Impingement Resulting in Femoral Notching and Elevated Metal-Ion Levels After Dual-Mobility Total Hip Arthroplasty.

A 60-year-old woman underwent revision total hip arthroplasty with a modular dual-mobility articulation for recurrent dislocation. At 1-year follow-up, the patient reported no dislocations but had occasional clicking and discomfort with extreme motion. A Dunn radiograph identified notching of the femoral stem, attributed to impingement. Metal ions were elevated without adverse local-tissue reaction. After 4.5 years of observation, the notch size remained stable. She denied pain. Neither stem fracture nor prosthetic dislocation occurred. Impingement against cobalt-chromium acetabular bearing surfaces can result in notching of titanium femoral components after total hip arthroplasty. Increased anteversion intended to protect against posterior dislocation may be a risk factor. Posterior notching is best visualized on Dunn views, so incidence may be underestimated. No associated femoral implant fractures were identified on literature review.

The modular mechanism of chromocenter formation in Drosophila.

A central principle underlying the ubiquity and abundance of pericentromeric satellite DNA repeats in eukaryotes has remained poorly understood. Previously we proposed that the interchromosomal clustering of satellite DNAs into nuclear structures known as chromocenters ensures encapsulation of all chromosomes into a single nucleus (Jagannathan et al., 2018). Chromocenter disruption led to micronuclei formation, resulting in cell death. Here we show that chromocenter formation is mediated by a 'modular' network, where associations between two sequence-specific satellite DNA-binding proteins, D1 and Prod, bound to their cognate satellite DNAs, bring the full complement of chromosomes into the chromocenter. D1 prod double mutants die during embryogenesis, exhibiting enhanced phenotypes associated with chromocenter disruption, revealing the universal importance of satellite DNAs and chromocenters. Taken together, we propose that associations between chromocenter modules, consisting of satellite DNA binding proteins and their cognate satellite DNA, package the Drosophila genome within a single nucleus.

Flares in Patients with Rheumatoid Arthritis after Total Hip and Total Knee Arthroplasty: Rates, Characteristics, and Risk Factors.

OBJECTIVE: Rates of total knee arthroplasty (TKA) and total hip arthroplasty (THA) remain high for patients with rheumatoid arthritis (RA), who are at risk of flaring after surgery. We aimed to describe rates, characteristics, and risk factors of RA flare within 6 weeks of THA and TKA. METHODS: Patients with RA were recruited prior to elective THA and TKA surgery and prospectively followed. Clinicians evaluated RA clinical characteristics 0-2 weeks before and 6 weeks after surgery. Patients answered questions regarding disease activity including self-reported joint counts and flare status weekly for 6 weeks. Per standard of care, biologics were stopped before surgery, while glucocorticoids and methotrexate (MTX) were typically continued. Multivariable logistic regression was used to identify baseline characteristics associated with postsurgical RA flares. RESULTS: Of 120 patients, the mean age was 62 years and the median RA duration 14.8 years. Ninety-eight (82%) met 2010/1987 American College of Rheumatology/European League Against Rheumatism criteria, 53 (44%) underwent THA (and the rest TKA), and 61 (51%) were taking biologics. By 6 weeks, 75 (63%) had flared. At baseline, flarers had significantly higher disease activity (as measured by the 28-joint Disease Activity Score), erythrocyte sedimentation rate, C-reactive protein, and pain. Numerically more flarers used biologics, but stopping biologics did not predict flares, and continuing MTX was not protective. A higher baseline disease activity predicted flaring by 6 weeks (OR 2.12, p = 0.02). CONCLUSION: Flares are frequent in patients with RA undergoing arthroplasty. Higher baseline disease activity significantly increases the risk. Although more patients stopping biologics flared, this did not independently predict flaring. The effect of early postsurgery flares requires further study.

A conserved function for pericentromeric satellite DNA.

A universal and unquestioned characteristic of eukaryotic cells is that the genome is divided into multiple chromosomes and encapsulated in a single nucleus. However, the underlying mechanism to ensure such a configuration is unknown. Here, we provide evidence that pericentromeric satellite DNA, which is often regarded as junk, is a critical constituent of the chromosome, allowing the packaging of all chromosomes into a single nucleus. We show that the multi-AT-hook satellite DNA-binding proteins, Drosophila melanogaster D1 and mouse HMGA1, play an evolutionarily conserved role in bundling pericentromeric satellite DNA from heterologous chromosomes into 'chromocenters', a cytological association of pericentromeric heterochromatin. Defective chromocenter formation leads to micronuclei formation due to budding from the interphase nucleus, DNA damage and cell death. We propose that chromocenter and satellite DNA serve a fundamental role in encapsulating the full complement of the genome within a single nucleus, the universal characteristic of eukaryotic cells.

Cytokine receptor-Eb1 interaction couples cell polarity and fate during asymmetric cell division.

Asymmetric stem cell division is a critical mechanism for balancing self-renewal and differentiation. Adult stem cells often orient their mitotic spindle to place one daughter inside the niche and the other outside of it to achieve asymmetric division. It remains unknown whether and how the niche may direct division orientation. Here we discover a novel and evolutionary conserved mechanism that couples cell polarity to cell fate. We show that the cytokine receptor homolog Dome, acting downstream of the niche-derived ligand Upd, directly binds to the microtubule-binding protein Eb1 to regulate spindle orientation in Drosophila male germline stem cells (GSCs). Dome's role in spindle orientation is entirely separable from its known function in self-renewal mediated by the JAK-STAT pathway. We propose that integration of two functions (cell polarity and fate) in a single receptor is a key mechanism to ensure an asymmetric outcome following cell division.

Identification of Three Rheumatoid Arthritis Disease Subtypes by Machine Learning Integration of Synovial Histologic Features and RNA Sequencing Data.

OBJECTIVE: In this study, we sought to refine histologic scoring of rheumatoid arthritis (RA) synovial tissue by training with gene expression data and machine learning. METHODS: Twenty histologic features were assessed in 129 synovial tissue samples (n = 123 RA patients and n = 6 osteoarthritis [OA] patients). Consensus clustering was performed on gene expression data from a subset of 45 synovial samples. Support vector machine learning was used to predict gene expression subtypes, using histologic data as the input. Corresponding clinical data were compared across subtypes. RESULTS: Consensus clustering of gene expression data revealed 3 distinct synovial subtypes, including a high inflammatory subtype characterized by extensive infiltration of leukocytes, a low inflammatory subtype characterized by enrichment in pathways including transforming growth factor ß, glycoproteins, and neuronal genes, and a mixed subtype. Machine learning applied to histologic features, with gene expression subtypes serving as labels, generated an algorithm for the scoring of histologic features. Patients with the high inflammatory synovial subtype exhibited higher levels of markers of systemic inflammation and autoantibodies. C-reactive protein (CRP) levels were significantly correlated with the severity of pain in the high inflammatory subgroup but not in the others. CONCLUSION: Gene expression analysis of RA and OA synovial tissue revealed 3 distinct synovial subtypes. These labels were used to generate a histologic scoring algorithm in which the histologic scores were found to be associated with parameters of systemic inflammation, including the erythrocyte sedimentation rate, CRP level, and autoantibody levels. Comparison of gene expression patterns to clinical features revealed a potentially clinically important distinction: mechanisms of pain may differ in patients with different synovial subtypes.

DrugBank 5.0: a major update to the DrugBank database for 2018.

DrugBank (www.drugbank.ca) is a web-enabled database containing comprehensive molecular information about drugs, their mechanisms, their interactions and their targets. First described in 2006, DrugBank has continued to evolve over the past 12 years in response to marked improvements to web standards and changing needs for drug research and development. This year's update, DrugBank 5.0, represents the most significant upgrade to the database in more than 10 years. In many cases, existing data content has grown by 100% or more over the last update. For instance, the total number of investigational drugs in the database has grown by almost 300%, the number of drug-drug interactions has grown by nearly 600% and the number of SNP-associated drug effects has grown more than 3000%. Significant improvements have been made to the quantity, quality and consistency of drug indications, drug binding data as well as drug-drug and drug-food interactions. A great deal of brand new data have also been added to DrugBank 5.0. This includes information on the influence of hundreds of drugs on metabolite levels (pharmacometabolomics), gene expression levels (pharmacotranscriptomics) and protein expression levels (pharmacoprotoemics). New data have also been added on the status of hundreds of new drug clinical trials and existing drug repurposing trials. Many other important improvements in the content, interface and performance of the DrugBank website have been made and these should greatly enhance its ease of use, utility and potential applications in many areas of pharmacological research, pharmaceutical science and drug education.

Different tissue phagocytes sample apoptotic cells to direct distinct homeostasis programs.

Recognition and removal of apoptotic cells by professional phagocytes, including dendritic cells and macrophages, preserves immune self-tolerance and prevents chronic inflammation and autoimmune pathologies. The diverse array of phagocytes that reside within different tissues, combined with the necessarily prompt nature of apoptotic cell clearance, makes it difficult to study this process in situ. The full spectrum of functions executed by tissue-resident phagocytes in response to homeostatic apoptosis, therefore, remains unclear. Here we show that mouse apoptotic intestinal epithelial cells (IECs), which undergo continuous renewal to maintain optimal barrier and absorptive functions, are not merely extruded to maintain homeostatic cell numbers, but are also sampled by a single subset of dendritic cells and two macrophage subsets within a well-characterized network of phagocytes in the small intestinal lamina propria. Characterization of the transcriptome within each subset before and after in situ sampling of apoptotic IECs revealed gene expression signatures unique to each phagocyte, including macrophage-specific lipid metabolism and amino acid catabolism, and a dendritic-cell-specific program of regulatory CD4+ T-cell activation. A common 'suppression of inflammation' signature was noted, although the specific genes and pathways involved varied amongst dendritic cells and macrophages, reflecting specialized functions. Apoptotic IECs were trafficked to mesenteric lymph nodes exclusively by the dendritic cell subset and served as critical determinants for the induction of tolerogenic regulatory CD4+ T-cell differentiation. Several of the genes that were differentially expressed by phagocytes bearing apoptotic IECs overlapped with susceptibility genes for inflammatory bowel disease. Collectively, these findings provide new insights into the consequences of apoptotic cell sampling, advance our understanding of how homeostasis is maintained within the mucosa and set the stage for development of novel therapeutics to alleviate chronic inflammatory diseases such as inflammatory bowel disease.

Total-Body Irradiation Exacerbates Dissemination of Cutaneous Candida Albicans Infection.

Exposure to radiation, particularly a large or total-body dose, weakens the immune system through loss of bone marrow precursor cells, as well as diminished populations of circulating and tissue-resident immune cells. One such population is the skin-resident immune cells. Changes in the skin environment can be of particular importance as the skin is also host to a number of commensal organisms, including Candida albicans , a species of fungus that causes opportunistic infections in immunocompromised patients. In a previous study, we found that a 6 Gy sublethal dose of radiation in mice caused a reduction of cutaneous dendritic cells, indicating that the skin may have a poorer response to infection after irradiation. In this study, the same 6 Gy sublethal radiation dose led to a weakened response to a C. ablicans cutaneous infection, which resulted in systemic dissemination from the ear skin to the kidneys. However, this impaired response was mitigated through the use of interleukin-12 (IL-12) administered to the skin after irradiation. Concomitantly with this loss of local control of infection, we also observed a reduction of CD4+ and CD8+ T cells in the skin, as well as the reduced expression of IFN-γ, CXCL9 and IL-9, which influence T-cell infiltration and function in infected skin. These changes suggest a mechanism by which an impaired immune environment in the skin after a sublethal dose of radiation increases susceptibility to an opportunistic fungal infection. Thus, in the event of radiation exposure, it is important to include antifungal agents, or possibly IL-12, in the treatment regimen, particularly if wounds are involved that result in loss of the skin's physical barrier function.

Interleukin-12 preserves the cutaneous physical and immunological barrier after radiation exposure.

The United States continues to be a prime target for attack by terrorist organizations in which nuclear detonation and dispersal of radiological material are legitimate threats. Such attacks could have devastating consequences to large populations, in the form of radiation injury to various human organ systems. One of these at risk organs is the cutaneous system, which forms both a physical and immunological barrier to the surrounding environment and is particularly sensitive to ionizing radiation. Therefore, increased efforts to develop medical countermeasures for treatment of the deleterious effects of cutaneous radiation exposure are essential. Interleukin-12 (IL-12) was shown to elicit protective effects against radiation injury on radiosensitive systems such as the bone marrow and gastrointestinal tract. In this article, we examined if IL-12 could protect the cutaneous system from a combined radiation injury in the form of sublethal total body irradiation and beta-radiation burn (ß-burn) directly to the skin. Combined radiation injury resulted in a breakdown in skin integrity as measured by transepidermal water loss, size of ß-burn lesion and an exacerbated loss of surveillant cutaneous dendritic cells. Interestingly, intradermal administration of IL-12 48 h postirradiation reduced transepidermal water loss and burn size, as well as retention of cutaneous dendritic cells. Our data identify IL-12 as a potential mitigator of radiation-induced skin injury and argue for the further development of this cytokine as a radiation countermeasure.

Optogenetic control of chemokine receptor signal and T-cell migration.

Adoptive cell transfer of ex vivo-generated immune-promoting or tolerogenic T cells to either enhance immunity or promote tolerance in patients has been used with some success. However, effective trafficking of the transferred cells to the target tissue sites is the main barrier to achieving successful clinical outcomes. Here we developed a strategy for optically controlling T-cell trafficking using a photoactivatable (PA) chemokine receptor. Photoactivatable-chemokine C-X-C motif receptor 4 (PA-CXCR4) transmitted intracellular CXCR4 signals in response to 505-nm light. Localized activation of PA-CXCR4 induced T-cell polarization and directional migration (phototaxis) both in vitro and in vivo. Directing light onto the melanoma was sufficient to recruit PA-CXCR4-expressing tumor-targeting cytotoxic T cells and improved the efficacy of adoptive T-cell transfer immunotherapy, with a significant reduction in tumor growth in mice. These findings suggest that the use of photoactivatable chemokine receptors allows remotely controlled leukocyte trafficking with outstanding spatial resolution in tissues and may be feasible in other cell transfer therapies.

Exposure to ionizing radiation induces the migration of cutaneous dendritic cells by a CCR7-dependent mechanism.

In the event of a deliberate or accidental radiological emergency, the skin would likely receive substantial ionizing radiation (IR) poisoning, which could negatively impact cellular proliferation, communication, and immune regulation within the cutaneous microenvironment. Indeed, as we have previously shown, local IR exposure to the murine ear causes a reduction of two types of cutaneous dendritic cells (cDC), including interstitial dendritic cells of the dermis and Langerhans cells of the epidermis, in a dose- and time-dependent manner. These APCs are critical regulators of skin homeostasis, immunosurveillance, and the induction of T and B cell-mediated immunity, as previously demonstrated using conditional cDC knockout mice. To mimic a radiological emergency, we developed a murine model of sublethal total body irradiation (TBI). Our data would suggest that TBI results in the reduction of cDC from the murine ear that was not due to a systemic response to IR, as a loss was not observed in shielded ears. We further determined that this reduction was due, in part, to the upregulation of the chemoattractant CCL21 on lymphatic vessels as well as CCR7 expressed on cDC. Migration as a potential mechanism was confirmed using CCR7(-/-) mice in which cDC were not depleted following TBI. Finally, we demonstrated that the loss of cDC following TBI results in an impaired contact hypersensitivity response to hapten by using a modified contact hypersensitivity protocol. Taken together, these data suggest that IR exposure may result in diminished immunosurveillance in the skin, which could render the host more susceptible to pathogens.

The proteasome activator PA200 regulates tumor cell responsiveness to glutamine and resistance to ionizing radiation.

The cellular response to ionizing radiation (IR) involves a variety of mechanisms to repair damage and maintain cell survival. We previously reported that the proteasome activator PA200 promotes long-term cell survival after IR exposure. The molecular function of PA200 is to enhance proteasome-mediated cleavage after glutamate; however, it is not known how this molecular function promotes survival after IR exposure. Here, we report that upon IR exposure, cellular demand for exogenous glutamine is increased. Cells containing PA200 are capable of surviving this IR-induced glutamine demand, whereas PA200-deficient cells show impaired long-term survival. Additional glutamine supplementation reverses the radiosensitivity of PA200-knockdown cells suggesting impaired glutamine homeostasis in these cells. Indeed, PA200-knockdown cells are unable to maintain intracellular glutamine levels. Furthermore, when extracellular glutamine is limiting, cells that contain PA200 respond by slowing growth, but PA200-knockdown cells and cells in which post-glutamyl proteasome activity is inhibited are nonresponsive and continue rapid growth. This cellular unresponsiveness to nutrient depletion is also reflected at the level of the mTOR substrate ribosomal S6 kinase (S6K). Thus, inability to restrict growth causes PA200-deficient cells to continue growing and eventually die due to lack of available glutamine. Together, these data indicate an important role for PA200 and post-glutamyl proteasome activity in maintaining glutamine homeostasis, which appears to be especially important for long-term survival of tumor cells after radiation exposure.

Migration of skin dendritic cells in response to ionizing radiation exposure.

We describe an imaging assay that monitors the migration of two unique subsets of immune dendritic cells (DC), interstitial dendritic cells (iDC) and Langerhans cells (LC), found in the dermal and epidermal layers of skin, respectively. Using this assay, we study responses of these cells to ionizing radiation. Results obtained using whole-mount histology and fluorescence microscopy suggest that ionizing radiation triggered the migration of both major histocompatibility complex (MHC) class II(+) iDC and Langerin(+) LC in a dose- and time-dependent manner. Migration appeared to be limited by local administration of recombinant IL-12, a potent immunostimulatory cytokine known to induce DNA repair. Those findings were extended to an in vivo model by injecting fluorescently conjugated anti-MHC class II antibodies intradermally into the ears of live, anesthetized mice and visualizing the DC population in the same ear before and after radiation exposure using confocal microscopy.

Antibody-labeled fluorescence imaging of dendritic cell populations in vivo.

We report an optical molecular imaging technique that exploits local administration of fluorophore-conjugated antibodies and confocal fluorescence microscopy to achieve high-contrast imaging of host cell populations in normal and tumor tissue in living mice. The method achieves micron-scale spatial resolution to depths greater than 100 mum. We illustrate the capabilities of this approach by imaging two dendritic cell populations in the skin and normal and tumor vasculature in vivo.