Myocardial Inflammation, Measured Using 18-Fluorodeoxyglucose Positron Emission Tomography With Computed Tomography, Is Associated With Disease Activity in Rheumatoid Arthritis

OBJECTIVE

To determine the prevalence and correlates of subclinical myocardial inflammation in patients with rheumatoid arthritis (RA).

METHODS

RA patients (n = 119) without known cardiovascular disease underwent cardiac 18-fluorodeoxyglucose (FDG) positron emission tomography with computed tomography (PET-CT). Myocardial FDG uptake was assessed visually and measured quantitatively as the standardized uptake value (SUV). Multivariable linear regression was used to assess the associations of patient characteristics with myocardial SUVs. A subset of RA patients who had to escalate their disease-modifying antirheumatic drug (DMARD) therapy (n = 8) underwent a second FDG PET-CT scan after 6 months, to assess treatment-associated changes in myocardial FDG uptake.

RESULTS

Visually assessed FDG uptake was observed in 46 (39%) of the 119 RA patients, and 21 patients (18%) had abnormal quantitatively assessed myocardial FDG uptake (i.e., mean of the mean SUV [SUV_mean ] ≥3.10 units; defined as 2 SD above the value in a reference group of 27 non-RA subjects). The SUV_mean was 31% higher in patients with a Clinical Disease Activity Index (CDAI) score of ≥10 (moderate-to-high disease activity) as compared with those with lower CDAI scores (low disease activity or remission) (P = 0.005), after adjustment for potential confounders. The adjusted SUV_mean was 26% lower among those treated with a non-tumor necrosis factor-targeted biologic agent compared with those treated with conventional (nonbiologic) DMARDs (P = 0.029). In the longitudinal substudy, the myocardial SUV_mean decreased from 4.50 units to 2.30 units over 6 months, which paralleled the decrease in the mean CDAI from a score of 23 to a score of 12.

CONCLUSION

Subclinical myocardial inflammation is frequent in patients with RA, is associated with RA disease activity, and may decrease with RA therapy. Future longitudinal studies will be required to assess whether reduction in myocardial inflammation will reduce heart failure risk in RA.

Calibration of crushable foam plasticity models for synthetic bone material for use in finite element analysis of acetabular cup deformation and primary stability

Polyurethane (PU) foam is a material often used in biomechanical experiments and demands for the definition of crushable foam plasticity (CFP) in numerical simulations of the primary stability and deformation of implants, to describe the crushing behaviour appropriately. Material data of PU foams with five different densities (10-40 pounds per cubic foot were ascertained experimentally in uniaxial compression test and used to calibrate CFP models for finite element modelling. Additionally, experimental and numerical deformation, push-out and lever-out tests of press-fit acetabular cups were carried out to assess the influence of the chosen material definition (linear elastic and CFP) on the numerical results. Comparison of the experimentally and numerically determined force-displacement curves of the uniaxial compression test showed a mean deviation of less than 3%. In primary stability testing, the deviation between the experimental and numerical results was in a range of 0%-27% for CFP modelling and 64%-341% for the linear elastic model. The material definition selected, highly influenced the numerical results in the current study. The use of a CFP model is recommended for further numerical simulations, when a deformation of the foam beyond the yield strength is likely to occur.

Biomechanical behavior of modular acetabular cups made of poly-ether-ether-ketone: A finite element study

After total hip arthroplasty, stress-shielding is a potential risk factor for aseptic loosening of acetabular cups made of metals. This might be avoided by the use of acetabular cups made of implant materials with lower stiffness. The purpose of this numerical study was to determine whether a modular acetabular cup with a shell made of poly-ether-ether-ketone or poly-ether-ether-ketone reinforced with carbon fibers might be an alternative to conventional metallic shells. Therefore, the press-fit implantation of modular cups with shells made of different materials (Ti6Al4V, poly-ether-ether-ketone, and poly-ether-ether-ketone reinforced with carbon fibers) and varying liner materials (ceramics and ultra-high-molecular-weight polyethylene) into an artificial bone cavity was simulated using finite element analysis. The shell material had a major impact on the radial shell deformation determined at the rim of the shell, ranging from 17.9 µm for titanium over 92.2 µm for poly-ether-ether-ketone reinforced with carbon fibers up to 475.9 µm for poly-ether-ether-ketone. Larger radial liner deformations (up to 618.4 µm) occurred in combination with the shells made of poly-ether-ether-ketone compared to titanium and poly-ether-ether-ketone reinforced with carbon fibers. Hence, it can be stated that conventional poly-ether-ether-ketone is not a suitable shell material for modular acetabular cups. However, the radial shell deformation can be reduced if the poly-ether-ether-ketone reinforced with carbon fiber material is used, while deformation of ceramic liners is similar to the deformation in combination with titanium shells.

Ultrafast glutamate sensors resolve high-frequency release at Schaffer collateral synapses

Glutamatergic synapses display a rich repertoire of plasticity mechanisms on many different time scales, involving dynamic changes in the efficacy of transmitter release as well as changes in the number and function of postsynaptic glutamate receptors. The genetically encoded glutamate sensor iGluSnFR enables visualization of glutamate release from presynaptic terminals at frequencies up to ∼10 Hz. However, to resolve glutamate dynamics during high-frequency bursts, faster indicators are required. Here, we report the development of fast (iGlu f ) and ultrafast (iGlu u ) variants with comparable brightness but increased Kd for glutamate (137 μM and 600 μM, respectively). Compared with iGluSnFR, iGlu u has a sixfold faster dissociation rate in vitro and fivefold faster kinetics in synapses. Fitting a three-state model to kinetic data, we identify the large conformational change after glutamate binding as the rate-limiting step. In rat hippocampal slice culture stimulated at 100 Hz, we find that iGlu u is sufficiently fast to resolve individual glutamate release events, revealing that glutamate is rapidly cleared from the synaptic cleft. Depression of iGlu u responses during 100-Hz trains correlates with depression of postsynaptic EPSPs, indicating that depression during high-frequency stimulation is purely presynaptic in origin. At individual boutons, the recovery from depression could be predicted from the amount of glutamate released on the second pulse (paired pulse facilitation/depression), demonstrating differential frequency-dependent filtering of spike trains at Schaffer collateral boutons.

Effects of interfacial micromotions on vitality and differentiation of human osteoblasts

Objectives

Enhanced micromotions between the implant and surrounding bone can impair osseointegration, resulting in fibrous encapsulation and aseptic loosening of the implant. Since the effect of micromotions on human bone cells is sparsely investigated, an in vitro system, which allows application of micromotions on bone cells and subsequent investigation of bone cell activity, was developed.

Methods

Micromotions ranging from 25 µm to 100 µm were applied as sine or triangle signal with 1 Hz frequency to human osteoblasts seeded on collagen scaffolds. Micromotions were applied for six hours per day over three days. During the micromotions, a static pressure of 527 Pa was exerted on the cells by Ti6Al4V cylinders. Osteoblasts loaded with Ti6Al4V cylinders and unloaded osteoblasts without micromotions served as controls. Subsequently, cell viability, expression of the osteogenic markers collagen type I, alkaline phosphatase, and osteocalcin, as well as gene expression of osteoprotegerin, receptor activator of NF-κB ligand, matrix metalloproteinase-1, and tissue inhibitor of metalloproteinase-1, were investigated.

Results

Live and dead cell numbers were higher after 25 µm sine and 50 µm triangle micromotions compared with loaded controls. Collagen type I synthesis was downregulated in respective samples. The metabolic activity and osteocalcin expression level were higher in samples treated with 25 µm micromotions compared with the loaded controls. Furthermore, static loading and micromotions decreased the osteoprotegerin/receptor activator of NF-κB ligand ratio.

Conclusion

Our system enables investigation of the behaviour of bone cells at the bone-implant interface under shear stress induced by micromotions. We could demonstrate that micromotions applied under static pressure conditions have a significant impact on the activity of osteoblasts seeded on collagen scaffolds. In future studies, higher mechanical stress will be applied and different implant surface structures will be considered.

Cite this article: J. Ziebart, S. Fan, C. Schulze, P. W. Kämmerer, R. Bader, A. Jonitz-Heincke. Effects of interfacial micromotions on vitality and differentiation of human osteoblasts. Bone Joint Res 2018;7:187–195. DOI: 10.1302/2046-3758.72.BJR-2017-0228.R1.

PERKAT RV: first in vivo data of a novel right heart assist device

AIMS

Mechanical right ventricular (RV) support offers a treatment option for critically ill patients with RV failure (RVF). We developed an assist device for rapid percutaneous implantation. The aim of the present study was to investigate the implantation procedure, haemodynamic performance and possible side effects of the novel right ventricular assist device - PERKAT RV - in an animal model.

METHODS AND RESULTS

The PERkutane KATheterpumptechnologie RV (PERKAT RV) device consists of a nitinol chamber covered by foil containing inflow valves. An outlet tube is attached to its distal part. The system is designed for 18 Fr percutaneous implantation. The chamber is unfolded in the inferior vena cava while the outlet tube bypasses the right heart with the tip in the pulmonary trunk. An IABP balloon is placed inside. Balloon deflation generates blood flow into the chamber; during inflation, blood is guided into the pulmonary arteries. Acute RVF was induced by venous injection of Sephadex in seven sheep for evaluation of the device. The PERKAT RV was able to improve haemodynamics immediately generating a median increase in cardiac output of 59%. Longer pump support was evaluated in a second study. Four sheep were supported for eight hours without any problems.

CONCLUSIONS

The percutaneous implantation and explantation of the PERKAT RV device was possible in the designed way. The sheep studies proved beneficial haemodynamic effects in acute RVF. The system offers easy and safe treatment in acute RVF.

Mechanical Properties of a Newly Additive Manufactured Implant Material Based on Ti-42Nb

The application of Ti-6Al-4V alloy or commercially pure titanium for additive manufacturing enables the fabrication of complex structural implants and patient-specific implant geometries. However, the difference in Young’s modulus of α + β-phase Ti alloys compared to the human bone promotes stress-shielding effects in the implant–bone interphase. The aim of the present study is the mechanical characterization of a new pre-alloyed β-phase Ti-42Nb alloy for application in additive manufacturing. The present investigation focuses on the mechanical properties of SLM-printed Ti-42Nb alloy in tensile and compression tests. In addition, the raw Ti-42Nb powder, the microstructure of the specimens prior to and after compression tests, as well as the fracture occurring in tensile tests are characterized by means of the SEM/EDX analysis. The Ti-42Nb raw powder exhibits a dendrite-like Ti-structure, which is melted layer-by-layer into a microstructure with a very homogeneous distribution of Nb and Ti during the SLM process. Tensile tests display Young’s modulus of 60.51 ± 3.92 GPa and an ultimate tensile strength of 683.17 ± 16.67 MPa, whereas, under a compressive load, a compressive strength of 1330.74 ± 53.45 MPa is observed. The combination of high mechanical strength and low elastic modulus makes Ti-42Nb an interesting material for orthopedic and dental implants. The spherical shape of the pre-alloyed material additionally allows for application in metal 3D printing, enabling the fabrication of patient-specific structural implants.

Mast cells decrease efficacy of anti-angiogenic therapy by secreting matrix-degrading granzyme B

Resistance towards VEGF-centered anti-angiogenic therapy still represents a substantial clinical challenge. We report here that mast cells alter the proliferative and organizational state of endothelial cells which reduces the efficacy of anti-angiogenic therapy. Consequently, absence of mast cells sensitizes tumor vessels for anti-angiogenic therapy in different tumor models. Mechanistically, anti-angiogenic therapy only initially reduces tumor vessel proliferation, however, this treatment effect was abrogated over time as a result of mast cell-mediated restimulation of angiogenesis. We show that mast cells secrete increased amounts of granzyme b upon therapy, which mobilizes pro-angiogenic laminin- and vitronectin-bound FGF-1 and GM-CSF from the tumor matrix. In addition, mast cells also diminish efficacy of anti-angiogenic therapy by secretion of FGF-2. These pro-angiogenic factors act beside the targeted VEGFA–VEGFR2-axis and reinduce endothelial cell proliferation and angiogenesis despite the presence of anti-angiogenic therapy. Importantly, inhibition of mast cell degranulation with cromolyn is able to improve efficacy of anti-angiogenic therapy. Thus, concomitant mast cell-targeting might lead to improved efficacy of anti-angiogenic therapy.

Resistance towards VEGF-centered anti-angiogenic therapy is an important clinical challenge. Here, the authors show that mast cells mediate resistance to anti-angiogenetic inhibitors by altering the proliferative and organizational state of endothelial cells through mobilization of FGF-1 and GM-CSF from the tumor matrix and secretion of FGF-2.

Mechanical Stability of the Taper Connection of Large Metal Femoral Heads With Adapter Sleeves in Total Hip Arthroplasty Analyzed Using Explicit Finite Element Simulations

BACKGROUND

Large diameter heads (LDHs) of metal-on-metal bearings in total hip arthroplasty provide increased range of motion and reduced dislocation rates. However, major concerns grew over high wear rates from the modular connection between femoral stem and head, especially in combination with adapter sleeves.

METHODS

A computational study on the taper connection stability of LDH (50 mm) with adapter sleeves of different lengths (S, M, L, and XL) compared with a standard femoral head (32 mm) without adapter sleeves was conducted using explicit finite element analyses. Four different impact configurations were considered resulting from varied mallet mass (0.5 vs 1.0 kg) and velocity (1.0 vs 2.0 m/s). The taper stability was evaluated by determination of the pull-off forces and micromotions due to simulated joint loads during walking (2 kN and 7.9 Nm, respectively). Moreover, the deformations of the adapter sleeves and the contact area in the taper connections were evaluated.

RESULTS

Although the pull-off forces of the LDH with different-sized adapter sleeves were comparable, contact area decreased and adapter sleeve deformations increased (up to 283%) with an increasing adapter sleeve length. Moreover, the micromotions of LDH with adapter sleeves were up to 7-times higher, as compared with the standard femoral head without an adapter sleeve.

CONCLUSION

The present numerical study confirms that the assembly technique of LDH with adapter sleeves reveals increased micromotions compared with standard femoral head sizes. We could demonstrate that deviations of the stem trunnion geometry and improper surgical instructions led to worse mechanical stability of the taper connection.

Abstract 278: PGC1α Activation Corrects Cardiac Dysfunction Caused by Anti-diabetic Dual-PPARα/γ Therapy

Peroxisome proliferator-activated receptor (PPAR) agonists are used in metabolic diseases. PPARα agonists target hyperlipidemia and PPARγ agonists correct hyperglycemia. Dual PPARα/γ agonists were developed to combine the benefits in type 2 diabetes patients. Despite their beneficial effect, PPARα/γ agonists caused cardiac dysfunction. We studied the mechanisms that underlie this toxic effect aiming to improve a failed therapy.

Wild type mice were fed with chow and high fat diets containing Tesaglitazar (TESA) a dual PPARα/γ agonist for 6 weeks. Although, TESA lowered plasma triglyceride and glucose levels compared to controls, 2D-echo revealed severe cardiac dysfunction. Assessment of the expression of cardiac fatty acid metabolism genes that are regulated by PPARs showed that mRNA and protein levels of PPARγ-coactivator (PGC1α), a regulator of mitochondrial biogenesis, had the most profound reduction. Furthermore, we observed increased acetylation of PGC1α levels, which indicates lower activation and lower mitochondrial respiration.

We then examined the mechanisms that underlie lower expression of PGC1α upon activation of PPARα and PPARγ. Thus, we administered C57BL/6 mice with both single PPARα and PPARγ agonists (WY14643 and rosiglitazone). This treatment reproduced the reduction in PGC1α expression that we observed with TESA. Moreover, mitochondria abundance was lower. Luciferase promoter analysis in a human cardiomyocyte cell line showed that PPARα and PPARγ compete for binding on PPAR elements of the human Pgc1a promoter, as well as that PPARα binding compromises PPARγ-mediated activation of the Pgc1α promoter.

Aiming to decipher the mechanism via which dual PPARα/γ activation increases acetylation and thus inhibits PGC1α, we measured cardiac protein levels of the deacetylase sirtuin 1 (SIRT1), which were lower in primary cardiomyocytes from TESA-treated mice.

We then treated mice with diet containing TESA and Resveratrol (RSV), which stimulates SIRT1. RSV attenuated TESA-driven cardiac dysfunction and corrected mitochondrial respiratory rates in primary cardiomyocytes.

We propose that SIRT1-mediated activation of PGC1α blunts the cardiotoxic effect of dual PPARα/γ agonists and improves their therapeutic potential.

Biocompatibility and Inflammatory Potential of Titanium Alloys Cultivated with Human Osteoblasts, Fibroblasts and Macrophages

The biomaterials used to maintain or replace functions in the human body consist mainly of metals, ceramics or polymers. In orthopedic surgery, metallic materials, especially titanium and its alloys, are the most common, due to their excellent mechanical properties, corrosion resistance, and biocompatibility. Aside from the established Ti6Al4V alloy, shape memory materials such as nickel-titanium (NiTi) have risen in importance, but are also discussed because of the adverse effects of nickel ions. These might be reduced by specific surface modifications. In the present in vitro study, the osteoblastic cell line MG-63 as well as primary human osteoblasts, fibroblasts, and macrophages were cultured on titanium alloys (forged Ti6Al4V, additive manufactured Ti6Al4V, NiTi, and Diamond-Like-Carbon (DLC)-coated NiTi) to verify their specific biocompatibility and inflammatory potential. Additive manufactured Ti6Al4V and NiTi revealed the highest levels of metabolic cell activity. DLC-coated NiTi appeared as a suitable surface for cell growth, showing the highest collagen production. None of the implant materials caused a strong inflammatory response. In general, no distinct cell-specific response could be observed for the materials and surface coating used. In summary, all tested titanium alloys seem to be biologically appropriate for application in orthopedic surgery.

Cross-cultural validity of the German version of the Pediatric Evaluation of Disability Inventory (PEDI-G)-a Rasch model application

AIM

The aim of this study was to evaluate the cross-cultural validity of the German version of the Pediatric Evaluation of Disability Inventory (PEDI-G) when used in Austria, Germany and Switzerland.

METHOD

A total of 118 girls and 144 boys participated in this study; 198 of the children (75.6%) had a developmental disability and 64 (24.4%) were without a known disability. The mean age was four years (range 11 months to 10 years and six months, SD 1.91). Item goodness of fit, differential item functioning (DIF) and differential test functioning (DTF) were evaluated by use of a Rasch model.

RESULTS

Twenty-four (11.6%) out of 206 items of the Functional Skills Scale and one (5%) out of 20 items of the Caregiver Assistance Scale demonstrated misfit according to the Rasch model. Thirty-four (16.5%) out of 206 items of the Functional Skills Scale and no item from the Caregiver Assistance Scale demonstrated DIF. Almost half (46%) of the items demonstrating misfit also demonstrated DIF, indicating an association between them. The DIF by country only demonstrated a minimal impact on the person measures of the PEDI-G.

INTERPRETATION

Even though some items did not meet the statistical and clinical criteria set, the PEDI-G can be used, on a preliminary basis as a valid tool to measure activities of daily living of children with and without a disability in these countries. Further larger studies are needed to evaluate more psychometric item properties of the PEDI-G in relation to context.

Influence of different grained powders and pellets made of Niobium and Ti-42Nb on human cell viability

Nowadays, biomaterials can be used to maintain or replace several functions of the human body if necessary. Titanium and its alloys, i.e. Ti6Al4V are the most common materials (70 to 80%) used for structural orthopedic implants due to their unique combination of good mechanical properties, corrosion resistance and biocompatibility. Addition of β-stabilizers, e.g. niobium, can improve the mechanical properties of such titanium alloys further, simultaneously offering excellent biocompatibility. In this in vitro study, human osteoblasts and fibroblasts were cultured on different niobium specimens (Nb Amperit, Nb Ampertec), Nb sheets and Ti-42Nb (sintered and 3D-printed by selective laser melting, SLM) and compared with forged Ti6Al4V specimens. Furthermore, human osteoblasts were incubated with particulates of the Nb and Ti-42Nb specimens in three concentrations over four and seven days to imitate influence of wear debris. Thereby, the specimens with the roughest surfaces, i.e. Ti-42Nb and Nb Ampertec, revealed excellent and similar results for both cell types concerning cell viability and collagen synthesis superior to forged Ti6Al4V. Examinations with particulate debris disclosed a dose-dependent influence of all powders with Nb Ampertec showing the highest decrease of cell viability and collagen synthesis. Furthermore, interleukin synthesis was only slightly increased for all powders. In summary, Nb Ampertec (sintered Nb) and Ti-42Nb materials seem to be promising alternatives for medical applications compared to common materials like forged or melted Ti6Al4V.

A one-stage cultivation process for lipid- and carbohydrate-rich biomass of Scenedesmus obtusiusculus based on artificial and natural water sources

A one-stage cultivation process of the microalgae Scenedesmus obtusiusculus with medium based on natural water sources was developed to enhance lipids and carbohydrates. A medium based on artificial sea water, Baltic Sea water and river water with optimized nutrient concentrations compared to the standard BG-11 for nitrate (-75%), phosphate and iron (-90%) was used for cultivation. Although nitrate exhaustion over cultivation resulted in nitrate limitation, growth of the microalgae was not reduced. The lipid content increased from 6.0% to 19.9%, an increase in oleic and stearic acid was observed. The unsaponifiable matter of the lipid fraction was reduced from 19.5% to 11.4%. The carbohydrate yield rose from 45% to 50% and the protein content decreased from 32.4% to 15.9%. Using natural water sources with optimized nutrient concentrations could open the opportunity to modulate biomass composition and to reduce the cultivation costs.