Osteogenesis and osteoclastogenesis on a chip: Engineering a self-assembling 3D coculture

Healthy bone is maintained by the process of bone remodeling. An unbalance in this process can lead to pathologies such as osteoporosis which are often studied with animal models. However, data from animals have limited power in predicting the results that will be obtained in human clinical trials. In search for alternatives to animal models, human in vitro models are emerging as they address the principle of reduction, refinement, and replacement of animal experiments (3Rs). At the moment, no complete in vitro model for bone-remodeling exists. Microfluidic chips offer great possibilities, particularly because of the dynamic culture options, which are crucial for in vitro bone formation. In this study, a scaffold free, fully human, 3D microfluidic coculture model of bone remodeling is presented. A bone-on-a-chip coculture system was developed in which human mesenchymal stromal cells differentiated into the osteoblastic lineage and self-assembled into scaffold free bone-like tissues with the shape and dimensions of human trabeculae. Human monocytes were able to attach to these tissues and to fuse into multinucleated osteoclast-like cells, establishing the coculture. Computational modeling was used to determine the fluid flow induced shear stress and strain in the formed tissue. Furthermore, a set-up was developed allowing for long-term (35 days) on-chip cell culture with benefits including continuous fluid-flow, low bubble formation risk, easy culture medium exchange inside the incubator and live cell imaging options. This on-chip coculture is a crucial advance towards developing in vitro bone remodeling models to facilitate drug testing.

Buried graphene heterostructures for electrostatic doping of low-dimensional materials

The fabrication and characterization of steep slope transistor devices based on low-dimensional materials requires precise electrostatic doping profiles with steep spatial gradients in order to maintain maximum control over the channel. In this proof-of-concept study we present a versatile graphene heterostructure platform with three buried individually addressable gate electrodes. The platform is based on a vertical stack of embedded titanium and graphene separated by an intermediate oxide to provide an almost planar surface. We demonstrate the functionality and advantages of the platform by exploring transfer and output characteristics at different temperatures of carbon nanotube field-effect transistors with different electrostatic doping configurations. Furthermore, we back up the concept with finite element simulations to investigate the surface potential. The presented heterostructure is an ideal platform for analysis of electrostatic doping of low-dimensional materials for novel low-power transistor devices.

Transfer-free graphene passivation of sub 100 nm thin Pt and Pt–Cu electrodes for memristive devices

Memristive switches are among the most promising building blocks for future neuromorphic computing. These devices are based on a complex interplay of redox reactions on the nanoscale. Nanoionic phenomena enable non-linear and low-power resistance transition in ultra-short programming times. However, when not controlled, the same electrochemical reactions can result in device degradation and instability over time. Two-dimensional barriers have been suggested to precisely manipulate the nanoionic processes. But fabrication-friendly integration of these materials in memristive devices is challenging.Here we report on a novel process for graphene passivation of thin platinum and platinum/copper electrodes. We also studied the level of defects of graphene after deposition of selected oxides that are relevant for memristive switching.

Updated S2 K guidelines for the management of bullous pemphigoid initiated by the European Academy of Dermatology and Venereology (EADV)

BACKGROUND

Bullous pemphigoid (BP) is the most common autoimmune subepidermal blistering disease of the skin and mucous membranes. This disease typically affects the elderly and presents with itch and localized or, most frequently, generalized bullous lesions. A subset of patients only develops excoriations, prurigo-like lesions, and eczematous and/or urticarial erythematous lesions. The disease, which is significantly associated with neurological disorders, has high morbidity and severely impacts the quality of life.

OBJECTIVES AND METHODOLOGY

The Autoimmune blistering diseases Task Force of the European Academy of Dermatology and Venereology sought to update the guidelines for the management of BP based on new clinical information, and new evidence on diagnostic tools and interventions. The recommendations are either evidence-based or rely on expert opinion. The degree of consent among all task force members was included.

RESULTS

Treatment depends on the severity of BP and patients' comorbidities. High-potency topical corticosteroids are recommended as the mainstay of treatment whenever possible. Oral prednisone at a dose of 0.5 mg/kg/day is a recommended alternative. In case of contraindications or resistance to corticosteroids, immunosuppressive therapies, such as methotrexate, azathioprine, mycophenolate mofetil or mycophenolate acid, may be recommended. The use of doxycycline and dapsone is controversial. They may be recommended, in particular, in patients with contraindications to oral corticosteroids. B-cell-depleting therapy and intravenous immunoglobulins may be considered in treatment-resistant cases. Omalizumab and dupilumab have recently shown promising results. The final version of the guideline was consented to by several patient organizations.

CONCLUSIONS

The guidelines for the management of BP were updated. They summarize evidence- and expert-based recommendations useful in clinical practice.

A new semi-orthotopic bone defect model for cell and biomaterial testing in regenerative medicine

In recent decades, an increasing number of tissue engineered bone grafts have been developed. However, expensive and laborious screenings in vivo are necessary to assess the safety and efficacy of their formulations. Rodents are the first choice for initial in vivo screens but their size limits the dimensions and number of the bone grafts that can be tested in orthotopic locations. Here, we report the development of a refined murine subcutaneous model for semi-orthotopic bone formation that allows the testing of up to four grafts per mouse one order of magnitude greater in volume than currently possible in mice. Crucially, these defects are also "critical size" and unable to heal within the timeframe of the study without intervention. The model is based on four bovine bone implants, ring-shaped, where the bone healing potential of distinct grafts can be evaluated in vivo. In this study we demonstrate that promotion and prevention of ossification can be assessed in our model. For this, we used a semi-automatic algorithm for longitudinal micro-CT image registration followed by histological analyses. Taken together, our data supports that this model is suitable as a platform for the real-time screening of bone formation, and provides the possibility to study bone resorption, osseointegration and vascularisation.

Artificial intelligence to improve decision making in transcatheter aortic valve implantation

Background

The current state of the art in the diagnosis and treatment of cardiovascular diseases has been based on evidence resulting from traditional trials as well as years of clinical experience. Due to interindividual differences and a huge number of possible cofounders, in interventional cardiology a linear algorithm is usually not able to precisely estimate individual risk, therapy, or outcome. With the technological evolution in deep machine learning (ML) and artificial intelligence (AI), clinicians may now address aspects that might not have been investigated previously, as supercomputers may handle the plethora of data that are generated as part of treatment. Ultimately, treatment recommendations and decisions may be made on a personalized level.

Purpose

The aim of this study was to apply AI to routine clinical practice to improve decision making in transcatheter aortic valve implantation (TAVI) to determine the best type and size of prosthesis personalized for each patient with pre-procedural risk stratification.

Methods

All patients included in the study were undergoing TAVI. To predict the clinical outcomes we applied a random forest classification, a ML method with high interpretability. For baseline data 58 features were chosen, including valve type and size used. After removing highly collinear features with a certain variance inflation factor, feature selection was based on impurity-based feature importance as well as permutation importance. The performance of the estimators was evaluated by a five-fold nested stratified cross-validation. To evaluate the model ROC and mean AUC scores were chosen.

Results

A total of 3882 patient datasets were included in this trial. The baseline characteristics were consistent with a high cardiovascular risk typical of this collective. Device success was achieved in 83.3%, pacemaker implantation was necessary in 12.2%, and aortic valvular insufficiency was observed in 2.5%. The 30-day mortality was 3.4% and one-year mortality was 12.7%. The mean AUC for the outcome parameters device success, aortic valvular insufficiency, any pacemaker operation, and 30-day and one-year mortality after five-fold cross validation were 0.61±0.03, 0.71±0.04, 0.66±0.04, 0.67±0.03, and 0.69±0.01, respectively.

Conclusions

We report preliminary data concerning a promising method to improve decision making in the context of TAVI evaluation and planning using ML algorithm. We showed the feasibility with acceptable AUC values for all outcome parameters. Thus, the integration of AI in TAVI strategy planning process offers a valuable tool providing patient focused personalized therapy.

Funding Acknowledgement

Type of funding sources: None.

A two-stage approach to primary TKA using articulating antibiotic-loaded spacers improve function and eradicate infection in septic arthritic knees

PURPOSE

The treatment of an infected arthritic knee might be challenging. The failure rate has been reported to be high for open or arthroscopic debridement. A subsequently high rate of infection has been noted in these patients undergoing primary total knee arthroplasty (TKA). In the present study, a two-stage approach using an articulating spacer was used. The hypothesis was that the procedure would eradicate the infection and improve pain and function in these patients.

METHODS

A total of 16 consecutive patients were enrolled in this retrospective study. The mean follow-up time was 6.1 years (range 2.0-9.9 years). Patients with advanced osteoarthritis and infection of the knee were included. All patients had previously undergone one or more failed arthroscopic or open procedures for the eradication of infection. All patients received the same homemade metal-on-plastic articulating antibiotic spacer. Double antibiotic therapy was given for 2 weeks intravenously and orally for 4 weeks. TKA implantation was performed 6 weeks after the first stage.

RESULTS

The infection was eradicated without recurrence in all patients. The functional results were significantly improved, and pain was significantly reduced after spacer and TKA implantation. The mean amount of knee flexion was 95 ± 30° preoperatively, and it increased to 109 ± 14° (p = 0.012) after spacer implantation and to 119 ± 10° (p = 0.002) after TKA implantation. The mean KSS objective was 58 ± 12 preoperatively, and it increased to 75 ± 14 (p < 0.0001) after spacer implantation and to 96 ± 3 (p < 0.0001) after TKA implantation. The mean KSS function was 17 ± 11 preoperatively, and it increased to 46 ± 10 (p < 0.0001) after spacer implantation and to 86 ± 6 (p < 0.0001) after TKA implantation. The mean VAS score was 65 ± 11 preoperatively, and it decreased to 2 ± 4 (p < 0.0001) after spacer implantation and to 1 ± 2 (p < 0.0001) after TKA implantation.

CONCLUSION

The two-stage procedure for the treatment of infected arthritic knees after failed eradication surgery was effective in all patients. Using an antibiotic articulating metal-on-plastic cement spacer showed improved functional results between the stages and at the final follow-up. No intra- or postoperative complications occurred.

The chloride channel CFTR is not required for cyst growth in an ADPKD mouse model

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by the development of bilateral renal cysts which enlarge continuously, leading to compression of adjacent intact nephrons. The growing cysts lead to a progressive decline in renal function. Cyst growth is driven by enhanced cell proliferation and chloride secretion into the cyst lumen. Chloride secretion is believed to occur mainly by the cAMP-activated cystic fibrosis transmembrane conductance regulator (CFTR), with some contribution by the calcium-activated chloride channel TMEM16A. However, our previous work suggested TMEM16A as a major factor for renal cyst formation. The contribution of CFTR to cyst formation has never been demonstrated in an adult ADPKD mouse model. We used mice with an inducible tubule-specific Pkd1 knockout, which consistently develop polycystic kidneys upon deletion of Pkd1. Cellular properties, ion currents, and cyst development in these mice were compared with that of mice carrying a co-deletion of Pkd1 and Cftr. Knockout of Cftr did not reveal any significant impact on cyst formation in the ADPKD mouse model. Furthermore, knockout of Cftr did not attenuate the largely augmented cell proliferation observed in Pkd1 knockout kidneys. Patch clamp analysis on primary renal epithelial cells lacking expression of Pkd1 indicated an only marginal contribution of CFTR to whole cell Cl^- currents, which were clearly dominated by calcium-activated TMEM16A currents. In conclusion, CFTR does not essentially contribute to renal cyst formation in mice caused by deletion of Pkd1. Enhanced cell proliferation and chloride secretion is caused primarily by upregulation of the calcium-activated chloride channel TMEM16A.

Induktion einer strickleiterartigen Narbe an der Wange einer 28-jährigen Frau nach Laserung eines Naevus araneus mittels KTP-Laser

Die 28-jährige Patientin stellte sich zur Behandlung einer kosmetisch störenden Gefäßläsion an der Wange vor. Es wurde eine Lasertherapie vorgeschlagen und vereinbart. Es entstanden unmittelbar nach der Laserbehandlung Schmerzen und eine Rötung; später eine entstellende Narbe.

Die Gutachter der Gutachterkommission bei der Ärztekammer Nordrhein beurteilten die Behandlung als fehlerhaft.

Laserbehandlungen zählen insgesamt zu den risikoreicheren Therapien in der Dermatologie. Häufiger als andere Behandlungsoptionen beurteilen die Begutachter die Behandlungen als fehlerhaft.

Patientensicherheit: Die Lasertherapie gehört zu den risikoreicheren Therapieoptionen in der Dermatologie

Seit der Erstbeschreibung von Lasern und den ersten Anwendungen in der Dermatologie hat die Lasertherapie innerhalb des dermatologischen therapeutischen Armamentariums enorm an Bedeutung zugenommen.

Da sie häufig bei ästhetischen Indikationen Anwendung findet, sind hohe Sicherheitsanforderungen zu gewährleisten, ansonsten kommt es zu unangenehmen juristischen Streitigkeiten. Eine retrospektive Analyse anhand der Fälle der Gutachterkammer für ärztliche Behandlungsfehler hat gezeigt, dass Lasertherapien zu den risikoreicheren therapeutischen Optionen in der Dermatologie gehören.

Ex vivo Bone Models and Their Potential in Preclinical Evaluation

PURPOSE OF REVIEW

Novel therapies for damaged and diseased bone are being developed in a preclinical testing process consisting of in vitro cell experiments followed by in vivo animal studies. The in vitro results are often not representative of the results observed in vivo. This could be caused by the complexity of the natural bone environment that is missing in vitro. Ex vivo bone explant cultures provide a model in which cells are preserved in their native three-dimensional environment. Herein, it is aimed to review the current status of bone explant culture models in relation to their potential in complementing the preclinical evaluation process with specific attention paid to the incorporation of mechanical loading within ex vivo culture systems.

RECENT FINDINGS

Bone explant cultures are often performed with physiologically less relevant bone, immature bone, and explants derived from rodents, which complicates translatability into clinical practice. Mature bone explants encounter difficulties with maintaining viability, especially in static culture. The integration of mechanical stimuli was able to extend the lifespan of explants and to induce new bone formation. Bone explant cultures provide unique platforms for bone research and mechanical loading was demonstrated to be an important component in achieving osteogenesis ex vivo. However, more research is needed to establish a representative, reliable, and reproducible bone explant culture system that includes both components of bone remodeling, i.e., formation and resorption, in order to bridge the gap between in vitro and in vivo research in preclinical testing.

International validation of the Bullous Pemphigoid Disease Area Index severity score and calculation of cut-off values for defining mild, moderate and severe types of bullous pemphigoid

BACKGROUND

The Bullous Pemphigoid Disease Area Index (BPDAI) score has been proposed to provide an objective measure of bullous pemphigoid (BP) activity.

OBJECTIVES

The objective of this study was to calculate BPDAI cut-off values defining mild, moderate and severe BP. We also aimed to assess the interrater reliability and correlation with the number of daily new blisters, and anti-BP180 and anti-BP230 antibodies.

METHODS

Severity scores were recorded by two blinded investigators. Anti-BP180 and anti-BP230 antibodies were measured using an enzyme-linked immunosorbent assay (ELISA). Cut-off values defining mild, moderate and severe subgroups were calculated based on the 25th and 75th percentiles of the BPDAI score.

RESULTS

In total, 285 patients with BP were enrolled from 50 dermatology departments in Europe. Median BPDAI activity was 37·5 points (range 0-164). Cut-off values corresponding to the first and third quartiles of the BPDAI score were 20 and 57, respectively; thus, these values were used to define mild (≤ 19), moderate (≥ 20 and ≤ 56) and severe (≥ 57) BP. The median BPDAI score for patients with ≤ 10 daily new blisters was 26 [interquartile range (IQR) 17-45], and for patients with > 10 daily new blisters the median score was 55 (IQR 39-82). The BPDAI intraclass correlation coefficient measured at baseline was 0·97 and remained higher than 0·90 up to month 6. The improvement in the BPDAI score was correlated with the absolute decrease in anti-BP180 ELISA value (Spearman's rank r = 0·34, P < 0·004), but not with anti-BP230 antibodies (r = 0·17, P = 0·15).

CONCLUSIONS

This study suggests cut-off values of 20-57 for BPDAI to distinguish mild, moderate and severe BP, and confirms that it is a robust tool to assess BP severity precisely.

Measuring mineralised tissue formation and resorption in a human 3D osteoblast-osteoclast co-culture model

In vitro tissue engineered bone constructs have been developed, but models which mimic both formation and resorption in parallel are still lacking. To be used as a model for the bone remodeling process, the formation and resorption of mineralised tissue volume over time needs to be visualised, localised and quantified. The goal of this study was to develop a human 3D osteoblast-osteoclast co-culture in which 1) osteoblasts deposit mineralised matrix, 2) monocytes differentiate into resorbing osteoclasts, and 3) the formation and resorption of mineralised matrix could be quantified over time using micro-computed tomography (μCT). Mesenchymal stromal cells were seeded on silk fibroin scaffolds and differentiated towards osteoblasts to create mineralised constructs. Thereafter, monocytes were added and differentiated towards osteoclasts. The presence of osteoblasts and osteoclasts was confirmed using immunohistochemistry. Osteoclastic activity was confirmed by measuring the increased release of osteoclast marker tartrate resistant acid phosphatase (TRAP), suggesting that osteoclasts were actively resorbing mineralised tissue. Resorption pits were visualised using scanning electron microscopy. Mineralised matrix formation and resorption were quantified using μCT and subsequent scans were registered to visualise remodelling. Both formation and resorption occurred in parallel in the co-culture. The resorbed tissue volume exceeded the formed tissue volume after day 12. In conclusion, the current model was able to visualise, localise and quantify mineralised matrix formation and resorption. Such a model could be used to facilitate fundamental research on bone remodeling, facilitate drug testing and may have clinical implications in personalised medicine by allowing the use of patient cells.

Long-Range Propagation and Interference of d-Wave Superconducting Pairs in Graphene

Recent experiments have shown that proximity with high-temperature superconductors induces unconventional superconducting correlations in graphene. Here, we demonstrate that those correlations propagate hundreds of nanometers, allowing for the unique observation of d-wave Andreev-pair interferences in YBa_{2}Cu_{3}O_{7}-graphene devices that behave as a Fabry-Perot cavity. The interferences show as a series of pronounced conductance oscillations analogous to those originally predicted by de Gennes-Saint-James for conventional metal-superconductor junctions. The present demonstration is pivotal to the study of exotic directional effects expected for nodal superconductivity in Dirac materials.

Localized Nanoresonator Mode in Plasmonic Microcavities

Submicron-thick hexagonal boron nitride crystals embedded in noble metals form planar Fabry-Perot half-microcavities. Depositing Au nanoparticles on top of these microcavities forms previously unidentified angle- and polarization-sensitive nanoresonator modes that are tightly laterally confined by the nanoparticle. Comparing dark-field scattering with reflection spectroscopies shows plasmonic and Fabry-Perot-like enhancements magnify subtle interference contributions, which lead to unexpected redshifts in the dark-field spectra, explained by the presence of these new modes.