Human monocyte response to particulate biomaterials generated in vivo and in vitro

A striated pattern of wear in ultrahigh-molecular-weight polyethylene components of Miller-Galante total knee arthroplasty

Wear of the polyethylene tibial components is a potential cause of failure in total knee arthroplasty. In addition to pitting, burnishing, and scratching, subtle striations on the bearing portion of the tibial surface have been observed in components retrieved relatively early after implantation. The striated pattern most typically occurred in areas centrally located within the articulating surface. The striations were anteroposterior directed and were identified as local cold flow at the surface. There was a strong correlation between the medial and lateral striated areas, suggesting that these patterns are related to cyclic rolling of the knee. The general characteristics and alignment of the striations could be attributed to the compressive and tractive forces occurring during femoral rollback. For the clinician, these results suggest that kinematics, as well as contact stress, should be considered when evaluating wear of polyethylene components.

Macrophage phagocytosis of polyethylene particulate in vitro

In this study, an in vitro model has been developed to examine the interactions of macrophages with ultrahigh molecular-weight polyethylene (UHMWPE) and high-density polyethylene (HDPE) particles. Polyethylene particles are the major constituent of the material debris formed as a result of orthopedic implant wear. However, the study of polyethylene particle interactions with cells has been limited. UHMWPE (18-20 microns) and HDPE (4-10 microns) were suspended in soluble collagen type I and subsequently solidified on glass coverslips. The particle chemistry was characterized by Fourier transform infra-red spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Mouse cell line macrophages (IC-21) were established on the collagen-particle substrata and maintained for up to 24 h. The response of the cells to the particles was examined by light and transmission electron microscopy (LM and TEM), as well as by scanning electron microscopy (SEM), and compared to cells on control collagen surfaces without particles. Histological analysis of the samples revealed that the macrophages surrounded larger particles (18-20 microns) and the cells appeared to be attached to the surface of the particles, and the smaller particles (4-10 microns) had been phagocytosed within 2 h. Inflammatory cytokines (TNF-alpha, IL-1 alpha, IL-1 beta, and IL-6), lysosomal enzymes (beta-galactosidase and hexosaminidase), and prostaglandin E2 were released into the medium, and IL-1 alpha, IL-1 beta, PGE2, beta-galactosidase, and hexosaminidase levels were significantly increased over collagen control values. The results demonstrate active phagochemotaxis by macrophages for wear particulates and validate this model as a means of studying the specific in vitro interactions of polyethylene with cells.

The John Charnley Award. Inhibition of wear debris mediated osteolysis in a canine total hip arthroplasty model

In this study the efficacy of an oral bisphosphonate therapy to inhibit wear debris mediated bone resorption was evaluated in a canine total hip replacement model. Adult canines were randomized to three groups (n = 8 each) with a right uncemented total hip replacement performed on each animal. Group I (control) received no particulate debris. In Groups II and III, a mixture of 1 x 10(9) particles were introduced into the proximal femoral gap intraoperatively. The particle mixture consisted of fabricated ultra high molecular weight polyethylene (mean 2.3 microns, 90% by number), titanium alloy (mean 3.1 microns, 5%), and cobalt chrome alloy (mean 0.8 micron, 5%). Group III canines additionally received oral drug therapy (5 mg once a day, alendronate sodium) which was begun on postoperative Day 7 and continued until the time of sacrifice. Postoperatively, all animals were allowed 24 weeks of full ambulation before euthanasia. Radiographs obtained preoperatively, postoperatively, and at time of sacrifice were evaluated for periprosthetic osteolysis. Interfacial tissues were examined histologically and placed in organ culture and the supernatants were assayed for prostaglandin E2 and interleukin-1. One animal receiving debris (Group II) suffered a periprosthetic fracture and was sacrificed from the study. Radiographically, one of eight Group I (control) and six of seven canines from Group II (debris) had periprosthetic radiolucencies with endosteal scalloping develop. In contrast, only one of eight animals from Group III (debris + alendronate) had periprosthetic radiolucencies develop. Whereas tissues from control animals were mostly fibrous and acellular, tissues from both experimental groups had significant macrophage infiltration. Levels of prostaglandin E2 and interleukin-1 were elevated significantly in periprosthetic tissues from both experimental groups compared with controls. Continuous administration of alendronate effectively inhibited bone lysis for the 24-week duration of the study. This is consistent with the literature indicating that alendronate is incorporated in the mineralizing matrix making it refractory to osteoclastic resorption. This report has significant clinical implications for controlling the most common cause of implant failure.

Modulation of the production of cytokines in titanium-stimulated human peripheral blood monocytes by pharmacological agents. The role of cAMP-mediated signaling mechanisms

Cytokines secreted by activated macrophages play a role in the development of osteolysis adjacent to prosthetic joints. To determine whether the synthesis of cytokines can be inhibited by pharmacological agents, we studied the role of the cAMP-protein kinase A signal transduction pathway in the synthesis of interleukin-6 and tumor necrosis factor-alpha and examined the effect of potential pharmacological regulators of this pathway in human peripheral blood monocytes stimulated with titanium particles. Dibutyryl cAMP enhanced the synthesis of interleukin-6 by titanium-stimulated monocytes and resulted in a marked increase (maximum, seventyfold) in the synthesis of interleukin-6 even in the absence of titanium particles. However, the active analogs (agonists) of cAMP, dibutyryl cAMP and Sp cAMP, inhibited the production of tumor necrosis factor-alpha by titanium-stimulated monocytes (the maximum effects resulted in complete inhibition), while the cAMP antagonist, Rp cAMP, enhanced the production of tumor necrosis factor-alpha. Additional agents that alter the intracellular levels of cAMP were examined for their effects on the synthesis of cytokines. Prostaglandins E1 and E2 were potent inhibitors of the synthesis of tumor necrosis factor-alpha but stimulated the synthesis of interleukin-6. In contrast, indomethacin enhanced the stimulatory effects of titanium particles on tumor necrosis factor-alpha, resulting in a more than threefold increase in the maximum levels of tumor necrosis factor-alpha. Phosphodiesterase inhibitors, such as isobutyryl methylxanthine and pentoxifylline, which increase intracellular levels of cAMP, caused a decrease in the production of tumor necrosis factor-alpha and an increase in the production of interleukin-6. In contrast, the fluoroquinolone antibiotic ciprofloxacin, which is also a phosphodiesterase inhibitor, caused a dose-dependent inhibition of the synthesis of both tumor necrosis factor-alpha and interleukin-6 by titanium-stimulated monocytes, suggesting that ciprofloxacin suppresses the synthesis of interleukin-6 through a mechanism that is independent of cAMP.

Comparison of biocompatibility of gel-derived bioactive ceramics in macrophage culture conditions

The behaviour of rat alveolar macrophages cultured in the presence of three new gel-derived ceramic biomaterials (CaO-P2O5-SiO2 system) with slightly different chemical compositions was examined. The abilities of these three materials to stimulate alveolar macrophages were compared. Non-treated and lipopolysaccharide-treated macrophages were used as control. The level of macrophage activation was determined by nitrite and prostaglandin E2 assay and respiratory burst measurement by chemiluminescence. The results of these studies showed different macrophage responses to these three relatively similar stimuli. Two of the studied materials were shown to be potent activators of respiratory burst and prostaglandin E2 secretion without any significant release of nitric oxide. On the contrary, the material characterized as the most surface reactive strongly affected only nitric oxide generation by the cells.

Prosthetic metals interfere with the functions of human osteoblast cells in vitro

The release of metals from total joint prostheses may contribute to periprosthetic bone loss manifested as osteolysis. The effects of titanium, cobalt, and chromium on human osteogenic sarcoma cells (osteoblastlike cells) were investigated in vitro. Titanium, cobalt, and chromium at concentrations of 1, 10, and 100 ng/ml did not cause any changes in the cell growth, viability, and injury after 72-hour incubation with the cells. Titanium, cobalt, and chromium at concentrations ranging from 0.01 to 100 ng/ml significantly enhanced the release of interleukin-1 beta and tumor necrosis factor-alpha by lipopolysaccharide stimulated human osteogenic sarcoma cells, whereas they did not alter the release of transforming growth factor-beta 1. Cobalt at concentrations ranging from 0.1 to 100 ng/ml significantly enhanced the release of interleukin-6, but titanium and chromium did not. Cobalt and chromium at concentrations of 10 and 100 ng/ml significantly inhibited the release of osteocalcin by human osteogenic sarcoma cells, whereas titanium had no effect. Titanium, cobalt, and chromium at concentrations of 10 and 100 ng/ml significantly inhibited the synthesis of Type I collagen by human osteogenic sarcoma cells. Cobalt and chromium inhibited the cell proliferation in response to lipopolysaccharide stimulation, whereas titanium did not. The data presented in this article suggest that the metal induced disregulation of cytokine release and osteoblast dysfunction may play an important role in the induction of osteolysis in patients with total joint arthroplasties.

Human monocyte/macrophage response to cobalt-chromium corrosion products and titanium particles in patients with total joint replacements

The responses of human peripheral blood monocytes of 10 normal volunteers and 14 patients with total hip replacements to particles of commercially pure titanium and chromium orthophosphate (a corrosion product from cobalt-chromium alloy implants) were studied. In addition, these phagocytosable particles were added to cultured mononuclear cells isolated from the interfacial membrane of 14 patients with failed implants. Peripheral blood monocytes from patients who had had a total hip replacement produced significantly higher levels of interleukin-1 (both interleukin-1 alpha and interleukin-1 beta) and prostaglandin E2 following particulate stimulation than those from normal volunteers. Supernatants from both titanium and chromium orthophosphate-stimulated peripheral blood monocytes from the volunteers and patients with total hip replacement induced bone resorption (assayed in organ cultures of newborn mouse calvariae) and the proliferation of human fibroblasts. The levels of bone resorption were significantly higher (p < 0.05) in patients with implants than in normal volunteers. There were no significant differences in the responses of cells between patients with focal osteolysis and those without osteolysis. Interfacial membrane mononuclear cells also produced high levels of interleukin-1 alpha, interleukin-1 beta, and prostaglandin E2 and expressed bone resorptive activities following stimulation with either titanium or chromium orthophosphate. More importantly, interfacial membrane mononuclear cells "spontaneously" produced high levels of prostaglandin E2 that were comparable with the response of peripheral blood monocytes stimulated with particulate wear debris. The clinical relevance of this study is 2-fold. First, mononuclear cells from patients with total hip replacement were some-how "sensitized" to metal particles in comparison with mononuclear cells from individuals without an implant. Second, the chromium orthophosphate corrosion product was a potent macrophage/monocyte activator and may contribute to macrophage-mediated osteolysis and aseptic loosening.

Suppression of osteoblast function by titanium particles

In order to understand the effect of particulate debris on osteoblast function, we studied the effect of different particles, including titanium and polystyrene, on bone collagen mRNA (messenger RNA) with the use of Northern blot hybridization analysis, and we studied the effect of the particles on the biosynthesis of bone collagen with analysis of 3H-proline incorporation and with the Western blot technique. The steady-state levels of mRNA for procollagens alpha1(I) and alpha1(III) were markedly suppressed in human MG-63 osteoblast-like cells exposed to phagocytosable titanium particles that were smaller than three micrometers. Both titanium and polystyrene particles smaller than three micrometers suppressed the expression of the gene that codes for collagen, and the suppression of the expression of the gene was related to the size but not to the composition of the particles. The biosynthesis of both type-I and type-III collagen also was decreased in cells that had been treated with titanium particles. Neither the viability nor the proliferation of cells was affected by particulate debris. These data indicate that phagocytosable titanium particles can significantly suppress the expression of the gene that codes for collagen in osteoblast-like cells (p < 0.05).

Effects of polyethylene on macrophages

A system was developed to expose macrophages to polyethylene in vitro. Exposure of macrophages to these particles in isolation led to the release of tumor necrosis factor alpha and prostaglandin E2. Exposure of macrophages in co-culture with osteoblasts to polyethylene particles increased the release of prostaglandin E2 and also led to the release of interleukin-6. Incubation of radiolabelled calvariae with conditioned medium from macrophages exposed to polyethylene particles alone or to particles in co-culture with osteoblasts led to bone resorption reflected by release of 45Ca. Incubation with pamidronate was effective in inhibiting resorption stimulated by conditioned medium from macrophages exposed to these particles alone or in co-culture with osteoblasts. This demonstrates that pamidronate, or other bisphosphonates, may be effective in inhibiting bone resorption at the implant/bone interface in association with the macrophage response to particulate polyethylene. Further investigation into the possible use of pamidronate or other bis-phosphonates in the treatment of aseptic loosening is warranted.

Titanium, chromium and cobalt ions modulate the release of bone-associated cytokines by human monocytes/macrophages in vitro

Osteolysis has become a major cause of aseptic loosening in total joint arthroplasty (TJA). Titanium, cobalt and chromium are commonly used in orthopaedic implants (e.g. joint prostheses). The release of bone-associated cytokines has been associated with the development of osteolysis in patients with prostheses. We evaluated the effects of these metals on the release of bone-associated cytokines (IL-1 beta, IL-6, TNF-alpha and TGF-beta 1) by human blood monocytes/macrophages and monocyte-like U937 cells upon lipopolysaccharide (LPS) stimulation, the cell proliferation, and their cytotoxic effects on these cells in vitro. We found that the release of IL-1 beta was enhanced by titanium, chromium and cobalt, the release of TNF-alpha was enhanced by titanium and chromium, and the release of IL-6 was enhanced by titanium. All three metal ions inhibited the release of TGF-beta 1. We also found that titanium and chromium, but not cobalt, enhanced blood monocyte/macrophage proliferation in response to LPS while only titanium enhanced U937 cell proliferation in response to LPS. The metals in concentrations ranging from 0.01 to 100 ngml-1 did not stimulate the cells to secrete detectable cytokines in the absence of LPS. Furthermore, a 4-h pre-exposure of blood monocytes/macrophages or U937 cells to the metals did not alter cytokine release when the metals were removed from the media prior to the addition of LPS. Similarly, a 4-h pre-exposure of blood monocytes/macrophages or U937 cells to LPS did not alter cytokine release when LPS was removed from the media prior to the addition of the metals. The metals did not reduce cell viability and induce cell injury after 72h incubation with the cells. The data suggest that the three metals at clinically relevant concentrations modulated cytokine expression, whereas they did not induce any cytotoxic effects. A metal-induced enhancement of bone-resorbing cytokine release with a concomitant inhibition of bone-forming cytokine release may be an important factor in the development of osteolysis, which can severely compromise the outcome of TJA.

Inhibition of T and B cell proliferation by titanium, cobalt, and chromium: role of IL-2 and IL-6

The mechanism by which an increased risk of prosthetic infection is induced in patients with total joint arthroplasties is poorly understood. The adverse effects of metallic corrosion products of a prosthesis on host defense mechanisms, particularly immune response and release of immunoregulatory cytokines, remain largely unknown. Titanium, cobalt, and chromium are the materials most often used for joint implantation. Therefore, this study was aimed at investigating the cytotoxicity of titanium, cobalt, and chromium and whether these metals affect T and B cell proliferation and the release of cytokines by human peripheral blood mononuclear cells (PBMC) in vitro. Metal cytotoxicity was not observed judging by cell viability and cell injury after PBMC was extensively exposed to the metals. Phytohemagglutinin (PHA)-induced T cell proliferation and lipopolysaccharide-induced B cell proliferation were significantly inhibited by titanium, chromium, and cobalt. The release of IL-2 and IL-6 by PHA-stimulated PBMC was significantly inhibited by titanium, chromium, and cobalt. Titanium did not alter IFN-gamma production, whereas chromium and cobalt significantly reduced IFN-gamma release by PHA-stimulated PBMC. The addition of IL-2 and IL-6 significantly restored the metal-induced inhibition of T cell and B cell proliferation, respectively. This study sheds light on how the metals impair immune response and cytokine release, suggesting that patients with an extensive exposure to the metals may develop immune dysfunctions. The compromised immune response induced by the metals might significantly contribute to an increased risk of infection in patients with joint prostheses.

Technique for generating submicrometer ultra high molecular weight polyethylene particles

Ultra high molecular weight polyethylene wear debris is believed to have a major role in aseptic loosening of prosthetic joints. In order to study the cellular and host response to this and other such particulate debris, a source of fine ultra high molecular weight polyethylene debris is needed. We have described a technique to fracture the GUR 4150 primary ultra high molecular weight polyethylene grain, which reproducibly generated particles less than 1 micron in size. Furthermore, the particle morphology was similar to that of ultra high molecular weight polyethylene particles generated in vivo and retrieved from interfacial tissues. The fabricated polyethylene particles ranged from 0.1 to 33 microns in diameter, with a mean of 2.3 +/- 0.2 micron. Sixty percent of the particles were smaller than 1 micron and 90% were smaller than 7 microns. Using filtration and sedimentation, it is possible to acquire finer particle fractions. These particles are currently being used for biological response studies.

Metal versus polyethylene wear particles in total hip replacements. A review

Research has recently been focused on the development of hip replacements with alternative bearing surfaces with cobalt chrome alloy, to avoid the production of polyethylene wear particles in hip replacements and polyethylene wear debris mediated bone lysis. Cobalt chrome on cobalt chrome bearing surfaces are being reevaluated. Characterization of wear particles and studies on the reaction of the body to these particles, have played an important role in the determination of the factors that cause aseptic loosening and will therefore play an important role in the comparison of metal on polyethylene and metal on metal hip prostheses. In this paper, a comparison between the different aspects of metal and polyethylene wear particles is made using data from the literature and the authors' experience. The authors conclude that techniques need to be optimized to isolate and characterize individual metal wear particles from periprosthetic tissues and they advocate the performance of in vitro studies with these in vivo generated wear particles or comparable particles.