Osseointegration of two types of titanium cylinders with geometric or trabecular microarchitecture: A nanotomographic and histomorphometric study.

Porous biomaterials promote osseointegration. We have prepared porous titanium cylinders by additive manufacturing from titanium beads. Two types of morphology were tested: cylinders with geometric pores or mimicking trabecular microarchitecture. Cylinders were decontaminated and cleaned by HF/HNO3 to remove unmelted balls. Surgical implantation in ewes was performed under general anesthesia and the animals were housed for 90 and 270days. The femoral condyles were collected and analyzed by nanoCT, embedded in pMMA and analyzed by histomorphometry. No significant difference was found in terms of bone volume or bone/titanium interface between the two types of cylinders. There was no evolution over time except for the mineralization rates which decreased, reflecting the effect of the aging of the animals. The influence of the pores (geometrical or "natural") did not influence osseointegration. HF/HNO3 etching treatments are effective on the outermost surfaces but do not seem to reach the central cavities of the samples. Finally, osseointegration seems to occur only in the few millimeters around the periphery of the implants and does not extend in the center. This is explained by the absence of stress transmission within the very rigid metal cylinders, preventing bone modeling and remodeling.

Hyaluronic Acid Stimulates Osseointegration of ß-TCP in Young and Old Ewes.

Cross-linked hyaluronic acid (HyAR) increases the local concentration of growth factors. We compared ß-TCP osseointegration in old and young ewes with/without HyAR addition. A blind tunnel was drilled on the medial femoral condyle of each knee in nine young and nine old ewes and was filled with ß-TCP, ß-TCP + HyAR or left unfilled. Double labeling with calcein allowed histodynamic analysis. Ewes were sacrificed at 84 days and the knees were harvested. MicroCT provided histomorphometric parameters: trabecular bone volume, residual volume of biomaterial. Histodynamic parameters were: mineralization rate, mineralized surfaces, bone formation rate. A non-parametric ANOVA and post hoc test analyzed differences between subgroups. Osseointegration of ß-TCP was similar in the aged/young grafted groups. Trabecular bone volume was significantly increased versus ungrafted animals (p < 0.001). There were no significant difference for bone volume, residual volume of biomaterial and histodynamic parameters when a single parameter was considered but additional effects of ß-TCP and HyAR were evidenced by 3D analysis. Addition of HyAR to ß-TCP does not significantly increase bone volume but tends to increase histodynamic parameters. However, considering the reduction of osteoblastic activity in aged animals, ß-TCP, and HyAR boosts osteoblastic activity. HyAR leads to an equivalent response between young and old animals.

Polyhydroxyalkanoate (PHBV) fibers obtained by a wet spinning method: Good in vitro cytocompatibility but absence of in vivo biocompatibility when used as a bone graft.

Polyhydroxyalkanoates (PHAs) are biomaterials widely investigated for tissue-engineering applications. In this regard, we describe a method to prepare fibers of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) by a wet-spinning technique. Polymer fibers were used to test the cytocompatibility of the material in vitro. We have investigated their behavior in vitro in presence of the osteoblast-like (SaOs2) and macrophage (J774.2) cell lines. The PHBV fibers used were 100-200µm in diameter and offered a large surface for cell adhesion, similar to that they encounter when apposed onto a bone trabeculae. The fiber surface possessed a suitable roughness, a factor known to favor the adherence of cells, particularly osteoblasts. PHBV fibers were degraded in vitro by J774.2 cells as erosion pits were observable by transmission electron microscopy. The fibers were also colonisable by SaOs2 cells, which can spread and develop onto their surface. However, despite this good cytocompatibility observed in vitro, implantation in a bone defect drilled in rabbit femoral condyles showed that the material was only biotolerated without any sign of osteoconduction or degradation in vivo. We can conclude that PHBV is cytocompatible but is not suitable to be used as a bone graft as it does not favor osteoconduction and is not resorbed by bone marrow macrophages.

Microcomputed tomography (microCT) and histology of the mandibular canal in human and laboratory animals.

The inferior alveolar nerve (IAN) is a sensitive branch of the trigeminal nerve. It has an intra-bone path in the mandible, inside the mandibular canal, where it is accompanied by lymph, venous and arterial vessels. We have studied the mandibular canal in human mandibles and in some laboratory animals (mice, rats, rabbits and cats). Microcomputed tomography evidenced that the walls of the canal are made with thin plates of trabecular bone with numerous fenestrations. This aspect is evidenced in dentate subjects and become more evident in edentulous subjects with atrophy of the alveolar bone. In rats and mice, the wall of the canal is also clearly composed of trabecular plates coming from the surrounding alveolar bone of the mandible. In the rabbit, similar findings are also observed but the trajectory of the canal is more difficult to identify. In the cat, the floor of the canal is composed of the cortical bone from the basilar cortex of the mandible and the roof has a trabecular nature. Vascular injections of gelatin-barium evidenced the arterial trajectories inside the bone in rats and humans. Undecalcified bone sections in human evidenced the histological aspect of the IAN and its connective sheets. Some nervous bundles can be observed outside the epineurium. Bone remodeling is observed on the wall of the mandibular canal. These descriptive findings have a clinical relevance in dental implantology or mandibular surgery.

Immune modulation by the hepatitis C virus core protein.

Hepatitis C virus (HCV) infection is currently the most important cause of chronic viral hepatitis in the world and one of the most frequent indications for liver transplantation. HCV uses different strategies to evade the innate and adaptive immune response, and this evasion plays a key role in determining viral persistence. Several HCV viral proteins have been described as immune modulators. In this review, we will focus on the effect of HCV nucleocapsid core protein in the function of immune cells and its correlation with the findings observed in HCV chronically infected patients. Effects on immune cell function related to both extracellular and intracellular HCV core localization will be considered. This review provides an updated perspective on the mechanisms involved in HCV evasion related to one single HCV protein, which could become a key tool in the development of new antiviral strategies able to control and/or eradicate HCV infection.

Phorbol ester-mediated re-expression of endogenous LAT adapter in J.CaM2 cells: a model for dissecting drivers and blockers of LAT transcription.

Linker for activation of T cells (LAT) is a raft-associated, transmembrane adapter protein critical for T-cell development and function. LAT expression is transiently upregulated upon T-cell receptor (TCR) engagement, but molecular mechanisms conveying TCR signaling to enhanced LAT transcription are not fully understood. Here we found that a Jurkat subline J.CaM2, initially characterized as LAT deficient, conditionally re-expressed LAT upon the treatment with a protein kinase C activator, phorbol 12-myristate 13-acetate (PMA). We took advantage of the above observation for studying cis-elements and trans-acting factors contributing to the activation-induced expression of LAT. We identified a LAT gene region spanning nucleotide position -14 to +357 relative to the ATG start codon as containing novel cis-regulatory elements that were able to promote PMA-induced reporter transcription in the absence of the core LAT promoter. Interestingly, a point mutation in LAT intron 1, identified in J.CaM2 cells, downmodulated LAT promoter activity by 50%. Mithramycin A, a selective Sp1 DNA-binding inhibitor, abolished LAT expression upon PMA treatment as did calcium ionophore ionomycin (Iono) and valproic acid (VPA), widely used as an anti-epileptic drug. Our data introduce J.CaM2 cells as a model for dissecting drivers and blockers of activation induced expression of LAT.

Identification of functional, short-lived isoform of linker for activation of T cells (LAT).

Linker for activation of T cells (LAT) is a transmembrane adaptor protein playing a key role in the development, activation and maintenance of peripheral homeostasis of T cells. In this study we identified a functional isoform of LAT. It originates from an intron 6 retention event generating an in-frame splice variant of LAT mRNA denoted as LATi6. Comparison of LATi6 expression in peripheral blood leukocytes of human and several other mammalian species revealed that it varied from being virtually absent in the mouse to being predominant in the cow. Analysis of LAT isoform frequency expressed from minigene splicing reporters carrying loss- or gain-of-function point mutations within intronic polyguanine sequences showed that these elements are critical for controlling the intron 6 removal. The protein product of LATi6 isoform (LATi6) ectopically expressed in LAT-deficient JCam 2.5 cell line localized correctly to subcellular compartments and supported T-cell receptor signaling but differed from the canonical LAT protein by displaying a shorter half-life and mediating an increased interleukin-2 secretion upon prolonged CD3/CD28 crosslinking. Altogether, our data suggest that the appearance of LATi6 isoform is an evolutionary innovation that may contribute to a more efficient proofreading control of effector T-cell response.

Observation of low- and high-energy Gamow-Teller phonon excitations in nuclei.

Gamow-Teller (GT) transitions in atomic nuclei are sensitive to both nuclear shell structure and effective residual interactions. The nuclear GT excitations were studied for the mass number A = 42, 46, 50, and 54 "f-shell" nuclei in ((3)He, t) charge-exchange reactions. In the (42)Ca → (42)Sc reaction, most of the GT strength is concentrated in the lowest excited state at 0.6 MeV, suggesting the existence of a low-energy GT phonon excitation. As A increases, a high-energy GT phonon excitation develops in the 6-11 MeV region. In the (54)Fe → (54)Co reaction, the high-energy GT phonon excitation mainly carries the GT strength. The existence of these two GT phonon excitations are attributed to the 2 fermionic degrees of freedom in nuclei.

A case of polyostotic osteosarcoma with kidney metastases in a dog: histopathology and microcomputed tomographic analysis.

A 7-year- old sexually intact female Leonberg dog was evaluated for chronic lameness of the right forelimb. The bitch showed mild hyperthermia (39.3°C), a decrease in its activity, a capricious appetite, a high weight loss (4 kg in 15 days) and a right foreleg lameness. A careful clinical examination revealed a deformation of the right proximal humerus and right tibia. Radiographic examination of the right tibia, right humerus showed osteolysis of both cortical and trabecular bone with a periosteal bone proliferation in the vicinal soft tissues. The owner having refused a bone biopsy, a treatment with NSAIDs and antibiotics was prescribed. After a marked improvement during the first two weeks, an increase in lameness and activity was observed. At that time, the owner accepted the bone biopsy. Histopathologic examination evidenced an osteosarcoma but the amount of available tissue was limited. Due to the poor prognosis, he declined treatment and decided to euthanize the dog. An osteosarcoma with a large chondroid component was observed at autopsy together with ossifying kidney metastases. Histological findings revealed a grade III osteosarcoma. Conventional and undecalcified histology and X-ray microcomputed tomography findings evidenced a large and partially mineralized osteoid part with a sunburst extension in the soft tissues. This is the first time that microCT and undecalcified analyses of an osteosarcoma are presented. The osteolytic and metaplastic bone foci were easily demonstrated by this method.

Changes in exhaled nitric oxide after inhalation challenge with occupational agents.

BACKGROUND AND OBJECTIVE: The use of fractional exhaled nitric oxide (FeNO) concentration has been proposed as a surrogate marker for monitoring airway response to specific inhalation challenge (SIC). We investigated the usefulness of FeNO measurements for monitoring airway response to SIC with occupational agents. Materialandmethods: Workers with suspected occupational asthma were recruited to undergo SIC with occupational agents and subsequently FeNO testing at baseline and 24 hours. RESULTS: Sixty-eight patients were evaluated, 45 of whom had a positive SIC. SIC-positive patients showed a significant increase in FeNO 24 hours postchallenge, with an increase ratio of 1.25 (95% CI, 1.05-1.48; P=.01); no increase was seen in patients with a negative SIC (P=.08). The predictive capacity of variations in FeNO showed that for each unit increase in FeNO, the probability of a positive SIC rose by 4%. A baseline FeNO value of 25 ppb predicted a positive SIC with 60% sensitivity and 80% specificity. The increase in %FeNO cutoff point providing maximal sensitivity and specificity for predicting a positive SIC was 41% (sensitivity 50%, specificity 95%). CONCLUSIONS: We demonstrated that asthmatic reactions induced by occupational agents during SICs are associated with a consistent increase in FeNO. However, the predictive diagnostic capacity of FeNO measurements is low. While FeNO may aid in the interpretation of SIC in some cases, it cannot be used as a general surrogate marker to predict or to assess SICs with occupational agents.

Tropomyosin IgE-positive results are a good predictor of shrimp allergy.

BACKGROUND: Shrimp is a common cause of food allergy. Our aims were to determine the value of IgE antibodies in the diagnosis of shrimp allergy and to study red shrimp (Solenocera melantho) tropomyosin both as a new allergen and as a cross-reactive IgE-binding protein. METHODS: We have studied 45 subjects. Skin prick test (SPT) was carried out in all subjects, and specific IgE (sIgE) to shrimp, recombinant and natural shrimp tropomyosins rPen a 1 and nPen m 1, recombinant Der p 10, and Dermatophagoides pteronyssinus was assessed by fluoroimmunoassay and/or immunoblotting. Double-blind, placebo-controlled food challenges were carried out to confirm diagnosis of shrimp allergy. Also, in vitro inhibition tests were performed to evaluate cross-reactivity. RESULTS: Shrimp allergy was confirmed in 18 shrimp-allergic patients. Skin prick test and IgE antibodies to shrimp were positive in all shrimp-allergic patients; sIgE to rPen a 1 was detected in 98% of these patients. Of the 18 shrimp-tolerant patients, 61% had positive SPT to shrimp, 55% were IgE-positive to shrimp, and 33% showed IgE antibodies to rPen a 1. Determination of IgE to rPen a 1 yielded a positive predictive value of 0.72 and a negative predictive value of 0.91. CONCLUSION: IgE levels to rPen a 1 provided additional value to the diagnosis of shrimp allergy. Some allergens in mite extract are recognized by patients who are allergic to shrimp, though their clinical relevance remains unknown.

Does milling one-piece titanium dental implants induce osteocyte and osteoclast changes?

One-piece dental implants avoid adverse effects sometimes associated with the traditional implant-abutment interface and may provide a suitable alternative to two-piece implants; however, one-piece implants often need in situ milling, which may exacerbate cell apoptosis from excessive heat at the bone-implant interface and induce secondary crestal bone loss. Twelve implants were placed in the metaphyses of two sheep under general anesthesia. Six implants were milled with a diamond bur while the other six implants remained intact. Animals were euthanized after four days, and bone blocks were harvested. Bone samples were studied without decalcification. Osteocytes were stained with Hoechst 33342 and osteoclasts by the TRAcP reaction. Both cell types, in the cortical and trabecular bone around the implant's cervical region, were counted utilizing morphometric methods. Values were compared to areas at a distance from the cervical region. No difference was observed between milled and unmilled implants, which suggested that the amount of generated heat did not provoke osteocyte loss or induce osteoclastogenesis. Intraoral abutment preparations did not increase cellular apoptosis at the bone-implant interface after four days in the ovine model.

Biofunctionality of MBCP ceramic granules (TricOs) plus fibrin sealant (Tisseel) versus MBCP ceramic granules as a filler of large periprosthetic bone defects: an investigative ovine study.

We aimed to quantify bone colonization toward an untreated titanium implant with primary stability following filling of the defect with micromacroporous biphasic calcium phosphate (MBCP) granules (TricOs) or MBCP granules mixed with fibrin sealant (Tisseel). Medial arthrotomy was performed on the knees of 20 sheep to create a bone defect (16 mm deep; 10 mm diameter), followed by anchorage of a titanium screw. Defects were filled with TricOs or TricOs-Tisseel granules, a perforated MBCP washer, a titanium washer and titanium screw. Sheep were euthanized at 3, 6, 12 and 26 weeks. From Week 12 onwards, the percentage of bone in contact with the 8 mm anchorage part of the screw increased in both groups, confirming its primary stability. At 26 weeks, whereas bone colonization was similar in both groups, biodegradation of ceramic was more rapid in the TricOs-Tisseel group (P = 0.0422). The centripetal nature of bone colonization was evident. Bone contact with the titanium implant surface was negligible. In conclusion, the use of a model that reproduces a large metaphyseal bone defect around a titanium implant with primary stability, filled with a mixture of either TricOs ceramic granules or TricOs granules mixed with Tisseel fibrin sealant, suggests that the addition of fibrin to TricOs enhances bone filling surgical technology.

Developments in injectable multiphasic biomaterials. The performance of microporous biphasic calcium phosphate granules and hydrogels.

Calcium phosphate bioceramic granules associated with hydrosoluble polymers were developed as bone substitutes for various maxillofacial and orthopaedic applications. These injectable bone substitutes, support and regenerate bone tissue and resorb after implantation. The efficiency of these multiphasic materials is due to the osteogenic and osteoconductive properties of the microporous biphasic calcium phosphate. The associated hydrosoluble polymers are considered as carriers in order to achieve the rheological properties of injectable bone substitutes (IBS). In this study, we used 2 semi synthetic hydrosoluble polymers of polysaccharidic origin. The hydroxy propyl methyl cellulose (HPMC), with and without silane, was combined with microporous BCP granules. The presence of silane induced considerable gelation of the suspension. The 2 IBS used (without gelation, IBS1, with gelation, IBS2) were implanted in critical size femoral epiphysis defects in rabbits. No foreign body reactions were observed in either sample. However, because of the higher density from gelation, cell colonisation followed by bone tissue ingrowth was delayed over time with IBS2 compared to the IBS1 without gelation. The results showed resorption of the BCP granule and bone ingrowth at the expense of both IBS with different kinetics. This study demonstrates that the hydrogel cannot be considered merely as a carrier. The gelation process delayed cell and tissue colonisation by slow degradation of the HPMC Si, compared to the faster release of HPMC with IBS1, in turn inducing faster permeability and spaces for tissue ingrowth between the BCP granules.

Finite element analysis of narrow dental implants.

Narrow-diameter implants (NDIs) traditionally have been associated to higher rates of failure in comparison with regular-diameter implants (RDIs) and wide-diameter implants (WDIs), since they generate a more unfavorable stress distribution in peri-implant bone. However, it is well known that the load sharing effect associated with prostheses supported by multiple implants (also called splinted prostheses) affords mechanical benefits. The present study involves finite element analysis (FEA) to determine whether the risks linked to NDIs could be mitigated by the mechanical advantages afforded by the splinting concept. For this purpose, a three-dimensional (3D) model of a real maxilla was reconstructed from computed tomography (CT) images, and different implants (NDIs, RDIs and WDIs) and prostheses were created using computer-aided design (CAD) tools. Biting forces were simulated on the prostheses corresponding to three different rehabilitation solutions: single-implant restoration, three-unit bridge and all-on-four treatment. Stress distribution around the implants was calculated, and overloading in bone was quantified within peri-implant volumes enclosed by cylinders with a diameter 0.1mm greater than that of each implant. The mechanical benefits of the splinting concept were confirmed: the peri-implant overloaded volume around NDIs splinted by means of the three-unit bridge was significantly reduced in comparison with the nonsplinted condition and, most importantly, proved even smaller than that around nonsplinted implants with a larger diameter (RDIs). However, splinted NDIs supporting the all-on-four prosthesis led to the highest risk of overloading found in the study, due to the increase in compressive stress generated around the tilted implant when loading the cantilevered molar.

Gas phase dehydration of glycerol to acrolein over WO3-based catalysts prepared by non-hydrolytic sol-gel synthesis.

Solid acid catalysts based on WO3-SiO2 and WO3-ZrO2-SiO2 were prepared by one-pot non-hydrolytic sol-gel method and tested in the gas phase glycerol dehydration to acrolein. Their structural and textural characteristics were determined by X-ray diffraction (XRD), N2 adsorption, X-ray energy dispersive spectroscopy (XEDS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Their acid characteristics were studied by both temperature programmed desorption of ammonia (NH3-TPD) and FTIR of adsorbed pyridine. Under our operating conditions, all the catalysts were active and selective in the transformation of glycerol to acrolein, which was always the main reaction product. The high selectivity to acrolein is achieved on catalysts presenting a higher proportion of Brønsted acid sites. In addition, the role of oxygen in the feed on catalytic performance of these catalysts is also discussed.

[Experimental evaluation of microscan assessment of bone fusion]. / Etude expérimentale de la microtomographie X dans l'évaluation de la fusion osseuse.

PURPOSE OF THE STUDY: Certain confirmation of bone fusion remains difficult to obtain after arthrodesis despite progress in imaging techniques. Microscanning enables both qualitative and quantitative analysis of the bone microarchitecture. The purpose of this study was to evaluate this technique using a cervical arthrodesis with an intersomatic cage on an animal model and to validate results with histological analysis and electron scan microscopy (SEM). MATERIAL AND METHODS: C3-C4 discectomy was performed in 8 goats divided into two groups. In group 1 (3 animals), PEEK cages were inserted without bone graft. In group 2 (5 goats) the same cage was inserted and filled with an autologous iliac graft. The animals were sacrificed at six months. The instrumented levels were analyzed with a microscan. Histological slides were obtained and SEM performed. RESULTS: Nonunion was observed in the three animals with an empty cage (group 1) while only one animal in group 2 presented nonunion. Histology and SEM confirmed the diagnosis established with the microscan which also enabled a 3D analysis of the sample and study of the trabecular architecture of the intersomatic graft. DISCUSSION: The microscan enabled a micrometric analysis of the sample. This is the only technique enabling 3D analysis (slices can be obtained in the three planes for 3D reconstruction) for both qualitative and quantitative assessment. Analysis of the trabecular microstructure constitutes a major progress in evaluating the mechanical value of the fusion. The sample is not destroyed and can be studied further with other biomechanical techniques. CONCLUSION: Microscanning is an important technical advancement for the analysis of bone fusion. Future applications will undoubtedly be numerous (follow-up after arthrodesis, analysis of the mechanical quality of a graft). In vivo applications will probably be adapted soon.

Functional expression of CD43 on human natural killer cells.

CD43 is the major leukocyte sialoglyco-protein that plays important functional roles in neutrophils and lymphocytes. However, the expression of CD43 on human natural killer (NK) cells and its participation in the regulation of NK activity has not been studied. We have therefore investigated the expression of CD43 isoforms on human NK cell subpopulations as well as the role of this molecule in NK cell activation and cytotoxicity. We found that CD56bright and CD56dim NK cells express different sialylated forms of CD43, observing that activation of the CD56bright NK cells induces the change of tetrasaccharide O-glycans to hexasaccharide O-glycans on CD43. Cross-linking of the molecule with mAbs results in a metalloprotease-dependent loss of CD43 from the NK cell surface, whereas soluble anti-CD43 mAbs induce a vigorous NK cell proliferation. This property is distinct from T cells, which proliferate after CD43 cross-linking only in the presence of monocytes. Occupancy of the CD43 receptor on NK cells transduces specific signals, leading to enhanced killing activity and tyrosine phosphorylation and de-phosphorylation of several substrates. We therefore propose that CD43 significantly contributes to the regulation of the NK cell function by participating in the control of effector/target interactions and, if pertinent, by transducing activation signals.