IL-6 and PGE2 release by human osteoblasts on implant materials

Enzymes and cytokines disease in total hip arthroplasty: promoters of immune loosening

Introducción. Una de las causas más importantes de falla de la prótesis de cadera lo constituye el fenómeno de aflojamiento, el cual se relaciona con la liberación de enzimas mediada por citocinas y produce la lisis del hueso que soporta el implante.Objetivo. Describir los mecanismos de interacción biológica de las moléculas promotoras del aflojamiento de la prótesis total de cadera que con mayor frecuencia están presentes en el proceso.Materiales y métodos. Se realizó una búsqueda de artículos originales y casos clínicos en las bases de datos PubMed y Scopus, sin límite de fecha de publicación, utilizando los términos MeSH “hip prosthesis loosening”, “aseptic loosening”, “cytokines” y “hip arthroplasty failure”. La extracción de datos se hizo mediante la lectura de 250 estudios, de los cuales se seleccionaron 66 para fines de redacción.Resultados. Los autores describen las moléculas más representativas implicadas en el aflojamiento de la prótesis de cadera, además se presentan las interacciones entre ellas.Conclusiones. Enzimas y citocinas han sido ampliamente estudiadas por cuatro décadas, aunque sus mecanismos de interacción son poco conocidos. Los autores proponen un mecanismo de interacción, proceso que podría denominarse “enfermedad de las enzimas y citocinas” o “aflojamiento inmunológico”.

Inflammatory Response of Human Peripheral Blood Mononuclear Cells and Osteoblasts Incubated With Metallic and Ceramic Submicron Particles

Inflammatory reactions associated with osteolysis and aseptic loosening are the result of wear particles generated at the articulating surfaces of implant components. The aim of the present study was to analyze the biological response of human osteoblasts and peripheral blood mononuclear cells (PBMCs) after exposure to metallic and alumina ceramic particles regarding cellular differentiation, cytokine release, and monocyte migration. Cells were exposed to particles (0.01 and 0.05 mg/ml) from an alumina matrix composite (AMC) ceramic and a CoCr28Mo6 alloy with an average size of 0.5 µm over 48 and 96 h. The expression rates of osteogenic (Col1A1, ALP) and pro-osteoclastic (RANK, Trap5b) differentiation markers as well as pro-osteolytic mediators (MMP-1, TIMP-1, IL-6, IL-8, MCP-1) were determined and soluble protein concentrations of active MMP-1, IL-6, IL-8, and pro-collagen type 1 in cell culture supernatants were evaluated. Additionally, the capacity of particle-treated osteoblasts to attract potentially pro-inflammatory cells to the site of particle exposure was investigated by migration assays using osteoblast-conditioned media. The cellular morphology and metabolism of human osteoblasts and adherent PBMCs were influenced by particle type and concentration. In human osteoblasts, Col1A1 expression rates and protein production were significantly reduced after exposing cells to the lower concentration of cobalt-chromium (CoCr) and AMC particles. Exposure to AMC particles (0.01 mg/ml) resulted in increased mRNA levels of RANK and Trap5b in adherent PBMCs. For MMP-1 gene expression, elevated levels were more prominent after incubation with CoCr compared to AMC particles in osteoblasts, which was not reflected by the protein data. Interleukin (IL)-6 and IL-8 mRNA and protein were induced in both cell types after treatment with AMC particles, whereas exposure to CoCr particles resulted in significantly upregulated IL-6 and IL-8 protein contents in PBMCs only. Exposure of osteoblasts to CoCr particles reduced the chemoattractant potential of osteoblast-conditioned medium. Our results demonstrate distinct effects of AMC and CoCr particles in human osteoblasts and PBMCs. Complex cell and animal models are required to further evaluate the impact of cellular interactions between different cell types during particle exposure.

Low doses of Co nanoparticles induce death and regulate osteogenic differentiation in MG‑63 cells

The aim of the present study was to investigate the effects of cobalt nanoparticles (CoNPs) on the proliferation and differentiation of human osteoblasts in vitro, and to investigate the molecular mechanisms via which CoNPs affect proliferation and differentiation of osteoblasts. The MG‑63 human osteoblast cell line was treated with different concentrations of CoNPs for 12 to 48 h in vitro. At each time point, cell morphology was observed and an MTT assay was performed to assess cell viability. Alkaline phosphatase (ALP), osteocalcin (BGLAP), collagen I (COL I), osteoprotegerin (OPG) and receptor activator of nuclear factor κ‑B ligand mRNA expression levels, and ALP, BGLAP and COL protein expression levels, were assessed by reverse transcription‑quantitative polymerase chain reaction and western blotting, respectively. The viability of MG‑63 cells decreased significantly after treatment with CoNPs. As CoNP concentration increased, a higher growth inhibition and cell death was observed. Compared with CoNPs, treatment with the same concentration of Co2+ may have a greater inhibitory effect on the growth of MG‑63 cells. CoNPs affected the mRNAs expression levels of ALP, BGLAP, COL I and OPG in MG‑63 cells, and reduced the protein expression levels of ALP, BGLAP and COL I. In conclusion, the present study demonstrated that CoNPs induce cytotoxic effects on MG‑63 cells by markedly reducing cell viability and inducing cell death at high concentrations. In addition, CoNPs may inhibit the function and differentiation of osteoblasts by affecting the mRNA and protein expression levels of associated genes. The results of the present study indicate that CoNPs may serve an important role in the aseptic loosening mechanism following total joint replacement surgery, particularly in situations where metal on metal prostheses are used. Further study into inhibiting this effect is required.

In Vitro Behavior of Primary Human Osteoblasts Onto Microrough Titanium Surface

OBJECTIVE

The aim of this study was to evaluate in vitro the behavior and the biocompatibility of primary human osteoblasts (HOs) grown onto different implant surface.

METHODS AND MATERIALS

HOs were cultured onto sandblasted/acid-etched (control group) and sandblasted/acid-etched followed by coating with inorganic ions (test group) experimental titanium discs. At established times, SEM analysis, LDH assay, MTT assay, and enzyme-linked immunosorbent assay for type 1 collagen, interleukin (IL)-6, and PGE2 secretion were performed.

RESULTS

Both surfaces promote HOs adhesion and proliferation. After 21 days, cells on test surfaces are well spread, flattened, and attached by cellular extensions, whereas cells on control discs appear mainly elongated. Lower LDH levels and higher values of MTT assay are recorded for cells on test respect to control surfaces at each experimental time. Type 1 collagen release increases until 14 days, significantly decreasing at day 21 in cells grown on both surfaces. IL-6 and PGE2 secretion shows a peak in control group samples at day 7, whereas their levels do not significantly modify in both groups at days 14 and 21.

CONCLUSION

Results indicate that the test group surface is more biocompatible, well tolerated, and suitable for supporting osteoblasts growth and proliferation.

Zoledronic acid at subtoxic dose extends osteoblastic stage span of primary human osteoblasts

OBJECTIVE

This study aimed to check the effect of zoledronic acid (ZA) at subtoxic dose on human osteoblasts (HOs) in terms of cell viability, apoptosis occurrence, and differentiation induction. ZA belongs to the family of bisphosphonates (BPs), largely used in the clinical practice for the treatment of bone diseases, often associated with jaw osteonecrosis onset. Their pharmacological action consists in the direct block of the osteoclast-mediated bone resorption along with indirect action on osteoblasts.

MATERIALS AND METHODS

HOs were treated choosing the highest limit concentration (10(-5) M) which does not induce toxic effects. Live/dead staining, flow cytometry, mitochondrial membrane potential assay, osteocalcin western blotting, gp38 RT-PCR, collagen type I, PGE2, and IL-6 ELISA assays were performed.

RESULTS

Similar viability level between control and ZA-treated samples is found along with no significant increase of apoptotic and necrotic cells in ZA-treated sample. To establish if an early apoptotic pathway was triggered, Bax expression and mitochondrial membrane potential were evaluated finding a higher protein expression in control sample and a good integrity of mitochondrial membrane in both experimental points. Type I collagen secretion and alkaline phosphatase (ALP) activity appear increased in ZA-treated sample, osteocalcin expression level is reduced in ZA-treated cells, whereas no modifications of gp38 mRNA level are evidenced. No statistical differences are identified in PGE2 secretion level whereas IL-6 secretion is lower in ZA-treated HOs with respect to control ones.

CONCLUSIONS

These results highlight that ZA, delaying the osteoblastic differentiation process versus the osteocytic lineage, strengthens its pharmacological activity enhancing bone density.

CLINICAL RELEVANCE

The knowledge of ZA effects on osteoblasts at subtoxic dose allows to improve therapeutic protocols in order to strengthen drug pharmacological activity through a combined action on both osteoclastic and osteoblastic cells.

The haematopoietic stem cell niche: new insights into the mechanisms regulating haematopoietic stem cell behaviour

The concept of the haematopoietic stem cell (HSC) niche was formulated by Schofield in the 1970s, as a region within the bone marrow containing functional cell types that can maintain HSC potency throughout life. Since then, ongoing research has identified numerous cell types and a plethora of signals that not only maintain HSCs, but also dictate their behaviour with respect to homeostatic requirements and exogenous stresses. It has been proposed that there are endosteal and vascular niches within the bone marrow, which are thought to regulate different HSC populations. However, recent data depicts a more complicated picture, with functional crosstalk between cells in these two regions. In this review, recent research into the endosteal/vascular cell types and signals regulating HSC behaviour are considered, together with the possibility of a single subcompartmentalised niche.

Microfluidic devices for studying heterotypic cell-cell interactions and tissue specimen cultures under controlled microenvironments

Microfluidic devices allow for precise control of the cellular and noncellular microenvironment at physiologically relevant length- and time-scales. These devices have been shown to mimic the complex in vivo microenvironment better than conventional in vitro assays, and allow real-time monitoring of homotypic or heterotypic cellular interactions. Microfluidic culture platforms enable new assay designs for culturing multiple different cell populations and∕or tissue specimens under controlled user-defined conditions. Applications include fundamental studies of cell population behaviors, high-throughput drug screening, and tissue engineering. In this review, we summarize recent developments in this field along with studies of heterotypic cell-cell interactions and tissue specimen culture in microfluidic devices from our own laboratory.

The biology of aseptic osteolysis

Total hip arthroplasty is one of the most commonly performed and successful elective orthopaedic procedures. However, numerous failure mechanisms limit the long-term success including aseptic osteolysis, aseptic loosening, infection, and implant instability. Aseptic osteolysis and subsequent implant failure occur because of a chronic inflammatory response to implant-derived wear particles. To reduce particulate debris and their consequences, implants have had numerous design modifications including high-molecular-weight polyethylene sockets and noncemented implants that rely on bone ingrowth for fixation. Surgical techniques have improved cementation with the use of medullary plugs, cement guns, lavage of the canal, pressurization, centralization of the stem, and reduction in cement porosity. Despite these advances, aseptic osteolysis continues to limit implant longevity. Numerous proinflammatory cytokines, such as interleukin-1, interleukin-6, tumor necrosis factor-alpha, and prostaglandin E2, have proosteoclastogenic effects in response to implant-derived wear particles. However, none of these cytokines represents a final common pathway for the process of particle-induced osteoclast differentiation and maturation. Recent work has identified the fundamental role of the RANKL-RANK-NF-kappaB pathway not only in osteoclastogenesis but also in the development and function the immune system. Thus, the immune system and skeletal homeostasis may be linked in the process of osteoclastogenesis and osteolysis.

Molecular interactions between breast cancer cells and the bone microenvironment drive skeletal metastases

Breast cancer cells preferentially spread to bone. Bone metastases are currently incurable and therefore better treatments need to be developed. Metastasis is an inefficient, multi-step process. Specific aspects of both breast cancer cells and the bone microenvironment contribute to the development of bone metastases. Breast cancers express chemokine receptors, integrins, cadherins, and bone-resorbing and bone-forming factors that contribute to the successful and preferential spread of tumor to bone. Bone is rich in growth factors and cell types that make it a hospitable environment for breast cancer growth. Once breast cancer cells enter the bone, a highly complex vicious cycle develops, in which breast cancer cells secrete factors that act on bone cells and other cells within the bone (stem cells, T cells, platelets, adipocytes, fibroblasts, and endothelial cells), causing them to secrete factors that act on adjacent cancer cells. The steps in the metastatic cascade and the vicious cycle within bone offer unique targets for adjuvant treatments to treat and cure bone metastases.

Elucidating in vitro cell-cell interaction using a microfluidic coculture system

This work presents a novel microfluidic coculture system that improves the accuracy of evaluating the interaction between cocultured cell types. A microfluidic coculture chip, fabricated by CO(2) laser direct-writing on polymethyl methacrylate (PMMA), was designed to separate two cell types using a microchannel, while permitting transfer of cellular media. The system has two up-stream wells and five down-stream wells. As an example, released inflammatory cytokines (e.g., interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha)), activated in up-stream macrophages, flow through a microfluidic mixing system, generating linear concentration gradients in down-stream wells and inducing down-stream osteoblasts to release prostaglandin E2 (PGE2), a well-known bone resorption marker. Osteoblast viability was assessed by 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTT) assay. This novel coculture system can be applied to evaluate cell-cell interaction while physically separating interacting cells.

Pulp-dentine complex changes and root resorption during intrusive orthodontic tooth movement in patients prescribed nabumetone

Pulpitis, external root resorption, and pain may be experienced during orthodontic movement. The use of nonsteroidal anti-inflammatory drugs (NSAIDs) has been suggested to control these changes. The purpose of this study was to observe pulp-dentinal reactions, root resorption, tooth pain, and tooth movement after the application of a 4-ounce intrusive orthodontic force to human maxillary first premolars in patients given the NSAID nabumetone. Thirty-four maxillary first premolars were evaluated. A placebo was prescribed to 17 patients after an intrusive force was activated and reactivated for an 8-week period on the right side. The same procedure was repeated on the left side after patients were given nabumetone. Pulp-dentinal reactions and external root resorption were evaluated by histology. Pain and movement were also evaluated. Nabumetone was found to be useful in reducing pulpitis, external root resorption, and pain caused by intrusive orthodontic movement, without altering tooth movement in response to the application of orthodontic force.

Biocompatibility and functionality of the degradable polymer alkylene bis(dilactoyl)-methacrylate for screw augmentationin vivo

Recently, a new degradable polymer has been developed on the basis of alkylene bis(dilactoyl)-methacrylate as an alternative material for screw augmentation. The polymer has been investigated in vitro and in a short-term experiment in rabbits exhibiting promising results. The aim of the present study was to investigate its long-term biocompatibility and mechanical functionality in a large animal model. The polymer was used for screw augmentation in the cancellous bone of the femoral condyle and tibia epiphysis of 12 sheep and was compared to polymethylmethacrylate (PMMA) augmented and nonaugmented screws. After an implantation period of 6 months, bone, regional lymph nodes, and several organs were histologically evaluated. The mechanical efficacy was investigated by a biomechanical pullout test. A lot of mononuclear macrophages and multinuclear foreign body giant cells with incorporated polymer particles indicate strong inflammatory reactions. Large osteolysis zones with osteoclasts were found in the surrounding polymer. The polymer was fragmented but not substantially degraded. Polymer particles were also found in the regional lymph nodes. Lung, liver, kidney, and spleen did not show any pathological signs. The pullout force of screws augmented with the new polymer was significantly reduced in comparison to PMMA augmented and nonaugmented screws, respectively. It was concluded that the material has poor biocompatibility and cannot be recommended for clinical application as screw augmentation material.