JAK inhibitors disrupt T cell-induced proinflammatory macrophage activation.

Objectives: Macrophage subsets, activated by T cells, are increasingly recognised to play a central role in rheumatoid arthritis (RA) pathogenesis. Janus kinase (JAK) inhibitors have proven beneficial clinical effects in RA. In this study, we investigated the effect of JAK inhibitors on the generation of cytokine-activated T (Tck) cells and the production of cytokines and chemokines induced by Tck cell/macrophage interactions.

Atypical chemokine receptor 4 shapes activated B cell fate.

Activated B cells can initially differentiate into three functionally distinct fates-early plasmablasts (PBs), germinal center (GC) B cells, or early memory B cells-by mechanisms that remain poorly understood. Here, we identify atypical chemokine receptor 4 (ACKR4), a decoy receptor that binds and degrades CCR7 ligands CCL19/CCL21, as a regulator of early activated B cell differentiation. By restricting initial access to splenic interfollicular zones (IFZs), ACKR4 limits the early proliferation of activated B cells, reducing the numbers available for subsequent differentiation.

Targeting danger molecules in tendinopathy: the HMGB1/TLR4 axis.

Objectives: To seek evidence of the danger molecule, high-mobility group protein B1 (HMGB1) expression in human tendinopathy and thereafter, to explore mechanisms where HMGB1 may regulate inflammatory mediators and matrix regulation in human tendinopathy.

Methods: Torn supraspinatus tendon (established pathology) and matched intact subscapularis tendon (representing 'early pathology') biopsies were collected from patients undergoing arthroscopic shoulder surgery. Control samples of subscapularis tendon were collected from patients undergoing arthroscopic stabilisation surgery.

MicroRNA29a Treatment Improves Early Tendon Injury.

Tendon injuries (tendinopathies) are common in human and equine athletes and characterized by dysregulated collagen matrix, resulting in tendon damage. We have previously demonstrated a functional role for microRNA29a (miR29a) as a post-transcriptional regulator of collagen 3 expression in murine and human tendon injury. Given the translational potential, we designed a randomized, blinded trial to evaluate the potential of a miR29a replacement therapy as a therapeutic option to treat tendinopathy in an equine model that closely mimics human disease.

Full Length Interleukin 33 Aggravates Radiation-Induced Skin Reaction.

The interleukin (IL)-1 family member IL-33 has been described as intracellular alarmin with broad roles in wound healing, skin inflammation but also autoimmunity. Its dichotomy between full length (fl) IL-33 and the mature (m) form of IL-33 and its release by necrosis is still not fully understood. Here, we compare functional consequences of both forms in the skin , and therefore generated two lines of transgenic mice which selectively overexpress mmIL-33 and flmIL-33 in basal keratinocytes.

MicroRNA-34a dependent regulation of AXL controls the activation of dendritic cells in inflammatory arthritis.

Current treatments for rheumatoid arthritis (RA) do not reverse underlying aberrant immune function. A genetic predisposition to RA, such as HLA-DR4 positivity, indicates that dendritic cells (DC) are of crucial importance to pathogenesis by activating auto-reactive lymphocytes. Here we show that microRNA-34a provides homoeostatic control of CD1c DC activation via regulation of tyrosine kinase receptor AXL, an important inhibitory DC auto-regulator.

Cardiosphere-Derived Cells Require Endoglin for Paracrine-Mediated Angiogenesis.

Clinical trials of stem cell therapy to treat ischemic heart disease primarily use heterogeneous stem cell populations. Small benefits occur via paracrine mechanisms that include stimulating angiogenesis, and increased understanding of these mechanisms would help to improve patient outcomes. Cardiosphere-derived-cells (CDCs) are an example of these heterogeneous stem cell populations, cultured from cardiac tissue.

MicroRNA-155 regulates monocyte chemokine and chemokine receptor expression in Rheumatoid Arthritis.

Objective: To test the hypothesis that miR-155 regulates monocyte migratory potential via modulation of chemokine and chemokine receptor expression in RA, and thereby is associated with disease activity.

Methods: The miR-155 copy-numbers in monocytes from peripheral blood (PB) of healthy (n = 22), RA (n = 24) and RA SF (n = 11) were assessed by real time-PCR using synthetic miR-155 as a quantitative standard. To evaluate the functional impact of miR-155, human monocytes were transfected with control or miR-155 mimic, and the effect on transcript levels, and production of chemokines was evaluated by Taqman low-density arrays and multiplex assays.

MicroRNA29a regulates IL-33-mediated tissue remodelling in tendon disease.

MicroRNA (miRNA) has the potential for cross-regulation and functional integration of discrete biological processes during complex physiological events. Utilizing the common human condition tendinopathy as a model system to explore the cross-regulation of immediate inflammation and matrix synthesis by miRNA we observed that elevated IL-33 expression is a characteristic of early tendinopathy. Using in vitro tenocyte cultures and in vivo models of tendon damage, we demonstrate that such IL-33 expression plays a pivotal role in the transition from type 1 to type 3 collagen (Col3) synthesis and thus early tendon remodelling.

MiR-155 has a protective role in the development of non-alcoholic hepatosteatosis in mice.

Hepatic steatosis is a global epidemic that is thought to contribute to the pathogenesis of type 2 diabetes. MicroRNAs (miRs) are regulators that can functionally integrate a range of metabolic and inflammatory pathways in liver. We aimed to investigate the functional role of miR-155 in hepatic steatosis.

The GATA1s isoform is normally down-regulated during terminal haematopoietic differentiation and over-expression leads to failure to repress MYB, CCND2 and SKI during erythroid differentiation of K562 cells.

Background: Although GATA1 is one of the most extensively studied haematopoietic transcription factors little is currently known about the physiological functions of its naturally occurring isoforms GATA1s and GATA1FL in humans-particularly whether the isoforms have distinct roles in different lineages and whether they have non-redundant roles in haematopoietic differentiation. As well as being of general interest to understanding of haematopoiesis, GATA1 isoform biology is important for children with Down syndrome associated acute megakaryoblastic leukaemia (DS-AMKL) where GATA1FL mutations are an essential driver for disease pathogenesis.

Methods: Human primary cells and cell lines were analyzed using GATA1 isoform specific PCR.

D6 facilitates cellular migration and fluid flow to lymph nodes by suppressing lymphatic congestion.

Lymphatic endothelial cells are important for efficient flow of antigen-bearing fluid and antigen-presenting cells (APCs) from peripheral sites to lymph nodes (LNs). APC movement to LNs is dependent on the constitutive chemokine receptor CCR7, although how conflicting inflammatory and constitutive chemokine cues are integrated at lymphatic surfaces during this process is not understood. Here we reveal a previously unrecognized aspect of the regulation of this process.

MicroRNA-155 as a proinflammatory regulator in clinical and experimental arthritis.

MicroRNA (miRNA) species (miR) regulate mRNA translation and are implicated as mediators of disease pathology via coordinated regulation of molecular effector pathways. Unraveling miR disease-related activities will facilitate future therapeutic interventions. miR-155 recently has been identified with critical immune regulatory functions.

IL-33 activates B1 cells and exacerbates contact sensitivity.

B1 B cells produce natural IgM and play a critical role in the early defense against bacterial and viral infection. The polyreactive IgM also contributes to the clearance of apoptotic products and plays an important role in autoimmune pathogenesis. However, the mechanism of activation and proliferation of B1 cells remains obscure.

Restoration of Runx1 expression in the Tie2 cell compartment rescues definitive hematopoietic stem cells and extends life of Runx1 knockout animals until birth.

Mice deficient in the runt homology domain transcription factor Runx1/AML1 fail to generate functional clonogenic hematopoietic cells and die in utero by embryonic day 12.5. We previously generated Runx1 reversible knockout mice, in which the Runx1 locus can be restored by Cre-mediated recombination.

Direct recognition of LPS by human but not murine CD8+ T cells via TLR4 complex.

LPS comprises a major PAMP and is a key target of the immune system during bacterial infection. While LPS can be recognised by innate immune cells via the TLR4 complex, it is unknown whether T lymphocytes, especially CD8(+) T cells are also capable of doing so. We report here that naive human CD8(+) T cells, after activation by TCR stimulation, express surface TLR4 and CD14.

Influence of Slc11a1 (formerly Nramp1) on DSS-induced colitis in mice.

Multiple genetic studies in humans indicate a role for solute carrier family 11a member 1 [SLC11A1; formerly natural resistance-associated macrophage protein 1 (NRAMP1)] in autoimmune disease susceptibility, including ulcerative colitis. Murine Slc11a1 has many pleiotropic effects on macrophage activation and proinflammatory responses. To determine which of these are important in ulcerative colitis, we established a phenotype for oral dextran sulfate sodium (DSS)-induced acute colitis in congenic Slc11a1 wild-type (wt) and mutant (mt) mice on a B10 background.

Galectin-3 is a negative regulator of lipopolysaccharide-mediated inflammation.

Galectin-3 is a beta-galactoside-binding lectin that plays an important role in inflammatory diseases. It also interacts with the surface carbohydrates of many pathogens, including LPS. However, its role in infection is not fully understood.

The atypical chemokine receptor D6 suppresses the development of chemically induced skin tumors.

A subset of CC chemokines, acting through CC chemokine receptors (CCRs) 1 to 5, is instrumental in shaping inflammatory responses. Recently, we and others have demonstrated that the atypical chemokine receptor D6 actively sequesters and destroys many of these proinflammatory CC chemokines. This is critical for effective resolution of inflammation in vivo.

Promotion of haematopoietic activity in embryonic stem cells by the aorta-gonad-mesonephros microenvironment.

We investigated whether the in vitro differentiation of ES cells into haematopoietic progenitors could be enhanced by exposure to the aorta-gonadal-mesonephros (AGM) microenvironment that is involved in the generation of haematopoietic stem cells (HSC) during embryonic development. We established a co-culture system that combines the requirements for primary organ culture and differentiating ES cells and showed that exposure of differentiating ES cells to the primary AGM region results in a significant increase in the number of ES-derived haematopoietic progenitors. Co-culture of ES cells on the AM20-1B4 stromal cell line derived from the AGM region also increases haematopoietic activity.

A murine specific expansion of the Rhox cluster involved in embryonic stem cell biology is under natural selection.

Background: The rodent specific reproductive homeobox (Rhox) gene cluster on the X chromosome has been reported to contain twelve homeobox-containing genes, Rhox1-12.

Results: We have identified a 40 kb genomic region within the Rhox cluster that is duplicated eight times in tandem resulting in the presence of eight paralogues of Rhox2 and Rhox3 and seven paralogues of Rhox4. Transcripts have been identified for the majority of these paralogues and all but three are predicted to produce full-length proteins with functional potential.

Labeling of hematopoietic stem and progenitor cells in novel activatable EGFP reporter mice.

Conditional activation and inactivation of genes using the Cre/loxP recombination system is a powerful tool for the analysis of gene function and for tracking cell fate. Here we report a novel silent EGFP reporter mouse line generated by enhancer trap technology using embryonic stem (ES) cells. Following transfection with the silent EGFP reporter construct, positive ES cell clones were treated with Cre recombinase.