Fibroblast activation protein inhibitor-positron emission tomography in aortitis: fibroblast pathology in active inflammation and remission.

OBJECTIVES: Epigenetically modified fibroblasts contribute to chronicity in inflammatory diseases. Reasons for the relapsing character of large vessel vasculitis (LVV) remain obscure, including the role of fibroblasts, in part due to limited access to biopsies of involved tissue.68Ga FAPI-46 (FAPI)-PET/CT detects activated fibroblasts in vivo. In this exploratory pilot study, we tested the detection of fibroblast activation in vessel walls using FAPI-PET/CT in LVV with aortitis. METHODS: Eight LVV patients with aortitis and eight age- and gender-matched controls were included. The distribution of FAPI uptake was evaluated in the aorta and large vessels. FAPI-uptake was compared with MRI inflammatory activity scores. Imaging results were compared with clinical parameters such as serum inflammatory markers, time of remission and medication. RESULTS: Three aortitis patients were clinically active and five in remission. Irrespective of activity, FAPI uptake was significantly enhanced in aortitis compared with controls. Patients in remission had a mean duration of remission of 2.8 years (range 1-4 years), yet significant FAPI uptake in the vessel wall was found. In remitted aortitis, MRI inflammatory scores were close to be negative, while in 4/5 patients visually identifiable FAPI uptake was observed. CONCLUSIONS: This pilot feasibility study shows significant tracer uptake in the aortic walls in LVV. FAPI positivity indicates ongoing fibroblast pathology in clinically remitted LVV.

[FAPI-PET-CT for quantification of the tissue response in rheumatic diseases]. / FAPI-PET/CT zur Quantifizierung der Gewebeantwort bei rheumatischen Erkrankungen.

Fibroblast activation protein (FAP) is mainly found on the surface of activated fibroblasts but is not expressed on the surface of inactive fibroblasts. Selective FAP inhibitors (FAPI), which are coupled to a radioactive tracer, can be used to quantify profibrotic and proinflammatory fibroblasts in patients using FAPI positron emission tomography (PET) computed tomography (CT). Following initial applications in neoplastic diseases, FAPI-PET/CT is also increasingly being applied in rheumatological diseases. The first studies have shown that in patients with systemic sclerosis (SSc) FAPI accumulates in actively fibrotically remodeled pulmonary and myocardial areas, that a high FAPI accumulation is associated with the risk of short-term progression and that this accumulation in the lungs regresses after successful treatment. In cases of immunoglobulin 4 (IgG4)-associated diseases (IgG4 rheumatic disease, RD), the FAPI signal correlates with the histological accumulation of activated fibroblasts and a poorer response to treatment to inhibit inflammation. Fibroblasts in chronically inflamed tissue, such as patients with inflammatory joint diseases, vasculitis or myositis, also express FAP and can be quantified by FAPI-PET/CT. The treatment-induced change of the phenotype from a destructive IL-6+/MMP3+THY1+ fibroblast subtype to an inflammation inhibiting CD200+DKK3+ subtype can be mechanistically demonstrated using FAPI-PET/CT. These studies provide indications that FAPI-PET/CT enables quantification of the tissue response in patients with fibrosing and chronic inflammatory diseases and can be used for patient stratification; however, further studies are essential for validation of the use of FAPI-PET/CT as a molecular imaging marker.

Senotherapeutics: Targeting senescence in idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a fatal chronic lung disease characterized by progressive scarring of the lung tissue, leading to respiratory failure. There is no cure for IPF, and current anti-fibrotic treatments modestly arrest its further progression. IPF prevalence and incidence increase with age, which is a recognized risk factor. Intense clinical and basic research over the last fifteen years has shown that hallmarks of accelerated aging are present in the lungs of patients with IPF. Different cell types in IPF lungs exhibit premature hallmarks of aging, including telomere attrition and cellular senescence. In this Review, we discuss recent insights into the mechanisms behind these age-related alterations and their contribution to the development of lung fibrosis. We focus on the genetic and molecular basis of telomere attrition in alveolar type II epithelial cells, which promote cellular senescence and lung fibrosis. Mechanistically, senescent cells secrete pro-fibrotic factors that activate scar-forming myofibroblasts. Ultimately, senescent alveolar epithelial cells lose their regenerative capacity, impeding fibrosis resolution. In addition, mitochondrial dysfunction is strongly associated with the appearance of senescent epithelial cells and senescent myofibroblasts in IPF, which persist in the fibrotic tissue by adapting their metabolic pathways and becoming resistant to apoptosis. We discuss emerging novel therapeutic strategies to treat IPF by targeting cellular senescence with the so-called senotherapeutics.

Blood CD3-(CD56 or 16)+ natural killer cell distributions are heterogeneous in healthy adults and suppressed by azathioprine in patients with ANCA-associated vasculitides.

BACKGROUND: Cytotoxic Natural Killer (NK) cells are increasingly recognized as a powerful tool to induce targeted cell death in cancer and autoimmune diseases. Still, basic blood NK cell parameters are poorly defined. The aims of this study were 1) to establish reference values of NK cell counts and percentages in healthy adults; 2) to describe these parameters in the prototype autoimmune disease group ANCA-associated vasculitis (AAV); and 3) to investigate whether NK cell counts and percentages may be used as activity biomarkers in the care of AAV patients, as suggested by a preceding study. METHODS: CD3-(CD56 or 16)+ NK cell counts and percentages were determined in 120 healthy adults. Lymphocyte subset and clinical data from two German vasculitis centers were analyzed retrospectively (in total 407 measurements, including 201/49/157 measurements from 64/16/39 patients with granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (EGPA), respectively). RESULTS: CD3-(CD56 or 16)+ NK cell counts and percentages in healthy adults were highly variable, not Gaussian distributed and independent of age and sex. NK cell percentages ranged from 1.9 to 37.9% of lymphocytes, and were significantly more dispersed in AAV (0.3 to 57.6%), while the median percentage was not different between AAV and healthy donors. In contrast, median NK cell counts were significantly lower in AAV compared to healthy donors. Sub-group analyses revealed that NK cell counts were low independent of AAV entity and disease activity. Azathioprine therapy was associated with significantly lower NK cell counts and percentages compared to non-azathioprine therapies. In 13.6% of azathioprine-treated patients, percentages were

Myofibroblast fate plasticity in tissue repair and fibrosis: Deactivation, apoptosis, senescence and reprogramming.

In response to tissue injury, fibroblasts differentiate into professional repair cells called myofibroblasts, which orchestrate many aspects of the normal tissue repair programme including synthesis, deposition and contraction of extracellular matrix proteins, leading to wound closure. Successful tissue repair responses involve termination of myofibroblast activities in order to prevent pathologic fibrotic scarring. Here, we discuss the cellular and molecular mechanisms limiting myofibroblast activities during physiological tissue repair, including myofibroblast deactivation, apoptosis, reprogramming and immune clearance of senescent myofibroblasts. In addition, we summarize pathological mechanisms leading to myofibroblast persistence and survival, a hallmark of fibrotic diseases. Finally, we discuss emerging anti-fibrotic therapies aimed at targeting myofibroblast fate such as senolytics, gene therapy, cellular immunotherapy and CAR-T cells.

Inhibition of NKp30- and 2B4-mediated NK cell activation by evolutionary different human and bovine CEACAM1 receptors.

Carcinoembryonicantigen-related cell adhesion molecule 1 (CEACAM1) is a receptor involved in the regulation of NK-cell function. In most species, the CEACAM1 cytoplasmic tail possesses a membrane-proximal ITIM paired with a membrane-distal immunoreceptor tyrosine-based switch motif (ITSM) signaling motif. Human CEACAM1 has phylogenetically relatively recently acquired a second ITIM instead of the ITSM and was shown to inhibit NKG2D-mediated NK-cell activation. Here, we compare the function of bovine and human CEACAM1. We show that in addition to NKG2D, human CEACAM1 can inhibit NK-cell activation via NKp30 or 2B4. Bovine CEACAM1, possessing an ITIM and an ITSM signaling motif, is also inhibitory. However, bovine CEACAM1 inhibition of NKp30-mediated lysis is less pronounced compared with its human counterpart. Bovine CEACAM1 inhibition is dependent on the membrane-proximal ITIM and our data suggest that also the membrane distal ITSM motif contributes to inhibitory signaling. Biochemically, human and bovine CEACAM1 can recruit the phosphatases SHP-1 and SHP-2 after receptor phosphorylation to a similar extend. Bovine CEACAM1 can additionally recruit the adapter molecule Ewing's sarcoma virus-activated transcript-2 (EAT-2), but not SLAM-associated protein (SAP). Taken together, we show that although human and bovine CEACAM1 are differentially equipped with ITIM and ITSM motifs, both receptors can inhibit NKp30 and 2B4 activation of NK cells.

Fcγ-receptor-IIIA bioactivity of circulating and synovial immune complexes in rheumatoid arthritis.

OBJECTIVE: Previous technical limitations prevented the proof of Fcγ-receptor (FcγR)-activation by soluble immune complexes (sICs) in patients. FcγRIIIa (CD16) is a risk factor in rheumatoid arthritis (RA). We aimed at determining the presence of CD16-activating sICs in RA and control diseases. METHODS: Sera from an exploratory cohort (n=50 patients with RA) and a validation cohort (n=106 patients with RA, 20 patients with psoriasis arthritis (PsA), 22 patients with systemic lupus erythematosus (SLE) and 31 healthy controls) were analysed using a new reporter cell assay. Additionally, 26 synovial fluid samples were analysed, including paired serum/synovial samples. RESULTS: For the first time using a reliable and sensitive functional assay, the presence of sICs in RA sera was confirmed. sICs possess an intrinsic capacity to activate CD16 and can be found in both synovial fluid and in blood. In low experimental dilutions, circulating sICs were also detected in a subset of healthy people and in PsA. However, we report a significantly increased frequency of bioactive circulating sICs in RA. While the bioactivity of circulating sICs was low and did not correlate with clinical parameters, synovial sICs were highly bioactive and correlated with serum autoantibody levels. Receiver operator curves indicated that sICs bioactivity in synovial fluid could be used to discriminate immune complex-associated arthritis from non-associated forms. Finally, circulating sICs were more frequently found in SLE than in RA. The degree of CD16 bioactivity showed strong donor-dependent differences, especially in SLE. CONCLUSIONS: RA is characterised by the presence of circulating and synovial sICs that can engage and activate CD16.

Oscillating latent dynamics in robot systems during walking and reaching.

Sensorimotor control of complex, dynamic systems such as humanoids or quadrupedal robots is notoriously difficult. While artificial systems traditionally employ hierarchical optimisation approaches or black-box policies, recent results in systems neuroscience suggest that complex behaviours such as locomotion and reaching are correlated with limit cycles in the primate motor cortex. A recent result suggests that, when applied to a learned latent space, oscillating patterns of activation can be used to control locomotion in a physical robot. While reminiscent of limit cycles observed in primate motor cortex, these dynamics are unsurprising given the cyclic nature of the robot's behaviour (walking). In this preliminary investigation, we consider how a similar approach extends to a less obviously cyclic behaviour (reaching). This has been explored in prior work using computational simulations. But simulations necessarily make simplifying assumptions that do not necessarily correspond to reality, so do not trivially transfer to real robot platforms. Our primary contribution is to demonstrate that we can infer and control real robot states in a learnt representation using oscillatory dynamics during reaching tasks. We further show that the learned latent representation encodes interpretable movements in the robot's workspace. Compared to robot locomotion, the dynamics that we observe for reaching are not fully cyclic, as they do not begin and end at the same position of latent space. However, they do begin to trace out the shape of a cycle, and, by construction, they are driven by the same underlying oscillatory mechanics.

SLE serum induces altered goblet cell differentiation and leakiness in human intestinal organoids.

Human intestinal epithelial cells are the interface between luminal content and basally residing immune cells. They form a tight monolayer that constantly secretes mucus creating a multilayered protective barrier. Alterations in this barrier can lead to increased permeability which is common in systemic lupus erythematosus (SLE) patients. However, it remains unexplored how the barrier is affected. Here, we present an in vitro model specifically designed to examine the effects of SLE on epithelial cells. We utilize human colon organoids that are stimulated with serum from SLE patients. Combining transcriptomic with functional analyses revealed that SLE serum induced an expression profile marked by a reduction of goblet cell markers and changed mucus composition. In addition, organoids exhibited imbalanced cellular composition along with enhanced permeability, altered mitochondrial function, and an interferon gene signature. Similarly, transcriptomic analysis of SLE colon biopsies revealed a downregulation of secretory markers. Our work uncovers a crucial connection between SLE and intestinal homeostasis that might be promoted in vivo through the blood, offering insights into the causal connection of barrier dysfunction and autoimmune diseases.

Effect of JAK Inhibition on the Induction of Proinflammatory HLA-DR+CD90+ Rheumatoid Arthritis Synovial Fibroblasts by Interferon-γ.

OBJECTIVE: Findings from recent transcriptome analyses of the synovium of patients with rheumatoid arthritis (RA) have revealed that 15-fold expanded HLA-DR+CD90+ synovial fibroblasts potentially act as key mediators of inflammation. The reasons for the expansion of HLA-DR+CD90+ synovial fibroblasts are unclear, but genetic signatures indicate that interferon-γ (IFNγ) plays a central role in the generation of this fibroblast subset. The present study was undertaken to investigate the generation, function and therapeutically intended blockage of HLA-DR+CD90+ synovial fibroblasts. METHODS: We combined functional assays using primary human materials and focused bioinformatic analyses of mass cytometry and transcriptomics patient data sets. RESULTS: We detected enriched and activated Fcγ receptor type IIIa-positive (CD16+) NK cells in the synovial tissue from patients with active RA. Soluble immune complexes were recognized by CD16 in a newly described reporter cell model, a mechanism that could be contributing to the activation of natural killer (NK) cells in RA. In vitro, NK cell-derived IFNγ induced HLA-DR on CD90+ synovial fibroblasts, leading to an inflammatory, cytokine-secreting HLA-DR+CD90+ phenotype. HLA-DR+CD90+ synovial fibroblasts consecutively activated CD4+ T cells upon receptor crosslinking via superantigens. HLA-DR+CD90+ synovial fibroblasts also activated CD4+ T cells in the absence of superantigens, an effect that was initiated by NK cell-derived IFNγ and that was 4 times stronger in patients with RA compared to patients with osteoarthritis. Finally, JAK inhibition in synovial fibroblasts prevented HLA-DR induction and blocked proinflammatory signals to T cells. CONCLUSION: The HLA-DR+CD90+ phenotype represents an activation state of synovial fibroblasts during the process of inflammation in RA that can be induced by IFNγ, likely generated from infiltrating leukocytes such as activated NK cells. The induction of these proinflammatory, interleukin-6-producing, and likely antigen-presenting synovial fibroblasts can be targeted by JAK inhibition.

HapFIC: An Adaptive Force/Position Controller for Safe Environment Interaction in Articulated Systems.

Haptic interaction is essential for the dynamic dexterity of animals, which seamlessly switch from an impedance to an admittance behaviour using the force feedback from their proprioception. However, this ability is extremely challenging to reproduce in robots, especially when dealing with complex interaction dynamics, distributed contacts, and contact switching. Current model-based controllers require accurate interaction modelling to account for contacts and stabilise the interaction. In this manuscript, we propose an adaptive force/position controller that exploits the fractal impedance controller's passivity and non-linearity to execute a finite search algorithm using the force feedback signal from the sensor at the end-effector. The method is computationally inexpensive, opening the possibility to deal with distributed contacts in the future. We evaluated the architecture in physics simulation and showed that the controller can robustly control the interaction with objects of different dynamics without violating the maximum allowable target forces or causing numerical instability even for very rigid objects. The proposed controller can also autonomously deal with contact switching and may find application in multiple fields such as legged locomotion, rehabilitation and assistive robotics.

Targeting of Janus Kinases Limits Pro-Inflammatory but Also Immunosuppressive Circuits in the Crosstalk between Synovial Fibroblasts and Lymphocytes.

Crosstalk between synovial fibroblasts (SF) and immune cells plays a central role in the development of rheumatoid arthritis (RA). Janus kinase inhibitors (JAKi) have proven efficacy in the treatment of RA, although clinical responses are heterogeneous. Currently, little is known regarding how JAKi affect pro- and anti-inflammatory circuits in the bidirectional interplay between SF and immune cells. Here, we examined the effects of tofacitinib, baricitinib and upadacitinib on crosstalk between SF and T or B lymphocytes in vitro and compared them with those of biologic disease modifying anti-rheumatic drugs (bDMARDs). JAKi dose-dependently suppressed cytokine secretion of T helper (Th) cells and decreased interleukin (IL)-6 and matrix metalloproteinase (MMP)3 secretion of SF stimulated by Th cells. Importantly, JAK inhibition attenuated the enhanced memory response of chronically stimulated SF. Vice versa, JAKi reduced the indoleamine-2,3-dioxygenase (IDO)1-mediated suppression of T cell-proliferation by SF. Remarkably, certain bDMARDs were as efficient as JAKi in suppressing the IL-6 and MMP3 secretion of SF stimulated by Th (adalimumab, secukinumab) or B cells (canakinumab) and combining bDMARDs with JAKi had synergistic effects. In conclusion, JAKi limit pro-inflammatory circuits in the crosstalk between SF and lymphocytes; however, they also weaken the immunosuppressive functions of SF. Both effects were dose-dependent and may contribute to heterogeneity in clinical response to treatment.

Increase of aerobic glycolysis mediated by activated T helper cells drives synovial fibroblasts towards an inflammatory phenotype: new targets for therapy?

BACKGROUND: A dysregulated glucose metabolism in synovial fibroblasts (SF) has been associated with their aggressive phenotype in rheumatoid arthritis (RA). Even though T helper (Th) cells are key effector cells in the propagation and exacerbation of synovitis in RA, little is known about their influence on the metabolism of SF. Thus, this study investigates the effect of Th cells on the glucose metabolism and phenotype of SF and how this is influenced by the blockade of cytokines, janus kinases (JAKs) and glycolysis. METHODS: SF from patients with RA or osteoarthritis (OA) were cultured in the presence of a stable glucose isotopomer ([U-13C]-glucose) and stimulated with the conditioned media of activated Th cells (ThCM). Glucose consumption and lactate production were measured by proton nuclear magnetic resonance (1H NMR) spectroscopy. Cytokine secretion was quantified by ELISA. The expression of glycolytic enzymes was analysed by PCR, western blot and immunofluorescence. JAKs were blocked using either baricitinib or tofacitinib and glycolysis by using either 3-bromopyruvate or FX11. RESULTS: Quiescent RASF produced significantly higher levels of lactate, interleukin (IL)-6 and matrix metalloproteinase (MMP) 3 than OASF. Stimulation by ThCM clearly changed the metabolic profile of both RASF and OASF by inducing a shift towards aerobic glycolysis with strongly increased lactate production together with a rise in IL-6 and MMP3 secretion. Interestingly, chronic stimulation of OASF by ThCM triggered an inflammatory phenotype with significantly increased glycolytic activity compared to unstimulated, singly stimulated or re-stimulated OASF. Finally, in contrast to cytokine-neutralizing biologics, inhibition of JAKs or glycolytic enzymes both significantly reduced lactate production and cytokine secretion by Th cell-stimulated SF. CONCLUSIONS: Soluble mediators released by Th cells drive SF towards a glycolytic and pro-inflammatory phenotype. Targeting of JAKs or glycolytic enzymes both potently modulate SF's glucose metabolism and decrease the release of IL-6 and MMP3. Thus, manipulation of glycolytic pathways could represent a new therapeutic strategy to decrease the pro-inflammatory phenotype of SF.

Activation of natural killer cells by rituximab in granulomatosis with polyangiitis.

OBJECTIVE: In the last few years, anti-CD20 antibody rituximab profoundly changed the therapeutic landscape of granulomatosis with polyangiitis (GPA). Here, we investigated whether natural killer (NK) cells may play a role in rituximab's mechanism of action in GPA. METHODS: B cell depletion, NK cell degranulation, and the expression of CD69 and CD16 on NK cells were measured in a series of in vitro experiments using peripheral blood mononuclear cells (PBMCs). In vivo activation of NK cells was investigated in patients receiving rituximab infusions. Cells were analyzed by seven-color flow cytometry. RESULTS: NK cells from GPA patients were activated by immobilized rituximab. Also soluble rituximab activated NK cells, provided that B cells were present. NK cells degranulated and expressed the activation marker CD69 while CD16 expression was decreased. This activation of NK cells by soluble rituximab was accompanied by a reduction of B cells. The next-generation anti-CD20 antibody obinutuzumab showed stronger effects compared to rituximab on both the reduction of B cells and the activation of NK cells. Finally, we found that rituximab led to the activation of NK cells in vivo, provided that B cells were not depleted due to prior rituximab infusions. CONCLUSION: B cell-bound rituximab activates NK cells in GPA. While NK cells therefore participate in rituximab's mechanism of action in humans, their potential may be more efficiently exploited, e.g., by Fc engineering of therapeutic antibodies.