Titanium particles inhibit osteoblast adhesion to fibronectin-coated substrates

The Effects of Biomaterial Implant Wear Debris on Osteoblasts

Aseptic loosening subsequent to periprosthetic osteolysis is the leading cause for the revision of arthroplasty failure. The biological response of macrophages to wear debris has been well established, however, the equilibrium of bone remodeling is not only dictated by osteoclastic bone resorption but also by osteoblast-mediated bone formation. Increasing evidence shows that wear debris significantly impair osteoblastic physiology and subsequent bone formation. In the present review, we update the current state of knowledge regarding the effect of biomaterial implant wear debris on osteoblasts. The interaction of osteoblasts with osteoclasts and macrophages under wear debris challenge, and potential treatment options targeting osteoblasts are also presented.

Cobalt, titanium and PMMA bone cement debris influence on mouse osteoblast cell elasticity, spring constant and calcium production activity

Periprosthetic osteolysis and implant loosening are the outcomes of wear debris generation in total joint replacements. Wear debris formed from the implanted materials consisting of metals, polymers, ceramic and bone cement initiate the immune system response. Often osteoblasts, the principal cell type in bone tissue adjacent to the prostheses, are directly impacted. In this study, the influence of cobalt, titanium and PMMA bone cement particles of different sizes, charges and compositions on mouse osteoblast adhesion, nanomechanics (elasticity and spring constant) and metabolic activity were investigated. These studies were accompanied by osteoblast mineralisation experiments and cell uptake after exposure to particles at defined time points. Our results demonstrate that alteration of the nanomechanical properties are mainly dependent on the metal type rather than nanoparticles size and concentration. Moreover, despite uptake increasing over exposure time, the cell characteristics exhibit changes predominately after the first 24 hours, highlighting that the cell responses to nanoparticle exposure are not cumulative. Understanding these processes is critical to expanding our knowledge of implant loosening and elucidating the nature of prosthetic joint failure.

Effects of thirty elements on bone metabolism

The human skeleton, made of 206 bones, plays vital roles including supporting the body, protecting organs, enabling movement, and storing minerals. Bones are made of organic structures, intimately connected with an inorganic matrix produced by bone cells. Many elements are ubiquitous in our environment, and many impact bone metabolism. Most elements have antagonistic actions depending on concentration. Indeed, some elements are essential, others are deleterious, and many can be both. Several pathways mediate effects of element deficiencies or excesses on bone metabolism. This paper aims to identify all elements that impact bone health and explore the mechanisms by which they act. To date, this is the first time that the effects of thirty minerals on bone metabolism have been summarized.

Titanium allergy: could it affect dental implant integration?

PURPOSE

Degradation products of metallic biomaterials including titanium may result in metal hypersensitivity reaction. Hypersensitivity to biomaterials is often described in terms of vague pain, skin rashes, fatigue and malaise and in some cases implant loss. Recently, titanium hypersensitivity has been suggested as one of the factors responsible for implant failure. Although titanium hypersensitivity is a growing concern, epidemiological data on incidence of titanium-related allergic reactions are still lacking.

MATERIALS AND METHODS

A computer search of electronic databases primarily MEDLINE and PUBMED was performed with the following key words: 'titanium hypersensitivity', 'titanium allergy', 'titanium release' without any language restriction. Manual searches of the bibliographies of all the retrieved articles were also performed. In addition, a complementary hand search was also conducted to identify recent articles and case reports.

RESULTS

Most of the literature comprised case reports and prospective in vivo/in vitro trials. One hundred and twenty-seven publications were selected for full text reading. The bulk of the literature originated from the orthopaedic discipline, reporting wear debris following knee/hip arthroplasties. The rest comprised osteosynthesis (plates/screws), oral implant/dental materials, dermatology/cardiac-pacemaker, pathology/cancer, biomaterials and general reports.

CONCLUSION

This review of the literature indicates that titanium can induce hypersensitivity in susceptible patients and could play a critical role in implant failure. Furthermore, this review supports the need for long-term clinical and radiographic follow-up of all implant patients who are sensitive to metals. At present, we know little about titanium hypersensitivity, but it cannot be excluded as a reason for implant failure.

Growth of human osteoblast-like cells on beta-tricalciumphosphate (TCP) membranes with different structures

Bioresorb, a bioactive, bioresorbable bone replacement material, consisting of pure beta-tricalciumphos phate (TCP) ceramic, was evaluated in cell culture with human osteoblast-like cells. The aim of our study was to investigate the influence of TCP on the growth behavior of human osteoblast-like cells. Different granule sizes and plate sizes were used in this study: Granule sizes 500-1000 microm, 1000-2000 microm and 2000-5000 microm; plate sizes 1.7 mm, 2.0 mm and 2.2 mm. Under scanning electron microscopic (SEM) observations the cell colonization on the surface of the biomaterial and the tissue compatibility were studied. Thin sections were used to study the growth of human osteoblast-like cells inside the biomaterial. It could be clearly shown that all investigated biomaterials are tissue compatible and that the size and structure (granule or plate) of the biomaterial effects the colonization rate. Bioresorb plates enhance the colonization comparable to granule. The results obtained by SEM and thin sections were confirmed immunhistochemically by the nonradioactive assay EZ4U - EASY FOR YOU.In conclusion, all investigated sizes and structures of Bioresorb are tissue compatible but the cell growth is much better on plates than on granule small in size. The results suggest that the plates may be favourable useful as scaffold for regrowth of bone.

Effects of titanium particle size on osteoblast functions in vitro and in vivo

The formation of titanium (Ti)-wear particles during the lifetime of an implant is believed to be a major component of loosening due to debris-induced changes in bone cell function. Radiographic evidence indicates a loss of fixation at the implant-bone interface, and we believe that the accumulation of Ti particles may act on the bone-remodeling process and impact both long- and short-term implant-fixation strengths. To determine the effects of various sizes of the Ti particles on osteoblast function in vivo, we measured the loss of integration strength around Ti-pin implants inserted into a rat tibia in conjunction with Ti particles from one of four size-groups. Implant integration is mediated primarily by osteoblast adhesion/focal contact pattern, viability, proliferation and differentiation, and osteoclast recruitment at the implant site in vivo. This study demonstrates the significant attenuation of osteoblast function concurrent with increased expression of receptor activator of nuclear factor kappaB ligand (RANKL), a dominant signal for osteoclast recruitment, which is regulated differentially, depending on the size of the Ti particle. Zymography studies have also demonstrated increased activities of matrix metalloproteinases (MMP) 2 and 9 in cells exposed to larger Ti particles. In summary, all particles have adverse effects on osteoblast function, resulting in decreased bone formation and integration, but different mechanisms are elicited by particles of different sizes.

The influence of wear particles in the expression of osteoclastogenesis factors by osteoblasts

Orthopedic implant failures are often associated with peri-implant osteolysis. Particles generated from the wear process have been suspected to play an important role in this situation. Indeed, the peri-implant osteolysis could be due to the presence of particles stimulating the osteoclastogenesis process. We hypothesize then that the presence of a low particle concentration positively influences osteoblasts to produce osteoclastogenesis factors. If true, this hypothesis would then support the idea that the particles could be at the origin of the process leading to implant loosening. To check the validity of this hypothesis, we quantified in vitro the production of different genes involved in the osteoclastogenesis process using primary isolated human osteoblasts treated or not with particles. Results showed that low concentrations of particles might have a stimulating effect on osteoblasts to produce osteoclastogenesis factors as demonstrated by the increase of RANKL and CSF-1 gene expression in the particle group.

Particle bioreactivity and wear-mediated osteolysis

This review focuses on wear debris-mediated osteolysis, a major factor compromising the long-term success of total joint arthroplasty. Studies on retrieved implants and animal models, as well as in vitro studies on particle bioreactivity, suggest that wear-mediated periprosthetic osteolysis is unlikely to be caused solely by 1 particular cell type or particulate species, but is rather the cumulative consequence of a number of biological reactions. Our recent findings suggest 3 novel mechanisms of particle bioreactivity that may contribute to osteolysis: 1) exacerbated inflammation caused by elevated reactive oxygen species production by activated macrophages and osteoclasts, (2) impaired periprosthetic bone formation secondary to disrupted osteogenesis, and (3) compromised bone regeneration resulting from increased cytotoxic response of mesenchymal osteoprogenitor cells. Understanding the pathogenesis of wear-mediated osteolysis is needed to improve orthopedic implant biocompatibility and wear reduction, and to develop effective pharmacotherapies.

Increased viable osteoblast density in the presence of nanophase compared to conventional alumina and titania particles

In the present in vitro study, osteoblast (bone-forming cells) viability and cell density were investigated when cultured in the presence of nanophase compared to conventional (i.e. micron) alumina and titania particles at various concentrations (from 10,000 to 100 microg/ml of cell culture media) for up to 6h. Results confirmed previous studies of the detrimental influences of all ceramic particulates on osteoblast viability and cell densities. For the first time, however, results provided evidence of increased apoptotic cell death when cultured in the presence of conventional compared to nanophase alumina and titania particles. Moreover, since material characterization studies revealed that the only difference between respective ceramic particles was nanometer- and conventional-dimensions (specifically, phase and chemical properties were similar between respective nanophase and conventional alumina as well as titania particles), these results indicated that osteoblast viability and densities were influenced solely by particle size. Such nanometer particulate wear debris may result from friction between articulating components of orthopedic implants composed of novel nanophase ceramic materials. Results of a less detrimental effect of nanometer--as compared to conventional-dimensioned particles on the functions of osteoblasts provide additional evidence that nanophase ceramics may become the next generation of bone prosthetic materials with increased efficacy and, thus, deserve further testing.

New insight into the mechanism of hip prosthesis loosening: effect of titanium debris size on osteoblast function

The incidence of rheumatoid arthritis and osteoarthritis is on the rise due to our expanding elderly population. Total joint arthroplasty is the most successful, prevalent treatment modality for these and other degenerative hip conditions. Despite the wide array of prosthetic devices commercially available, hip prostheses share a common problem with a gradual and then accelerating loss of bone tissue and bone-implant interface integrity, followed by implant instability and loosening. Implant failure is largely the result of inevitable wear of the device and generation of wear debris. To provide information for the development of improved prosthetic wear characteristics, we examined the effects of size-separated titanium particles on bone forming cell populations. We demonstrate unequivocally that particle size is a critical factor in the function, proliferation, and viability of bone-forming osteoblasts in vitro. In addition, we have elucidated the time-dependent distribution of the phagocytosed particles within the osteoblast, indicating an accumulation of particles in the perinuclear area of the affected cells. The report finds that particle size is a critical factor in changes in the bone formation-related functions of osteoblasts exposed to simulate wear debris, and that 1.5-4 microm titanium particles have the greatest effect on osteoblast proliferation and viability in vitro. The size of titanium particles generated through wear of a prosthetic device may be an important consideration in the development of superior implant technology.

Direct and indirect induction of apoptosis in human mesenchymal stem cells in response to titanium particles

The most frequent complication of total joint arthroplasty is periprosthetic osteolysis initiated by an inflammatory response to orthopaedic wear debris, which if left untreated, can result in implant instability and failure, eventually requiring revision surgery. We have previously reported that osteogenic differentiation of human marrow stroma-derived mesenchymal stem cells (hMSCs) is suppressed upon exposure to titanium particles, accompanied by reduced bone sialoprotein (BSP) gene expression, diminished production of collagen type I and BSP, decreased cellular viability and proliferation, and inhibition of extracellular matrix mineralization. In this study, we have further investigated hMSC cytotoxicity upon exposure to submicron particles of commercially pure titanium (cpTi) and zirconium oxide (ZrO(2)). Our results showed that direct exposure to cpTi and ZrO(2) particles compromises cell viability through the induction of apoptosis, eliciting increased levels of the tumor suppressor proteins p53 and p73, in a manner dependent on material composition, particle dosage, and time. Additionally, conditioned medium collected from hMSCs exposed to cpTi particles, but not to ZrO(2) particles, is cytotoxic to hMSCs, inducing apoptosis in the absence of particles. These findings demonstrate that exposure to orthopaedically derived wear particles can compromise hMSC viability through the direct and indirect induction of apoptosis. Thus, prolonged in vivo exposure of marrow-derived hMSCs to implant-derived wear debris is likely to reduce the population of viable osteoprogenitor cells, and may contribute to poor periprosthetic bone quality and implant loosening.

Human serum opsonization of orthopedic biomaterial particles: protein-binding and monocyte/macrophage activation in vitro

Wear particles generated after total joint arthroplasty activate monocyte/macrophages and incite formation of a granulomatous periprosthetic tissue associated with bone loss and implant loosening. This study tested the hypothesis that selective opsonization of orthopedic implant biomaterial wear particles by human serum proteins influences monocyte/macrophage activation. Serum protein binding to metallic, polymeric, and ceramic particles was determined by one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Individual proteins bound to particles were subsequently identified using two-dimensional SDS-PAGE, microsequencing techniques, and SWISS-PROT analysis. Effects of selective protein opsonization on particle-induced monocyte/macrophage activation were assessed by quantification of interleukin-1beta, interleukin-6, and tumor necrosis factor-alpha release. Results from one-dimensional gel analyses revealed distinct serum protein-binding patterns specific for each material tested. Two-dimensional gel analysis together with amino acid sequencing of the prominent protein species confirmed the presence of albumin and alpha-1-antitrypsin bound to all particles tested. In contrast to the metallic particles, apolipoprotein was a major species associated with polymeric particles. Opsonization of PMMA particles with purified preparations of each of the identified proteins showed that albumin significantly enhanced particle-induced monocyte/macrophage activation. These data confirm orthopedic biomaterial specific binding of human serum proteins and demonstrate that albumin exacerbates particle-induced monocyte/macrophage activation. Alterations in the chemical and surface properties of orthopedic biomaterials to modulate protein interactions may improve implant longevity.

Large-scale gene expression analysis of osteoblasts cultured on three different Ti-6Al-4V surface treatments

To improve implant biocompatibility, we developed a simple cost-effective thermal surface treatment allowing an increase in the oxide layer thickness of a titanium (Ti) alloy used in orthopaedic implants. The goal of this study was to test in vitro the reaction of osteoblasts to the developed surface treatment and to compare it to the osteoblast reaction to two other surface treatments currently used in the practice of implant surgery. Quantification of osteoblast gene expression on a large scale was used in this study. The kinetics of gene expression over 120 h was followed for 58 genes to quantify the effect of the developed surface treatment. Twenty eight genes were further selected to compare the effects of surface treatments on osteoblasts. Based on the genes studied, we could propose a general pathway for the cell reaction according to the surface treatments used: (1) metal ion release changes the time course of gene expression in the FAK pathway; (2) once the accumulation of metal ions released from the Ti surface exceeds a threshold value, cell growth is diminished and apoptosis may be activated; (3) PTK up-regulation is also induced by metal ion release; (4) the expression of Bcl-2 family and Bax may suggest that metal ions induce apoptosis. The developed treatment seems to increase the Ti-6Al-4V biocompatibility as highlighted by the lower impact of this treatment by the different pathways studied, on the lower inflammatory reaction that could be induced, as well as by the lower induced osteoblast apoptosis compared to the two other surface treatments.

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.

Viability, adhesion, and bone phenotype of osteoblast-like cells on polyelectrolyte multilayer films

The aim of this study was to develop new biocompatible coatings for bone implants by the alternating deposition of oppositely charged polyelectrolytes. Polyelectrolyte films were built up with different terminating layers on which SaOS-2 osteoblast-like cells and human periodontal ligament (PDL) cells were grown. The terminating layer was made of one of the following polyelectrolytes: poly(ethylene imine) (PEI), poly(sodium 4-styrenesulfonate) (PSS), poly(allylamine hydrochloride) (PAH), poly(L-glutamic acid) (PGA), or poly(L-lysine) (PLL). Cell adherence, viability, stability of osteoblast phenotype, and inflammatory response were studied. Adherence and viability were good on all terminating layers except the PEI-terminating layer, which was cytotoxic. Maintenance of osteoblast phenotype marker expression was observed on PSS- and PGA-terminating films for both cell types, whereas downregulation, associated with the induction of Interleukin-8 (IL-8) secretion, was detected on PEI and PAH for both cell types and on PLL for PDL cells. These results suggested a good biocompatibility of PSS- and PGA-ending films for PDL cells and of PSS-, PGA-, and PLL-terminating films for SaOS-2 cells. As a result, polyelectrolyte multilayer films could emerge as new alternatives for implant coatings.

The effects of calcium phosphate cement particles on osteoblast functions

Calcium phosphate cements (CPC) are increasingly used in the orthopedic field. This kind of cement has potential applications in bone defect replacements, osteosynthetic screw reinforcements or drug delivery. In vivo studies have demonstrated a good osteointegration of CPC. However, it was also observed that the resorption of CPC could create particles. It is known from orthopedic implant studies that particles can be responsible for the peri-implant osteolysis. Biocompatibility assessment of CPC should then be performed with particles. In this study, we quantified the functions of osteoblasts in the presence of beta-TCP, brushite and cement particles. Two particle sizes were prepared. The first one corresponded to the critical diameter range 1-10 microm and the second one had a diameter larger than 10 microm. We found that CPC particles could adversely affect the osteoblast functions. A decrease in viability, proliferation and production of extracellular matrix was measured. A dose effect was also observed. A ratio of 50 CPC particles per osteoblast could be considered as the maximum number of particles supported by an osteoblast. The smaller particles had stronger negative effects on osteoblast functions than the larger ones. Future CPC development should minimize the generation of particles smaller than 10 microm.