Introduction Although the presence of bone marrow lesions (BMLs) on magnetic resonance images is strongly associated with osteoarthritis progression and pain, the underlying pathology is not well established. The aim of the present study was to evaluate the architecture of subchondral bone in regions with and without BMLs from the same individual using bone histomorphometry.

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ObjectivesGenetic variations in TNFAIP3 (A20) de-ubiquitinase (DUB) domain increase the risk of systemic lupus erythematosus (SLE) and rheumatoid arthritis. A20 is a negative regulator of NF-κB but the role of its DUB domain and related genetic variants remain unclear. We aimed to study the functional effects of A20 DUB-domain alterations in immune cells and understand its link to SLE pathogenesis.MethodsCRISPR/Cas9 was used to generate human U937 monocytes with A20 DUB-inactivating C103A knock-in (KI) mutation. Whole genome RNA-sequencing was used to identify differentially expressed genes between WT and C103A KI cells. Functional studies were performed in A20 C103A U937 cells and in immune cells from A20 C103A mice and genotyped healthy individuals with A20 DUB polymorphism rs2230926. Neutrophil extracellular trap (NET) formation was addressed ex vivo in neutrophils from A20 C103A mice and SLE-patients with rs2230926.ResultsGenetic disruption of A20 DUB domain in human and murine myeloid cells did not give rise to enhanced NF-κB signalling. Instead, cells with C103A mutation or rs2230926 polymorphism presented an upregulated expression of PADI4, an enzyme regulating protein citrullination and NET formation, two key mechanisms in autoimmune pathology. A20 C103A cells exhibited enhanced protein citrullination and extracellular trap formation, which could be suppressed by selective PAD4 inhibition. Moreover, SLE-patients with rs2230926 showed increased NETs and increased frequency of autoantibodies to citrullinated epitopes.ConclusionsWe propose that genetic alterations disrupting the A20 DUB domain mediate increased susceptibility to SLE through the upregulation of PADI4 with resultant protein citrullination and extracellular trap formation.

The respiratory tract is normally kept essentially free of bacteria by cilia-mediated mucus transport, but in chronic obstructive pulmonary disease (COPD) and cystic fibrosis (CF), bacteria and mucus accumulates instead. To address the mechanisms behind the mucus accumulation, the proteome of bronchoalveolar lavages from COPD patients and mucus collected in an elastase-induced mouse model of COPD was analyzed, revealing similarities with each other and with the protein content in colonic mucus. Moreover, stratified laminated sheets of mucus were observed in airways from patients with CF and COPD and in elastase-exposed mice. On the other hand, the mucus accumulation in the elastase model was reduced in Muc5b-KO mice. While mucus plugs were removed from airways by washing with hypertonic saline in the elastase model, mucus remained adherent to epithelial cells. Bacteria were trapped on this mucus, whereas, in non-elastase-treated mice, bacteria were found on the epithelial cells. We propose that the adherence of mucus to epithelial cells observed in CF, COPD, and the elastase-induced mouse model of COPD separates bacteria from the surface cells and, thus, protects the respiratory epithelium.

ObjectiveTo investigate the role of hypoxia in the pathology of osteoarthritic (OA) bone by exploring its effect on the phenotype of isolated primary osteoblasts from patients with knee OA.MethodsOA bone samples were collected at the time of elective joint replacement surgery for knee or hip OA. Normal bone samples were collected postmortem from cadaver donors. Primary osteoblasts were isolated from knee OA bone chips and cultured under normoxic or hypoxic (2% O2) conditions. Alkaline phosphatase activity was quantified using an enzymatic assay, and osteopontin and prostaglandin E2 (PGE2) production was assayed by enzyme-linked immunosorbent assay. Total RNA was extracted from bone and osteoblasts, and gene expression was profiled by quantitative reverse transcription–polymerase chain reaction.ResultsHuman OA bone tissue sections stained positively for carbonic anhydrase IX, a biomarker of hypoxia, and exhibited differential expression of genes that mediate the vasculature and blood coagulation as compared to those found in normal bone. Culture of primary osteoblasts isolated from knee OA bone under hypoxic conditions profoundly affected the osteoblast phenotype, including the expression of genes that mediate bone matrix, bone remodeling, and bone vasculature. Hypoxia also increased the expression of cyclooxygenase 2 and the production of PGE2 by OA osteoblasts. Osteoblast expression of type II collagen α1 chain, angiopoietin-like 4, and insulin-like growth factor binding protein 1 was shown to be mediated by hypoxia-inducible factor 1α. Chronic hypoxia reduced osteoblast- mineralized bone nodule formation.ConclusionThese findings demonstrate that hypoxia can induce pathologic changes in osteoblast functionality consistent with an OA phenotype, providing evidence that hypoxia is a key driver of OA pathology.

This review aims to address the mechanisms of compromised immune tolerance contributing to the development and maintenance of Alopecia Areata (AA). Our goal is to also highlight future treatment opportunities and therapeutics that will safely and efficiently restore hair growth and maintain patients in remission. AA is a presumptive autoimmune disorder that coincides and genetically clusters to several other autoimmune diseases. In this review, we pay attention to the learnings from the mechanistic research and drug development in these other autoimmune conditions. Interestingly, most of these diseases have been linked to compromised central and peripheral tolerance, and increased intestinal inflammation with enhanced gut permeability. Break of tolerance and priming of the autoreactive T-cells to attack antigenic epitopes in the hair follicle most likely requires several steps which include escape from negative selection and compromised peripheral tolerance. Local skin-related changes are also of importance due to the patchy manifestation of the skin areas with loss of hair, particularly in the early disease. Here, we discuss the defective mechanisms of tolerance, both central and peripheral, and hypothesize that the disease is driven by areas of tolerance break, and that these could be targeted for successful therapeutic interventions.

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With the increasing amount of image data collected from biomedical experiments there is an urgent need for smarter and more effective analysis methods. Many scientific questions require analysis of image subregions related to some specific biology. Finding such regions of interest (ROIs) at low resolution and limiting the data subjected to final quantification at full resolution can reduce computational requirements and save time. In this paper we propose a three-step pipeline: First, bounding boxes for ROIs are located at low resolution. Next, ROIs are subjected to semantic segmentation into sub-regions at mid-resolution. We also estimate the confidence of the segmented sub-regions. Finally, quantitative measurements are extracted at full resolution. We use deep learning for the first two steps in the pipeline and conformal prediction for confidence assessment. We show that limiting final quantitative analysis to sub-regions with full confidence reduces noise and increases separability of observed biological effects.