Osteosarcopenia in hip fracture: taking cues from pathophysiology for clinical practice.

Hip fractures are common in older and frail adults, and the risk of adverse outcomes and mortality is significantly increased in patients affected by osteosarcopenia. Identifying particularly vulnerable subjects is a critical step to act aimed at promoting postoperative recovery and reducing the risk of adverse events. However, the diagnostic criteria that are currently used to establish the severity of osteosarcopenia are not easily applicable in patients with hip fractures and impaired mobility. In this review, the new knowledge on the pathophysiology of osteosarcopenia that provides several cues for studying biomarkers potentially useful in clinical practice is summarized. Although significant progress has been obtained in understanding the biological mechanisms leading to the involution of the bone- muscle unit, further studies are needed to identify clinically relevant biomarkers and their diagnostic accuracy in establishing the severity of the osteosarcopenia, predicting adverse outcomes, and guiding physicians in choosing appropriate therapeutic interventions.

Change in FGF-2 circulating levels after arterial embolization in patients with bone metastases.

Arterial embolization, aimed at the mechanical occlusion of tumor-feeding vessels, represents a satisfactory palliative therapy for bone metastases. In this study, we evaluated if the circulating levels of three factors related to the metastatic process change in response to embolization. Seven patients who underwent embolization of a single skeletal metastasis from carcinomas were analyzed prospectively. Circulating levels of Vascular Endothelial Growth Factor A (VEGF-A), Fibroblast Growth Factor 2 (FGF-2), and Tartrate-Resistant Acid Phosphatase-5b Isoform (TRACP5b) were evaluated before and after embolization at 1, 3, and 6 months. According to morphological and clinical evaluations, all the embolizations were successful. VEGF-A and TRACP5b did not show significant changes after the treatment. On the contrary, FGF-2 signifi- cantly decreased 1 month after the treatment. FGF-2 appears as a promising candidate for monitoring the efficacy of emboli- zation in patients with osteolytic metastases.

Association between markers of bone loss and urinary lithogenic risk factors in osteopenic postmenopausal women.

In this study, we explored if urinary lithogenic risk parameters could have some application for monitoring bone health status. We recruited 20 women with postmenopausal osteopenia and a negative medical history for nephrolithiasis. Markers of lithogenic risk were evaluated on 24-h urine and fastingmorning urine. Serum levels of bone turnover markers (BTM) were measured in fasting-blood samples. We found that cross-linked telopeptide of type I collagen (CTX) was significantly correlated with 24-h calcium excretion. N-terminal propeptide of type I procollagen (PINP) correlated with 24-h excretion of potassium, calcium and citrate. CTX had considerably increased in patients with pH less than 5.5. Low citrate levels (less than 3.3 mmol/24 h) were associated with lower levels of CTX and PINP. Our findings suggest that a low-grade acidosis and some lithogenic risk factors are detectable in a proportion of patients with postmenopausal osteopenia. Further studies are necessary to confirm that this evaluation could be clinically relevant.

Metal hypersensitivity testing in patients undergoing joint replacement: a systematic review.

We report a systematic review and meta-analysis of the peer-reviewed literature focusing on metal sensitivity testing in patients undergoing total joint replacement (TJR). Our purpose was to assess the risk of developing metal hypersensitivity post-operatively and its relationship with outcome and to investigate the advantages of performing hypersensitivity testing. We undertook a comprehensive search of the citations quoted in PubMed and EMBASE: 22 articles (comprising 3634 patients) met the inclusion criteria. The frequency of positive tests increased after TJR, especially in patients with implant failure or a metal-on-metal coupling. The probability of developing a metal allergy was higher post-operatively (odds ratio (OR) 1.52 (95% confidence interval (CI) 1.06 to 2.31)), and the risk was further increased when failed implants were compared with stable TJRs (OR 2.76 (95% CI 1.14 to 6.70)). Hypersensitivity testing was not able to discriminate between stable and failed TJRs, as its predictive value was not statistically proven. However, it is generally thought that hypersensitivity testing should be performed in patients with a history of metal allergy and in failed TJRs, especially with metal-on-metal implants and when the cause of the loosening is doubtful.

Bone regeneration and stem cells.

This invited review covers research areas of central importance for orthopaedic and maxillofacial bone tissue repair, including normal fracture healing and healing problems, biomaterial scaffolds for tissue engineering, mesenchymal and foetal stem cells, effects of sex steroids on mesenchymal stem cells, use of platelet-rich plasma for tissue repair, osteogenesis and its molecular markers. A variety of cells in addition to stem cells, as well as advances in materials science to meet specific requirements for bone and soft tissue regeneration by addition of bioactive molecules, are discussed.

Bone-targeted doxorubicin-loaded nanoparticles as a tool for the treatment of skeletal metastases.

Bone metastases contribute to morbidity in patients with common cancers, and conventional therapy provides only palliation and can induce systemic side effects. The development of nanostructured delivery systems that combine carriers with bone-targeting molecules can potentially overcome the drawbacks presented by conventional approaches. We have recently developed biodegradable, biocompatible nanoparticles (NP) made of a conjugate between poly (D,L-lactide-co-glycolic) acid and alendronate, suitable for systemic administration, and directly targeting the site of tumor-induced osteolysis. Here, we loaded NP with doxorubicin (DXR), and analyzed the in vitro and in vivo activity of the drug encapsulated in the carrier system. After confirming the intracellular uptake of DXR-loaded NP, we evaluated the anti-tumor effects in a panel of human cell lines, representative for primary or metastatic bone tumors, and in an orthotopic mouse model of breast cancer bone metastases. In vitro, both free DXR and DXR-loaded NP, (58-580 ng/mL) determined a significant dose-dependent growth inhibition of all cell lines. Similarly, both DXR-loaded NP and free DXR reduced the incidence of metastases in mice. Unloaded NP were ineffective, although both DXR-loaded and unloaded NP significantly reduced the osteoclast number at the tumor site (P = 0.014, P = 0.040, respectively), possibly as a consequence of alendronate activity. In summary, NP may act effectively as a delivery system of anticancer drugs to the bone, and deserve further evaluation for the treatment of bone tumors.

Interferon-alpha inhibits in vitro osteoclast differentiation and renal cell carcinoma-induced angiogenesis.

Bone is a common site of osteolytic and richly vascularized metastases of renal cell carcinoma (RCC) and Interferon (IFN)-alpha based therapies have been considered for the treatment of patients affected by this disease. The effects of IFN-alpha on metastatic RCC patients have been related to its immunomodulatory, and cytotoxic activity on tumor cells, but there could be an effect also on tumor induced osteoclast differentiation and bone angiogenesis. When osteoclasts obtained from human peripheral blood mononuclear cells, cultured in the presence of receptor activator of nuclear factor-kappaB (RANKL) and macrophage-colony stimulating factor (M-CSF), were treated with IFN-alpha, the expression of bone tartrate resistant acid phosphatase (TRACP) type 5b was reduced, as well as calcium-phosphate resorption activity and expression of pro-osteoclatic transcription factor c-Fos. IFN-alpha modulation of angiogenesis was studied by analysis of proliferation, survival, and migration of a bone endothelial cell line (BBE), and by the analysis of pro-angiogenic factor expression in RCC cell lines. IFN-alpha inhibited bone endothelial cell proliferation and the expression of FGF-2, while the vascular endothelial growth (VEGF) did not show any significant variation. Moreover, IFN-alpha inhibited the migration induced by the RCC through the impairment of fibroblast growth factor-2 (FGF-2) secretion. These data demonstrate multiple activities of IFN-alpha on renal cancer-induced bone disease, in addition to its recognized role as a cytotoxic and immunomodulatory agent, because they indicate its ability to reduce bone resorption and to impair tumor-associated angiogenesis, and they also suggest the use of IFN-alpha to treat skeletal metastases of other carcinomas.

Systemic cross-linked N-terminal telopeptide and procollagen I C-terminal extension peptide as markers of bone turnover after total hip arthroplasty.

There is no diagnostic, non-invasive method for the early detection of loosening after total hip arthroplasty. In a pilot study, we have analysed two serum markers of bone remodelling, procollagen I C-terminal extension peptide (PICP) and cross-linked N-terminal telopeptide (NTx), as well as the diagnostic performance of NTx for the assessment of osteolysis. We recruited 21 patients with loosening (group I), 18 with a well-fixed prosthesis (group II) and 17 at the time of primary arthroplasty for osteoarthritis (OA) (group III). Internal normal reference ranges were obtained from 30 healthy subjects (group IV). The serum PICP level was found to be significantly lower in patients with OA and those with loosening, when compared with those with stable implants, while the NTx level was significantly increased only in the group with loosening, suggesting that collagen degradation depended on the altered bone turnover induced by the implant. This hypothesis was reinforced by the finding that the values in the pre-surgery patients and stable subjects were comparable with the reference range of younger healthy subjects.A high specificity and positive predictive value for NTx provided good diagnostic evidence of agreement between the test and the clinical and radiological evaluations. The NTx level could be used to indicate stability of the implant. However, further prospective, larger studies are necessary.

Evaluation of osteoblast-like cell response to Proroot MTA (mineral trioxide aggregate) cement.

Some endodontic sealers have been shown to cause local and systemic effects, mainly due to microleakage of chemicals from the sealer. To avoid the risk of toxic effects in vivo, the biological compatibility of filling materials has to be assessed. In vitro compatibility of Proroot MTA cement in comparison with two different fillers used in clinical practice, was examined by testing the adherence, viability, proliferation and secretion of collagen of osteoblast-like cells. In our experimental system, Saos-2 cells challenged with Proroot MTA for 24 and 72 h showed a better behaviour than the cells exposed to the other compounds under assay. We found that the cells attached to the rough surface of Proroot MTA cement and spread onto the rough surface. Moreover, the cells on Proroot MTA were viable, grew, and released some collagen even at 72 h, while cell metabolism and growth was dramatically reduced onto sEBA and amalgam surfaces. A parallel behaviour was found after the cells were challenged with extracts of the different fillers. In conclusion, according to our in vitro study, Proroot MTA showed a good interaction with bone-forming cells: such behaviour may partially account for its satisfying clinical performance.

The influence of alumina and ultra-high molecular weight polyethylene particles on osteoblast-osteoclast cooperation.

Particle-induced macrophage activation, mainly by UHMWPE wear, has been recognized as the biological mechanism leading to periprosthetic bone resorption, which is responsible for the loosening of the total hip replacements (THR). Ceramic-on-ceramic implants have been advocated as a means of reducing wear products. Many studies investigated the effect of alumina (Al(2)O(3)) particles on monocytes/macrophages, but only limited information are available on their participation to bone turnover. An in vitro model was performed to investigate how Al(2)O(3) and UHMWPE particles may influence the osteoblast-osteoclast interaction: human osteoblasts (HOB) were obtained from trabecular bone, while osteoclasts were derived from peripheral blood mononuclear cells (PBMC) of healthy donors. The amount of IL6, TNF alpha, GM-CSF, and other factors acting on the bone turnover, i.e. the 'receptor activator of NF kappa B' ligand (RANKL) and osteoprotegerin (OPG), was detected in culture medium of particle-challenged HOB (HOB-CM). The Al(2)O(3) and UHMWPE particles did not affect either cell viability or TNF and GM-CSF release, while the increase in IL6 release seemed to be dependent on the particle concentration. UHMWPE increased the release of RANKL from HOB, while OPG and OPG-to-RANKL ratio were significantly inhibited. The ability of HOB-CM to promote osteoclastogenesis was tested via osteoblast/monocyte cooperation: after seven days of culture UHMWPE HOB-CM induced a large amount of multinucleated TRAP-positive giant cells, as well as significantly reduced the amount of IL6, GM-CSF and RANKL in the supernatant. With regard to the inductive effect on the osteoclastogenesis, our results show that the Al(2)O(3) wear debris are less active.

Ion release in stable hip arthroplasties using metal-on-metal articulating surfaces: a comparison between short- and medium-term results.

The use of metallic heads articulating with metallic cups could solve the problem of polyethylene (PE) wear in total hip replacement (THR) with metal-on-PE bearings. A conspicuous release of metal ions from new models of metal-on-metal bearings has been found in the short-term, but it is yet unclear whether the medium-term corrosion rate is high or, on the contrary, it becomes negligible, because of the continuous surface finishing. Our purpose was to compare the serum ion values (nanograms per milliliter) in 15 patients with metal-on-metal stable prosthesis (Group A), in the short-term (subgroup A(1); mean follow-up: 24 mo) and medium-term (subgroup A(2); mean follow-up: 52 mo), in order to determine whether the ion release decreased with time of implant. Chromium (Cr), cobalt (Co), molybdenum (Mo) and aluminum (Al) were analyzed. Twenty-two presurgical patients were used for comparison (Group B). The reference range was obtained from a population of 27 healthy subjects (Group C). Co and Cr levels in the medium-term (subgroup A(2)) were not decreased in comparison with the short-term values (subgroup A(1)) and were significantly higher (p < 0.001) than presurgical and reference values. Otherwise, Mo and Al concentrations were not significantly increased in comparison with reference values. In conclusion, despite the apparent advantage of metal-on-metal coupling, especially in younger patient populations, there is a major concern about the extent and duration of the relevant "internal" exposure to Cr and Co ions. This exposure should be carefully monitored, in order to clarify the biologic effects of ion dissemination and, consequently, to identify risks concerning long-term toxicity of metals.

Biologic effects of surface roughness and fluorhydroxyapatite coating on osteointegration in external fixation systems: an in vivo experimental study.

The concomitant influence of surface roughness and fluorhydroxyapatite (FHA) coating of titanium (Ti) implants on bone response was investigated. For this purpose, titanium screw-shaped implants with a lower degree (Y371) and a higher degree (TiPore300) of surface roughness, coated with FHA and uncoated, were transversally inserted into the diaphyses of sheep tibiae for 12 weeks. Four sheep received Y371 (group A) and Y371 + FHA (group B) screws and four sheep received TiPore300 (group C) and TiPore300 + FHA (group D) screws. For each type of material, the morphology and microstructure of implant-facing bone were evaluated. The host bone of each tibia was used as a control. In all groups the bone tissue did not reach a complete maturation. The higher degree of roughness, perhaps due to an excessive irregularity of the surface, induced the worst osteointegration: a fibrous tissue layer between screw and new bone tissue was often present. Nevertheless, as viewed by XRD, no crystallographic change of the apatite lattice was observed in any of the implants. In contrast, the microhardness value, an index of bone mineralization, was higher in the uncoated screws and decreased progressively in the following order: group C > group A > group B > group D. The association of plasma spraying with roughness treatment constitutes a complex system that seems to interfere with bone mineralization. A chemical change of the surface, perhaps with more Ti release or more coating degradation, could be responsible for such impairment. The authors emphasize the necessity for simultaneous evaluation of surface topography and chemistry as well as an improvement in plasma-spraying and post-processing techniques and in standard procedures for materials characterization.

Osteoblast growth and function in porous poly epsilon -caprolactone matrices for bone repair: a preliminary study.

Current methods for the replacement of skeletal tissue involve the use of autografts, allografts and, recently, synthetic substitutes, which provide a proper amount of material to repair large bone defects. Engineered bone seems a promising approach, but a number of variables have to be set prior to any clinical application. In this study, four different poly caprolactone-based polymers (PCL) were prepared and tested in vitro using osteoblast-like Saos-2 cells. Differences among three-dimensional polymers include porosity, addition of hydroxyapatite (HA) particles, and treatment with simulated body fluid. Biochemical parameters to assess cell/material interactions include viability, growth, alkaline phosphatase release, and mineralization of osteoblastic cells seeded onto three-dimensional samples, while their morphology was observed using light microscopy and SEM. Preliminary results show that the polymers, though degrading in the medium, have a positive interaction with cells, as they support cell growth and functions. In the short-term culture (3-7 days) of Saos-2 on polymers, little differences were found among PCL samples, with the presence of HA moderately improving the number of cells onto the surfaces. In the long term (3-4 weeks), it was found that the HA-added polymers obtained the best colonization by cells, and more mineral formation was observed after coating with SBF. It can be concluded that PCL is a promising material for three-dimensional scaffold for bone formation, and the presence of bone-like components improves osteoblast activity.

Nitric oxide synthase in tissues around failed hip prostheses.

Nineteen patients who had undergone hip revision surgery for aseptic loosening of joint prostheses were studied. Tissue samples were harvested at the interface between bone and implant, either at the stem or at the cotyle level. Immunohistochemistry was performed on tissue sections to detect nitric oxide synthase (NOS), the enzyme which enables the synthesis of nitric oxide (NO), a molecule which can activate bone resorption. Quantitative analysis of the positive cells and correlation with the presence of particulate wear debris and radiological data were performed. The authors observed a trend towards a moderate increase in positive cells due to inducible NOS in tissues containing particulate wear debris, especially of a plastic material. This increase, however, did not achieve statistical significance. On the contrary, there was a statistical correlation between iNOS (inducible NOS) and the severity of osteolysis around the prosthetic implant. Pharmacological control of the biosynthesis of NO may be considered in the prevention or treatment of loosening.

Ion release in patients with metal-on-metal hip bearings in total joint replacement: a comparison with metal-on-polyethylene bearings.

Polyethylene (PE) wear has been shown to be a problem in long-term joint replacement using metal-on-PE bearing. The use of metallic heads articulating with metallic cups could solve this problem: success will be enhanced if wear and corrosion of the articulating surfaces are maintained at a low level. New models with metal-on-metal bearing have been proposed, to be used mainly for young subjects: such coupling seems to have a reduced release, but it is unclear yet if the medium-term corrosion rate is really negligible or, on the contrary, it is significantly higher than in the metal-on-PE bearing. Aim of our study was the comparison of ion release in the serum of two groups of patients who had the same type of stable cementless prosthesis, but different bearing: twenty-six patients with metal-on-metal (Group A) and fifteen patients with metal-on-PE bearing (Group B) were examined. The follow-up was 14-38 months for group A and 18-34 months for group B. The serum concentration of chromium (Cr), cobalt (Co) and molybdenum (Mo) was measured. Twenty-two patients before surgery were used for comparison (Group C). The reference values were obtained from a population of twenty-two healthy subjects (Group D). Our findings indicate that metal-on-metal bearings produce a significantly higher systemic release of cobalt and chromium (ng/ml) when compared with levels found in metal-on-PE, pre-surgery and reference groups. Such a high release should induce to improve the bearing materials or, at least, to study the biologic fate of metal ions and consequently their long-term effects. In such a way a risk-to-benefit ratio for the patient could be established.

Platelet activation after in vitro contact with seven acrylic bone cements.

Seven acrylic bone cements were evaluated: Cemex Rx (Tecres S.p.a., Italy), Cemex Isoplastic (Tecres S.p.a., Italy), Zimmer Low Viscosity Cement (L.V.C., Zimmer, IN, USA), Zimmer bone cement - dough type (Zimmer, IN, USA), CMW (DePuy International Ltd., UK), Cerim LT (Cremascoli S.r.l., Italy), and Palacos (Merck, Wehreim, Germany). The cements after polymerization were put in contact in vitro with platelet-rich plasma. Plasma in contact only with siliconated glass was used as the negative control. After contact, platelet number, beta-thromboglobulin (beta-TG), and transforming growth factor-beta1 (TGF-beta1) were determined. The Wilcoxon signed rank test showed Palacos R and L.V.C. induced a significant decrease of platelet number compared with the negative control. All cements determined a significant increase in beta-TG. CMW 3, Palacos, L.V.C., and Zimmer dough type determined a significant increase in TGF-beta1 compared with the negative control.

Platelet release of transforming growth factor-beta and beta-thromboglobulin after in vitro contact with acrylic bone cements.

Three methacrylate-based bone cements used for the fixation of joint prostheses were evaluated: Sulfix-60 (Sulzer Orthopedic Inc., Baar, Switzerland). CMW1 (DePuy International Ltd., England). and CMW2 (DePuy International Ltd., England). The cements after polymerization were put in contact in vitro with platelet-rich plasma. Plasma, in contact only with siliconized glass, was used as a negative control. After contact, platelet number. beta-thromboglobulin (beta-TG), and transforming growth factor-beta1 (TGF-beta1) were determined. The Student's paired t test showed that the ccments induced no significant modifications of platelet number. CMWI and Sulfix-60 determined a significant increase in beta-TG compared with the negative control. All cements determined a significant increase in TGF-beta1. Significant differences were also seen in the levels of beta-TG and TGF-beta1 between cements with a content of benzoyl peroxide < 1 (Sulfix-60) and those with a content > 1 (CMW1 and CMW2). The cement with zirconium dioxide (Sulfix-60) produced higher levels of beta-TG and TGF-beta1, compared to those with barium sulphate (CMW1 and CMW2). In conclusion, all the cements induced the secretion of TGF-beta1 CMW1 and Sulfix-60 determined also a significant release of beta-TG. Platelet activation induced by the cements from one side could contribute to the pathogenesis of deep venous thrombosis, that often occurs after prosthetic implant and is caused also by other factors, including surgical trauma and venous stasis. From the other side, activated platelets can release growth factors favoring bone formation.

In vitro testing of the potential for orthopedic bone cements to cause apoptosis of osteoblast-like cells.

The purpose of this study was to investigate in vitro the apoptosis- and/or necrosis-inducing potential of polymethylmethacrylate (PMMA)-based bone cements for prosthetic surgery. Four bone cements widely used in orthopedics were tested as extracts onto osteoblast-like MG-63 cells and for comparison, HL-60 cells, which are remarkably sensitive to apoptotic stimuli. Neutral red uptake (NRU) was used to measure cell viability while Hoechst 33258 staining was used to detect DNA content. Apoptosis was characterized using a BrdU-based ELISA assay for DNA fragmentation and examined by fluorescence microscopy using acridine orange and propidium iodide staining of nuclei. The generation of reactive oxygen species (ROS), which could mediate apoptosis, was verified using dichlorofluorescein-diacetate (DCFH-DA) oxidation to DCF. After 24 h of challenge of the cells with the four cement extracts, the viability of either MG-63 or HL-60 cells was found to be unaltered, as recorded by NRU. Apoptotic cell death was induced by three cements in HL-60, whereas MG-63 cells were significantly affected by the four cements tested: the finding of DNA fragments both in the cytoplasm and supernatants of MG-63 after 24 h demonstrated that these cells underwent late-apoptosis secondary necrosis. Fluorescent staining of the nuclei confirmed the results obtained with the ELISA test. Oxygen free radicals were elicited by two cements in HL-60 cells, while MG-63 did not generate ROS in response to cements. This study helps to gain more insight into the mechanism of cell death induced by PMMA-based cements and suggests apoptosis of osteoblasts as a part of the tissue reaction around cemented prostheses.

Gene expression of bone-associated cytokines in MG63 osteoblast-like cells incubated with acrylic bone cement extracts in minimum essential medium.

This study examined the effects of in vitro challenge with four polymerized acrylic bone cements (Sulfix-60, CMW 1, CMW 2, and CMW 3) on the expression of interleukin-1beta (IL-1beta), interleukin-6 (IL-6), and transforming growth factor-beta1 (TGF-beta1) mRNAs in the osteoblast-like cell line MG63. The extracts of the cements in minimal essential medium (MEM) were tested following 1-h and 7-day curing. A semi-quantitative analysis of the cytokine-specific mRNAs was carried out by agarose gel densitometry and expression was compared with the GAPDH housekeeping gene. The ratio between cytokine gene expression and GAPDH expression was calculated. The mRNA specific for the bone-resorbing cytokines IL-1beta and IL-6 was low in basal conditions. IL-1beta mRNA increased only after incubation with the extract of CMW 1 following 1-h curing. The mRNA specific for the bone-resorbing cytokine IL-6 also increased after contact with CMW 1 at both curing times. Sulfix-60 and CMW 3 following 7-day curing, but not after 1 h, induced higher levels of IL-6 mRNA than the control. CMW 2 after 1-h curing constantly determined the expression of IL-6 mRNA, but at low levels. The mRNA specific for TGF-beta1 was also expressed by the MG63 osteoblast-like cells in basal conditions. The levels increased after contact with Sulfix-60 after 7-day curing and with CMW 1 after 1-h curing. CMW 2 after 7-day curing decreased TGF-beta1 mRNA. In conclusion, the highest expression of the cytokines IL-1beta, IL-6, and TGF-beta1 mRNA was determined by CMW 1. If the results are confirmed in vivo, the increased expression of the osteolytic cytokines induced by the bone cement might result in loosening of the prosthesis, even with all the restrictions of an in vitro study on continuous cell lines.

Interleukin-6 expression by osteoblast-like MG63 cells challenged with four acrylic bone cements.

Periprosthetic osteolysis is a major clinical problem in total hip and total knee arthroplasty and polymethylmethacrylate (PMMA) is a possible etiologic factor. Recently, increasing importance was ascribed to interleukin-6 (IL-6) as an agent favouring bone resorption. The aim of the present study was to investigate the role of bone cements on IL-6 production by MG63. The effect of four acrylic bone cements (Sulfix-60, CMW 1, CMW 2, and CMW 3) on the protein release and mRNA expression of IL-6 in osteoblast-like cell line MG63 was examined using IL-1beta (0.2 microg ml(-1)) as the positive control. The extracts in minimum essential medium (MEM) of the cements were tested, following 1-h and 7-day curing. CMW 1 and CMW 2 significantly increased the IL-6 release into the culture media (p < 0.01). The cells incubated with Sulfix-60 and CMW 3 produced no significantly different levels of IL-6 than the basal production. A positive correlation was found between the concentration of IL-6 and the contents of benzoylperoxide (p = 0.0003) and barium sulphate (p < 0.0001). MG63 expressed IL-6 mRNA constitutively, as demonstrated by the positivity of the negative controls too. We conclude that CMW 1 and CMW 2 increase the production of IL-6 in MG63 cells. The response to Sulfix-60 and CMW 3 is not significantly greater than the negative control.