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

IL-18: The Forgotten Cytokine in Dengue Immunopathogenesis

Dengue fever is an infection by the dengue virus (DENV) transmitted by vector mosquitoes. It causes many infections in tropical and subtropical countries every year, thus posing a severe disease threat. Cytokine storms, one condition where many proinflammatory cytokines are mass-produced, might lead to cellular dysfunction in tissue/organ failures and often facilitate severe dengue disease in patients. Interleukin- (IL-) 18, similar to IL-1β, is a proinflammatory cytokine produced during inflammation following inflammasome activation. Inflammatory stimuli, including microbial infections, damage signals, and cytokines, all induce the production of IL-18. High serum IL-18 is remarkably correlated with severely ill dengue patients; however, its possible roles have been less explored. Based on the clinical and basic findings, this review discusses the potential immunopathogenic role of IL-18 when it participates in DENV infection and dengue disease progression based on existing findings and related past studies.

Programmed BMP-2 release from biphasic calcium phosphates for optimal bone regeneration

This study aimed to fabricate a multi-layered biphasic calcium phosphate (BCP) platform for programmed bone morphogenetic protein-2 (BMP-2) release, which means to block the initial burst release and promote releasing during the differentiation phase of osteogenic cells. And it is to confirm in vivo whether this platform has osteogenic inductivity even when extremely low doses of BMP-2 are loaded compared to the conventional soaking method. Our strategy consisted of preparing a multilayer coating on BCP to minimize the contact between BMP-2 and BCP and allow the loading of BMP-2. The multilayer, which is surface-modified on BCP, is composed of an organosilicate and a natural polymer-based layer-by-layer (LbL) film. We applied (3-Aminopropyl)triethoxysilane (APTES) as an organosilicate was used for amine-functionalized BCP and (collagen/heparin)₅ film was used to delay and sustain BMP-2 release. The coated multilayer not only reduced the initial burst release by more than 50% but also loaded more BMP-2. For in vivo experiment, histomorphometric analysis, it was observed that the BCP platform loaded with extremely low concentration BMP-2 (0.01 mg/ml) induced a significantly larger amount of new bones at 8 weeks compared to the conventional soaking method in the rabbit calvarium onlay graft model.

Factors Influencing the Interactions in Gelatin/Hydroxyapatite Hybrid Materials

The most severe problem in bone regeneration is the defect in the interface. We prepared four types of implantation scaffolds of crosslinked gelatin (GE)/hydroxyapatite (HAp) to study the factors influencing interface interactions, they are film-crosslinked GE scaffold, gel-crosslinked GE scaffold, solid-crosslinked GE/HAp scaffold and gel-crosslinked GE/HAp scaffold. HAp could penetrate the entire GE matrix completely in four successive steps: physical preparation of a gel; chemical crosslinking; incubation in modified simulated body fluid (m-SBF) and freeze-drying. The penetrative nucleation and growth of HAp and the influencing factors in the GE matrix were investigated to ameliorate the interface interactions between organic and inorganic layers. During development of penetrative nucleation and growth, a tight connection was built between organic and inorganic layers, B-type carbonated HAp was formed after incubation with m-BSF, and the apatite content could be controlled. In summary, enhanced interface relies on not only the pre-seeded hydroxyapatite (HAp) as crystal nuclei but also the sufficient space for ions with high concentration to diffuse in.

The in vitro and in vivo anti-melanoma effects of hydroxyapatite nanoparticles: influences of material factors

Background

Treatment for melanoma is a challenging clinical problem, and some new strategies are worth exploring.

Purpose

The objective of this study was to investigate the in vitro and in vivo anti-melanoma effects of hydroxyapatite nanoparticles (HANPs) and discuss the involved material factors.

Materials and methods

Five types of HANPs, ie, HA-A, HA-B, HA-C, HA-D, and HA-E, were prepared by wet chemical method combining with polymer template and appropriate post-treatments. The in vitro effects of the as-prepared five HANPs on inhibiting the viability of A375 melanoma cells and inducing the apoptosis of the cells were evaluated by Cell Counting Kit-8 analysis, cell nucleus morphology observation, flow cytometer, and PCR analysis. The in vivo anti-melanoma effects of HANPs were studied in the tumor model of nude mice.

Results

The five HANPs had different physicochemical properties, including morphology, size, specific surface area (SSA), crystallinity, and so on. By the in vitro cell study, it was found that the material factors played important roles in the anti-melanoma effect of HANPs. Among the as-prepared five HANPs, HA-A with granular shape, smaller size, higher SSA, and lower crystallinity exhibited best effect on inhibiting the viability of A375 cells. At the concentration of 200 μg/mL, HA-A resulted in the lowest cell viability (34.90%) at day 3. All the HANPs could induce the apoptosis of A375 cells, and the relatively higher apoptosis rates of the cells were found in HA-A (20.10%) and HA-B (19.41%) at day 3. However, all the HANPs showed no inhibitory effect on the viability of the normal human epidermal fibroblasts. The preliminary in vivo evaluation showed that both HA-A and HA-C could delay the formation and growth speed of melanoma tissue significantly. Likely, HA-A exhibited better effect on inhibiting the growth of melanoma tissue than HA-C. The inhibition rate of HA-A for tumor tissue growth reached 49.1% at day 23.

Conclusion

The current study confirmed the anti-melanoma effect of HANPs and provided a new idea for the clinical treatment of melanoma.

Strontium-Substituted Bioceramics Particles: A New Way to Modulate MCP-1 and Gro-α Production by Human Primary Osteoblastic Cells

Background: To avoid morbidity and limited availability associated with autografts, synthetic calcium phosphate (CaP) ceramics were extensively developed and used as bone filling materials. Controlling their induced-inflammatory response nevertheless remained a major concern. Strontium-containing CaP ceramics were recently demonstrated for impacting cytokines’ secretion pattern of human primary monocytes. The present study focuses on the ability of strontium-containing CaP to control the human primary bone cell production of two major inflammatory and pro-osteoclastogenic mediators, namely MCP-1 and Gro-α, in response to ceramics particles. Methods: This in vitro study was performed using human primary osteoblasts in which their response to ceramics was evaluated by PCR arrays, antibody arrays were used for screening and real-time PCR and ELISA for more focused analyses. Results: Study of mRNA and protein expression highlights that human primary bone cells are able to produce these inflammatory mediators and reveal that the adjunction of CaP in the culture medium leads to their enhanced production. Importantly, the current work determines the down-regulating effect of strontium-substituted CaP on MCP-1 and Gro-α production. Conclusion: Our findings point out a new capability of strontium to modulate human primary bone cells’ communication with the immune system.

Poly-L-Lactic Acid β-Tricalcium Phosphate Screws: A Preliminary In Vivo Biocompatibility Study

The aim of this study is to assess the biocompatibility of two types of Poly-L-lactic acid (PLLA) screws (with either hydroxiapatite (HA) or β-tricalcium phosphate (β-TCP)) implanted in the left femur of four sheep euthanized at 42, 50, 57 and 84 days after surgery. Titanium screws were also implanted for comparison purposes. No signs of inflammation were seen in the 240 specimens. A rating of “+/-”for macrophages and “-”for neutrophils was assigned to all specimens. All specimens were assigned a rating which ranged from “+/-” to “+++” for fibroblasts and osteoblasts. The presence of macrophages, neutrophils and fibroblasts/osteoblasts was not statistically different for the four implantation periods. PLLA implants with β-TCP have a biocompatibility comparable to PLLA implants with HA.

Endotoxin contamination: a key element in the interpretation of nanosafety studies

The study of toxicity and potential risks of engineered nanoparticles is of particular importance in nanomedicine. Endotoxin, a common contaminant of bacterial origin, has biological effects that can mask the true biological effects of nanoparticles, if its presence is overlooked. In this review, we report the features of nanoparticle contamination by endotoxin, and the different biological effects of endotoxin-contaminated nanoparticles. We will describe different methods for endotoxin detection applied to nanoparticles, and discuss their pros and cons. Eventually, we describe various methods for eliminating endotoxin contamination in nanoparticles. Although there is no universal technique for efficiently removing endotoxin from nanoparticles, specific solutions can be found case by case, which can allow us to perform nanosafety studies in biologically relevant conditions.

Guided bone regeneration using resorbable membrane and different bone substitutes: Early histological and molecular events

Bone insufficiency remains a major challenge for bone-anchored implants. The combination of guided bone regeneration (GBR) and bone augmentation is an established procedure to restore the bone. However, a proper understanding of the interactions between the bone substitute and GBR membrane materials and the bone-healing environment is lacking. This study aimed to investigate the early events of bone healing and the cellular activities in response to a combination of GBR membrane and different calcium phosphate (CaP) materials. Defects were created in the trabecular region of rat femurs, and filled with deproteinized bovine bone (DBB), hydroxyapatite (HA) or strontium-doped HA (SrHA) or left empty (sham). All the defects were covered with an extracellular matrix membrane. Defects were harvested after 12h, 3d and 6d for histology/histomorphometry, immunohistochemistry and gene expression analyses. Histology revealed new bone, at 6d, in all the defects. Larger amount of bone was observed in the SrHA-filled defect. This was in parallel with the reduced expression of osteoclastic genes (CR and CatK) and the osteoblast-osteoclast coupling gene (RANKL) in the SrHA defects. Immunohistochemistry indicated fewer osteoclasts in the SrHA defects. The observations of CD68 and periostin-expressing cells in the membrane per se indicated that the membrane may contribute to the healing process in the defect. It is concluded that the bone-promoting effects of Sr in vivo are mediated by a reduction in catabolic and osteoblast-osteoclast coupling processes. The combination of a bioactive membrane and CaP bone substitute material doped with Sr may produce early synergistic effects during GBR.

STATEMENT OF SIGNIFICANCE

The study provides novel molecular, cellular and structural evidence on the promotion of early bone regeneration in response to synthetic strontium-containing hydroxyapatite (SrHA) substitute, in combination with a resorbable, guided bone regeneration (GBR) membrane. The prevailing view, based mainly upon in vitro data, is that the beneficial effects of Sr are exerted by the stimulation of bone-forming cells (osteoblasts) and the inhibition of bone-resorbing cells (osteoclasts). In contrast, the present study demonstrates that the local effect of Sr in vivo is predominantly via the inhibition of osteoclast number and activity and the reduction of osteoblast-osteoclast coupling. This experimental data will form the basis for clinical studies, using this material as an interesting bone substitute for guided bone regeneration.

Inflammatory response to nano- and microstructured hydroxyapatite

The proliferation and activation of leukocytes upon contact with a biomaterial play a crucial role in the degree of inflammatory response, which may then determine the clinical failure or success of an implanted biomaterial. The aim of this study was to evaluate whether nano- and microstructured biomimetic hydroxyapatite substrates can influence the growth and activation of macrophage-like cells. Hydroxyapatite substrates with different crystal morphologies consisting of an entangled network of plate-like and needle-like crystals were evaluated. Macrophage proliferation was evaluated on the material surface (direct contact) and also in extracts i.e. media modified by the material (indirect contact). Additionally, the effect of supplementing the extracts with calcium ions and/or proteins was investigated. Macrophage activation on the substrates was evaluated by quantifying the release of reactive oxygen species and by morphological observations. The results showed that differences in the substrate's microstructure play a major role in the activation of macrophages as there was a higher release of reactive oxygen species after culturing the macrophages on plate-like crystals substrates compared to the almost non-existent release on needle-like substrates. However, the difference in macrophage proliferation was ascribed to different ionic exchanges and protein adsorption/retention from the substrates rather than to the texture of materials.

Peptide decorated nano-hydroxyapatite with enhanced bioactivity and osteogenic differentiation via polydopamine coating

To be better used as implant materials in bone graft substitutes, bioactivity and osteogenesis of nano-hydroxyapatite (nano-HA) need to be further enhanced. Inspired by adhesive proteins in mussels, here we developed a novel bone forming peptide decorated nano-HA material. In this study, nano-HA was coated by one-step pH-induced polymerization of dopamine, and then the peptide was grafted onto polydopamine (pDA) coated nano-HA (HA-pDA) through catechol chemistry. Our results demonstrated that the peptide-conjugated nano-HA crystals could induce the adhesion and proliferation of MG-63 cells. Moreover, the highly alkaline phosphatase activity of the functionalized nano-HA indicated that the grafted peptide could maintain its biological activity after immobilization onto the surface of HA-pDA, especially at the concentration of 100μg/mL. These modified nano-HA crystals with better bioactivity and osteogenic differentiation hold great potential to be applied as bioactive materials in bone repairing, bone regeneration and bio-implant coating applications.

Inflammatory cell response to calcium phosphate biomaterial particles: an overview

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

Effect of strontium-substituted biphasic calcium phosphate on inflammatory mediators production by human monocytes

Calcium phosphate materials are widely used as bone substitutes because of their properties close to those of the mineral phase of bones. Nevertheless, after several months, calcium phosphate-based materials release particles that may be phagocytosed by monocytes, leading to an inflammatory reaction. Strontium is well known to counteract the osteoporosis process, but little is known about its effect on inflammatory processes. The purpose of this work was to study the effect of biphasic calcium phosphate (BCP) particles substituted with strontium on the inflammatory reaction. Human primary monocytes stimulated or not by lipopolysaccharide (LPS) were exposed to BCP particles containing strontium for 6 and 24 h. Inflammatory mediators (cytokines and matrix metalloproteinases (MMPs)) production was then quantified by ELISA and zymography. We observed that the presence of strontium had few effects on unstimulated cells, but it decreased the production of pro-inflammatory cytokines and the chemokine interleukin 8 in LPS-stimulated cell-conditioned medium. This work suggests for the first time that strontium may be involved in the control of inflammatory processes following BCP phagocytosis by human monocytes.

Cytotoxicity of hydroxyapatite nanoparticles is shape and cell dependent

Nanosized hydroxyapatite (nHA) has been proposed as drug delivery vehicles because of its biocompatibility. While the possible risks of nHA inducing inflammation have been highlighted, the specific influence of varying nHA particle morphology is still unclear. In order to establish this understanding, nHA of four different shapes--needle (nHA-ND), plate (nHA-PL), sphere (nHA-SP) and rod (nHA-RD)--were synthesized. The particle effects with the concentration of 10-300 μg/mL on cytotoxicity, oxygen species generation, production of inflammatory cytokines (TNF-α and IL-6), particle-cell association and cellular uptake were evaluated on BEAS-2B and RAW264.7 cells. Results show that nHA-ND and nHA-PL induced the most significant cell death in BEAS-2B cultures compared to nHA-SP and nHA-RD. Necrosis-apoptosis assay by FITC Annexin V and propidium iodide (PI) staining revealed loss of the majority of BEAS-2B by necrosis. No significant cell death was recorded in RAW264.7 cultures exposed to any of the nHA groups. Correspondingly, no significant differences were observed in TNF-α level for RAW264.7 cells upon incubation with nHA of different shapes. In addition, nHA-RD exhibited a higher degree of particle-cell association and internalization in both BEAS-2B and RAW264.7 cells, compared to nHA-ND. The phenomena suggested that higher particle-cell association and increased cellular uptake of nHA need not result in increased cytotoxicity, indicating the importance of particle shape on cytotoxicity. Specifically, needle- and plate-shaped nHA induced the most significant cell-specific cytotoxicity and IL-6 expression but showed the least particle-cell association. Taken collectively, we demonstrated the shape-dependent effects of nHA on cytotoxicity, inflammatory cytokine expression and particle-cell association.

The association of human primary bone cells with biphasic calcium phosphate (βTCP/HA 70:30) granules increases bone repair

This work evaluates the suitability of biphasic calcium phosphate (BCP) granules (β-TCP/HA 70:30) as potential carriers for cell-guided bone therapy. The BCP granules were obtained by synthesis in the presence of wax, thermal treatment, crushing and sieving and characterized by scanning electron microscopy (SEM), X-ray diffraction and Fourier transform infrared spectroscopy. The cytocompatibility of the BCP granules was confirmed by a multiparametric cytotoxicity assay. SEM analysis showed human bone cell adhesion and migration after seeding onto the material. Rat subcutaneous xenogeneic grafting of granules associated to human bone cells revealed a more accentuated moderate chronic inflammatory infiltrate, without signs of a strong xenoreactivity. Histomorphometrical analysis of bone repair of defects in rat skulls (∅ = 5 mm) has shown that bone cell associated-BCP and autograft promoted a two- and threefold increase, respectively, on new bone formation after 45 days, as compared to BCP alone and blood clot. The increase in bone repair supports the suitability the biocompatible (70:30) BCP granules as injectable and mouldable scaffolds for human cells in bone bioengineering.

Integrated risk assessment of a hydroxyapatite-protein-composite for use in oral care products: a weight-of-evidence case study

Risk assessment of cosmetic ingredients represents a regulatory standard requirement in Europe and other regions. An integrated approach was designed to assess the safety of HPC, a particulate composite of hydroxyapatite and protein (gelatin) for use in oral care products, employing a weight-of-evidence assessment and considering specific physico-chemical properties and exposure conditions. An initial evaluation of the constituents suggested that their chemical nature does not represent a particular health hazard per se. Hydroxyapatite is the main component of teeth and bones in mammals; gelatin is used in food and assumed to be safe once a BSE/TSE risk has been excluded. In vitro screening tests were chosen to further evaluate the biocompatibility: Hen's egg test-chorioallantoic membrane (HET-CAM) to assess irritating effects towards mucous membranes; MTT cytotoxicity test with 3T3 fibroblasts; human corneal epithelial models to investigate inflammatory mediators and cytotoxicity; macrophage assays to measure cytotoxicity, inflammatory mediators and oxidative stress. Together with results from clinical studies, exposure estimates and analyses of kinetic properties, the presented information provides sound evidence to support the safe use of HPC. This is an example of a risk assessment for cosmetic use of small particles without the need for additional animal studies.

Assays on the influence of biomaterials on allogeneic rejection in tissue engineering

In tissue engineering, innate responses to biomaterial scaffolds will affect rejection of allogeneic cells. Biomaterials directly influence innate and adaptive immune cell adhesion, reactive oxygen intermediate production, cytokine secretion, nuclear factor-kappa B nuclear translocation, gene expression, and cell surface markers, all of which are likely to affect allogeneic rejection responses. A major goal in tissue engineering is to induce transplant tolerance, potentially by manipulating the biomaterial component. This review describes methods of measuring responses of macrophages, dendritic cells, and T cells stimulated in vitro and in vivo and addresses key factors in assay development. Such tests include mixed leukocyte reactions, enzyme-linked immunosorbent spot assays, trans-vivo delayed-type hypersensitivity assays, and measurement of dendritic cell subsets and anti-donor antibodies; we propose extending these studies to tissue engineering.

Biological response of osteosarcoma cells to size-controlled nanostructured hydroxyapatite

Osteosarcoma is a primary malignant bone tumor, most prevalent in children and adolescents, and is usually highly aggressive and eventually lethal. Despite multimodal therapies, there is no effective approach to treat this malignant disease. In this study, we observed the biological response of osteosarcoma cells to two kinds of hydroxyapatite nanoparticles (Nano HA), NanoHA-S and NanoHA-L. These nanospheres have the same crystallinity (phase) and morphology, but they differ in size. Cells treated with two kinds of Nano HA were inhibited and mainly led to apoptotic cell death. Caspase-9-dependent intrinsic apoptotic pathway plays a role. It was interesting that the suppression and the apoptosis of osteosarcoma cells was directly related to the size of nanoparticles and that the larger-sized Nano HA exhibited more effectiveness than the smaller one. This in vitro study suggested the potential of size-controlled calcium phosphate nanoparticles for use in therapeutic replacement and reconstruction of bone merits after osteosarcoma extraction.

Exposure of the murine RAW 264.7 macrophage cell line to hydroxyapatite dispersions of various composition and morphology: assessment of cytotoxicity, activation and stress response

Cellular stress responses leading to the release of cytotoxic mediators are discussed as indicators of the hazard presented by particles, and in particular ultrafine particles or nanomaterials. The present study was designed to investigate effects of the following materials on RAW 264.7 macrophages: three hydroxyapatite materials of various morphologies, i.e., nano-sized with rod-like (HA-NR), plate-like (HA-NP) or needle-shaped (HA-NN) morphology, and an irregularly shaped composite of hydroxyapatite and protein (HPC) in the low micrometer range. Concentrations of 50, 100, 500, 1000 and 5000 microg/ml were applied and cells were analyzed for viability (XTT-test), cytokine production (TNF-alpha) and induction of nitric oxide (NO) after 18 and 42 h. DQ12 quartz and lipopolysaccharide (LPS) served as positive controls. Up to concentrations of 500 microg/ml, cell viability was not considerably impaired by the test samples at both timepoints. Overall, viability was about one order of magnitude higher than with comparable concentrations of quartz. TNF-alpha release was induced in all samples after 18 h, with HA-NR showing the most pronounced induction at 100 microg/ml, still clearly below the LPS signal. No or little induction was observed after 42 h. NO production was low after 18 and 42 h. The results support the conclusion that the tested materials exhibit good biocompatibility and are safe to use.

Morphometric immunohistochemical examination of the inflammatory tissue reaction after implantation of calcium phosphate-coated titanium plates in rats

Calcium phosphate (CaP) preparations are established coatings for titanium-based medical implants used for bone reconstruction. However, biodegradation of the coating can result in microparticles that subsequently cause inflammatory reactions. The present study was therefore aimed at investigating the inflammatory response to two series of CaP-coated titanium plates: Ti-brushite (Ti-B) and Ti-hydroxyapatite (Ti-H) implants. Fifteen male LEW.1A rats received one plate of each series and a pellet (5 x 2 mm) of sol-gel derived silica/CaP (SCP implants) implanted into the back musculature. After 7, 14 and 28 days, five rats were killed and the implants were removed with the surrounding tissue. Quantitative immunohistochemistry was performed on frozen sections. Total monocytes/macrophages, tissue macrophages, T-cells, MHC-class-II-positive cells and proliferating cells were counted. For the Ti-B implants, the number of monocytes/macrophages remained constant while the other cell populations increased. In contrast, for the Ti-H implants the number of monocytes/macrophages decreased while the other cell populations remained constant. The SCP implants demonstrated degradation and scattering into smaller particles with an increase for all cell populations except the proliferating cells. Human mesenchymal stem cells demonstrated adherence and a flat morphology on Ti-B and Ti-H implants and no remarkable difference between both implants. Taken together, the in vivo data demonstrate that the short-term inflammatory response against a hydroxyapatite coating is lower in comparison to a brushite coating, and that the morphology of cells growing in vitro is similar on both layers.

In Vitro Study on Different Cell Response to Spherical Hydroxyapatite Nanoparticles

Hydroxyapatite (HA) is widely used in filling of bone defects and coating on metal parts of prosthetic implants due to its excellent biocompatibility, bioactivity, and bone-bonding properties. It has been demonstrated that micro-sized HA particles cause inflammatory reaction, especially for the needle shaped particles. However, little effort has been concentrated on the cell responses of the spherical HA nanoparticles. The aim of the present work is to chemically and physically characterize the synthesized HA nanoparticles and to investigate the in vitro cell responses. X-ray diffraction, electron microscopy, nitrogen adsorption, and Fourier transform infrared spectroscopy revealed that the particles consisted of nearly spherical crystallites of carbonate-substituted HA with size of 20—40 nm and specific surface area of 75 m2/g. L929 cell proliferation experiments demonstrate that the spherical HA nanoparticles is more biocompatible than commercially available HA. On the other hand, U2-OS cell test results show that the inhibition rate of the spherical HA nanoparticles increases with time and concentration. The half effective inhibitory concentration (IC50) of the nanoparticles was determined to be 50.8 μg/mL at 72 h. All these data indicated that the synthesized spherical nanocrystalline HA particles can function as an effective biomaterial for bone tumorectomy repair, while having little adverse effect.

Interleukin 18 and periodontal disease

Cytokines are of major importance in periodontal disease progression. It is generally agreed that control of the Th1/Th2 balance is central to the immunoregulation of periodontal disease. There is increasing evidence in humans that the stable periodontal lesion is mediated by Th1 cells, while the progressive lesion sees a shift toward Th2 cells. Equally, there is conflicting evidence, mainly in animal models, that bone loss is mediated by Th1 responses, and that Th2 responses are protective. In the presence of IL-12, IL-18 induces Th1 responses while, in the absence of IL-12, it promotes Th2 responses. It is clear, therefore, that since IL-18 has the ability to induce either Th1 or Th2 differentiation, it becomes important to consider its role in periodontal disease. This review endeavors to give an overview of this cytokine and its relevance for periodontal disease.

Influence of Different Hydroxyapatite Particles on the Behavior of Highly Malignant Melanoma Cells

The aim of this study is to reveal the response of highly malignant tumor cell to different hydroxyapatite particles. Human’s highly malignant melanoma (MM) cell line A875 is exposed to two kinds of short-rod hydroxyapatite particles. After incubated with hydroxyapatite particles at different time points, the effects of MM cell morphology, proliferation and invasion are evaluated by SEM, MTT, and MMP2 protein immunohistochemistry respectively. SEM figures show that superficial sentus of MM cells reduce; more secretion is found; and smaller HA particles have more obvious effect. At the same time, no statistic difference can be found in MTT assay and MMP2 expression measurement. This study also provides useful information about biosecurity of hydroxyapatite ceramic in transplantation after highly malignant tumor excision.

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

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