data, performed using the FullProf computing program, and TEM. Microstructural analysis shows anisotropic extension along the [00l] crystallographic direction (i.e. elongated crystallites shape) of both investigated samples. The average crystallite sizes of 10 and 8 nm were estimated for BHAp and CHAp, respectively. The FTIR and R spectroscopy studies show that carbonate ions substitute both phosphate and hydroxyl ions in the crystal structure of BHAp as well as in CHAp, indicating that both of them are mixed AB-type of CHAp. The thermal behaviour and carbonate content were analysed using thermogravimetric and differential thermal analysis. The carbonate content of about 1 wt.% and phase transition, at near 790 °C, from HAp to β-tricalcium phosphate were determined in both samples. The quality of synthesized CHAp powder, particularly, the particle size distribution and uniformity of morphology, was analysed by a particle size analyser based on laser diffraction and field emission scanning electron microscopy, respectively. These data were used to discuss similarity between natural and synthetic CHAp. Good correlation between the unit cell parameters, average crystallite size, morphology, carbonate content and crystallographic positions of carbonate ions in natural and synthetic HAp samples was found.

Bone reaction to a biomimetic third-generation hydroxyapatite coating and new surface treatment for the Symax hip stem

Four uncemented Symax hip stems were extracted at three weeks and nine, 13 and 32 months, respectively, for reasons other than loosening. The reasons for implant removal were infection in two cases, recurrent dislocation in one and acetabular fracture in one. They were analysed to assess the effect and behaviour of an electrochemically deposited, completely resorbable biomimetic BONIT-hydroxyapatite (HA) coating (proximal part) and a DOTIZE surface treatment (distal part) using qualitative histology, quantitative histomorphometry and scanning electron microscopy (SEM). Early and direct bone-implant bonding with signs of active remodelling of bone and the HA coating were demonstrated by histology and SEM. No loose BONIT-HA particles or delamination of the coating were observed, and there was no inflammation or fibrous interposition at the interface.

Histomorphometry showed bone-implant contact varying between 26.5% at three weeks and 83.5% at 13 months at the HA-coated implant surface. The bone density in the area of investigation was between 24.6% at three weeks and 41.1% at 32 months. The DOTIZE surface treatment of the distal part of the stem completely prevented tissue and bone apposition in all cases, thereby optimising proximal stress transfer.

The overall features of this implant, in terms of geometry and surface texture, suggest a mechanically stable design with a highly active biomimetic coating, resulting in rapid and extensive osseo-integration, exclusively in the metaphyseal part of the stem. Early remodelling of the HA coating does not seem to have a detrimental effect on short-term bone-implant coupling. There were no adverse effects identified from either the BONIT-HA coating or the DOTIZE surface treatment.

Size dependent induction of proinflammatory cytokines and cytotoxicity of particulate beta-tricalciumphosphate in vitro

Cellular responses to particulate calcium phosphate ceramics can lead to inflammatory reactions under certain conditions that depend on particle composition, size and morphology. In this context, the potential influence of varying sizes of particulate beta-tricalciumphosphate (beta-TCP) on the induction of inflammation and cytotoxicity remains to be determined. The present work investigates the effects of beta-TCP particles of five different sizes (1, 3, 13, 32 and 40 μm) on human peripheral blood mononuclear cells (PBMC) in vitro concerning the release of TNF-alpha, IL-1beta and IL-8 after six and 18 h of incubation (ELISA) as well as intracellular TNF-alpha, IFN-gamma, IL-1alpha, IL-1beta and IL-8 levels within distinct PBMC subpopulations after 12 h (FACS). Potential cytotoxic effects were determined by assaying lactate dehydrogenase (LDH) and morphological analyses (electron microscopy). Beta-TCP 1 μm did not induce any cytokine after 6 h but slightly increases TNF-alpha, IL-1beta and IL-8 release after 18 h. Larger particles (32 and 40 μm) consistently caused higher levels of cytokine release by increasing the fraction of cytokine producing monocytes. They also caused higher levels of LDH release as did smaller, phagocytosable particles. These data suggest a less inflammatory and cytotoxic profile of beta-TCP devices with a smaller primary particle size when compared to larger particles.

The Use of Ceramics as Bone Substitutes in Revision Hip Arthroplasty

The number of grafting procedures, including those performed in primary and revision hip arthroplasty, continues to rise around the world. Demand for musculoskeletal donor tissue now outstrips supply. There is no single bone substitute that is ideal for all circumstances. Bone substitutes act as a scaffold and are usually osteoconductive. They are rarely osteoinductive; if they are, a molecular bond is formed between the graft and host bone, improving fixation and longevity. Bone graft substitutes are very rarely osteogenic. There is a growing body of clinical evidence supporting the use of bone graft substitutes in vivo for complex hip arthroplasty.

Proinflammatory and osteoclastogenic effects of beta-tricalciumphosphate and hydroxyapatite particles on human mononuclear cells in vitro

Particulate wear debris can activate defence cells and osteoclasts at the bone-implant interface possibly leading to bone resorption and implant failure. Cellular responses and inflammatory effects have been reported for particulate hydroxyapatite (HA). However, the immunological effects of particulate beta-tricalciumphosphate (beta-TCP) have not been studied and the question of whether beta-TCP is more biocompatible in this regard as is HA remains to be determined. Therefore the present work investigates effects of endotoxin-free HA and beta-TCP particles of the same size (d(50)=1 microm) and dose (SAR 10:1) on human peripheral blood mononuclear cells in vitro. The production of proinflammatory cytokines (TNF-alpha, IL-1beta, IL-8) and cytokines connected to osteoclast and dendritic cell differentiation (OPG, RANKL, M-CSF, GM-CSF) was determined by ELISA. After 6 and 18 h of incubation HA and beta-TCP caused a quite similar induction of TNF-alpha, IL-1beta and IL-8. Effects of particles on the production of M-CSF and OPG were not detectable. However, in sharp contrast to HA, beta-TCP caused less induction of GM-CSF and not any of RANKL, both known for promoting dendritic cells and osteoclastogenesis respectively. Therefore these in vitro data suggest that wear debris of beta-TCP poses lesser risk of the detrimental effects of osteoclast induction known from HA.

Hydroxyapatite nano and microparticles: correlation of particle properties with cytotoxicity and biostability

Synthetic colloid and gel hydroxyapatite (HA) nanoparticles (NPs) were spray dried to form microparticles (MPs). These are intended for use as slow release vaccine vectors. The physico-chemical properties of gel and colloid NPs and MPs were compared to those of HA obtained commercially. Their cytotoxicity to human monocytes'-derived macrophages (HMMs) was assessed in vitro using a range of techniques. These included the MTT assay, LDH leakage and a confocal based live-dead cell assay. Cytotoxicity differed significantly between preparations, with the suspended gel preparation being the most toxic (31-500 microg/ml). Other preparations were also toxic but only at higher concentrations (>250 microg/ml). Transmission electron microscopy (TEM) and stereology showed variable cellular uptake and subsequent dissolution of the various forms of HA. We have demonstrated that HA particle toxicity varied considerably and that it was related to their physico-chemical properties. Cell death correlated strongly with particle load. The intracellular dissolution of particles as a function of time in HMM suggests that increased cytoplasmic calcium load is likely to be the cause of cell death. Some HA NPs eluded the phagocytic pathway and a few were even seen to enter the nuclei through nuclear pores.

Tricalcium phosphate bone substitute in corrective osteotomy of the distal radius

AIM

To evaluate the outcome of using tricalcium phosphate (TCP) as void filler and structural support in corrective opening-wedge osteotomy of the distal radius.

METHODS

A consecutive series of 17 patients with malunited dorsally angulated distal radius fracture underwent corrective osteotomy using plates, screws and TCP blocks. Results were evaluated postoperatively with DASH at 6 months with radiography at 8-12 weeks and 0.5-3.5 years.

RESULTS

Mean DASH score improved from 52 (S.D. 22) preoperatively to 30 (S.D. 22) postoperatively. There was one non-union. There was also a mean loss of radial length of 1.1mm (S.D. 1.0mm) between the first postoperative radiograph and final follow-up. Radiolucent zones were observed around the TCP grafts after 6-8 weeks in 10/14 cases, but could not be statistically correlated with the slight loss of reduction.

CONCLUSIONS

TCP seems to be an alternative to iliac crest bone grafting in corrective osteotomies of the distal radius. The shortening observed over time may be attributable to inflammation induced by the TCP.

In vitro evaluation of nanosized carbonate-substituted hydroxyapatite and its polyhydroxyethylmethacrylate nanocomposite

Nanometer scale carbonate-substituted hydroxyapatite (nanoCHA) particles were prepared and examined using transmission electron microscopy, which revealed their polycrystalline nature with a rod-like morphology (20-30 nm in width and 50-80 nm in length). In vitro cytotoxicity study showed that there was some evidence of lactate dehydrogenase (LDH) release when macrophages were in contact with high concentrations of nanoCHA particles. The levels of LDH release decreased significantly with a reduction in nanoCHA concentration. A similar trend was observed for the inflammatory cytokine TNF-alpha. nanoCHA particles with high carbonate content induced a high level of TNF-alpha release. Biological testing using a human osteoblast (HOB) cell model found that HOB cells were able to grow and proliferate on a nanoCHA deposited surface. Well organized actin fibers were observed for HOB cells in contact with nanoCHA particles with low carbonate content and the cell proliferation rate was higher on these particles in comparison with those of high carbonate nanoCHA particles. Therefore, low carbonate nanoCHA particles were incorporated into poly-(2-hydroxyethylmethacrylate) matrix to make a nanocomposite. It was found that the nanoCHA composite was hydrophilic and became rubber-like after hydration. Both 20 wt % and 40 wt % composites were able to induce the formation of bone-like apatite after immersion in simulated body fluid. A high bioactivity of the composite was obtained with high loading of the nanoCHA filler. These results demonstrate the potential of formulating nanocomposites for biomedical applications.

PLD bioactive ceramic films: the influence of CaO-P2O5 glass additions to hydroxyapatite on the proliferation and morphology of osteblastic like-cells

This work consists on the evaluation of the in vitro performance of Ti6Al4V samples PLD (pulsed laser deposition) coated with hydroxyapatite, both pure and mixed with a CaO-P2O5 glass. Previous studies on immersion of PLD coatings in SBF, showed that the immersion apatite films did not present the usual cauliflower morphology but replicated the original columnar structure and exhibited good bioactivity. However, the influence of glass associated to hydroxyapatite concerning adhesion, proliferation and morphology of MG63 cells on the films surface was unclear. In this study, the performance of these PLD coated samples was evaluated, not only following the physical-chemical transformations resulting from the SBF immersion, but also evaluating the cytocompatibility in contact with osteoblast-like MG63 cells. SEM and AFM confirmed that the bioactive ceramic PLD films reproduce the substrate's surface topography and that the films presented good adherence and uniform surface roughness. Physical-chemical phenomena occurring during immersion in SBF did not modify the original columnar structure. In contact with MG63 cells, coated samples exhibited very good acceptance and cytocompatibility when compared to control. The glass mixed with hydroxyapatite induced higher cellular proliferation. Cells grown on these samples presented many filipodia and granular structures, typical features of osteoblasts.

Inflammatory reaction in rats muscle after implantation of biphasic calcium phosphate micro particles

Several studies have shown that macro micro porous bioceramics ectopically implanted promote bone tissue formation. This study aims at investigating the inflammatory response towards biphasic calcium phosphate (BCP) ceramic micro particles. BCP composed of hydroxyapatite (HA) and beta-tricalcium phosphate, HA/beta -TCP ratio of 50/50, were prepared by sintering at 1200 degrees C for 5 h. After crushing, 3 fractions of BCP micro particles < 20, 40-80 and 80-200 micro m were sieved. The micro particles were carefully characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser scattering. The inflammatory reactions induced by BCP micro particles implanted in quadriceps muscles of rats for 7, 14 and 21 days were studied by histology (n = 8/group). A fibrous tissue encapsulation of the BCP micro particles implanted in muscle tissue was observed and fibrosis was similar for the 3 groups of micro particles. The comparison of the cellular response indicated that the total number of cells was significantly higher for BCP < 20 micro m than for 40-80 and 80-200 micro m (p < 0.0001). The number of macrophages was relatively higher for the smallest than for the intermediate and largest fractions (p < 0.0001). The relative percentage of giant cells was higher for the intermediate and largest size of particles than for the smallest. The number of lymphocytes was comparable for the 3 fractions and after the 3 delays. Therefore, the BCP micro particles < 20 micro m initiated an inflammatory response which might play an important role in osteogenesis.

Biological roles of carboxymethyl-chitin associated for the growth factor production

Many techniques to restore cartilage defection have been tried. However, the development is still under way because of problems, including loosening of artificial joint, degenerative change of compensated tissue, risk of viral transmission via allograft/autograft, and cost of therapeutic materials for repair. In the previous research, we found that complementing cartilage defective part with carboxymethyl-chitin (CM-chitin)/beta-tricalcium phosphate composite induced regeneration of cartilage in rabbits in vivo, and it is presumable that CM-chitin plays a key role in chondrogenesis causing the regeneration of cartilage. However, the induction mechanism of chondrogenesis with CM-chitin is still unclear. In this study, we investigated the cell responses to CM-chitin by using peritoneal exudate cell (PEC) in mice and found that CM-chitin induced the expression of inflammatory cytokines and growth factors, both of which are both considered to correlate with chondrogenesis. After intraperitoneal injection CM-chitin showed enhanced expressions of mRNA of interleukin-1beta (IL-1beta), interleukin-6 (IL-6), keratinocyte-derived chemokine, tumor necrosis factor-alpha, and transforming growth factor-beta1 (TGF-beta1) in PEC as observed by reverse transcriptase polymerase chain reaction. Productions of TGF-beta1 protein were confirmed by enzyme linked immunosorbant assay. It was also shown that mononuclear cells in PEC were responsible for the TGF-beta1 production. These results suggest that CM-chitin is an inductor of inflammatory cytokines and growth factors and may contribute to regeneration of cartilage.

Clinical experience with metal-on-metal total joint replacements: Indications and results

Survivorship of total joint arthroplasty depends on the durability of fixation and durability of articulation. The metal-on-polyethylene articular couple has been the most widely used. Polyethylene wear (and the associated cytochemical events that culminate in osteolysis) has been identified as a major factor adversely influencing the durability of joint replacement. This stimulated the orthopaedic community to explore the possibility of using alternative bearings with lower wear rates.

Hard-on-hard bearings have been shown to be associated with reduced wear. Metal-on-metal bearings have wear rates that are 20-100 times lower than metal on conventional polyethylene. However, patients with metal-on-metal articulations have increased levels of cobalt and chromium in the serum and urine, and this has raised concerns about toxicity, mutagenesis, and hypersensitivity. At this stage there is no epidemiological evidence to suggest that the risk of carcinogenesis is anything more than theoretical.

Successful long-term results have been reported with the cast cobalt-chromium metal-on-metal couples of the mid-1960s. Tissues retrieved at revision of these implants did not show the giant-cell inflammatory response associated with polyethylene particles. Several researchers have reported excellent mid-term results with the current generation of high-precision metal-on-metal bearings.

Importance of the surface area ratio on cytokines production by human monocytes in vitro induced by various hydroxyapatite particles

A possible complication associated with the implantation of hydroxyapatite (HA)-based prosthesis is the release of particles. Those particles can be phagocyted by monocytes that are among the first cells to colonize the inflammatory site. The activated monocytes produce inflammatory mediators, such as cytokines, which cause osteoclasts activation. It has previously been demonstrated using a surface area ratio (ratio of the total surface of the given particles to the surface area of cells) of 1 to 1 that there was a correlation between the expression and production of cytokines induced by HA. The present work studies the effect of physical characteristics of HA particles on the production of various inflammatory cytokines (tumour necrosis factor-alpha, interleukin (IL)-6, and IL-8) and anti-inflammatory cytokine (IL-10). However, the experiments were performed using a surface area ratio of 10 to 1. Our data demonstrate that all the particles, whatever their characteristics, induced a high expression of cytokines but the production was different, meaning that there was a post-transcriptional regulation. The size and sintering temperature seemed to be a characteristics that were less important compared to the shape; the needle particles appeared to induce the most important production of all the cytokines studied.

The effect of the physical characteristics of hydroxyapatite particles on human monocytes IL-18 production in vitro

Hydroxyapatite (HA) is widely used to coat the metal parts of prosthetic implants in order to improve their biocompatibility and as a bone defect filling material. HA has been demonstrated to produce particles at the prosthetic interface that lead to an activation of phagocytic cells that induce a cascade reaction leading to bone resorption and aseptic loosening. Monocytes/macrophages are commonly observed in the interface tissue, and are among the first cells to colonize the inflammatory site where they play a key role in the immune response. IL-18 is a pro-inflammatory cytokine. Monocytes/macrophages were described as IL-18 producing cells. IL-18 works antagonistically to IL-6, which activates osteoclastogenesis. In the present study, we investigated the ability of HA particles to induce the production of active IL-18 by human monocytes according to particle characteristics (size, sintering temperature and shape). Our study demonstrates, for the first time, that HA particles are capable of stimulating the production of the proinflammatory cytokine IL-18 in human monocytes according to their particle characteristics. The expression and the production of IL-18 was modified by the parameter studied. The difference observed between the expression and the production could be explain by the production of ICE. The needle shaped particles induced the larger production of IL-18.

Conquest of a worldwide human disease: particle-induced periprosthetic osteolysis

It is rare in the long history of human disease to encounter a completely unique disease. In the 21st century, when it does occur, the disease commonly is man-made, as is true for periprosthetic osteolysis. However, it also is rare to unravel the mysteries of a biologic process as complex as periprosthetic osteolysis in slightly longer than one generation and even less common to create the means for the worldwide prevention of an entire disease. Such is the story of periprosthetic osteolysis. The adventure from the iatrogenic creation of the disease to the identification of its pathology, to the understanding of its molecular biology and, subsequently, to its prevention, during a period of four decades, is a fascinating story of medical detective work.

Bone bonding to hydroxyapatite and titanium surfaces on femoral stems retrieved from human subjects at autopsy

The success of clinical results obtained with many hydroxyapatite (HA)-coated prosthetic designs has deflected attention from the need to extend the life of the HA coating on the device. In the current study the percentages of HA and titanium surfaces to which bone was bonded, on HA-coated and non-coated titanium femoral stems retrieved from human subjects, were evaluated. Plasma-sprayed hydroxyapatite (PSHA)-coated devices demonstrated wide variability in the percentage of the PSHA coating remaining on the stems. The coating was missing from a substantial portion of a stem after only about 6 months of implantation. The percentage of revealed metal to which bone was bonded was significantly less than the percentage of the HA coating demonstrating such bonding. The revealed metal to which bone was bonded was comparable to the same value for a separate group of non-PSHA-coated titanium stems. If HA-coatings degrade over time precipitous decline in performance may occur even after several functional years. Many ultrastructural features of the bone bonded to the HA coatings on these implants from human subjects were comparable to those found on HA-coated devices implanted in a canine model.

Development of multinuclear giant cells during the degradation of Bioglass® particles in rabbits

Bioglass particles of the compositions 45s5, 52s, and 55s were implanted in the distal femoral epiphysis of rabbits. Animals were sacrificed at 7, 28, and 84 days postoperatively and specimens investigated using electron microscopy and electron dispersive X-ray analysis. The intention was to correlate the finding of different types of multinuclear giant cells (MNGC) in the center of the implantation bed with earlier hypothesized accumulated particle eluates and changed particle compositions. The distribution of Si, Na, Ca, P, O, S, and Cl throughout the implantation bed was analyzed. Bioglass particles degraded either in Si-rich remnants or in CaP-shells. MNGC of foreign body giant cell type in high numbers as well as of osteoclast-like type at later time intervals in small numbers were found on the surface of Si-rich as well as on Ca- and P-rich particle remnants. Osteoclast-like cells were detected on the particles after transformation in CaP-shells. It is concluded that the formation of different types of MNGC is determined by the composition of the substrate, that is, osteoclast-like cells develop exclusively on resorbable substrates. The absolute number of MNGC depended on the time after implantation and the solubility of the implant. Bone bonding, however, only occurred on Ca- and P-rich surfaces.

MMP-2, MMP-9 and their inhibitors TIMP-2 and TIMP-1 production by human monocytes in vitro in the presence of different forms of hydroxyapatite particles

After calcium-phosphates biomaterials based implantation like hydroxyapatite (HA) coating, particles are released in the periprosthetic tissues. Wear-debris induced fibrous membranes contain macrophage subsets that can produce metalloproteinases (MMPs), which are considered to be key enzymes in extra-cellular matrix turnover. Tissue inhibitors of metalloproteinases (TIMPs) are important regulator of MMPs activity. Interleukin-1 mainly produced by monocytes can also regulate MMPs production. In the present work, we have evaluated the effect of HA particles characteristics (size, shape and sintering temperature) on the MMP-2, -9 and their respective inhibitors TIMP-2, -1 production. Our results demonstrate that sintering temperature (that modify crystal size and surface area) have little effect on MMPs and TIMPs production. Non-phagocytable particles induced more MMP-9, although phagocytable particles induced more IL-1beta release. The shape of the particles was the most important factor since needle-shaped particles induced the most significant up-regulated expression of MMPs and IL-1beta.

In vivo behavior of three different injectable hydraulic calcium phosphate cements

Two dicalcium phosphate dihydrate (DCPD) hydraulic cements and one apatite hydraulic cement were implanted in epiphyseal and metaphyseal, cylindrical bone defects of sheep. The in vivo study was performed to assess the biocompatibility of the DCPD cements, using the apatite cement as control. After time periods of 2, 4 and 6 months the cement samples were clinically and histologically evaluated. Histomorphometrically the amount of new bone formation, fibrous tissue and the area of remaining cement were measured over time. In all specimens, no signs of inflammation were detectable either macroscopically or microscopically. All cements were replaced by different amounts of new bone. The two DCPD-cements showed the highest new bone formation and least cement remnants at 6 months, whereas the apatite was almost unchanged over all time periods.

Characterization of a bovine collagen–hydroxyapatite composite scaffold for bone tissue engineering

Different biomaterials have been used as scaffolds for bone tissue engineering. Here we characterize a biomaterial composed of sintered (1100 degrees C) and powdered hydroxyapatite (HA) and type I collagen (Coll), both of bovine origin, designed for osteoconductive and osteoinductive scaffolds. Coll/HA proportions were 1/2.6 and 1/1 (wet weight), and particles sizes varied from 200 to 400 microm. Vv (volume density) and Sv (surface to volume density) for the HA particles in the composite ranged from 0.48 +/- 0.06 to 0.55 +/- 0.02 and 5.090 +/- 0.545 to 6.366 +/- 0.289 microm(-1), respectively. Due to the relatively small changes in Vv and Sv, a macroporosity could be characterized for the biocomposite. X-ray diffraction and infrared spectroscopy showed that the sintered bone was composed essentially of HA with minimum additional groups such as surface calcium hydroxide, surface and crystal water, free carbon dioxide and possibly brushite. Mass spectrometry detected carbonates at A and B sites of HA, and weakly bound to the structure. Human osteoblasts adhered and spread on both the HA particle surface and the collagen fibers, which seemed to guide cells between adjacent particles. The biocomposite studied has several characteristics considered as ideal for its use as a scaffold for osteoconduction and osteoinduction.

Importance of hydroxyapatite particles characteristics on cytokines production by human monocytes in vitro

Calcium phosphate bioceramics have been applied as bone substitutes for several decades. Aseptic loosening after total joint arthroplasty is a major problem in orthopaedic surgery. Hydroxyapatite particles from materials wear have been reported as the main cause of implant failure. For this reason, an investigation into possible wear particles from materials used in the implant may lead to longevity after arthroplasty. Monocytes are among the first cells to colonize the inflammatory site. In the present study, we have evaluated the inflammatory response after exposition to particles with different characteristics (size, sintering temperature and shape). Our data demonstrate that the most important characteristic was the shape and the size of the particles. The needle shaped particles induced the larger production of TNF-alpha, IL-6 and IL-10 by cells. To a less manner, the smallest particles induced an increase of the expression and production of the cytokines studied (TNF-alpha, IL-6 and IL-10). The sintering temperature appeared to be a less important characteristic even though it was involved in the dissolution/precipitation process.

Effect of cryoglobulin and crystalcryoglobulin on TNF-alpha production by normal human monocytes

OBJECTIVES

We recovered an IgG1-kappa cryocrystalglobulin in synovial fluid and membrane specimens from a patient with destructive arthropathy. In the present study, we investigated its proinflammatory properties by measuring its effects on TNF-alpha production by normal human monocytes.

MATERIALS AND METHODS

Normal human monocytes isolated by plastic adhesion were cultured in microtiter plates. Adherent monocytes were cultured for 6, 8, and 24 hours with sterile cryocrystalglobulin (150 microg/mL and 2 mg/mL), type I noncrystallised cryoglobulin (same concentrations), monosodium urate (MSU) crystals (2 mg/mL), LPS (10 microg/mL), or medium alone. Supernatant TNF-a concentrations were assayed using an ELISA.

RESULTS

Cryocrystalglobulin had no effect on TNF-alpha production by normal human monocytes. Noncrystallised cryoglobulin increased TNF-alpha levels in supernatants in a time-dependent and concentration-dependent fashion. This increase was significantly less marked than the increases achieved with MSU crystals or LPS.

CONCLUSION

IgG1kappa cryocrystalglobulin has no effect on TNF-alpha production by normal human monocytes. Fc region changes within the cryocrystalglobulin molecule may explain this finding.

Matrix engineering for osteogenic differentiation of rabbit periosteal cells using alpha-tricalcium phosphate particles in a three-dimensional fibrin culture

Tissue engineering using periosteal cells is a promising approach for bioactive bone repair. Of central importance in tissue engineering is the cell-matrix interaction. In the present study we tested in vitro the influence of alpha-tricalcium phosphate (alpha-TCP) particles on the expression of osteogenic markers in rabbit periosteal cells embedded in specially manufactured fibrin beads. After cell isolation from tibial periosteum of New Zealand White rabbits, and following monolayer culture, cells were embedded in alginate-fibrin beads containing 7.5% alpha-TCP particles and, as a control group, in beads without particles. The alginate was extracted immediately after polymerization. The beads were cultivated for at least 53 days. The DNA content, alkaline phosphatase activity, and osteocalcin level were determined. In monolayer culture the number of cells increased 6.5-fold. DNA content increased in both three-dimensional culture groups but was significantly higher in the beads containing alpha-TCP. Alkaline phosphatase activity increased in both groups without significant differences. Osteocalcin content was significantly higher in the beads containing alpha-TCP than it was in those without alpha-TCP. These observations indicate that matrix engineering using inorganic particles in fibrin culture can influence the osteogenic differentiation of mesenchymal cells. The three-dimensional culture system presented here facilitates the preparation of grafts for bone reconstruction.

Material fundamentals and clinical performance of plasma-sprayed hydroxyapatite coatings: a review

The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has aroused as many controversies as interests over the last decade. Although faster and stronger fixation and more bone growth have been revealed, the performance of HA-coated implants has been doubted. This article will initially address the fundamentals of the material selection, design, and processing of the HA coating and show how the coating microstructure and properties can be a good predictor of the expected behavior in the body. Further discussion will clarify the major concerns with the clinical use of HA coatings and introduce a comprehensive review concerning the outcomes experienced with respect to clinical practice over the past 5 years. A reflection on the results indicates that HA coatings can promote earlier and stronger fixation but exhibit a durability that can be related to the coating quality. Specific relationships between coating quality and clinical performance are being established as characterization methods disclose more information about the coating.

Physicochemical study of plasma-sprayed hydroxyapatite-coated implants in humans

This study represents the first report of the physical and chemical changes occurring in coatings of failed hydroxyapatite (HA)-coated titanium implants obtained from a comprehensive, multicenter human dental implant study. A total of 53 retrieved samples were obtained and compared with unimplanted controls with the same manufacturer and similar manufacture dates. Forty-five retrieved implants were examined for surface characteristics and bulk composition. Implants were staged based on implantation history: stage 1 (implants retrieved between surgical placement and surgical uncovering), stage 2 (implants retrieved at surgical uncovering and evaluation), stage 3 (implants retrieved between surgical uncovering evaluation and occlusal loading), and stage 4 (implants retrieved after occlusal loading). Scanning electron microscopy showed progressive coating thinning with implantation time. At later stages, bare Ti metal was detected by energy-dispersive X-ray analysis and electron spectroscopy for chemical analysis. Increases in Ti and Al (2-7.5 atm % each) were detected at the apical ends of all stage 4 samples. In unimplanted coatings, X-ray diffraction analysis demonstrated the presence of amorphous calcium phosphate, beta-tricalcium phosphate, tetracalcium phosphate, and calcium oxide in addition to large hydroxyapatite crystals (c axis size, D002 = 429 +/- 13 A; a axis size, D300 = 402 +/- 11 A, a/c aspect ratio 0.92). The nonapatitic phases disappeared with increased implantation time, although there was a persistence of amorphous calcium phosphate. Bulk coating chemical analysis showed that Ca/P ratios for implant controls (1.81 +/- 0.01) were greater than stoichiometric HA (1.67) and decreased for implant stages 3 and 4 (1.69 +/- 0.09 and 1.67 +/- 0.09, respectively), explained by the dissolution of the non apatitic phases. Crystal sizes also changed with implantation times, being smaller than the control at all but stage 4. Fourier transform infrared analyses agreed with these results, and also indicated the accumulation of bone (protein and carbonate-apatite) in the retrieved coatings. The accumulation of bone was not stage dependent. These findings indicate that there was some biointegration with the surrounding bone, but the greatest changes occurred with the HA coating materials, their loss, and chemical change.

A methodological study for the analysis of apatite-coated dental implants retrieved from humans

The stability of thermally processed hydroxyapatite coatings for oral and orthopedic bioprostheses has been questioned. Information on the chemical changes, which occur with hydroxyapatite biomaterials post-implantation in humans, is lacking. The purpose of this investigation was to begin to examine post-implantation surface changes of hydroxyapatite-coated implants using scanning electron microscopy (SEM), x-ray microanalysis (EDAX), Fourier transform infrared spectroscopy (FTIR), and x-ray diffraction (XRD). Three retrieved dental implant specimens from humans following clinical failure due to peri-implantitis were examined. Unimplanted cylinders served as controls. Clinically, the retrieved specimens were all enveloped by a fibrous tissue capsule with bone present at the apical extent of the implant. SEM analysis showed that the retrieved surfaces were coated with both calcified and proteinaceous deposits. EDAX scans of the retrieved specimens demonstrated evidence of hydroxyapatite coating loss reflected by increasing titanium and aluminum signals. Other foreign ions such as sodium, chloride, sulfur, silica, and magnesium were detected. XRD of the control specimens showed that the samples were predominantly apatite; however, two peaks were detected in the diffraction pattern, which are not characteristic of hydroxyapatite, indicating that small amounts of one or more other crystalline phases were also present. The retrieved specimens showed slightly larger average crystal size relative to the control sample material, and the non-apatite lines were not present. FTIR evaluation of the retrieved specimens revealed the incorporation of carbonate and organic matrix on or into the hydroxyapatite. Narrowing of and increased detail in the phosphate peaks indicated an increase in average crystal size and/or perfection relative to the controls, as did the XRD results. Based on these results, we conclude that chemical changes may occur within the coating, with the incorporation of carbonate and concomitant reduction in hydroxyapatite coating thickness. Thermodynamic dissolution-reprecipitation of the coating itself and subsequent surface insult by bacterial and local inflammatory components may be involved with these changes.

Abrasive waterjet peening: a new method of surface preparation for metal orthopedic implants

Abrasive waterjet (AWJ) peening is a new mechanical surface treatment process envisioned for use on metal orthopedic implants. The process utilizes an abrasive waterjet to simultaneously texture and work harden the surface of a metal substrate through controlled hydrodynamic erosion. In this study, a titanium alloy (Ti6Al4V) was subjected to AWJ peening over a range of parametric conditions. The textured surfaces were quantified in terms of the apparent interdigitation volume (V(i)), the effective stress concentration factor (K(t)) posed by the surface topography, and the magnitude of residual stress (sigma(r) ). Topographical features of the prepared surfaces were determined using contact profilometry, and X-ray diffraction was used in evaluating the in-plane residual stress. It was found that a large range in V(i) (9.4-43.8 microm(3)/microm(2)) and K(t) (1.3-2.7) are available through selection of the AWJ peening process parameters. Furthermore, a compressive residual stress (-409 +/- sigma(r) +/- -33) was found to result within the surface of the Ti6Al4V substrates regardless of treatment conditions. When compared to a titanium plasma spray coating used for cementless fixation, the AWJ peened Ti6Al4V exhibited a surface topography with significantly lower effective stress concentration and higher compressive residual stress. Based on results from this study, AWJ peening may serve as a new method of surface treatment for metal orthopedic implants, which supports the development of stable primary fixation and simultaneously enhances the component fatigue strength.

Particulate wear debris activates protein tyrosine kinases and nuclear factor kappaB, which down-regulates type I collagen synthesis in human osteoblasts

Particulate wear debris generated mechanically from prosthetic materials is phagocytosed by a variety of cell types within the periprosthetic space including osteoblasts, which cells with an altered function may contribute to periprosthetic osteolysis. Exposure of osteoblast-like osteosarcoma cells or bone marrow-derived primary osteoblasts to either metallic or polymeric particles of phagocytosable sizes resulted in a marked decrease in the steady-state messenger RNA (mRNA) levels of procollagen alpha1[I] and procollagen alpha1[III]. In contrast, no significant effect was observed for the osteoblast-specific genes, such as osteonectin and osteocalcin (OC). In kinetic studies, particles once phagocytosed, maintained a significant suppressive effect on collagen gene expression and type I collagen synthesis for up to five passages. Large particles of a size that cannot be phagocytosed also down-regulated collagen gene expression suggesting that an initial contact between cells and particles can generate gene responsive signals independently of the phagocytosis process. Concerning such signaling, titanium particles rapidly increased protein tyrosine phosphorylation and nuclear transcription factor kappaB (NF-kappaB) binding activity before the phagocytosis of particles. Protein tyrosine kinase (PTK) inhibitors such as genistein and the NF-kappaB inhibitor pyrrolidine dithiocarbamate (PDTC) significantly reduced the suppressive effect of titanium on collagen gene expression suggesting particles suppress collagen gene expression through the NF-kappaB signaling pathway. These results provide a mechanism by which particulate wear debris can antagonize the transcription of the procollagen alpha1[I] gene in osteoblasts, which may contribute to reduced bone formation and progressive periprosthetic osteolysis.

Interactions of hydroxyapatite and fluorapatite particles on human osteoarthritis type B synoviocytes: effects on interleukin-1 alpha levels and lipoxygenase pathways

We investigated the effects of the biomaterials hydroxyapatite (HAP) and fluorapatite (FAP) on cultured human osteoarthritis type B synoviocytes by analyzing interleukin-1 alpha (IL-1 alpha) production and arachidonic acid metabolism via lipoxygenase pathways. A portion of opsonized particles was endocytosed and was found in numerous phagolysosomes in human synoviocyte cytoplasms. The present study demonstrates that HAP and FAP calcined at 700 degrees C induced a decrease in IL-1 alpha production but markedly decreased the synthesis of lipoxygenase products after 1-month incubation with the particles. This model will allow us to study the possible inflammatory response (arachidonic acid metabolism, proinflammatory cytokines) that can be induced by any biomaterials used in orthopedics.

Effect of a ceramic and a non-ceramic hydroxyapatite on cell growth and procollagen synthesis of cultured human gingival fibroblasts

BACKGROUND

Ceramic hydroxyapatites and non-ceramic hydroxyapatites have been used extensively as alloplastic materials for bone reconstruction. However, different forms of hydroxyapatite induce different types of tissue response.

METHODS

Human gingival fibroblasts (FMM1 cells) were used to analyze ceramic and non-ceramic hydroxyapatite biocompatibility. The cells were grown on surfaces covered either by collagen (control group), collagen plus ceramic hydroxyapatite, or collagen plus non-ceramic hydroxyapatite. Scanning electron microscopy, growth and cell viability curves, and procollagen immunoprecipitation were obtained. For the growth and viability curves, 10(4) cells were seeded on 60 mm dishes. Cells from each group were counted, in triplicate, at 1, 3, 4, 5, and 6 days after seeding using the Trypan blue dye exclusion assay.

RESULTS

The cells grew in close contact with both types of hydroxyapatite particles. No differences were found in the amount of procollagen synthesis among any experimental group. The cultures treated with ceramic hydroxyapatite had a growth delay for the first 5 days. There was no difference in cell viability between the control group and the non-ceramic hydroxyapatite group. However, cultures treated with ceramic hydroxyapatite showed significantly lower viability percentages than the other groups.

CONCLUSIONS

Hydroxyapatite supports cell growth and fibroblast metabolism including collagen production, and hence is biocompatible. Cell viability and structural studies showed that non-ceramic hydroxyapatite has relevant physical and biological properties as an implant material.

Assessment of resorbable bioactive material for grafting of critical-size cancellous defects

Bioactive glasses form a surface apatite layer in vivo that enhances the formation and attachment of bone. Sol-gel Bioglass graft material provides greater nanoscale porosity than bioactive glass (on the order of 50-200 A), greater particle surface area, and improved resorbability, while maintaining bioactivity. This study histologically and biomechanically evaluated, in a rabbit model, bone formed within critical-sized distal femoral cancellous bone defects filled with 45S5 Bioglass particulates, 77S sol-gel Bioglass, or 58S sol-gel Bioglass and compared the bone in these defects with normal, intact, untreated cancellous bone and with unfilled defects at 4, 8, and 12 weeks. All grafted defects had more bone within the area than did unfilled controls (p < 0.05). The percentage of bone within the defect was significantly greater for the 45S5 material than for the 58S or 77S material at 4 and 8 weeks (p < 0.05), yet by 12 weeks equivalent amounts of bone were observed for all materials. By 12 weeks, all grafted defects were equivalent to the normal untreated bone. The resorption of 77S and 58S particles was significantly greater than that of 45S5 particles (p < 0.05). Mechanically, the grafted defects had compressive stiffness equivalent to that of normal bone at 4 and 8 weeks. At 12 weeks, 45S5-grafted defects had significantly greater stiffness (p < 0.05). At 8 and 12 weeks, all grafted defects had significantly greater stiffness than unfilled control defects (p < 0.05). In general, the 45S5-filled defects exhibited greater early bone ingrowth than did those filled with 58S or 77S. However, by 12 weeks, the bone ingrowth in each defect was equivalent to each other and to normal bone. The 58S and 77S materials resorbed faster than the 45S5 materials. Mechanically, the compressive characteristics of all grafted defects were equivalent or greater than those of normal bone at all time points.